在新疆天山大地形背景下,实现了中国气象局研发的高分辨率气候业务预测系统CMA-CPSv3(China Meteor-ological Administration-Climate Prediction System version 3)在天山北坡经济带的本地化应用,分别评估控制预报、传统集合平均预报以及改进后的最优概率阈值集合方法(deterministic ensemble forecast using a probabilistic threshold,DEFPT)对该区域次季节-季节降水的预测水平.评估结果表明:基于CMA-CPSv3预测系统的DEFPT方法可以提升天山北坡次季节-季节尺度1～5 mm阈值降水落区以及持续性的预测效果,优于传统集合平均预报和控制预报.从2016年7月29日—8月2日、2017年6月7-12日以及2020年7月8-12日时段发生在天山北坡的降水事件个例分析结果看,不论从降水落区、降水异常还是降水持续性,DEFPT集合预报在天山北坡西部和南部均有更好的效果,但在天山北坡东部和北部预测能力相对略低,这与该区域水汽的预报偏差增大有关.

利用近30 a中国地面气象台站1767站的逐月降水资料、同期NOAA的扩展重建(Extended Reconstructed SST V3b)海表温度资料和NCEP/NCAR大气再分析资料,分析了2011年夏季(6-8月)东北太平洋海温异常对西南地区极端干旱事件的影响机理.结果 表明:2011年夏季西南地区降水呈现极端偏少的特征,区域平均降水距平为-270 mm,小于负两倍标准差,降水负异常极小值区域主要位于滇黔桂三地交界处.2011年夏季西南地区降水极端负异常与东北太平洋海表温度异常偶极型(NorthEast Pacific SSTA Dipole,NEPD)分布存在联系.将热带东北太平洋[90°～120°W,5°～20°N]海温负/正异常、中纬度北太平洋[150°～170°W,37°～45°N]海温正/负异常定义为NEPD负/正位相.NEPD负位相事件引起了热带中东太平洋对流层低层东风异常,并通过中纬度纬向东传波列引起远东地区位势高度正异常,减弱了西太平洋副热带高压,不利于西南暖湿气流向中国西南地区输送;同时,西南地区对流层低层辐散、高层辐合,受异常下沉气流控制.上述条件共同作用造成了2011年西南地区夏季降水极端负异常.

The characteristics of flood season daily precipitation were analyzed in the term of rainfall amount, frequency and intensity using the hourly data in Anhui during 1981-2010. The main results are as follows. (1) The daily rainfall amount and frequency have two diurnal peaks, one in the early morning and the other in the late afternoon,while the rainfall intensity doesn't reflect an obvious peak. The peaks of light and moderate rain days lie in afternoon, and there are two peaks in heavy rain days. However, the peak of torrential rain days lies in morning. These differences are due to the different lasting rainfall events. (2)The spatial distributions of rainfall have large diurnal variation with considerable regional features. As amount of daily rainfall increasing,the spatial distribution of peak time performs less consistent. (3)In the 30 years, the annual change of afternoon-peak in rain amount and intensity is almost the same, reflecting an increase between 1993 and 2010. There are more stations of morning peak time in weak monsoon years than strong monsoon years.

Huaihe River is one of the main rivers in China.It lies between the Yellow River and Yangtze River.Since ancient times,floods and droughts occurred frequently in Huaihe River Basin with significant casualties and economic losses.In developing measures for disaster prevention or emergency response for disaster relief,the study of floods and droughts caused by precipitation anomaly in Huaihe River Basin should be strengthened.Based on the observation dataset,this study not only defines the precipitation transition events from spring to summer,but also produces its intensity using total seasonal precipitation.The precipitation transition from spring to summer is analyzed by using the 30 gauge stations in Huaihe River Basin during 1961-2014.The typical patterns of Wet-Wet and Dry-Wet transitions generally occurred and their intensities were stronger in the past 54 years.The results indicate that temporal variation of transition event shows interannual and interdecadal variabilities.The significant decrease trend of transition frequency is detected during 1961-1979 and 2000-2010,but it has increased in recent years.The transitions often occur in more than one-third stations over half sample periods.This study applies the Season-reliant Empirical Orthogonal Function(S-EOF) analysis to detect major modes of seasonal precipitation.Based on S-EOF method,the cumulative variance contribution of the first mode is up to 34.4％.The principal component 1 (PC 1) illustrates the continuous positive precipitation anomaly in spring and summer in most areas,and it is worthy to notice the rising of its time coefficient in past few years.Otherwise,transition from negative to positive precipitation anomaly and interdecadal variation of time coefficient are shown by PC2.Furthermore,results show that PC1 relates to continuous E1 Nifio event from early winter to spring,positive East Asian subtropical westerly anomaly at 200 hPa in spring,positive Indian Ocean Dipole and south wind anomaly at 850 hPa over eastern China from spring to summer.The reverse occurs during a continuous negative phase scenario.The negative SSTA in eastern coast of China,the significant changes of northward East Asian subtropical westerly,and the shift of meridional wind anomaly at 850 hPa over southeastern China cross seasons play important roles in the occurrence of PC2 in Huaihe River.

将大尺度半分布式水文模型VIC应用到黄河上中游流域(花园口水文断面以上),并利用区域气候模式RegCM4.0单向嵌套全球气候模式BCC_CSM1.1,动力降尺度到黄河流域的模拟结果驱动VIC模型,开展在新的典型浓度路径下(RCP4.5和RCP8.5)黄河流域未来气候和水文变化的离线模拟.模拟结果显示,在RCP4.5和RCP8.5排放情景下,黄河流域21世纪平均地表气温相对于1971-2000年均呈显著上升趋势,2019-2048年上升1.2-1.5℃,2069-2098年上升2.19-3.9℃.未来年平均降水量有微弱的增大,2019-2048年增幅为6％左右,2069-2098年增幅为1.4％-5.6％.未来蒸发量增大明显,2069-2098年年平均蒸发量最大可增加9.6％.2019-2048年花园口水文站的年平均径流量增大3.4％-7.4％,2069-2098年年平均径流量转为减少,减幅为3.3％-5.3％.黄河上游地区未来气候和水文变化趋势与黄河流域基本一致,但未来年径流量变幅低于黄河流域,相对比较稳定.