Large-scale water cycle around the Baiu frontal zone associated with abnormal weather conditions

为了了解东亚地区暖季异常天气条件下的水循环特征，利用中国提供的降水资料和SSM/I资料(19.35 GHz和85.5 GHz，用Liu和Curry(1992)的算法)进行了分析。主要研究结果如下：1.研究结果。1991年梅雨期，淮河流域中国段发生特大洪水。特别是在7月初最大洪水发生的时候，活跃的梅雨锋仍然存在，位置没有变化。有趣的是，持续锋区由降雨量超过50毫米/天的大范围“强降雨区”(经向宽度约200公里)组成。此外，不仅南部边界的大量水汽流入，而且北部的极小水汽流出导致了整个期间极大的锋面尺度水汽辐合及其集中。1993年夏天(酷凉的Summe…即使在8月，SSM/I资料估计的总降雨量也很大，这与持续的白云锋面有关。此外，台风的贡献也很大。前一个事实似乎主要是由于以下大气条件造成的：1)横跨白云锋面的低层温度梯度异常大得多；2)白云锋面位于南移的缓慢移动的高层槽南缘附近，与北纬60 N以北的极锋区明显分开。从SSM/I资料中提取的降水和水汽信息对1988.4年7月中旬前后观测到的中尺度降水系统的数值预报有很大影响。1994年夏季日本中部和东部的干旱在秋季有所缓解。然而，1995年夏季的干旱在秋季变得更加严重。异常情况的季节变化年复一年将是相当复杂的，是未来一个值得注意的问题。较少

As a step for understanding the water cycle in East Asia associcated with the abnormal weather conditions in warm season, analyzes were investigated, by using the precipitation data provided by China and those derived from SSM/I date (19.35 GHz and 85.5 GHZ.the algorithm by Liu and Curry (1992) were used). The main results are as follows.1. In the Meiyu season of 1991 the extreme flood occurred in the Huaihe River Basin in China. Especially in early July when the biggest flood occurred, the active Meiyu front persisted without change in its location. Interestingly, the persistent frontal zone consisted of the wide-spread "heavy rainfall area" (its meridional width of about 200 km) with rainfall amount more than 50 mm/day. Furthermore, not only the huge moisture inflow from the southern boundary but also very small outflow from the north resulted in the extremely large "frontal-scale" moisture convergence and its concentration throughout this period.2. In 1993 summer (extreme cool summe … More r in Japan), the total rainfall amount estimated by the SSM/I data was very large associated with the persistent Baiu front even in August. Furthermore, the contribution of the Typhoon was also large. The former fact seems to be largely due to the following atmospheric conditions : 1) the anomaly of the low-level temperature gradient across the Baiu front was much larger, 2) the Baiu front was located near the southern edge of the southward-shifted slow-moving upper-level trough, with its distinct separation from the polar frontal zone to the north of 60 N.3. The rainfall and the moisture informations derived from the SSM/I data showed a large impact to the numerical prediction of the meso-scale rainfall systems observed around the middle of July 1988.4. The drought in the middle and the eastern part of Japan in 1994 summer was moderated in autumn. However, the drought in 1995 summer became more serious in autumn. The seasonal change of the anomalous conditions would be rather complicated year to year and is a reamaining problem in the future. Less