Graphical Abstract

Previous Issue

JMSJ, 2020, Vol. 98, No. 1 (February)

Invited Review Articles

Ito et al. (2020)

Ito, K., C.-C. Wu, K. T. F. Chan, R. Toumi, and C. Davis, 2020: Recent progress in the fundamental understanding of tropical cyclone motion. J. Meteor. Soc. Japan, 98, 5-17.
https://doi.org/10.2151/jmsj.2020-001Graphical Abstract

Plain Language Summary: Because of its importance of the tropical cyclone (TC) track, extensive studies have been carried out. While the understanding of the motion of TCs is fairly mature, notable advancements are still being made very recently. This paper summarizes new concepts and updates to the existing theories, particularly since 2014, as follows: revisiting the concept of steering flow, barotropic framework, recurvature, influence of topography, role of atmosphere-ocean interaction, large scale features, and dynamics of large forecast errors in TC tracks.

Highlights:

 

Luo et al. (2020)

Luo, Y., R. Xia, and J. C. L. Chan, 2020: Characteristics, physical mechanisms, and prediction of pre-summer rainfall over South China: research progress during 2008-2019. J. Meteor. Soc. Japan, 98, 19-42.
https://doi.org/10.2151/jmsj.2020-002Graphical Abstract

Plain Language Summary: Pre-summer rainy season (April to mid-June) over South China is characterized by high intensity and frequent occurrence of heavy rainfall in the East Asian monsoon region. This review describes recent progress in the research related to such a phenomenon, including the temporal and spatial characteristics of the rainfall, new insights into the relevant multiscale processes governing initiation and development of rainstorms, and convection-permitting modeling studies aiming at improving the quantitative precipitation forecast skill.

Highlights:

 

Articles

Seo et al. (2020)

Seo, J. M., H. Lee, S. Moon, and J.-J. Baik, 2020: How mountain geometry affects aerosol-cloud-precipitation interactions: Part I. Shallow convective clouds. J. Meteor. Soc. Japan, 98, 43-60.
https://doi.org/10.2151/jmsj.2020-003Graphical Abstract

Plain Language Summary: We examine how mountain upslope geometry controls aerosol effects on orographic precipitation from shallow warm convective clouds through idealized simulations using the WRF model with a bin microphysics scheme. The windward-width of the mountain controls advection timescale of liquid drops. Greater aerosol loading leads to reduction and downstream shift of precipitation. The aerosol effects are more clearly seen when the windward-width of the mountain is narrower.

Highlights:

 

Fudeyasu et al. (2020)

Fudeyasu, H., R. Yoshida, M. Yamaguchi, H. Eito, C. Muroi, S. Nishimura, K. Bessho, Y. Oikawa, and N. Koide, 2020: Development conditions for tropical storms over the western North Pacific stratified by large-scale flow patterns. J. Meteor. Soc. Japan, 98, 61-72.
https://doi.org/10.2151/jmsj.2020-004Graphical Abstract

Plain Language Summary: This study investigated the characteristics and environmental conditions of tropical cyclones (TCs) over the western North Pacific from 2009 to 2017 that dissipated before reaching tropical storm strength (TDs) under unfavorable environmental conditions; we compared these with TCs that reached tropical storm strength (TSs) in terms of modulations of relevant large-scale flow patterns. The flow patterns were categorized based on five factors: shear line (SL), confluence region (CR), monsoon gyre (GY), easterly waves (EW), and Rossby wave energy dispersion from a preexisting cyclone (PTC). Among 476 cases, 263 TDs were detected using best-track data and early stage Dvorak analysis.

Highlights:

 

Hohenegger et al. (2020)

Hohenegger, C., L. Kornblueh, D. Klocke, T. Becker, G. Cioni, J. F. Engels, U. Schulzweida, and B. Stevens, 2020: Climate statistics in global simulations of the atmosphere, from 80 to 2.5 km grid spacing. J. Meteor. Soc. Japan, 98, 73-91.
Special Edition on DYAMOND: The DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains
https://doi.org/10.2151/jmsj.2020-005Graphical Abstract

Plain Language Summary: General Circulation Models (GCMs) are complex tools embodying physical principles to represent the statistics of the climate system. Limitations in computer resources impose constraints on the resolution of such models and hence on the scales of the atmospheric processes that such models can explicitly represent. Both the chosen grid spacing and the employed model formulation affect the quality of a simulation. In this study, we examine the convergence behavior of a GCM by systematically varying its grid spacing. We objectively assess the convergence by comparing differences resulting from changes in grid spacing to differences resulting from using distinct model formulations. For the investigated statistics of the climate system, our study thus indicates at which grid spacing model formulation becomes more important than grid spacing.

Highlights:

 

Lin et al. (2020)

Lin, Y.-F., C.-C. Wu, T.-H. Yen, Y.-H. Huang, and G.-Y. Lien, 2020: Typhoon Fanapi (2010) and its interaction with Taiwan terrain - Evaluation of the uncertainty in track, intensity and rainfall simulations. J. Meteor. Soc. Japan, 98, 93-113.
https://doi.org/10.2151/jmsj.2020-006Graphical Abstract

Plain Language Summary: Taiwan topography is considered a critical factor affecting the track, intensity, and rainfall for the landfalling tropical cyclone (TC), but the uncertainty of its impact in the simulations has not been thoroughly explored in the literature. Using an ensemble Kalman filter–based vortex initialization method, this paper evaluates the impact of Central Mountain Range (CMR) on the uncertainty in forecasting track, intensity, and rainfall of Typhoon Fanapi (2010) and explores the sources of the uncertainty in the simulation.

Highlights:

 

Umezawa et al. (2020)

Umezawa, T., S. J. Andrews, and T. Saito, 2020: A cryogen-free automated measurement system of stable carbon isotope ratio of atmospheric methane. J. Meteor. Soc. Japan, 98, 115-127.
https://doi.org/10.2151/jmsj.2020-007Graphical Abstract

Plain Language Summary: Methane (CH4) plays an important role in climate change and atmospheric chemistry. The stable carbon isotope ratio of atmospheric methane (δ13C-CH4) is useful for separating contributions of different CH4 source types. We set up a new measurement system for δ13C-CH4, optimized for the automated analysis of air samples. The system is operated with no use of cryogens (e.g., liquid nitrogen) and attained reproducibility sufficient to analyze atmospheric variations (~0.1‰). Automated continuous measurements of ambient air characterized imprint of local methane sources well. Future measurement operation will provide a large number of atmospheric δ13C-CH4 data.

Highlights:

 

Miao et al. (2020)

Miao, J.-E., and M.-J. Yang, 2020: A modeling study of the severe afternoon thunderstorm event at Taipei on 14 June 2015: The roles of sea breeze, microphysics, and terrain. J. Meteor. Soc. Japan, 98, 129-152.
https://doi.org/10.2151/jmsj.2020-008Graphical Abstract

Plain Language Summary: On 14 June 2015, a severe afternoon thunderstorm event developed within the Taipei basin, producing intense rainfall (with rainfall rate of 131 mm h-1) and urban-scale flooding. This study uses high-resolution simulations (with the finest horizontal grid size of 500 m) to successfully reproduce this thunderstorm event, and performs numerical experiments to examine the interactions between sea breeze, cold-air outflow, and local coastal terrain of Mount Datun.

Highlights:

 

Ha et al. (2020)

Ha, K.-J., J.-H. Yeo, Y.-W. Seo, E.-S. Chung, J.-Y. Moon, X. Feng, Y.-W. Lee, and C.-H. Ho, 2020: What caused the extraordinarily hot 2018 summer in Korea? J. Meteor. Soc. Japan, 98, 153-167.
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-009Graphical Abstract

Plain Language Summary: This study intends to diagnose an extraordinary heatwave (HW) in 2018 that the Korean Peninsula (KP) has experienced extreme heat throughout July and August with the highest temperature and longest consecutive hot days on record since 1907. The causes of these abnormal temperature patterns were examined with the difference from other episodic events as in 1994.

