Regional climate modeling using regional climate models (RCMs) has matured over the past decade to enable meaningful utilization in a broad spectrum of applications. In this paper, the latest progress in regional climate modeling studies is reviewed, including RCM development, applications of RCMs to Challenges and potential directions of future research in this important area are discussed, with focus on those that have received less attention previously, such as the importance of ensemble simulations, further development and improvement of the regional climate modeling approach, modeling extreme climate events and sub-daily variation of clouds and precipitation, model evaluation and diagnostics, applications of RCMs to climate process studies and seasonal predictions, and development of regional earth system models.It is believed that with the demonstrated credibility of RCMs in reproducing not only monthly to seasonal mean climate and interannual variability, but also the extreme climate events when driven by good quality reanalysis and continuous improvements in the skill of global general circulation models (GCMs) in simulating large-scale atmospheric circulation, regional climate modeling will remain an important dynamical downscaling tool for providing the needed information for assessing climate change impacts, and seasonal climate predictions, and a powerful tool for improving our understanding of regional climate processes. Internationally coordinated efforts can be developed to further advance regional climate modeling studies. It is also recognized that since the final quality of the results from nested RCMs depends in part on the realism of the large-scale forcing provided by GCMs, the reduction of errors and improvement in physics parameterizations in both GCMs and RCMs remain a priority for the climate modeling community.

31°N approximately). In addition, major drought/flood events considering severity, persistency, and spatial coverage were also identified. On the centennial time scales, precipitation variation in eastern China exhibited four dry epochs (500s -870s, 1000s -1230s, 1430s -1530s and 1920s -1990s) and three wet epochs (880s -990s, 1240s -1420s and 1540s -1910s), with multi-decadal dry/wet fluctuations within each epoch. However, variation showed strong regional differences, for example, opposite trends were found in the Jiang-Nan area and Jiang-Huai area during the 11 -13th centuries and in the North China Plain and JiangNan area since the 16th century. The data also showed 16 drought and 18 flood events in eastern China, with the most severe drought event occurring in 1634 -1644. Droughts dominated in the 12 -14th centuries, but since the middle of the17th century eastern China has been more subject to flooding. The severity of floods during the 20th century was comparable in intensity to historical times, but the droughts were usually less severe.

Phenological cold/warm events recorded in Chinese historical documents are used to reconstruct, at 10-30 years' resolution, winter half-year (October to April) temperatures for the past 2000 years in the central region of eastern China. Because of the uneven spatial and temporal distribution of the phenological records, the reconstruction of the regional mean temperature involves two steps: reconstruction for individual sites within the region and calculation of the regional mean. For a single site, the reconstruction involves: identifying the difference in dates in phenological events for both historical and modern records; establishing the conversion function between the date difference and temperature change from the modern records; and converting the historical records into temperature variation. The spatial representativeness of the individual sites is studied by examining the correlation between individual sites and regional mean temperature from modern instrumental data. The correlation is then used as the basis for constructing the regional mean winter half-year temperature for the past 2000 years. From the beginning of the Christian era, climate became cooler at a rate of 0.17°C per century, and around the ad 490s temperature reached about 1°C lower than that of the present (the 1951-80 mean). Then, abruptly, temperature entered a warm epoch from the ad 570s to 1310s with a warming trend of 0.04°C per century; the peak warming was about 0.3-0.6°C higher than present for 30-year periods, but over 0.9°C warmer on a 10-year basis. After the ad 1310s, temperature decreased rapidly at a rate of 0.10°C per century; the mean temperatures of the four cold troughs were 0.6-0.9°C lower than the present, with the coldest value 1.1°C lower. Temperature has been rising rapidly during the twentieth century, especially for the period 1981-99, and the mean temperature is now 0.5°C higher than for 1951-80. The most interesting aspect over the past 2000 years has been the rapid transitions between cold and warm periods.

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[1] Recent studies indicated that the spatial pattern and temporal variability of summer rainfall over eastern China are well correlated with the Pacific Decadal Oscillation (PDO). Here we used a data set of the drought/flood index (a proxy of summer rainfall) since 1470 AD to reconstruct the annual PDO index. The reconstruction indicates that the PDO is a robust feature of North Pacific climate variability throughout the study period, however, the major modes of oscillation providing the basic PDO regime timescale have not been persistent over the last 530 years. The quasi-centennial (75 -115-yr) and pentadecadal (50 -70-yr) oscillations dominated the periods before and after 1850, respectively. Our analysis suggest that solar forcing fluctuation on quasi-centennial time scale (Gleissberg cycle) could be the pace-maker of the PDO before 1850, and the PDO behavior after 1850 could be due, in part, to the global warming.