Hirokazu Endo

Future Change in Extratropical Cyclones Associated with Change in the Upper Troposphere

AbstractFuture changes in Northern Hemisphere wintertime storm activity as a consequence of global warming are investigated using the AGCM of Meteorological Research Institute (MRI-AGCM) with horizontal grid sizes of 60 and 20 km. A future (2075–99) climate experiment, in which the change in sea surface temperature (SST) derived from the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel ensemble mean is added to observed SST, is compared with a present-day (1979–2003) climate experiment. Results of three-member simulations using the 60-km model are presented. A single simulation using the 20-km model is also presented, showing that similar results are obtained.In the future climate experiment, the number of intense cyclones (sea level pressure below 980 hPa) shows a significant increase whereas the number of total cyclones shows a significant decrease, similar to the results obtained from the CMIP3 models themselves. The increase in intense cyclones is seen on the polar side and downstream ...

Thermodynamic and dynamic effects on regional monsoon rainfall changes in a warmer climate

This study investigates thermodynamic and dynamic effects on regional monsoon rainfall changes in a warmer climate, by using 20 climate model outputs in the Coupled Model Intercomparison Project (CMIP) Phase 5. In a warmer climate, rainfall is projected to increase in most monsoon regions. However, the rates of increase are quite different among the monsoon regions. A diagnosis based on a linearized moisture budget equation reveals that the regional differences of the rainfall change are largely explained by differences in the dynamic effect. In the Asian monsoon regions, monsoon circulation slows down at a much lower rate than in the other monsoon regions; in addition, surface evaporation increases at a higher rate, resulting in a much larger increase in rainfall. These features are commonly found in both CMIP Phase 3 and Phase 5 model projections.

Over 5,000 Years of Ensemble Future Climate Simulations by 60-km Global and 20-km Regional Atmospheric Models

AbstractAn unprecedentedly large ensemble of climate simulations with a 60-km atmospheric general circulation model and dynamical downscaling with a 20-km regional climate model has been performed to obtain probabilistic future projections of low-frequency local-scale events. The climate of the latter half of the twentieth century, the climate 4 K warmer than the preindustrial climate, and the climate of the latter half of the twentieth century without historical trends associated with the anthropogenic effect are each simulated for more than 5,000 years. From large ensemble simulations, probabilistic future changes in extreme events are available directly without using any statistical models. The atmospheric models are highly skillful in representing localized extreme events, such as heavy precipitation and tropical cyclones. Moreover, mean climate changes in the models are consistent with those in phase 5 of the Coupled Model Intercomparison Project (CMIP5) ensembles. Therefore, the results enable the a...

Application of Cluster Analysis to Climate Model Performance Metrics

The overall performance of general circulation models is often investigated on the basis of the synthesis of anumberofscalar performancemetricsofindividualmodelsthatmeasurethereproducibilityofdiverseaspects of the climate. Because of physical and dynamic constraints governing the climate, a model’s performance in simulatingacertainaspectoftheclimateissometimesrelatedcloselytothatinsimulatinganotheraspect,which results in significant intermodel correlation between performance metrics. Numerous metrics and intermodel correlations may cause a problem in understanding the evaluation and synthesizing the metrics. One possible way to alleviate this problem is to group the correlated metrics beforehand. This study attempts to use simple cluster analysistogroup43performancemetrics. Two clusteringmethods, theK-means and the Wardmethods, yield considerably similar clustering results, and several aspects of the results are found to be physically and dynamically reasonable. Furthermore, the intermodel correlation between the cluster averages is considerably lower than that between the metrics. These results suggest that the cluster analysis is helpful in obtaining the appropriate grouping. Applications of the clustering results are also discussed.

Projecting Changes of the Asian Summer Monsoon Through the Twenty-First Century

This chapter provides an updated review of our current understanding of future changes in the Asian summer monsoon. It is based on recent studies that include analysis of the state-of-the-art CMIP5 model simulations together with projections of extremes and regional-scale climate from higher-resolution models. It is projected that both the amount and intensity of Asian summer monsoon rainfall are likely to increase under global warming, and that the rate of increase will be higher than that in other monsoon regions, which suggests a substantial increase in the risk of extreme rainfall events.