Highlights:

 

Takemura and Mukougawa (2020)

Takemura, K.,and H. Mukougawa, 2020: Dynamical relationship between quasi-stationary Rossby wave propagation along the Asian jet and Pacific-Japan pattern in boreal summer. J. Meteor. Soc. Japan, 98, 169-187.
https://doi.org/10.2151/jmsj.2020-010Graphical Abstract

Plain Language Summary: To reveal a new possible process linking the quasi-stationary Rossby wave propagation over Eurasia along the Asian jet and the Pacific-Japan (PJ) pattern through the Rossby wave breaking (RWB) east of Japan during boreal summer, this study conducts a lag composite analysis of the past 44 RWB events. The results of this paper show that the quasi-stationary Rossby wave propagation along the Asian jet can excite the PJ pattern, through high potential vorticity (PV) intrusion toward the subtropical western North Pacific associated with the RWB and the consequent enhanced convection over the region.

Highlights:

 

Tomita et al. (2020)

Tomita, T., T. Shirai, and T. Yamaura, 2020: Effects of the Australian winter monsoon on the persistence of La Niña events. J. Meteor. Soc. Japan, 98, 189-211.
https://doi.org/10.2151/jmsj.2020-011Graphical Abstract

Plain Language Summary: La Niña (LN) events generally persist longer than El Niño (EN) events. This study revealed that the anomalous Australian winter monsoon (AWM) maintains LN events long through strengthening the convective activity in and around the Indonesian maritime continent (IMC) from March to August (Figure 1). First, LN forces the surface temperature in the northern Australian continent (NAC) low by modifying surface soil moisture and downward shortwave radiation flux there. Formed large surface temperature difference between the IMC and the NAC drives the stronger-thanusual AWM, which maintains LN events long. LN seems to have a self-sustained mechanism with a positive feedback with the AWM, which may be called the LN-AWM feedback. EN does not have such a feedback mechanism so that EN events end in the period of March–August.

Highlights:

 

Li et al. (2020)

Li, Z., Y. Luo, Y. Du, and J. C. L. Chan, 2020: Statistical characteristics of pre-summer rainfall over South China and associated synoptic conditions. J. Meteor. Soc. Japan, 98, 213-233.
https://doi.org/10.2151/jmsj.2020-012Graphical Abstract

Plain Language Summary: After the South China Sea (SCS) monsoon onset, an increase in domain-averaged rainfall accumulation and a generally enhanced convective intensity over South China (SC) during Apr-Jun were previously noticed. This study comparatively examines the characteristics of rainfall over the west-inland, east-inland, and coastal regions of SC during pre- and post-monsoon onset periods, and discuss the associated synoptic conditions and physical mechanisms.

Highlights:

 

Yokoyama et al. (2020)

Yokoyama, C., H. Tsuji, and Y. N. Takayabu, 2020: The effects of an upper-tropospheric trough on the heavy rainfall event in July 2018 over Japan. J. Meteor. Soc. Japan, 98, 235-255.
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-013Graphical Abstract

Plain Language Summary: Heavy rainfall occurred over a broad portion of western Japan on July 5–8, 2018. We found that the heavy rainfall was brought by a well-organized rainfall system, which was maintained under relatively stable and very humid conditions compared with the climatology. An upper-tropospheric trough, which lingered around the Korean Peninsula, played an important role in producing the humid stratification. By examining dynamical ascent associated with the trough and diabatic ascent separately, we found that dynamical ascent helped to moisten a relatively deep layer of the mid- to lower troposphere in conjunction with southerly horizontal moisture flux.

Highlights:

 

JMSJ, 2020, Vol. 98, No. 2 (April)

Invited Review Articles

Sui et al. (2020)

Sui, C.-H., M. Satoh, and K. Suzuki, 2020: Precipitation efficiency and its role in cloud-radiative feedbacks to climate variability. J. Meteor. Soc. Japan, 98, 261-282.
https://doi.org/10.2151/jmsj.2020-024Graphical Abstract

Plain Language Summary: This is a review for studies of cloud and climate from the perspective of Precipitation Efficiency (PE) that is a measure of the portion of total condensation rate in a convective system that is converted into precipitation flux at the surface. PEs have been defined and estimated from microscopic and macroscopic perspectives. We review these studies for various types and systems of convection using observational and modeling approaches. We also review studies about key cloud physical processes in shallow and deep convection and cloud-radiation changes with climate warming in view of PE.

Highlights:

 

Articles

Chen et al. (2020)

Chen, W., Z. Guan, H. Yang, and Q. Xu, 2020: East Asian-Australian monsoon variations and their impacts on regional climate during boreal summer. J. Meteor. Soc. Japan, 98, 283-297.
https://doi.org/10.2151/jmsj.2020-014Graphical Abstract

Plain Language Summary: The East Asian summer monsoon (EASM) and the Australian winter monsoon (AWM) are two important components of the Asian-Australian monsoon system during boreal summer. Our results demonstrate that AWM and EASM are closely related to each other even after ENSO and IOD signals are filtered out. When the Australian winter monsoon is anomalously strong, the cold Australian High and the WPSH both intensify and the East Asian summer monsoon becomes stronger to the south of 30oN. The simultaneous variations of these two monsoons would have remarkable impacts on climate in the Asian-Australian region.

Highlights:

 

Jayalakshmi et al. (2020)

Jayalakshmi, J., B. K. Seela, P.-L. Lin, P. K. Wang, C.-H. Tseng, K. K. Reddy, H. Hashiguchi, L. Feng, S. K. Das, and C. K. Unnikrishnan, 2020: Raindrop size distribution characteristics of Indian and Pacific Ocean tropical cyclones observed at India and Taiwan sites. J. Meteor. Soc. Japan, 98, 299-317.
https://doi.org/10.2151/jmsj.2020-015Graphical Abstract

Plain Language Summary: For the first time, we investigated the raindrop size distribution (RSD) characteristics of the Indian Ocean and Pacific Ocean tropical cyclones (TCs) using ground-based Parsivel disdrometer measurements in south India and south Taiwan observational sites, respectively. Disdrometers observations show that the mid-size and large drops were more in number in the Pacific Ocean TCs than the Indian Ocean TCs, and these two oceanic TCs showed significant differences in RSD empirical relations (Dm-R, log10Nw-R, μ-Λ Dmm , log10Nw-Dm , and Z-R ). Relatively a higher convective activity and water vapor in the Pacific Ocean TCs than the Indian Ocean TCs resulted in distinct RSD features between the two oceanic TCs through different microphysical processes.

Highlights:

 

Aono et al. (2020)

Aono, K., T. Iwasaki, and T. Sasai, 2020: Effects of wind-evaporation feedback in outer regions on tropical cyclone development. J. Meteor. Soc. Japan, 98, 319-328.
https://doi.org/10.2151/jmsj.2020-017Graphical Abstract

Plain Language Summary: Tropical cyclone (TC) intensification is widely understood according to the wind-evaporation feedback. In the conventional framework, many authors have discussed the increase of sea surface evaporation as the surface wind increases near the eyewall. On the other hand, we discuss the surface evaporation decrease as the wind speed decreases in the outer region. Idealized numerical experiments showed that the increased surface evaporation in the outer region significantly weakens the TC and reduces its size. The radial contrast is suggested to have more importance for the TC organization than the water vapor mixing ratio itself. This is a very different interpretation of the wind-evaporation feedback on TC development from the conventional idea.

