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

利用中国提供的降水资料和SSM/I资料（19.35 GHz和85.5 GHZ，采用Liu和咖喱（1992）的算法），分析了东亚地区暖季异常天气条件下的水循环。主要研究结果如下：1. 1991年梅雨期淮河流域发生了特大洪水。特别是在7月上旬最大洪水发生时，活跃的梅雨锋位置保持不变。有趣的是，持续锋区由降雨量超过50 mm/天的广泛的“强降雨区”（其宽度约为200 km）组成。此外，不仅南部边界的大量水汽入流，北部边界的少量水汽出流也导致了这一时期极大的“锋尺度”水汽辐合和集中. 1993年夏季（极凉夏季 ...更多信息 r在日本），SSM/I资料估计的总降水量是非常大的，即使在8月持续的Baiu锋。此外，台风的贡献也很大。前一种情况的出现主要是由于以下大气条件造成的：（1）白乌锋低层温度梯度距平较大;（2）白乌锋位于南移的高空慢速槽的南部边缘附近，与60 N以北的极锋区明显分离。由SSM/I资料得到的降水和水汽信息对1988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的影响。1994年夏季日本中东部的干旱在秋季有所缓和。1995年夏季的干旱在秋季更为严重。异常条件的季节性变化在年际间是相当复杂的，是今后需要解决的问题。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