JMSJ, 2015, Vol. 93, No. 2 (April)
Murazaki et al. (2015)
Murazaki, K., H. Tsujino, T. Motoi, and K. Kurihara, 2015: Influence of the Kuroshio large meander on the climate around Japan based on a regional climate model. J. Meteor. Soc. Japan, 93, 161-179.
http://dx.doi.org/10.2151/jmsj.2015-009 Graphical Abstract
- The impact of the Kuroshio large meander on the climate around Japan was investigated by using a high-resolution North Pacific Ocean General Circulation Model and a 20km resolution regional climate model. The conclusions of an 8-year composite analysis of the model simulation for the Kuroshio large meander and straight path are as follows.
- Substantial decreases in the frequency of precipitation over the ocean are caused in both winter and summer by the cold sea surface temperature anomaly caused by the Kuroshio large meander (Fig.1).
- Similar effects are evident over the land area of Japan, although they are less intense, at most 20-50% of magnitude over the cold sea surface temperature anomaly area, and limited to the coastal region on the Pacific Ocean side in the central part of the country (Figs.2 and 3).
Noda et al. (2015)
Noda, A. T., M. Satoh, Y. Yamada, C. Kodama, T. Miyakawa, and T. Seiki, 2015: Cold and warm rain simulated using a nonhydrostatic model without cumulus
parameterization, and their responses to global warming. J. Meteor. Soc. Japan, 93, 181-197.
http://dx.doi.org/10.2151/jmsj.2015-010 Graphical Abstract
- The increase of precipitation in the higher horizontal resolution model (7 km) was caused by the increase of both cold and warm rain. The net increase of cold rain occurred due to the increase of stronger precipitation (>40 mm hr−1), most of which compensated for the decrease of weaker precipitation (<40 mm hr−1). In contrast, warm rain increased in almost all ranges of precipitation intensity.
- The lifespan of warm clouds in a warmer atmosphere was reduced in most of the SST anomaly regimes.
Enomoto et al. (2015)
- Two formulations approximating singular-vector and adjoint methods are derived using an ensemble forecast to identify the sensitive initial perturbations that grow in a specified region at the verification time.
- Sensitivity analysis over Japan shows that the two methods can identify the sensitive regions more specifically than the regions with large ensemble spread for a mid-latitude cyclone in January and a tropical cyclone in August 2003 (Figure 4).
- For an August 2002 storm in Europe, the cyclone deepens a few hPa in its north-east sector with more precipitation north of the Alps more consistently with observations in a global 20-km resolution simulation perturbed with ensemble singular vector.
Shusse et al. (2015)
Shusse, Y., M. Maki, S. Shimizu, K. Iwanami, T. Maesaka, S. Suzuki, N. Sakurai, R. Misumi, 2015: Relationship between precipitation core behavior in cumulonimbus clouds and surface rainfall intensity on 18 August 2011 in the Kanto region, Japan. J. Meteor. Soc. Japan, 93, 215-228.
http://dx.doi.org/10.2151/jmsj.2015-012 Graphical Abstract
- The behavior of the precipitation cores (PCOs) in three cumulonimbus clouds and their relationship with temporal variations in surface rainfall intensity are analyzed using 3D X-band dual-polarization radar data every 2 min. A PCO region was defined as a 3D contiguous region that contained one local maximum of horizontal radar reflectivity Zh. After the automatic detection and subjective tracking of PCO regions, 15 PCOs were identified during the total lifespan of the three cumulonimbus clouds.
- The PCOs generally descended towards the ground after their appearance aloft (Figs. 9–11). Of the 12 temporal peaks in maximum surface rainfall intensity (>10 mm h–1) recorded from the three cumulonimbus clouds, 10 were associated with the descent of PCOs. In each cumulonimbus cloud, the first PCO was detected 10–12 min before the rainfall heavier than 10 mm h–1 was recorded. These results indicate that the behavior of PCOs is closely related to the onset of strong surface rainfall and subsequent fluctuations in surface rainfall intensity.
Matsumura et al. (2015)
Matsumura, S., K. Yamazaki, and T. Sato, 2015: Role of Siberian land-atmosphere coupling in the development of the August Okhotsk High in 2008. J. Meteor. Soc. Japan, 93, 229-244.
http://dx.doi.org/10.2151/jmsj.2015-013 Graphical Abstract
- Snow cover in eastern Siberia plays a critical role in land-atmosphere climate system (Fig. 1). The snow-hydrological effect is prominent during summertime; i.e., less snow cover in spring results in less snowmelt water and correspondingly lower soil moisture in summer, resulting in turn in reduced cloudiness, evaporation and precipitation (higher surface air temperature).
- As a result of surface heating through the climate memory effect, in late summer, tropospheric heating is caused by condensation heating associated with ascending air masses and adiabatic heating of descending air masses, thereby forming a stronger upper-level anticyclone with a westward tilt.
- We examined the influence of springtime snow cover on the formation of the late summer Okhotsk High (OH) with the baroclinicity, using a regional climate model. The August OH in 2008 develops with a distinct baroclinic structure due to increased surface heating that is related to land-atmosphere coupling in response to reduced spring snow cover in eastern Siberia (Fig. 2). A reanalysis data also indicates that the formation mechanism of the OH clearly differs between early and late summer, because it changes from a nearly barotropic to a baroclinic structure. The land-atmosphere coupling can help to reinforce and maintain the baroclinic structure through surface heating, forming strong surface anticyclone to the southeast over the Sea of Okhotsk.