Highlights:

 

Tomita and Yamaura (2020)

Tomita, T., and T. Yamaura, 2020: Interannual variability of Baiu frontal activity in May and its connectivity with June. J. Meteor. Soc. Japan, 98, 329-351.
https://doi.org/10.2151/jmsj.2020-018Graphical Abstract

Plain Language Summary: The Baiu front (BF) is climatologically formed in May in the western North Pacific. This study investigated the interannual variability of Baiu frontal activity (BFA) in May (BFA-M) and its connectivity with June. First, an anomalous circulation centered around Taiwan, which is interpreted as a moist Rossby wave from the equatorial Kelvin–Rossby wave packet, controls the interannual variability with modifying southerlies from the tropics (Fig. 1). Second, a biennial tendency characterizes the interannual variability of BFA-M with a tripole SSTA pattern and anomalous Walker circulations in the tropical Pacific (Fig. 2), both of which are suitable for confining the disintegration of the equatorial Kelvin–Rossby wave packet in the western Pacific and guiding the northwestward propagation of the moist Rossby wave. With the phase reversal of this moist Rossby wave, the biennial tendency remains in the western part of the BF from May to mid-June.

Highlights:

 

Naoe et al. (2020)

Naoe, H., T. Matsumoto, K. Ueno, T. Maki, M. Deushi, and A. Takeuchi, 2020: Bias correction of multi-sensor total column ozone satellite data for 1978-2017. J. Meteor. Soc. Japan, 98, 353-377.
https://doi.org/10.2151/jmsj.2020-019Graphical Abstract

Plain Language Summary: In this study, we have constructed a merged dataset using 20 available satellite Level 2 total column ozone (TCO) datasets over 40 years from 1978 to 2017. The individual datasets and the merged dataset are corrected against selected Dobson and Brewer spectrophotometer TCO measurements by two methods: simple linear regression (SLR) as a function of time, and multiple linear regression (MLR) as a function of time, solar zenith angle, and effective ozone temperature.

Highlights:

 

Yang et al. (2020)

Yang, H., L. Wu, and T. Xie, 2020: Comparisons of four methods for tropical cyclone center detection in a high-resolution simulation. J. Meteor. Soc. Japan, 98, 379-393.
https://doi.org/10.2151/jmsj.2020-020Graphical Abstract

Plain Language Summary: Detecting tropical cyclone (TC) centers is a challenge in understanding TC inner-core dynamics. Four frequently used center detecting methods are evaluated in a highresolution simulation of Hurricane Wilma (2005). The vertical tilt the minimum pressure variance center (MVC) and the potential vorticity centroid center (PVC) are generally smooth, while the relative tracks of the maximum tangential wind center (MTC) and the pressure centroid center (PCC) contain abrupt changes. The MVC also leads to the strongest symmetric structure in the tangential wind, PV, and radial PV gradient in the eyewall region. This study suggests that the MVC should be selected in the study of inner-core processes.

Highlights:

 

Stevens et al. (2020)

Stevens, B., C. Acquistapace, A. Hansen, R. Heinze, C. Klinger, D. Klocke, H. Rybka, W. Schubotz, J. Windmiller, P. Adamidis, I. Arka, V. Barlakas, J. Biercamp, M. Brueck, S. Brune, S. A. Buehler, U. Burkhardt, G. Cioni, M. Costa-Suròs, S. Crewell, T. Crüger, H. Deneke, P. Friederichs, C. C. Henken, C. Hohenegger, M. Jacob, F. Jakub, N. Kalthoff, M. Köhler, T. W. van Laar, P. Li, U. Löhnert, A. Macke, N. Madenach, B. Mayer, C. Nam, A. K. Naumann, K. Peters, S. Poll, J. Quaas, N. Röber, N. Rochetin, L. Scheck, V. Schemann, S. Schnitt, A. Seifert, F. Senf, M. Shapkalijevski, C. Simmer, S. Singh, O. Sourdeval, D. Spickermann, J. Strandgren, O. Tessiot, N. Vercauteren, J. Vial, A. Voigt, and G. Zängl, 2020: The added value of large-eddy and storm-resolving models for simulating clouds and precipitation. J. Meteor. Soc. Japan, 98, 395-435.
Special Edition on DYAMOND: The DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains
https://doi.org/10.2151/jmsj.2020-021Graphical Abstract

Plain Language Summary: This study investigates, if atmospheric models with horizontal resolutions of 100 m to 2 km are able to better simulate key features, like clouds and precipitation, of the climate system than currently used models employing much coarser resolution and parameterized convection. Precipitation characteristics are much more realistic in the simulations with explicitly convection, already at kilometer resolutions. Increasing resolution to hectometer scales improves the simulation of precipitation only modestly, but substantially improves the simulation of clouds. The results suggest that new climate models, which explicitly resolve convection and the interaction with its environment, offer exciting opportunities to learn about the climate system.

Highlights:

Miyamoto et al. (2020)

Miyamoto, Y., S. Nishizawa, and H. Tomita, 2020: Impacts of number of cloud condensation nuclei on two-dimensional moist Rayleigh convection. J. Meteor. Soc. Japan, 98, 437-453.
https://doi.org/10.2151/jmsj.2020-023Graphical Abstract

Plain Language Summary: The impacts of number of cloud condensation nuclei (CCN) on moist Rayleigh convection were examined by using a simple 2D fluid model with a double moment microphysics model. The effect is most prominent in the initially formed convection, whereas the convection in the quasi-steady state does not significantly depend on the number of CCN. It is suggested that the former convection forms by local buoyancy, while the latter is largely influenced by boundaries.

Highlights:

 

Notes and Correspondence

Duc et al. (2020)

Duc, L., K. Saito, and D. Hotta, 2020: An explanation for the diagonally predominant property of the positive symmetric ensemble transform matrix. J. Meteor. Soc. Japan, 98, 455-462.
https://doi.org/10.2151/jmsj.2020-022Graphical Abstract

Plain Language Summary: The ensemble transform matrix T in the Ensemble Transform Kalman Filter is observed to have the diagonally predominant property, i.e. the diagonal terms are at least an order of magnitude larger than the off-diagonal terms, but why it possesses such a property has not been well understood. This property has shown to have a close connection to the fact that T is the closest matrix to a scalar multiple of the identity I. This fact reveals that T can be decomposed into a sum of a diagonal matrix D and a full matrix P whose Frobenius norms are proportional, respectively, to the mean and the standard deviation of the spectrum of T. In general cases, these norms are not much different but the fact that the number of non-zero elements of P is the square of ensemble size while that of D is the ensemble size causes the large difference in the orders of elements of P and D.

Highlights:

 

Geng et al. (2020)

Geng, B., M. Katsumata, and K. Taniguchi, 2020: Modulation of the diurnal cycle of precipitation near the southwestern coast of Sumatra by mixed Rossby-gravity waves. J. Meteor. Soc. Japan, 98, 463-480.
Special Edition on Years of the Maritime Continent (YMC)
https://doi.org/10.2151/jmsj.2020-026Graphical Abstract

Plain Language Summary: The impact of mixed Rossby-gravity waves (MRGWs) on the diurnal cycle of precipitation over the southwestern coastal area of Sumatra was investigated using data captured during a pilot field campaign of the Years of the Maritime Continent (YMC) project. The results suggest that local convergence induced by the land–sea contrast is mainly responsible for driving the diurnal cycle. Notwithstanding, MRGWs exert a significant impact on the amplitude of diurnal convection and precipitation by modulating the dynamic structure of the atmosphere.

Highlights:

 

JMSJ, 2020, Vol. 98, No. 3 (June)

Invited Review Articles

Kato (2020)

Kato, T., 2020: Quasi-stationary band-shaped precipitation systems, named “senjo-kousuitai”, causing localized heavy rainfall in Japan. J. Meteor. Soc. Japan, 98, 485-509.
https://doi.org/10.2151/jmsj.2020-029Graphical Abstract

Plain Language Summary: Localized heavy rainfall events with 3-houly accumulated precipitation amounts larger than 200 mm are often observed in Japan. Such events are majorly brought from quasi-stationary band-shaped precipitation systems, named as “senjo-kousuitai” in Japanese. Senjo-kousuitai is defined as a band-shaped heavy rainfall area with the length of 50-300 km and the width of 20-50 km, produced by successively formed and developed convective cells, lining up to organize multi-cell clusters, and passing or stagnating at almost the same place for a few hours.

