JMSJ, 2016, Vol. 94A (January)
Special Issue on Research on Dynamical and Statistical Downscaling Approaches Around the Asia-Oceania Region
Kitoh et al. (2016)
Kitoh, A., T. Ose, and I. Takayabu, 2016: Dynamical downscaling for climate projection with high-resolution MRI AGCM-RCM. J. Meteor. Soc. Japan, 94A, 1-16.
https://doi.org/10.2151/jmsj.2015-022 Graphical Abstract
- A direct dynamical downscaling with a regional climate model (RCM) embedded within an atmosphere-ocean coupled general circulation model (AOGCM) is broadly used but is subject to systematic biases such as in sea surface temperature (SST) in their present-day simulations, which may cause unexpected effects on future projections and lead to difficult interpretation of climate change.
- A high-resolution atmospheric general circulation model (AGCM)–RCM system (Figure 1) is one of methods to minimize the effects of such biases.
- A Meteorological Research Institute AGCM with 20-km grids is successfully applied to project future changes in weather extremes such as tropical cyclones and rain systems that cause heavy rainfall and strong winds. Regional downscaling with a few-km mesh RCM is then performed over certain area such as Japan to investigate local extreme rainfall events and their future changes.
Tamaki et al. (2016)
Tamaki, Y., M. Inatsu, R. Kuno, and N. Nakano, 2016: Sampling downscaling in summertime precipitation over Hokkaido. J. Meteor. Soc. Japan, 94A, 17-29.
https://doi.org/10.2151/jmsj.2015-023 Graphical Abstract
- The sampling downscaling (SmDS) method (Fig. 1) in which a regional atmospheric model is integrated for sampled years was conducted for summertime precipitation over Hokkaido.
- We selected the top and bottom two years of the general circulation model (GCM) projection onto the first SVD mode (sampling index as in Fig. 1) where heavy precipitation is correlated with the moisture flux convergence in the synoptic field.
- The spatial distribution in the mean precipitation in SmDS was similar to that in the dynamical downscaling for 30 years (Fig. 2). This indicates that SmDS can be applied to the place where the synoptic field strongly controls the local precipitation.
- We also statistically considered the error in SmDS. It turned out that the mean in SmDS depended on the correlation coefficient between local and synoptic variables, the number of samples, and the standard deviation of seasonal mean precipitation. It was also demonstrated the SmDS selected the group of years where extreme events likely occurred and another group where they rarely occurred.
Takayabu et al. (2016)
Takayabu, I., H. Kanamaru, K. Dairaku, R. Benestad, H. von Storch, and J. H. Christensen, 2016: Reconsidering the quality and utility of downscaling. J. Meteor. Soc. Japan, 94A, 31-45.
Li et al. (2016)
- We test the use of four reanalysis data sets (NCEP1, ERAint, CFSR, JRA55) in constraining dynamical downscaling by assessing the skill of the reconstruction of the coastal winds of the Yellow Sea using the COSMO model in CLimate Mode (CCLM) with 7-km resolution.
- The downscaled simulations yield good-quality wind products; the simulations driven by ERAint, JRA55 and CFSR are consistent with each other in the reproduction of local wind speed and direction, and much better than the one downscaling from NCEP1 (Fig. 1).
- The simulated winds tend to overestimate observed low wind speeds and to underestimate observed high wind speeds; they are better at reproducing intermediate winds (4 – 12 m/s).
- The quality of the modeled wind direction is strongly associated with the wind speed intensities, exhibiting less error variability of wind direction at strong wind speeds than at light wind speeds (Fig. 2).
Ham et al. (2016)
Ham, S., J.-W. Lee, and K. Yoshimura, 2016: Assessing future climate changes in the East Asian summer and winter monsoon using Regional Spectral Model. J. Meteor. Soc. Japan, 94A, 69-87.
https://doi.org/10.2151/jmsj.2015-051 Graphical Abstract
- From future climate projection, the increasing temperature trends of each RCP scenario are consistently reproduced in RSM downscaling; in particular, the result from the RCP 8.5 experiment shows a significantly steeper trend in increasing temperature.
- The East Asian monsoon is intensified in future climate projection by the strengthening North Pacific subtropical high and Okhotsk high in summer and intensified Siberian high in winter. These changes lead to an increase in precipitation for the summer and a decrease for winter.
- High-resolution RCM data make it possible to use various climatic elements, such as variation in the strength and/or frequency of monsoons, typhoons, and so on.
Bhatt et al. (2016)
Bhatt, B. C., S. Sobolowski, and A. Higuchi, 2016: Simulation of diurnal rainfall variability over the maritime continent with a high-resolution regional climate model. J. Meteor. Soc. Japan, 94A, 89-103.
https://doi.org/10.2151/jmsj.2015-052 Graphical Abstract
- We evaluated the diurnal precipitation variability over the tropical maritime continent from both satellite observations and dynamically downscaled high-resolution (25-10km) simulations using the WRF model.
