Statistical Downscaling for Multi-Model Ensemble Prediction of Summer Monsoon Rainfall in the Asia-Pacific Region Using Geopotential Height Field

The 21-yr ensemble predictions of model precipitation and circulation in the East Asian and western North Pacific （Asia-Pacific） summer monsoon region （0°-50°N, 100° 150°E） were evaluated in nine different AGCM, used in the Asia-Pacific Economic Cooperation Climate Center （APCC） multi-model ensemble seasonal prediction system. The analysis indicates that the precipitation anomaly patterns of model ensemble predictions are substantially different from the observed counterparts in this region, but the summer monsoon circulations are reasonably predicted. For example, all models can well produce the interannual variability of the western North Pacific monsoon index （WNPMI） defined by 850 hPa winds, but they failed to predict the relationship between WNPMI and precipitation anomalies. The interannual variability of the 500 hPa geopotential height （GPH） can be well predicted by the models in contrast to precipitation anomalies. On the basis of such model performances and the relationship between the interannual variations of 500 hPa GPH and precipitation anomalies, we developed a statistical scheme used to downscale the summer monsoon precipitation anomaly on the basis of EOF and singular value decomposition （SVD）. In this scheme, the three leading EOF modes of 500 hPa GPH anomaly fields predicted by the models are firstly corrected by the linear regression between the principal components in each model and observation, respectively. Then, the corrected model GPH is chosen as the predictor to downscale the precipitation anomaly field, which is assembled by the forecasted expansion coefficients of model 500 hPa GPH and the three leading SVD modes of observed precipitation anomaly corresponding to the prediction of model 500 hPa GPH during a 19-year training period. The cross-validated forecasts suggest that this downscaling scheme may have a potential to improve the forecast skill of the precipitation anomaly in the South China Sea, western North Pacific and the East Asia Pacific regions, wh     

地质流体热力学性质的蒙特卡罗模拟

地质流体的热力学性质对研究它们在各种地质作用中的地球化学行为起着十分重要的作用。研究地质流体的传统方法有实验方法和经验、半经验模型方法。这些方法的应用范围一般只能涵盖整个地球温压条件中极为有限的区间。新兴的计算机模拟提供了研究地质流体的第三条途径 ,即通过“计算机实验”的方法 ,模拟极限温压条件下地质流体系统的热力学特性和微观性质。与传统方法相比它有优越性 ,且越来越受到地球化学家们的重视。蒙特卡罗法是流体计算机模拟的主要方法和手段之一 ,吉布斯系综法的提出 ,又显示出用蒙特卡罗法在研究物质相平衡和相变特性方面特有的能力。近来 ,人们把蒙特卡罗法应用于地质流体的研究 ,已取得了一些可喜的成果。但是 ,目前在地质研究中蒙特卡罗模拟大部分还局限于相对简单的系统 ,对于成分较复杂的系统 (特别是含水混合物 )的研究还有许多工作要做