Highlights:

 

Articles

Ma et al. (2020)

Ma, Y., V. Chandrasekar, and S. K. Biswas, 2020: A Bayesian correction approach for improving Dual-frequency Precipitation Radar rainfall rate estimates. J. Meteor. Soc. Japan, 98, 511-525.
Special Edition on Global Precipitation Measurement (GPM): 5th Anniversary
https://doi.org/10.2151/jmsj.2020-025Graphical Abstract

Plain Language Summary: The accurate estimation of precipitation is an important objective for the Dual-frequency Precipitation Radar (DPR), which is located on board the Global Precipitation Measurement (GPM) satellite core observatory. This study proposes a Bayesian correction (BC) approach to improve the DPR’s instantaneous rainfall rate product, where ground dual-polarization radar (GR) observations are used as references. Rainfall intensities such as light, moderate, and heavy rain and their variable influences on the model’s performance are considered.

Highlights:

 

Cui et al. (2020)

Cui, Y., Z. Ruan, M. Wei, F. Li, and R. Ge, 2020: Vertical structure and dynamical properties during snow events in middle latitudes of China from observations by the C-band vertically pointing radar. J. Meteor. Soc. Japan, 98, 527-550.
https://doi.org/10.2151/jmsj.2020-028Graphical Abstract

Plain Language Summary: The 4 shallow snow events (echo top <8 km) and 2 deep events (>10 km) were observed by the C-band vertically pointing radar with frequency modulation continuous wave technology (CVPR-FMCW). The snow clouds were divided into generating cell (GC) and stratiform (St) regions. The fall streaks (FSs) associated with GCs were embedded in the St regions. The vertical air velocity (Wa ) and reflectivity-weighted particle fall speed (Vz ) values were retrieved more precisely using bimodal Doppler spectra. The characteristics of GC regions, as well as the average reflectivity gradients and dynamical properties inside and outside GCs and FSs were quantified.

Highlights:

 

Dueben et al. (2020)

Dueben, P. D., N. Wedi, S. Saarinen, and C. Zeman, 2020: Global simulations of the atmosphere at 1.45 km grid-spacing with the Integrated Forecasting System. J. Meteor. Soc. Japan, 98, 551-572.
Special Edition on DYAMOND: The DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains,
https://doi.org/10.2151/jmsj.2020-016Graphical Abstract

Plain Language Summary: Numerical weather and climate models represent the dynamics of the atmosphere on a numerical grid. As the resolution of this grid is increasing, more and more details can be resolved within the atmosphere model. This comes at a price of increased computational cost paired with additional challenges to run on current and future supercomputers in an energyefficient manner and to manage the resulting data.

This paper presents global simulations of the atmosphere at an unprecedented level of resolution with 1.45 km grid-spacing that allow to represent important features of atmospheric dynamics, such as large thunderstorm systems, explicitly within simulations. The Integrated Forecasting System is used to perform such simulations that show the full complexity for the representation of the atmosphere that would be used in operational weather predictions.

The performance of simulations is diagnosed when running the Integrated Forecasting System on the fastest supercomputer in Europe, called Piz Daint and based at CSCS in Switzerland. Important choices for the model configuration at this unprecedented resolution are discussed and evaluated.

Highlights:

 

Radhakrishna et al. (2020)

Radhakrishna, B., K. Saikranthi, and T. N. Rao, 2020: Regional differences in raindrop size distribution within Indian subcontinent and adjoining seas as inferred from global precipitation measurement dual-frequency precipitation radar. J. Meteor. Soc. Japan, 98, 573-584.
Special Edition on Global Precipitation Measurement (GPM): 5th Anniversary
https://doi.org/10.2151/jmsj.2020-030Graphical Abstract

Plain Language Summary: Information on raindrop size is useful not only for understanding microphysics of precipitation but also for improving quantitative precipitation estimation, attenuation correction in satellite communications and soil erosion estimates. Understanding the dominant microphysical processes occurring in different climatic regions is also essential for improving the numerical weather prediction (NWP) models. However, measurements of raindrop size are sparse over Indian region, hampering our understanding on the variability of rain drop size in different climatic zones within the South Asian Monsoon. Global Precipitation Mission (GPM) retrieved mass weighted mean diameters (Dm) have been used, for the first time, to understand microphysical variations in different climatic zones of India. Rain rate stratified raindrop size exhibits large spatial variations with larger Dm in dry regions and smaller Dm over oceans. Significant evaporation in dry regions of India and low-level hydrometeor growth over oceans are found to be the dominant microphysical processes controlling the rain drop size. It is also noted that bigger cloud drops not always yield bigger rain drops, particularly over dry continental regions, because of the microphysical processes during the drop descent.

Highlights:

 

Geng and Katsumata (2020)

Geng, B., and M. Katsumata, 2020: An algorithm for detecting and removing the spurious differential phase observed by C-band polarimetric radar in the rain. J. Meteor. Soc. Japan, 98, 585-613.
Special Edition on Years of the Maritime Continent (YMC)
https://doi.org/10.2151/jmsj.2020-031Graphical Abstract

Plain Language Summary: An algorithm is developed to detect the spurious differential phase ФDP and specific differential phase KDP in the rain. The development and validation of the algorithm was conducted using the data observed by the C-band polarimetric radar aboard the research vessel Mirai during a pilot field campaign of the Years of the Maritime Continent (YMC) project. The algorithm developed in this study facilitates the quality control of ФDP and KDP.

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Shibata and Lehmann (2020)

Shibata, K., and R. Lehmann, 2020: Partitioning of ozone loss pathways in the ozone quasi-biennial oscillation simulated by a chemistry-climate model. J. Meteor. Soc. Japan, 98, 615-636.
https://doi.org/10.2151/jmsj.2020-032Graphical Abstract

Plain Language Summary: Ozone loss pathways due to NOx, HOx, ClOx, Ox, and BrOx catalytic cycles and their rates in the ozone quasi-biennial oscillation (QBO) simulated by a chemistry-climate model of the Meteorological Research Institute of Japan are evaluated by using an objective pathway analysis program (PAP). The QBO amplitude of the sum of all cycles amounts to about 4 and 14 % of the annual mean of the total ozone loss rate at 10 and 20 hPa, respectively. The contribution of catalytic cycles to the QBO of the ozone loss rate is found to be as follows: NOx cycles contribute the largest fraction (50-85 %) of the QBO amplitude of the total ozone loss rate; HOx cycles are the second-largest (20-30 %) below 30 hPa and the third-largest (about 10 %) above 20 hPa; Ox cycles rank third (5-20 %) below 30 hPa and second (about 20 %) above 20 hPa; ClOx cycles rank fourth (5-10 %); and BrOx cycles are almost negligible.

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Cao et al. (2020)

Cao, X., R. Wu, N. Wei, and Y. Dai, 2020: Location of the preferred region for tropical cyclogenesis in strong monsoon trough pattern over the western North Pacific. J. Meteor. Soc. Japan, 98, 637-654.
https://doi.org/10.2151/jmsj.2020-034Graphical Abstract

Plain Language Summary: The processes of tropical cyclone (TC) genesis in strong monsoon trough pattern over the western North Pacific (WNP) are examined using reanalysis data and numerical experiments. Composite analysis showed that more TCs are likely to form in the central WNP and that fewer TCs appear in the western and eastern WNP. Numerical experiments with the same weak artificial vortices inserted into eight different regions of the monsoon trough showed that weak tropical disturbances tend to develop more rapidly in the central WNP, whereas weak tropical disturbances tend to develop more slowly in the eastern and western WNP. The failure of TC genesis in the western WNP is due to the decrease of the moisture and heat. And large vertical wind shear and dry conditions hinder the intensification of tropical disturbances in the eastern WNP.