- The WRF model simulation captures the precipitation diurnal cycle well compared to TRMM 3B42 although the model overestimates the amplitude. The exaggerated precipitation amplitude over land by all the WRF simulation (with different convective schemes) indicates that mechanisms related to boundary layer transfer and convective lifting-condensation-precipitation are likely not well reproduced by the respective parameterization schemes. Convection permitting scales (≤4km) my be necessary in order to better diagnose and address these issues.
- The two leading EOF´s can explain most of the variation of diurnal precipitation. From the PC analysis, it is known that PC1 and PC2 both lead the TRMM 3B42 by about 3 hours over the maritime continent (Fig. 1). The exact casue for this mismatch in timing is not known but commonly described shortcomings that could contribute are underrepresentation of cloud development, lateral entrainment/detrainment rates in deep and shallow convection etc.
Muramatsu et al. (2016)
Muramatsu, T., T. Kato, M. Nakazato, H. Endo, and A. Kitoh, 2016: Future change of tornadogenesis-favorable environmental conditions in Japan estimated by a 20-km-mesh atmospheric general circulation model. J. Meteor. Soc. Japan, 94A, 105-120.
https://doi.org/10.2151/jmsj.2015-053 Graphical Abstract
- This is the first study to assess future changes in the occurrence of environmental conditions favorable for strong tornadoes (F2 or greater on the Fujita scale) in Japan using the results of climate experiments under the A1B emissions scenario with a 20-km-mesh, high-resolution atmospheric global circulation model.
- Nearly a doubling of the FSC was projected in almost all areas of the Japanese Islands in MAM and on the Japan Sea side of the Japanese Islands in JJA (Fig.1c and 1f).
- Future increases of the FSC are mainly caused by intensification of atmospheric instability caused by increases of the water-vapor mixing ratio and a temperature rise in the lower troposphere.
Hibino et al. (2016)
Hibino, K., and I. Takayabu, 2016: A trade-off relation between temporal and spatial averaging scales on future precipitation assessment. J. Meteor. Soc. Japan, 94A, 121-134.
https://doi.org/10.2151/jmsj.2015-056 Graphical Abstract
- The present study showed the dependence of the detectability of the precipitation change signal toward the end of the 21st century on the temporal and spatial averaging scales and proposed a trade-off relation between them (Fig. 5).
- The characteristics of the trade-off relation are found to differ qualitatively depending on latitude: the tropics, the mid-latitudes, and the subpolar regions (Fig. 6).
- The result of the trade-off relation is closely related to the precipitation power spectrum representing spatio-temporal scales of precipitation-related meteorological phenomena, e.g., baroclinic waves.
- The trade-off relation is obtained quantitatively and provides useful information for climate change impact assessments using various temporal and spatial scales or resolutions.
Kieu et al. (2016)
Kieu, X., H. Vu, T. Nguyen, D. Le, L. Nguyen, I. Takayabu, H. Sasaki, and A. Kitoh, 2016: Rainfall and tropical cyclone activity over Vietnam simulated and projected by the non-hydrostatic regional climate model – NHRCM. J. Meteor. Soc. Japan, 94A, 135-150.
https://doi.org/10.2151/jmsj.2015-057 Graphical Abstract
- The non-hydrostatic regional climate model (NHRCM) is used to simulate and project rainfall and tropical cyclone (TC) activity over Vietnam.
- Using outputs of the Meteorological Research Institute atmospheric general circulation model 3.2 with RCP8.5 scenario, the NHRCM model shows that the projected rainfall will clearly decrease in Northwest and Central Vietnam in June-August, while remarkably increase in Northeast and Central Vietnam in September-November in near and far future.
- Projected TCs indicate a decrease in both TC number and activity area. Rainfall induced by TCs increases in North Vietnam in the projected climate as compared to the baseline period. It also increases in Mid-Central Vietnam in near future, but decreases in southern Central Vietnam in near and far future.
Basconcillo et al. (2016)
Basconcillo, J., A. Lucero, A. Solis, R. Sandoval, Jr., E. Bautista, T. Koizumi, and H. Kanamaru, 2016: Statistically downscaled projected changes in Seasonal Mean Temperature and Rainfall in Cagayan Valley, Philippines. J. Meteor. Soc. Japan, 94A, 151-164.
https://doi.org/10.2151/jmsj.2015-058 Graphical Abstract
- Regarding seasonality, dry months (March-April-May) will continue to remain dry but within the rainy season, July and November are likely to become more notable wet months (Fig. 1).
