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近52年淮河流域的梅雨
Meiyu of the Huaihe Basin in Recent 52 Years
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摘要: 气候资料表明梅雨期不仅出现于长江中下游区，也会出现于淮河流域中南部。为此应用淮河流域分布均匀的5站日雨量资料结合西太平洋副热带高压脊线的季节进程划分出近52年（1953—2004年）淮河流域梅雨期。该处梅雨期和长江中下游沿江区一样十分显著，其平均入梅及出梅期分别比长江中下游沿江区推迟5 d和7 d，其梅雨量年际丰枯是形成该地区汛期旱涝的主要因素。江淮流域梅雨在多数年趋势一致，但有1/4年份淮河梅雨与长江中下游沿江区距平符号相反。1979年附近淮河梅雨出现突变，即由此前的梅雨偏少、出梅偏早趋势突变为有较大振幅的2.2~2.3年短波振荡，梅雨量大及出梅迟年明显增多。在1979年前后也因此出现了两段梅雨异常期：1958—1966年淮河枯梅期和1979—1987年淮河丰梅期。进一步发现7月东亚中纬沿海槽的伸缩对淮河梅雨量、出梅的影响比鄂霍次克海高压及乌拉尔高压更显著。Abstract: Climate data show that the Meiyu period exists not only in the mid lower Yangtze Basin (MLYB), but also prevails in central southern part of the Huaihe Basin. Then using the daily rainfall data of 5 stations evenly distributed in the latter region with the consideration of seasonally moving process of the pentad ridge's line of west Pacific high, Meiyu periods of the Huaihe Basin (HB) in recent 52 years (1953—2004) are delimited. They are very significant as the same exist in the MLYB, their average onset and ending dates are June 25 and July 21, later than the average Meiyu periods of MLYB by 5 days and 7 days respectively. However the inter annual changes of the HB Meiyu are large, the range of onset days reaches 41 days and the amplitude of ending dates approaches 2.5 months in the recent 52 years. In 8 years (occupying 15.4%), the HB Meiyu are absent, but plenty numbers of the HB Meiyu(exceeding the average value of more than 20%)also occur in 18 years (occupying 34.6%). As early Meiyu period (EMP) has appeared in MLYB, it also occurs in Huaihe Basin during 5 years, they arethe certain kind of Meiyu periods appearing abnormally early in May, however after they end, the summer monsoon rain belts of east China (SMRBEC) retreat to south un til the beginning of the main Meiyu period in June/July. The inter annual change of the HB Meiyu plays a key role which causes the summer trend of whether drought or flood in these regions. Most anomalies of the Meiyu amount both in the Huaihe Basin and in the MLYB have the same sign; however the opposite signs to each other have appeared in 1/4 of the cases. The inter annual changes of the HB Meiyu have enhanced since late 1970s, such abrupt change of the HB Meiyu means the weak condition with earlier ending dates in former stage abruptly transforms into a new stage around 1979, having the following characteristics:higher amount of HB Meiyu with later ending dates accompanied by strong short waves of 2.2—2.3 years. The average HB Meiyu amount of the latter 26 years since 1979 is higher than the former 26 years by nearly 30%, such contrast is especially significant between the following 2 stages:the anomalous weak HB Meiyu in 1958—1966 and the anomalous plenty HB Meiyu in 1979—1987. From the point of atmospheric circulation, it is found that the July coastal trough (at 500 hPa level) in the mid latitudes of East Asia (JCTEA) tends to move southward more frequently since 1979, then the west Pacific high and its northern SMRBEC retreat accompanied by the delay of HB Meiyu and the higher amounts. Such JCTEA has bigger influence on the HB Meiyu and its ending dates than those of either Okhotsk high or Ural high. First analysis shows that the abrupt change since 1979 may be closely associated with many effects of anthropogenic activities in different scales, such as the enhanced global warming, the increasing smoke and dusts over central eastern China due to the acceleration of industrialization etc.