Highlights:

 

Notes and Correspondence

Naoi et al. (2020)

Naoi, M., Y. Kamae, H. Ueda, and W. Mei, 2020: Impacts of seasonal transitions of ENSO on atmospheric river activity over East Asia. J. Meteor. Soc. Japan, 98, 655-668.
https://doi.org/10.2151/jmsj.2020-027Graphical Abstract

Plain Language Summary: Atmospheric Rivers (ARs), narrow water vapor transport bands over the mid-latitude, often cause natural disaster when they make landfall. Occurrence frequency of ARs is perturbated over East Asia in association with seasonal transitions of the El Niño Southern Oscillation. A rapid transition from preceding-winter El Niño to summertime La Niña results in more AR occurrence through enhancement and northward expansion of the anticyclone over the western North Pacific.

Highlights:

 

JMSJ, 2020, Vol. 98, No. 4 (August)

Articles

Kawano and Kawamura (2020)

Kawano, T., and R. Kawamura, 2020: Genesis and maintenance processes of a quasi-stationary convective band that produced record-breaking precipitation in northern Kyushu, Japan on 5 July 2017. J. Meteor. Soc. Japan, 98, 673-690.
https://doi.org/10.2151/jmsj.2020-033Graphical Abstract

Plain Language Summary: A quasi-stationary convective band that persisted for approximately ten hours caused precipitation in the northern part of Kyushu Island, Japan on 5 July 2017. The extreme amount of rainfall produced by this convective band caused a number of landslides and flash floods and resulted in a severe disaster. The Weather and Research and Forecasting (WRF) model simulations revealed that a quasi-stationary convergence zone in the low level played a crucial role in generating and maintaining the convective band.

Highlights:

 

Takamura and Wada (2020)

Takamura, N., and A. Wada, 2020: Unusual characteristics of extratropical transition of typhoons in August 2016. J. Meteor. Soc. Japan, 98, 691-706.
https://doi.org/10.2151/jmsj.2020-035Graphical Abstract

Plain Language Summary: To identify the unusual characteristics such as frequent landfall and extratropical transition in August 2016, this study examines typhoons in August and September by conducting k-means cluster, cyclone phase space and composite analyses and case study. We also compare the results of the analyses for this period with those in August from 2001 to 2015 and those in September 2016. As a result, the synoptic environments around the typhoons explain the unusual track and the frequent extratropical transition in August 2016.

Highlights:

 

Wang et al. (2020)

Wang, C.-C., K.-Y. Lin, C. A. Davis, S.-Y. Huang, S. C.-S. Liu, K. Tsuboki, and B. J.-D. Jou, 2020: A modeling study on the impacts of Typhoon Morakot’s (2009) vortex structure on rainfall in Taiwan using piecewise potential vorticity inversion. J. Meteor. Soc. Japan, 98, 707-733.
https://doi.org/10.2151/jmsj.2020-036Graphical Abstract

Plain Language Summary: In this study, the impacts of Typhoon Morakot’s (2009) vortex structure on the extreme rainfall in Taiwan are investigated through modeling with an application of piecewise potential vorticity (PV) inversion. The control experiment (C0), starting at 0000 UTC 7 August or 15 h before landfall, reproduces the event realistically and is validated against the observations. By altering the PV perturbation inside 750 km from its center, we conduct sensitivity experiments in which the size and/or circulation strength of Morakot is reduced/weakened in the initial field in several different ways.

Highlights:

 

Feng et al. (2020)

Feng, T., X.-Q. Yang, L. Wu, R. Huang, and D. Yang, 2020: How do the monsoon trough and the tropical upper-tropospheric trough affect synoptic-scale waves: A comparative study. J. Meteor. Soc. Japan, 98, 735-754.
https://doi.org/10.2151/jmsj.2020-037Graphical Abstract

Plain Language Summary: As an important precursor for tropical cyclone formation, a conventional synoptic-scale disturbance is usually identified from lower-tropospheric winds over the western North Pacific. However, another type of disturbance with the maximum perturbation in the upper troposphere may be misidentified. Comparing two long-lasting synoptic-scale wave events in 2004 and 2006, the present study showed that the disturbances occurred in the upper troposphere in 2006 while in the lower troposphere in 2004. Such a difference is ascribed to the large-scale background modulated by both the monsoon trough and the tropical upper-tropospheric trough.

Highlights:

 

Yamaji et al. (2020)

Yamaji, M., H. G. Takahashi, T. Kubota, R. Oki, A. Hamada, and Y. N. Takayabu, 2020: 4-year climatology of global drop size distribution and its seasonal variability observed by spaceborne Dual-frequency Precipitation Radar. J. Meteor. Soc. Japan, 98, 755-773.
Special Edition on Global Precipitation Measurement (GPM): 5th Anniversary
https://doi.org/10.2151/jmsj.2020-038Graphical Abstract

Plain Language Summary: Global-scale spatial distributions of rainfall drop size (mean diameter; Dm) are newly obtained by using 4-year accumulated products from the spaceborne precipitation radar. Relationship between Dm and precipitation rate is not a simple one-to-one relationship. Focusing on the seasonal variation in Dm over the northwest Pacific Ocean, the results indicate that the variation in Dm is related to the seasonal change of the dominant precipitation systems.

Highlights:

 

Yamaguchi and Maeda (2020)

Yamaguchi, M., and S. Maeda, 2020: Increase in the number of tropical cyclones approaching Tokyo since 1980. J. Meteor. Soc. Japan, 98, 775-786.
https://doi.org/10.2151/jmsj.2020-039Graphical Abstract

Plain Language Summary: This study investigated whether tropical cyclones (TCs) approaching Tokyo have changed in terms of number and environmental conditions using observational and reanalysis data during the geostationary satellite era (1980-2019). The number of TCs approaching the southern coast of Japan, including Tokyo, has increased over the last 40 years. The environmental conditions for TC development have become more favorable, with warmer sea surface temperature, less vertical wind shear, and more moisture in the atmosphere. In addition, the translation speed of TCs has decreased, which indicates a longer influence time.

Highlights:

 

Jin et al. (2020)

Jin, K., F. Wang, Q. Zong, P. Qin, and C. Liu, 2020: An updated estimate of the urban heat island effect on observed local warming trends in mainland China's 45 urban stations. J. Meteor. Soc. Japan, 98, 787-799.
https://doi.org/10.2151/jmsj.2020-040Graphical Abstract

Plain Language Summary: Surface air temperature (SAT) in many Chinese cities has experienced dramatic increase due to rapid urbanization and global warming. This study built several linear regression equations by linking SAT trend with a modified urban impact indicator. Severe UHI effects on annual mean and minimum SATs of the 45 urban stations in mainland China during 1954–2013 are found.

Highlights:

 

Nishii et al. (2020)

Nishii, K., B. Taguchi, and H. Nakamura, 2020: An atmospheric general circulation model assessment of oceanic impacts on extreme climate events over Japan in July 2018. J. Meteor. Soc. Japan, 98, 801-820.
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-041Graphical Abstract

Plain Language Summary: Oceanic impacts on anomalous atmospheric circulation that caused the heavy rain event and heat wave observed in July 2018 over Japan are investigated. While a pair of anticyclonic and cyclonic anomalies during the heavy rain was unlikely forced by the sea surface temperature anomaly (SSTa), a warm anticyclonic anomaly over Japan during the heat wave was partly forced by the SSTa in the midlatitude North Pacific Ocean as well as in the Tropics.

Highlights:

 

Kawabata and Yamaguchi (2020)

Kawabata, Y., and M. Yamaguchi, 2020: Probability ellipse for tropical cyclone track forecasts with multiple ensembles. J. Meteor. Soc. Japan, 98, 821-833.
https://doi.org/10.2151/jmsj.2020-042Graphical Abstract

Plain Language Summary: The effectiveness of the probability ellipse for tropical cyclone (TC) track forecasts is investigated with multiple ensembles from the Japan Meteorological Agency (JMA), the European Centre for Medium-Range Weather Forecasts (ECMWF), the U.S. National Centers for Environmental Prediction (NCEP), and the Met Office in the United Kingdom (UKMO), for all TCs from 2016 to 2018. The multiple ensembles composed of these four global ensembles are capable of predicting the situation-dependent uncertainties of TC track forecasts appropriately in both the along-track and cross-track directions.