- In both stations, the future projections show more pronounced double peaks in the annual cycle of rainfall compared to the 20th century – the first peak between July and September, and the second in November. In fact, July precipitation shows substantial increases (typically +50 to +100mm) in all models, scenarios, and stations, suggesting a shift of rainfall distribution to earlier in the rainy season.
- Analysis of aggregated projected annual maximum (Tmax) and minimum temperature (Tmin) (2011-2040) in Cagayan Valley reveals higher increase in Tmin compared to Tmax. The rate of increase in Tmin under A1B is 0.07°C per year and 0.05°C per year for Tmax. Under A2 scenario, the rate of temperature increase is slightly smaller: 0.05°C and 0.04°C per year (Tmin and Tmax, respectively). This differentiated projection for Tmax and Tmin suggests that diurnal temperature range will be smaller in the future.
Cruz et al. (2016)
Cruz, F. T., H. Sasaki, and G. T. Narisma, 2016: Assessing the sensitivity of the Non-hydrostatic Regional Climate Model to boundary conditions and convective schemes over the Philippines. J. Meteor. Soc. Japan, 94A, 165-179.
https://doi.org/10.2151/jmsj.2015-059 Graphical Abstract
- The Non-hydrostatic Regional Climate Model (NHRCM) was used to simulate present-day climate over the Philippines at 50 km resolution, using two sets of boundary conditions (ECMWF ERA-Interim and the NCEP/NCAR Reanalysis Project NNRP1), as well as two convective parameterization schemes in the model (Grell and Kain-Fritsch).
- While the seasonality of temperature and rainfall are simulated reasonably well for the Philippines, NHRCM has an overall cold and dry bias over land; the degree of which depends on the boundary condition and convective scheme used (Figure 1).
- Using the Grell scheme results in low temperature bias with high skill scores, while the Kain-Fritsch scheme gives low rainfall bias with high correlation and skill scores. The boundary conditions also influence model skill, such that the model bias tends to be lower for temperature when ERA-Interim is used, but lower for rainfall with NNRP1 (Figure 1).
Notes and Correspondence
Kanada et al. (2016)
Kanada, S., and A. Wada, 2016: Sensitivity to horizontal resolution of the simulated intensifying rate and inner-core structure of typhoon Ida, an extremely intense typhoon. J. Meteor. Soc. Japan, 94A, 181-190.
https://doi.org/10.2151/jmsj.2015-037 Graphical Abstract
- The model-resolution sensitivity of simulated intensifying and deepening rates of an extremely intense tropical cyclone, Typhoon Ida (1958), was investigated by using the Japan Meteorological Agency/Meteorological Research Institute nonhydrostatic atmospheric model with horizontal resolutions of 20 (NHM20), 10 (NHM10), 5 (NHM5), and 2 km (NHM2).
- The results revealed great differences in the intensifying and deepening rates and their associated structural changes among simulations.
- Only the cloud-resolving 2km model, with explicit microphysics, could reproduce the observed maximum intensity and extreme intensification rate of the typhoon realistically since the model could produce the deep, intense and upright updrafts inside the radius of maximum wind speed around the vorticity-rich area over the strong near-surface inflow.
Takayabu et al. (2016)
- This paper clarifies that the skillful time-scale characteristic of a model is one of the key factors to reproduce the amount precipitation at a specific place with the model. A comparison with data from an operational observing site of the Japan Meteorological Agency in Tokyo revealed that a model needed at least 5-km-grid resolution (NHRCM05) to represent the power spectrum of hourly precipitation.
- Figure 1 indicates the PDF of hourly precipitaion around the Tokyo site. It is difficult to characterize extreme hourly precipiation by using the AGCM20/60 models. However, the NHRCM05 model could simulate extreme precipitaion events.
- To clarify the cause of the difference, we obtained a power spectrum of precipitaion (Fig.2). We found that they were very similar at frequencies lower than 1 cycle per day (CPD). However, at frequencies greater than 1CPD, the simulated power was lower in lower resolution models (AGCM20/60).
Ham et al. (2016)
Ham, S., K. Yoshimura, and H. Li, 2016: Historical dynamical downscaling for East Asia with the atmosphere and ocean coupled regional model. J. Meteor. Soc. Japan, 94A, 199-208.
https://doi.org/10.2151/jmsj.2015-046 Graphical Abstract
- A regional atmosphere-ocean coupled model, RSM-ROMS, was applied to dynamically downscale the global reanalysis data over the East Asian region for the first time.
- Spatial distribution of net heat flux, precipitation, and surface air temperature were improved from the atmosphere-only run throughout the period, though sea surface temperature (SST) was degraded due to that observed SST was forced in the atmosphere-only run.
- The inconsistency between the impacts on SST ant the other variables may indicate remaining uncertainty in the coupling and/or boundary layer processes.