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图 1 1951—2000年我国东部(110°~120°E)平均旬降水量的经向-时间变化[5](单位:mm)
Fig. 1 Meridian-time variations of the 10 d average precipitation in east China(110°—120°E)during 1951—2000(unit:mm)
图 2 淮河流域(图中白色区)及其5个雨量站在我国东部的位置
Fig. 2 Locations of the Huaihe Basin(white area)with its 5 rainfall stations in east China
图 3 1953—2002年淮河干流区5站(东台、淮阴、蚌埠、阜阳和信阳)夏季逐日总雨量平均演变和雨日出现天数的逐日演变
Fig. 3 1953—2002 summer daily variations of rainy indices of the Huaihe Basin daily rainfall for the sum of 5 stations and number of rainy days for the whole of 5 stations
图 4 1953—2003年淮河梅雨量(a), 淮河干流区5站夏季总雨量(b), 长江中下游梅雨量(c)和长江中下游沿江区5站夏季总雨量(d)分别与全国268站夏季(总)雨量的相关分布图
(实心圆代表淮河5站, 实心矩形框代表长江中下游5站)
Fig. 4 Correlation distributions for summer rainfall of 268 stations in China with Huaihe Basin Meiyu amounts(a), with summer rainfall of the whole 5 basic stations(SRW5BS)in the Huaihe Basin(b), with the mid-lower Yangtze Basin(MLYB)Meiyu amounts(c)and with another SRW5BS along the MLYB(d)in 1953—2003 respectively
图 5 淮河梅雨量、长江中下游梅雨量与全国268站夏季(总)雨量的高相关区(信度达到95%)分布对比(a)以及淮河干流区5站夏季总雨量, 长江中下游沿江5站夏季总雨量与全国268站夏季(总)雨量的高相关区分布对比(b)(实心圆代表淮河5站, 三角形代表长江中下游5站)
Fig. 5 Comparison of high correlation reg ions(exceeding 95% confidence limit)for summer rainfall of 268 station in China(SR268)with the Huaihe Basin Meiyu amounts and the MLYB Meiyu amounts respectively(a), comparsion also for high correlation regions of SR268 with SRW5BS in the Huaihe Basin and with another SRW5BS along MLYB respectively(b)
图 6 淮河入梅期(a), 出梅期(b)及梅雨量(c)的逐年演变及每10年滑动梅雨量标准差演变曲线(d)
Fig. 6 Annual variation of the Meiyu onset day(a), ending date(b), the Meiyu amounts(c)in the Huaihe Basin and the curve of standard deviation of the 10-year running average Huaihe Basin Meiyu amounts(d)
图 7 淮河入梅期(a), 出梅期(b)和梅雨量(c)的每10年滑动值标准差的M-K统计量曲线
(其中直线表示信度为99. 9%的临界线)
Fig. 7 The M-K statistical curves of the standard deviations of the 10-year running average of Meiyu onset day(a), ending date(b), the Meiyu amounts(c)
(the horizontal line denotes the degree of confidence at 99. 9%)
图 8 淮河梅雨两异常时期的全国7月雨量平均距平分布(单位:mm)(a)1958—1966年,(b)1979—1987年
Fig. 8 Distributions of July rainfall anomalies in China during 2 abnormal stages of the Huaihe Basin Meiyu respectively(unit:mm)(a)1958—1966,(b)1979—1987
图 9 7月北半球500 hPa平均高度场(单位:dagpm)及其与淮河梅雨量的相关分布(a)1958—1966年平均高度图, (b)1979—1987年平均高度图,(c)近52年淮河梅雨量与当年7月500 hPa高度场的显著高相关区分布
Fig. 9 500 hPa height fields(unit:dagpm)of the Northern Hemisphere averaged in July during 1958—1966(a), 1979—1987(b), distribution of high correlation region between the Huaihe Basin Meiyu amounts and 500 hPa height fields in July(c)
表 1 淮河干流区集中雨期标准
Table 1 Standards for defining the concentrated rainy periods of the main stream region in the Huaihe Basin
表 2 近52年淮河和长江中下游两区梅雨量强度的3等级出现率
Table 2 Percentage of the occurrences for 3 classes of the Meiyu amounts in the Huaihe Basin and the mid-lower Yangtze Basin(MLYB)
表 3 近52年10个淮河流域最大夏雨年、淮河5站最大夏雨年和淮河最大梅雨量年的对比
Table 3 Comparison of ordinal numbers for 10 maximal years of summer rainfall for the whole Huaihe Basin, 10 maximal years of summer rainfall of 5 basic stations and 10 maximal Huaihe Basin Meiyu years
表 4 两区梅雨量距平百分数对比显著年(单位:%)
Table 4 Significantly contrasting years for the Meiyu anomaly percentages in 2 regions(unit:%)
表 5 1953—2004年淮河梅雨演变的显著周期(单位:a)
Table 5 Significant periods of the Huaihe Basin Meiyu during 1953—2004(unit:a)
表 6 两异常时段淮河梅雨量有关要素的对比
Table 6 Comparison of associated elements of the Huaihe Basin Meiyu during 2 anomalos stages
表 7 1953—2004年淮河梅雨量有关要素的相关系数
Table 7 Correlation coefficients of assoiated elements of the Huaihe Basin Meiyu during 1953—2004
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