Highlights:

 

Hirockawa et al. (2020)

Hirockawa, Y., T. Kato, H. Tsuguti, and N. Seino, 2020: Identification and classification of heavy rainfall areas and their characteristic features in Japan. J. Meteor. Soc. Japan, 98, 835-857.
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-043Graphical Abstract

Plain Language Summary: We propose a new procedure for the objective identification and classification of heavy rainfall areas (HRAs) to advance the understanding of mesoscale convective systems (MCSs) in Japan. The distributions of accumulated precipitation amounts are evaluated from the radar/raingauge-analyzed precipitation amounts and characteristic features of HRAs are examined. The HRAs extracted during the warm season (April–November) in 2009–2018 are classified into four types (e.g., linear-stationary, linear, stationary, and others) from their morphological features and temporal variations.

Highlights:

 

Tsuji et al. (2020)

Tsuji, H., C. Yokoyama, and Y. N. Takayabu, 2020: Contrasting features of the July 2018 heavy rainfall event and the 2017 Northern Kyushu rainfall event in Japan. J. Meteor. Soc. Japan, 98, 859-876.
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-045Graphical Abstract

Plain Language Summary: Precipitation characteristics and environment are compared between two rainfall events in Japan: the July 2018 heavy rainfall event (2018 case) and the 2017 Northern Kyushu rainfall event (2017 case). The 2018 case was characterized by long-lasting heavy precipitation over a wide area, well-organized moderately tall precipitation systems, stable and very moist environment compared with the climatology, and large quasi-geostrophic forcing associated with an upper tropospheric trough. In contrast, the 2017 case was characterized by short-term extreme precipitation over a narrow area, exceptionally tall precipitation systems, unstable and moist environment compared with the climatology, and weak quasi-geostrophic forcing. These contrasts are similar to those found between composites of extremely heavy rainfall events and extremely tall convection events in the previous statistical study by Hamada and Takayabu (2018, doi:10.1175/JCLI-D-17-0632.1).

Highlights:

 

JMSJ, 2020, Vol. 98, No. 5 (October)

Invited Review Articles

Mesinger and Veljovic (2020)

Mesinger, F., and K. Veljovic, 2020: Topography in weather and climate models: Lessons from cut-cell Eta vs. European Centre for Medium-Range Weather Forecasts experiments. J. Meteor. Soc. Japan, 98, 881-900.
https://doi.org/10.2151/jmsj.2020-050Graphical Abstract

Plain Language Summary: Advantages and issues of methods of incorporating topography in weather and climate models are summarized. Terrain-following coordinates used in almost all major models do have issues with steepness of model terrain exceeding a given limit. Immersed boundary methods accept both the grid and the model topography as they are and address prescription of boundary conditions and adjustments of physics parameterizations. Cut-cell schemes prescribe bottoms of their lowest cells to define topography and are able to use finite-volume discretizations. New views are offered via analyses of experiments driving cut-cell Eta by European Centre for Medium-Range Weather Forecasts (EC) 32-day ensemble members.

Highlights:

 

Articles

Song et al. (2020)

Song, H.-J., S. Kim, S. Roh, and H. Lee, 2020: Difference between Cloud Top Height and Storm Height for heavy rainfall using TRMM measurements. J. Meteor. Soc. Japan, 98, 901-914.
Special Edition on Global Precipitation Measurement (GPM): 5th Anniversary
https://doi.org/10.2151/jmsj.2020-044Graphical Abstract

Plain Language Summary: This study investigates the cloud top height (CTH) and storm height (SH) characteristics of heavy rain clouds from Tropical Rainfall Measuring Mission (TRMM) measurements. Continental heavy rainfall (e.g., Central Africa and the United States) is characterized by high SH under the strong instability and relatively dry conditions. In contrast, heavy rain events in Korea and Japan are mostly related with the lowest CTH, SH, and ice water content under the thermodynamically near-neutral but humid environments, representing unique monsoon feature in the world. Similar SH and humid features are also found in the northwestern Pacific; however, this region exhibits high CTH and CTH−SH values in the highest convective instability condition.

Highlights:

 

Nakamura et al. (2020)

Nakamura, Y., T. Miyakawa, and M. Satoh, 2020: The role of Typhoon Kilo (T1517) in the Kanto-Tohoku heavy rainfall event in Japan in September 2015. J. Meteor. Soc. Japan, 98, 915-926.
https://doi.org/10.2151/jmsj.2020-046Graphical Abstract

Plain Language Summary: The Kanto-Tohoku heavy rainfall event in September 2015 is characterized by two typhoons, Etau (T1518) and Kilo (T1517). This study investigates the role of typhoon Kilo on the heavy rainfall. We carried out 3 numerical experiments: the control experiment (CTL), the early initialized experiment (EARLY) and the moisture-removed experiment (RH0). We found that southeasterly wind effectively supplied moisture to the Kanto region. The high-pressure ridge is an important factor for northwestward moisture supply, and stronger simulated Kilo disturbs the ridge, resulting in decreased precipitation.

Highlights:

 

Ose et al. (2020)

Ose, T., Y. Takaya, S. Maeda, and T. Nakaegawa, 2020: Resolution of summertime East Asian pressure pattern and southerly monsoon wind in CMIP5 multi-model future projections. J. Meteor. Soc. Japan, 98, 927-944.
https://doi.org/10.2151/jmsj.2020-047Graphical Abstract

Plain Language Summary: The southerly surface wind index over the summertime East Asia (SWI) is strengthened in the future in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). However, the differences among the models are much larger than the ensemble average (Fig. 1a). The empirical orthogonal function (EOF) analysis is applied to the future changes in the East Asian surface pressure pattern responsible for the SWI. The ensemble average and five EOF modes for the pressure patterns and the associated precipitation changes are identified, and their possible sources are examined. The first mode is high surface pressure anomalies over low Asia Pacific sea surface temperature. The second mode is related to warm temperature anomalies over the Northern Hemisphere continents. The third mode is characterized with suppressed vertical motions over the northern Indian and Pacific oceans. The fourth mode is the Okhotsk High. The fifth mode represents the east–west contrast of the southern East Asian surface pressure anomalies.

Highlights:

 

Chen et al. (2020)

Chen, X., X. Huang, Y. Cai, H. Shen, and J. Lu, 2020: Intra-day forecast of ground horizontal irradiance using long short-term memory network (LSTM). J. Meteor. Soc. Japan, 98, 945-957.
https://doi.org/10.2151/jmsj.2020-048Graphical Abstract

Plain Language Summary: Accurate forecast of ground horizontal irradiance (GHI) is one of the key issues for power grid managements with large penetration of solar energy. A challenge for solar forecasting is to forecast the solar irradiance with a lead time of 1-8 hours, termed as intra-day forecast. This study investigated a machine-learning algorithm, Long Short-Term Memory (LSTM) model, to predict the GHI in 1-8 hours. The results show that, for a 1-4 hour lead time, the LSTM model can predict GHIs better than random-forest forecast (another machine-learning algorithm), and numerical weather forecast by the Weather Research and Forecasting (WRF) model. The LSTM model performs better in fall and winter than in spring and summer, and better under clear-sky conditions than under cloudy conditions. Using adjacent information from the reanalysis as extra inputs can further improve the forecast performance.

Highlights:

 

Chen et al. (2020)

Thundathil, R., T. Schwitalla, A. Behrendt, S. K. Muppa, S. Adam, and V. Wulfmeyer, 2020: Assimilation of lidar water vapour mixing ratio and temperature profiles into a convection-permitting model. J. Meteor. Soc. Japan, 98, 959-986.
https://doi.org/10.2151/jmsj.2020-049Graphical Abstract

Plain Language Summary: Ground-based lidar instruments measure profiles of atmospheric moisture and temperature with very high quality and resolution. We show that these data improve the forecasts of the Weather Research and Forecasting (WRF) model. Our model has a grid resolution of 2.5 km, which permits to resolve deep convection. In order to use the new data, we developed a forward operator for the direct assimilation of water vapour mixing ratio (WVMR), a primary variable in the prognostic equations of the WRF model.

