초하우계의 지속적 항우일에 관한 연구 : 한국과 일본의 구주를 중심으로 = On the Persistent Rainy Day in the Early Summer Rainy Season over South Korea and Kyushu , Japan

다국어 초록 (Multilingual Abstract)

The purpose of this paper is to examine the definition and occurrence characteristics of the persistent rainy day in the early summer rainy season over South Korea and Kyushu, Japan. The results are as follows.
1) The wet spell of length k day is defined as k days when rainfall continues more than 1mm per day. We can make a frequency table(observed frequency) of the wet spell of each length at a station for a given period(in this paper, June and July, 1941∼1980). The probability of rainy day be P, and the probability of no rain day is 1-P(let's it be Q). If there is no persistence in daily rainfall, the occurrence probability of the wet spell of length k is P^kQ². If the total days are N(=61×40=2, 440), then the expected frequency(caculated frequency) of the wet spell of length k is NP^kQ² with the above hypothesis. Therefore, we can say that the persistent rainy day in the sense of the probability that the wet spell is longer than the first wet spell of which the observed frequency is higher than the calculated frequency on no persistence hypothesis(Table 1). By carefull examination of synoptic conditions of daily rainfall at some stations, we can define the persistent rainy day as the wet spell is longer than 3 days(* in Table 1). Expected number of days of the persistent rainy day is 7∼12 days in one rainy season(Fig. 4).
2) Contributions of the persistent rainy days to total precipitation of June and July are more than 50% at most stations(Fig. 3).
3) There is a high frequency of the persistent rainy day in the first and second ten days of June over Kyushu, and also in the third ten days of June and the first ten days of July over Korea and Kyushu(Fig. 5). In the second ten days of July the occurrence frequency of the persistent rainy day over Korea is different from that over Kyushu.
4) Total occurrence frequency of the persistent rainy day at each year(Fig. 6) corresponds to the activity of the early summer rainy seasons of East Asia; in years with many persistent rainy days the early summer rainy seasons are to be active.
5) The total occurrence frequency of the persistent rainy day appears to be ralated to the strength and northward displacement of the North-west Pacific Anticyclone and chatacteristics of the atmospheric circulation in middle-high latitudes. In a year with many persistent rainy days in June, the North-west Pacific Anticyclone was very strong and shifted northwardly, and cold air advection over the North-east Part of China from higher latitudes was strengthened(Fig. 7). In July the developments of the Okhotsk Anticyclone and the North-west Pacific Anticyclone were followed by a high frequency of the persistent rainy day(Fig. 8).