VARIABILITY OF DAILY PRECIPITATION IN CHINA(1980-1993): PCA AND WAVELET ANALYSIS OF OBSERVATION AND ECMWF REANALYSIS DATA

In this study, principal component analysis(PCA) and complex Morlet wavelet transform were used with daily rainfall in China for the period 1980-1993(1 May-31 Dec.) from observation and ECMWF reanalysis to study its variability and evaluate the validation of reanalyzed precipitation. The results showed that northward movement of the summer rain belt was a wavelike propagation, which was always accompanied by rainfall breaks and could be treated as one event under time scale of about 1 month only. The first 4 EOFs accounted for 28% and 35% of total variance from observation and reanalysis, respectively, and were roughly consistent with each other. The first and third EOFs for observation mainly represented interweekly, interseasonal and interannual variations and contained some summer intraseasonal fluctuations also. The second and fourth ones mainly represented some rather strong summer intraseasonal fluctuations for a paticular year and contained interweekly, interseasonal and interannual variations also. Although there is still room for improvement, the ECMWF reanalysis is the best available dataset with global coverage and daily variability.

应用CGDPA评估中国大陆地区IMERG的降水估计精度

应用国家气象信息中心基于地面雨量计的逐日降水分析产品CGDPA (China Gauge-Based Daily Precipitation Analysis)为基准数据,采用定量和分类评分指标分析了2014年9月—2015年8月中国大陆地区全球降水观测GPM (Global Precipitation M easurement)多星集成降水产品IM ERG (Integrated M ulti-satellite Retrievals for GPM)的精度。结果表明:1) IMERG日平均降水量能够较好地反映我国降水量的空间分布特点(局部地区偏低),季节平均降水强度的空间分布与CGDPA具有较好的一致性(尤其中东部和南部)。2) IMERG与CGDPA日平均降水量的相关系数在大部分地区介于0. 2～0. 5,只有少数地区超过0. 6,局部地区甚至出现负相关。3) IM ERG在中国大陆东部的降水估计精度明显优于西部,但东部绝大部分地区IMERG日降水量比CGDPA偏低10%～30%,甚至更低。4) IMERG与CGDPA降水概率密度相差最大的是微量降雨,其次是中雨,其他降水强度则相差很小。5)各季节IMERG探测降水的准确率POD都比较低,空报率FAR则比较高,临界成功指数CSI也比较低。

中国大陆TMPA降水产品气候态的评估

利用逐日全国降水分析产品,对2012年12月下旬发布的最新版本的TRMM等多源卫星降水估算产品(TMPA)进行评估,评估时间从2008年9月到2012年8月。从评估结果来看,研究产品3B42V7产品与CPAP产品具有高的相关性,两者的相关系数达到了0.94,相对误差在—0.11%左右,标准偏差约为0.53 mm·d^(-1)。实时产品3B42RT产品与CPAP产品的相关性相对较差,相关系数为0.75,相对误差也上升到了39.3%,标准偏差为1.25 mm·d^(-1)。3B42RT产品在我国西部高估了降水,全年的相对误差为116.60%(春夏秋冬四季分别为104.52%、105.73%、117.64%和326.60%);3B42V7产品的相对误差仅为0.82%(春夏秋冬四季分别为2.25%、1.24%、—5.27%和—24.64%)。