Highlights:

 

Miyamoto et al. (2020)

Miyamoto, Y., Y. Sato, S. Nishizawa, H. Yashiro, T. Seiki, and A. T. Noda, 2020: An energy balance model for low-level clouds based on a simulation resolving mesoscale motions. J. Meteor. Soc. Japan, 98, 987-1004.
https://doi.org/10.2151/jmsj.2020-051Graphical Abstract

Plain Language Summary: A new energy balance model is proposed to determine the cloud fraction of low-level clouds by assuming that the horizontal cloud field consists of several individual cloud cells having a similar structure. Using a high-resolution simulation dataset with a wide numerical domain, an energy budget analysis revealed that the energy injected into the domain by surface flux is approximately balanced with the energy loss due to radiation and advection due to large-scale motion. A simple model for the cloud fraction is developed from the energy conservation equation. The cloud fraction diagnosed using the model developed in this study was able to quantitatively capture the simulated cloud fraction.

Highlights:

 

Cao et al. (2020)

Cao, X., R. Wu, Y. Dai, and J. Xu, 2020: A comparison of the effects of an upper-level anticyclone and a lower-level cyclone on tropical cyclogenesis in idealized simulations. J. Meteor. Soc. Japan, 98, 1005-1027.
https://doi.org/10.2151/jmsj.2020-052Graphical Abstract

Plain Language Summary: The effects of an upper-level anticyclonic circulation and a lower-level cyclonic circulation on tropical cyclone (TC) genesis are examined by idealized simulations. The simulation results show that the upper-level anticyclonic circulation makes a negative contribution to TC genesis, whereas the lower-level cyclonic circulation makes a positive contribution. The upper-level anticyclonic circulation results in slower TC genesis due to a large vertical zonal wind shear that shifts the upper-level vortex eastward from its initial position, which is unfavorable for the vertical alignment and warm core maintenance of the vortex. The initial upper-level anticyclonic circulation is not necessary for TC genesis, and the strong upper-level anticyclonic circulation generally observed with a strong TC should be regarded as a result of deep convection. In contrast, strong lower-level winds due to the superposition of the large-scale lower-level cyclonic circulation and vortex induce large surface heat fluxes and vorticity, leading to strengthened convection and diabatic heating and a quick build-up of positive vorticity, resulting in rapid TC genesis.

Highlights:

 

Hermoso et al. (2020)

Hermoso, A., V. Homar, S. J. Greybush, and D. J. Stensrud, 2020: Tailored ensemble prediction systems: Application of seamless scale bred vectors. J. Meteor. Soc. Japan, 98, 1029-1050.
https://doi.org/10.2151/jmsj.2020-053Graphical Abstract

Plain Language Summary: Uncertainties in numerical weather forecasting derived from an imperfect knowledge of the initial conditions are coped with ensemble forecasting. Breeding technique provides a simple and low computationally expensive ensemble generation strategy. The technique aims at capturing growing errors, obtained from the difference between control and perturbed runs at regular time intervals. Modifications to the traditional arithmetic rescaling are investigated, including logarithmic and orthogonal rescaling. In addition, the Bred Vectors Tailored Ensemble Perturbations method is designed to control the spatial scale of the perturbations. This technique outperforms traditional breeding techniques in terms of diversity (ensemble dimension) and skill.

Highlights:

 

Wang et al. (2020)

Wang, K., G. Chen, X. Bi, D. Shi, and K. Chen, 2020: Comparison of convective and stratiform precipitation properties in developing and nondeveloping tropical disturbances observed by the Global Precipitation Measurement over the western North Pacific. J. Meteor. Soc. Japan, 98, 1051-1067.
Special Edition on Global Precipitation Measurement (GPM): 5th Anniversary
https://doi.org/10.2151/jmsj.2020-056Graphical Abstract

Plain Language Summary: A disturbance that develops into a tropical cyclone (TC) over the western North Pacific (WNP) needs to satisfy two essential preconditions in terms of precipitation characteristics from Global Precipitation Measurement (GPM). First, a large fraction of stratiform precipitation covers the region that is within 400 km from the disturbance center. Second, strong convective precipitation occurs within the inner-core (within 200 km of the disturbance center) region. In the TC formation process, the disturbances experience a remarkably more oscillatory process in the inner-core region than in the outer-core region.

Highlights:

 

Notes and Correspondence

Ohno et al. (2020)

Ohno, T., A. T. Noda, and M. Satoh, 2020: Impacts of sub-grid ice cloud physics in a turbulence scheme on high clouds and their response to global warming. J. Meteor. Soc. Japan, 98, 1069-1081.
https://doi.org/10.2151/jmsj.2020-054Graphical Abstract

Plain Language Summary: It has been recognized that the turbulent effects influence the cloud dynamics and the representation of moist process is critical for the performance of the sub-grid-scale (SGS) turbulence schemes. This note reports on the large impact of the representation of ice phase clouds in the turbulent closure scheme on the high clouds and their response to global warming, which underlines the critical nature of the treatment of SGS ice clouds which reflects a realistic ice condensation physics not only for a better representation of high clouds in the current climate but for an improved projection of changes of high clouds due to global warming.

Highlights:

 

Krzyścin (2020)

Krzyścin, J., 2020: Is the Antarctic ozone hole recovering faster than changing the stratospheric halogen changes? J. Meteor. Soc. Japan, 98, 1083-1091.
https://doi.org/10.2151/jmsj.2020-055Graphical Abstract

Plain Language Summary: Large ozone deficit over Antarctica has been observed regularly in austral spring since the early 1980s. The size and depth of the ozone hole vary considerably from year-to-year. The hole appears to have lost strength in the past 20 years because of declining levels of the man-made ozone-depleting chemicals in the stratosphere. This paper introduces indices for tracing the hole recovery: percentage of the healed amount of the ozone hole metric (total column ozone, hole area, and mass of ozone loss within the hole) by 2019, and the metric recovery year. In late winter and early spring, the metrics show stronger hole recovery than expected based on recent changes in ozone-depleting substances in the stratosphere.

Highlights:

 

JMSJ, 2020, Vol. 98, No. 6 (December)

Invited Review Articles

Kawai and Shige (2020)

Kawai, H., and S. Shige, 2020: Marine low clouds and their parameterization in climate models. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-059Graphical Abstract

Plain Language Summary: The first part of this review paper aims to provide readers with a broad range of meteorological backgrounds with basic information on marine low clouds and their importance in climate simulations. In the latter half of the paper, the concept of cloud parameterizations that determine cloud fraction and cloud water content in global climate models is introduced.

Highlights:

 

Articles

Liao et al. (2020)

Liao, L., R. Meneghini, A. Tokay, and H. Kim, 2020: Assessment of Ku- and Ka-band Dual-frequency radar for snow retrieval. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-057Graphical Abstract

Plain Language Summary: Dual-frequency radars have been increasingly used for detecting and retrieving frozen precipitation. However, retrieval of snow parameters has two principal errors, namely, the differences between the assumed particle size distribution (PSD) model from the actual PSD and inadequacies in characterizing the single-scattering properties of snowflakes. This study is aimed at evaluating uncertainties of snow precipitation estimation associated with the PSD models and scattering models and understanding their respective contributions to overall uncertainties for gaining insight into how to improve the retrieval methods for the GPM DPR operating at the Ku- and Ka-bands.

