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长江流域水分收支以及再分析资料可用性分析

期刊名称：气象学报，2007, 65(3):416-427
时间：0
分类：P468[天文地球—大气科学及气象学]
作者机构：[1]国家气象中心,北京100081, [2]中国科学院大气物理研究所,LASG,北京100029, [3]中国科学院研究生院,北京100039
相关基金：资助课题：国家气象局气候变化专项（CCSF2007-9）;国家自然科学基金项目（40135020,90502003,40221503,40475027）;国家重点基础研究发展规划项目（2004CB418307）.
相关项目：东亚和西太平洋区域气候变异机理和预测理论

关键词：长江流域, 水分收支, 再分析资料, Yangtze River basin, Water budget, Evaluation.

中文摘要：

首先利用实测资料定量计算了长江流域水分收支的各分量,包括降水、径流、蒸发、水汽辐合等,分析其季节循环、年际变化以及线性趋势变化。结果表明,多年平均该流域是水汽汇区,主要来自平均流输送造成的水汽辐合,而与天气过程密切相关的瞬变波则主要造成流域的水汽辐散。蒸发所占比例接近于径流,对流域水分循环十分重要。大部分要素的季节变化和年际变化都很大,只有蒸发和大气含水量的年际变化较小。降水和平均流输送造成的水汽辐合一般在6月达到年内最大,12月达到年内最小,而径流和大气含水量则一般滞后1个月于7月达到年内最大,1月降为年内最小。1958-1983年,夏半年降水略微增加,冬半年略微减少,各月实测径流为弱的增长趋势,但均不显著,年平均蒸发亦无显著的趋势变化。然后将实测资料同ECMWF及NCEP/NCAR再分析资料作进一步对比分析,以检验两套再分析资料对长江流域水分循环的描述能力。在量值上,NCEP/NCAR再分析资料中的降水、蒸发、径流均比实测偏大很多,大气含水量及由平均流输送所造成的水汽辐合则偏小很多;ECMWF再分析资料中的降水量、径流量基本上与实测接近,蒸发量偏大,大气含水量及由平均流输送所造成的水汽辐合偏小,但比NCEP/NCAR再分析资料要接近实测。另外,该两套再分析资料均可以较好地描述长江流域水分收支的季节循环和年际变化,而且同样是ECMWF再分析资料与实测资料的一致性更好。但是两套再分析资料在1958-1983年均存在十分夸张的线性趋势变化,尤其是ECMWF再分析资料。

英文摘要：

The surface and atmospheric water budgets for the Yangtze River basin were examined using the available observations, ECMWF and NCEP/NCAR reanalysis data during 1958 to 1983 and 1990 to 2000 respectively, and the water budget components in this study include precipitation, runoff, evaporation, moisture convergence and so on. Based on the observations, the water budgets for the Yangtze River basin and their seasonal cycle, interannual variations, and linear tends were analyzed. On the average of long time, the river basin area is a moisture sink. It＇s interesting that the water vapor is transported to the basin area by the mean air flow instead of the transient eddies which are close associated with synoptic systems and always diverges moisture out of the river basin. On the surface, the evaporation is almost equal to the runoff, and plays a very important role in the water cycle of the river basin. Evident annual and interannual variabilities exist in most components of the atmospheric and surface water budgets, and only the interannual variations of evaporation and precipitable water are smaller. Precipitation and moisture convergence by the mean transport both peak in June and then decrease till December. But the maxima and minima of runoff and precipitable water occur in July and January, respectively, one month later than those of precipitation. During 1958 to 1983, precipitation slightly increased in summer half year and decreased in winter half year insignificantly, and insignificant increasing trends existed in the annual mean evaporation and stream flow. Furthermore, the contrast analyses of ECMWF and NCEP/NCAR reanalysis data were performed to evaluate their performances in describing the hydrological cycle in the Yangtze River basin. Firstly, the NCEP/ NCAR reanalysis data overestimate precipitation, runoff, and evaporation, while underestimate precipitable water and moisture convergence as compared with the observations. In the ECMWF reanalysis data, the precipitation and runoff are basically clos