Takahashi et al. (2015)
Takahashi, T., T. Kawano, and M. Ishihara, 2015: Different precipitation mechanisms produce heavy rain with and without lightning in Japan. J. Meteor. Soc. Japan, 93, 245-263.
http://dx.doi.org/10.2151/jmsj.2015-014 Graphical Abstract
- During summer, disturbed weather brings frequent bouts of heavy rain to Japan in two types of cloud systems, one with high lightning activity and other with low lightning frequency. Five heavy rain cases in 2008-2009 were selected for this study: High lightning events (Hofu and Zoshigaya) and weak lightning events (Sasaguri, Dazaifu, and Sayo). To find the bases for this difference, data were compared with videosonde data from various cloud systems across East and Southeast Asia.
- On average, in the Graupel-Mixed group, compared to the Frozen Drop group, radar echo intensity decreased with height less strongly. In the high-lightning-activity, heavy-rain events (Hofu, Zoshigaya), compared to the low-lightning-activity, heavy rain events (Sasaguri, Sayo), high radar echo extended to substantially higher altitude and decreased with height somewhat less strongly.
- The difference in lapse rates suggests a difference in precipitation particle distributions; that is, in weak lapse rate clouds (high lightning), graupel dominate while in a steep lapse rate clouds (low lightning), frozen drops dominate.
- The main reason for the weakness of electrical activity in frozen-drop-dominated clouds is probably that the concentration of ice crystals is too low to support much riming electrification.
Jin et al. (2015)
Jin, D., Z. Guan, J.Cai, and W. Tang, 2015: Interannual variations of regional summer precipitation in Mainland China and their possible relationships with different teleconnections in the past five decades. J. Meteor. Soc. Japan, 93, 265-283.
http://dx.doi.org/10.2151/jmsj.2015-015 Graphical Abstract
- Using observational rainfall data at 596 meteorological stations in mainland China from 1961 to 2008, the authors identified 21 regions for June-July-August mean rainfall anomalies by employing the rotated empirical orthogonal function (REOF) decompositions (Fig.1). These 21 regions cover most territory of China. The rainfall variations in any one of these 21 regions are almost statistically independent of those in the others, suggesting the variations of summertime mean rainfall are very regional.
- Rainfall variations in different regions are found to be possibly influenced by different factors including both/either signals from tropics and/or teleconnections from mid-high latitudes by conducting a survey with some indices of sea surface temperature anomalies (SSTA) such as DMI (the Indian Ocean dipole mode index) and teleconnection patterns such as PJ (the Pacific-Japan (PJ) teleconnection index).
Nakayama et al. (2015)
Nakayama, T., H. Suzuki, S. Kagamitani, Y. Ikeda, A. Uchiyama, and Y. Matsumi, 2015: Characterization of a three wavelength photoacoustic soot spectrometer (PASS-3) and a photoacoustic extinctiometer (PAX). J. Meteor. Soc. Japan, 93, 285-308.
http://dx.doi.org/10.2151/jmsj.2015-016 Graphical Abstract
- Performance of two commercially available instruments, three-wavelength photoacoustic soot spectrometer (PASS-3, λ = 405, 532, 781 nm) and photoacoustic extinctiometer (PAX, λ = 375nm), for the measurement of the light absorption and scattering coefficients of aerosols based on photoacoustic spectroscopy and reciprocal nephelometry were characterized.
- A significant particle size dependency was observed for the calibration factors for scattering measurements at 532 nm, likely due to a combination of differences in the polarization states of the lasers relative to the scattering planes and the large truncation angle, while no significant particle size dependencies were observed at 375, 405, and 781 nm (Fig. 1).
- The calibration factors for absorption measurements determined based on the light absorption of NO2 molecules at 375 and 405 nm were 48 and 36% smaller than those for the poly-disperse soot particles, likely due to the influence of photolysis of NO2, although good agreement was observed at 532 nm (Fig. 2).
Kashimura et al. (2015)
Kashimura, H., and S. Yoden, 2015: Regime diagrams of solutions in an idealized quasi-axisymmetric model for superrotation of planetary atmospheres. J. Meteor. Soc. Japan, 93, 309-326.
http://dx.doi.org/10.2151/jmsj.2015-017 Graphical Abstract
- This paper presents regime diagrams showing the parametric dependence of dynamical balance in a superrotating atmosphere produced in a quasi-axisymmetric idealized system with strong horizontal diffusion studied previously by the present authors (Yamamoto and Yoden 2013). In this system, the superrotation is maintained by the Gierasch (1975) mechanism.
- Boundaries of the regimes based on the dynamical balance (denoted by C1, C0, G1, G0, H1, and H0) are determined by analyzing the theoretical model proposed in Yamamoto and Yoden. A parametric limit showing a lower limit for the horizontal diffusion in the Gierasch mechanism is also estimated from the theoretical model and included in the regime diagrams (NG).
- The theoretical regime diagram tells us that the superrotation in the cyclostrophic balance is realized when the horizontal Ekman number is in a certain range of two to three orders as shown by the shape of C1 and C0 regions in panels (c) and (d). Its width is mainly controlled by the vertical Ekman number.
- Compared with numerical solutions, the theoretical regime diagrams agree well with the numerical results in most regions, showing the validity of the theoretical model. The fact that multiple equilibrium solutions are obtained in NG region as in panel (a) shows that the Gierasch mechanism can maintain the superrotation even with the horizontal diffusion weaker than the predicted lower limit but cannot generate it from a motionless state.