Climate change poses a deadly heat wave risk to South Asia due to population density, poverty, and outdoor working conditions.

Because of their dependence on water, natural and human systems are highly sensitive to changes in the hydrologic cycle. The authors introduce a new measure of hydroclimatic intensity (HY-INT), which integrates metrics of precipitation intensity and dry spell length, viewing the response of these two metrics to global warming as deeply interconnected. Using a suite of global and regional climate model experiments, it is found that increasing HY-INT is a consistent and ubiquitous signature of twenty-first-century, greenhouse gas–induced global warming. Depending on the region, the increase in HY-INT is due to an increase in precipitation intensity, dry spell length, or both. Late twentieth-century observations also exhibit dominant positive HY-INT trends, providing a hydroclimatic signature of late twentieth-century warming. The authors find that increasing HY-INT is physically consistent with the response of both precipitation intensity and dry spell length to global warming. Precipitation intensity increases because of increased atmospheric water holding capacity. However, increases in mean precipitation are tied to increases in surface evaporation rates, which are lower than for atmospheric moisture. This leads to a reduction in the number of wet days and an increase in dry spell length. This analysis identifies increasing hydroclimatic intensity as a robust integrated response to global warming, implying increasing risks for systems that are sensitive to wet and dry extremes and providing a potential target for detection and attribution of hydroclimatic changes.

The temporal and spatial characteristics of trends in extreme indices over Korea between 1971 and 2100 are investigated using daily minimum (Tmin) and maximum (Tmax) temperature and precipitation data from a regional climate projection at 20 km grid spacing. Five temperature–based indices and five precipitation–based indices are selected to comprehensively consider the frequency, intensity, and persistence of extreme events. In addition, Mann–Kendall tests are used to detect the statistical significance of trends in these indices. For validation during the reference period (1971–2000), the model reasonably simulates the temporal and spatial pattern of the trend. The model captures observed direction and magnitude well in various types of extremes. Indices based on Tmin show a considerable change towards warmer climate conditions while indices based on Tmax do not reveal any distinct trend, implying an asymmetric response of Tmin and Tmax to global warming. Indices of the frequency and intensity of heavy precipitation show a significant increase, whereas the duration of dry and wet consecutive days shows no change. For future projections, the temperature–based indices exhibit a much more significant and consistent trend than the precipitation–based indices, with statistical significance at the 95% confidence level for all indices. The frequency and intensity of heavy precipitation are projected to increase in the 21st century, continuing the trend of the reference climate. Although the future projected changes in the duration of consecutive dry and wet days are not statistically significant, the signal becomes more pronounced with respect to the reference simulation. Copyright © 2010 Royal Meteorological Society

This study investigates the capability of the regional climate model, RegCM3, to simulate fine-scale regional climate over a narrow peninsula or archipelago. The model is run in one-way double-nested mode with one mother domain and two nested domains. The mother domain encompasses the eastern and southern regions of Asia and adjacent oceans with a grid spacing of 60 km. The first nested domain focuses on the Korean peninsula and the second one covers the Philippine archipelago with a grid spacing of 20 km. The simulation spans a period of 5 years and 1 month, from November 2000 to December 2004. The sensitivity of the two convection schemes, namely, the Grell scheme (Grell) and the MIT-Emanuel scheme (EMU), is studied. Model results obtained with both the Grell and EMU show reasonable performance in capturing the seasonal variation and the spatial characteristics of the East Asian monsoon. However, the Grell simulation appears to have persistent cold and dry biases in the summer season. There is a definite improvement in these model deficiencies by the implementation of EMU. Although the temperature fields in the Grell and EMU simulations are essentially the same in terms of the spatial distribution, the EMU simulation is quantitatively in better agreement with the observed estimates, indicating a substantial reduction in the cold bias. Further, in comparison with the Grell simulation, the EMU simulation shows an improvement in the timing and amplitude of the rain band propagating northward. The spatial distributions of precipitation also have good quality, capturing the localized maxima over Korea. The frequency distributions of daily temperature and precipitation simulated by EMU are closer to observations than those of the Grell simulation. It is found that the convective precipitation derived from different convection parameterizations is a major contributor to the performance of the model in summer. Copyright © 2008 Royal Meteorological Society