Through modeling and international exchange, the Abdus Salam International Centre for Theoretical Physicsis fostering advanced climate research in countries where scientific resources are often scarce. P opulations in economically developing nations (EDNs) depend extensively on climate for their welfare (e.g., agriculture, water resources, power generation, industry) and likewise are vulnerable to variability in the climate system, whether due to anthropogenic forcing or natural processes. Furthermore, changes in atmospheric composition (e.g., greenhouse gases and aerosols) and land cover are likely to significantly alter regional climates (Nakicenovic et al. 2001), thereby affecting local socioeconomic development and livelihoods of EDN populations. Therefore, the evaluation of climate change and variability at seasonal-to-multidecadal time scales is of great benefit to these regions.Climate models, both global and regional, are the primary tools that aid in our understanding of the many processes that govern the climate system. In the past, a lack of computational resources has hindered the use of climate models by EDN scientists. However, in the last decade the computing power of the common desktop personal computer (PC) has dramatically increased •

Up-to-date regional and local assessments of changing climate extremes are important to allow countries to make informed decisions on mitigation and adaptation strategies, and to put these changes into a global context. A workshop for countries from the Indo-Pacific region has brought together daily observations from 13 countries for an analysis of climate extremes between 1971 and 2005. This paper makes use of the workshop outcomes and post-workshop analyses to build on previous work in Southeast Asia to update the assessment of changing climate extremes using newly available station data. We utilise a consistent and widely tested methodology to allow a direct comparison of the results with those from other parts of the world. The relationship of inter-annual variability in the climate extremes indices with sea surface temperature (SST) patterns has been investigated with a focus on the influence of the El Niño-Southern Oscillation phenomenon. The results support findings from elsewhere around the globe that warm extremes, particularly at night, are increasing and cold extremes are decreasing. Trends in precipitation extremes are less spatially consistent across the region.  Royal Meteorological Society and Crown

The South Asian summer monsoon (SASM) is a continental scale weather phenomenon, which fluctuates at a range of temporal and spatial scales. Although majority of global climate models are broadly able to simulate the large scale characteristics of the SASM, they generally have major deficiencies such as constraints in reproducing observed mean precipitation. It is generally anticipated that higher resolution regional climate models (RCMs) would be able to simulate an improved mean state owing to their capacity to better simulate fine temporal and spatial scale features and variability. Here, we analyse SASM simulations using a contemporary Hadley Centre RCM, forced by ERA‐Interim reanalysis and observed sea surface temperature, at medium (0.44°) and high (0.11°) horizontal resolutions. Evaluation of the results show that, compared to the medium resolution RCM, the high resolution RCM is able to better resolve the interaction of the low level monsoon flow with the Himalayan orography leading to added value in simulating many aspects of SASM precipitation such as the seasonal mean, relative frequency distribution of daily precipitation, and various metrics of precipitation extremes. In contrast to many previous studies, maximum added value is note along the Indo‐Gangetic plain rather than over the complex Himalayas, and the added values of up to 5 mm day−1 and 50 days are noted for mean precipitation and number of wet days, respectively over the region. Similarly, added values of up to 15 and 3 mm day−1 are noted for 95th percentile of daily precipitation and simple daily intensity index, respectively over central India and the Himalayan range. These results suggest that higher resolution RCMs have the potential to add more value when downscaling global climate model climate change projections.

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The South Asian summer monsoon (SASM) exhibits large variability in the intraseasonal scale, and active and break cycles of monsoon constitute dominant mode of this variability. This has been subject of many model‐based studies as improved simulation of intraseasonal features also leads to better representation of the seasonal mean characteristics. We evaluate a recent Hadley centre regional climate model's performance, at low and high resolutions and forced by a reanalysis, in simulating various characteristics associated with intraseasonal variability of SASM. In particular, we compare the spatial patterns of precipitation and upper level circulation composites for active and break spells and, timing, frequency and duration of those spells. We found improvements in simulation of active and break composite precipitation in the high‐resolution simulation. These improvements probably come from improved position of the monsoon trough particularly over west India for active composite and improved low‐level flow particularly south of the Himalaya for break composite. Moreover, enhanced capacity of the model at high resolution to resolve atmospheric motions and interaction of moisture laden low‐level flow with the steep Himalayan orography is likely to contribute in reduction of excess precipitation over Indo‐Gangetic plain. Similarly, improvements over east Nepal for break spells are likely to come from model's ability to effectively capture precipitation enhancements that arise from orographic‐forced and mid‐tropospheric ascending motions. However, mixed results are obtained for temporal statistics associated with occurrence of active and break events. We also compare the model performance in simulating precipitation extremes over Nepal. The timing of extreme precipitation occurrence in relation to peak monsoon months and break spells, and contribution of the extreme cumulative precipitation to the seasonal total are improved in the high‐resolution simulation.