Highlights:

 

Takemura and Mukougawa (2020)

Takemura, K., and H. Mukougawa, 2020: Maintenance mechanism of Rossby wave breaking and Pacific-Japan pattern in boreal summer. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-061Graphical Abstract

Plain Language Summary: A maintenance mechanism for Rossby wave breaking (RWB) east of Japan and Pacific-Japan (PJ) pattern in boreal summer, which are triggered due to Rossby wave propagation along the Asian jet, is diagnosed by lag composite, correlation, and forward trajectory analyses, using a reanalysis dataset. A comparison between the composites of 7 persistent and 7 non-persistent cases, which are classified from the past 44 RWB cases, indicates that the persistent case shows the stronger and longer-lived Rossby wave propagation along the Asian jet. The subsequent stronger RWB in the persistent case causes the consequential formation of the more enhanced PJ pattern, through the stronger high potential vorticity intrusion toward the subtropical western North Pacific (WNP). The other main findings are summarized as follows.

Highlights:

 

Harada et al. (2020)

Harada, Y., H. Endo, and K. Takemura, 2020: Characteristics of large-scale atmospheric fields during heavy rainfall events in western Japan: Comparison with an extreme event in early July 2018. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-062Graphical Abstract

Plain Language Summary: To explore large-scale atmospheric factors causing heavy rainfall events that occurred widely in western Japan, a composite analysis of atmospheric fields during the past heavy rainfall events in the region is performed. We also investigate atmospheric fields during an extreme heavy rainfall event that occurred in early July 2018 (HR18).

Highlights:

 

Iwakiri and Watanabe (2020)

Iwakiri, T., and M. Watanabe, 2020: Multiyear La Niña impact on summer temperature over Japan. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-064Graphical Abstract

Plain Language Summary: La Niña event often occurs in two consecutive years and is known as multiyear La Niña. Two distinct mechanisms bring different type hot summer in Japan during multiyear event. First year tend to be warm over the southwestern Japan in late summer, while second year experiences hot conditions over the northeastern Japan in midsummer. Both mechanisms are excited by suppressing convective activity over the central and eastern equatorial Pacific.

Highlights:

 

Tamura and Sato (2020)

Tamura, K., and T. Sato, 2020: Responses of polar mesocyclone genesis to topographic forcing along the eastern coast of Eurasian continent. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-065Graphical Abstract

Plain Language Summary: Polar mesocyclones (PMCs) genesis over the offshore west of Hokkaido is affected by the mountains at the eastern end of the Eurasian continent. In the experiment without the mountains, strong westerly from the continent blow over the southern part of offshore west of Hokkaido. Consequently, PMCs tend to make landfall earlier and before reaching maturity. In contrast, the low-level wind over the Strait of Tartary prior to PMC genesis is unaffected by the removal of the mountains. Thus, topographic effects are not important for PMC genesis in this region.

Highlights:

 

Oizumi et al. (2020)

Oizumi, T., K. Saito, L. Duc, and J. Ito, 2020: Ultra-high resolution numerical weather prediction with a large domain using the K computer. Part 2: The case of the Hiroshima heavy rainfall event on August 2014 and dependency of simulated convective cells on model resolutions. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-060Graphical Abstract

Plain Language Summary: This study conducts the Ultra-high-resolution (5-km to 250-m grid spacing) numerical weather prediction (NWP) experiments and investigates the impacts of model resolutions on the Hiroshima heavy rain event in August 2014. The results show that the finer resolution model well reproduces the torrential rain event and the simulated convective cores (CCs) tend to converge when the resolution goes beyond 500 m.

Highlights:

 

Nayak and Takemi (2020)

Nayak, S., and T. Takemi, 2020: Clausius-Clapeyron scaling of extremely heavy precipitations: Case studies of the July 2017 and July 2018 heavy rainfall events over Japan. J. Meteor. Soc. Japan, 98,
Special Edition on Extreme Rainfall Events in 2017 and 2018
https://doi.org/10.2151/jmsj.2020-058Graphical Abstract

Plain Language Summary: The usefulness of Clausius-Clapeyron (CC) scaling in explaining extremely heavy precipitations is explored in the present-day climate and in pseudo-global-warming (PGW) conditions. This is analyzed by conducting regional-scale numerical simulations for two recent extreme rainfall events that occurred in Japan: the case in northern Kyushu during 5-6 July 2017 and the case in Shikoku Island during 5-8 July 2018.This study conducts the Ultra-high-resolution (5-km to 250-m grid spacing) numerical weather prediction (NWP) experiments and investigates the impacts of model resolutions on the Hiroshima heavy rain event in August 2014. The results show that the finer resolution model well reproduces the torrential rain event and the simulated convective cores (CCs) tend to converge when the resolution goes beyond 500 m.

Highlights:

 

Zhou et al. (2020)

Zhou, X., L. Wu, Q. Liu, and Y. Zheng, 2020: Influence of low-level, high-entropy air in the eye on tropical cyclone intensity: A trajectory analysis. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-063Graphical Abstract

Plain Language Summary: Whether the high-entropy eye air can substantially increase tropical cyclone (TC) intensity through mixing with eyewall air and enhancing eyewall convection is still a scientific issue. This study quantitatively evaluates the relative importance of the entrainment of this air by trajectory analysis. The result suggests that the low-level, high-entropy air from the eye has little direct influence on TC intensity by providing relatively small mass and thermodynamic contributions.

Highlights:

 

Kawazoe et al. (2020)

Kawazoe, S., M. Fujita, S. Sugimoto, Y. Okada, and S. Watanabe, 2020: Projected changes of extremely cool summer days over northeastern Japan simulated by 20 km-mesh large ensemble experiment. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-067Graphical Abstract

Plain Language Summary: Future changes to extreme cool days (ECDs) during the summer season (June – August) in northeast Japan is examined using the database for Policy Decision making for Future climate change (d4PDF) large ensemble experiments. We applied self-organizing maps (SOMs) to mean sea level pressure (MSLP) patterns, which were then classified into four clusters with high ECD occurrences. The response of the four clusters to a 2K and 4K warming scenarios was investigated, focusing on the role of low-level thermal advection.

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Yamaguchi and Maeda (2020)

Yamaguchi, M., and S. Maeda, 2020: Slowdown of Typhoon Translation Speeds in Mid-latitudes in September Influenced by the Pacific Decadal Oscillation and Global Warming. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-068Graphical Abstract

Plain Language Summary: This study investigated whether the translation speed of tropical cyclones (TCs) has slowed in the western North Pacific basin during a post-geostationary satellite era from 1980-2019. Analyses of observational data and atmospheric reanalysis products revealed that the TC translation speed has significantly diminished over Japan, the East China Sea and their surrounding areas in September over the last 40 years. Historical model simulations with and without observational global warming trends reveal two main factors responsible for the translation speed slowdown: the Pacific Decadal Oscillation and global warming. Model simulations for a future warmer climate show that global warming further reduces the steering flows, leading to more slowly-moving TCs in autumn in the future.

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Huang et al. (2020)

Huang, Q., X. Ge, and M. Peng, 2020: Impacts of an upper-level easterly wave on the sudden track change of Typhoon Megi (2010). J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-069Graphical Abstract

Plain Language Summary: The Advanced Weather Research and Forecasting (WRF-ARW) model is used to investigate possible influences of a predominantly upper-level easterly wave (EW) on Typhoon Megi’s (2010) sharp northward turn on 20 October, 2010 after passing over the Philippines. In the presence of the upper-level easterly wave (EW), the simulation reasonably well produced the sudden track change of Megi.

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Arnold et al. (2020)

Arnold, N. P., W. M. Putman, and S. R. Freitas, 2020: Impact of resolution and parameterized convection on the diurnal cycle of precipitation in a global nonhydrostatic model. J. Meteor. Soc. Japan, 98,
https://doi.org/10.2151/jmsj.2020-066Graphical Abstract

Plain Language Summary: We evaluate the diurnal cycle of precipitation and organized convection in a set of nonhydrostatic global model runs with horizontal grid spacing ranging from 50 km to 3.5 km, using the NASA GEOS model, with scale-aware Grell-Freitas parameterized convection. The 3.5 km experiments are repeated with Grell-Freitas turned off, and again with scale-awareness disabled, to illustrate the impact of parameterized convection.

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