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1998年夏季我国东部降水与大气环流异常及其低频特征
Abnormality of Summertime Precipitation of Eastern China and General Circulation with LFO in 1998
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摘要: 东亚夏季风环流的异常对该地区降水异常有重要影响, 而低频降水又是季风活动的一个主要特征。研究揭示了1998年降水异常及其低频变化等观测事实，分析讨论了大尺度环流的4个异常特征。结果表明：1998年汛期长江流域出现二度梅，10~20 d低频振荡具有普遍性，而30~50 d的地域性较为明显；西太平洋副热带高压位置的异常、欧亚大陆中高纬度持续阻塞高压、高空西风带急流轴线活动异常及二次季风涌的出现及其相互配合是长江流域降水异常的主要影响系统。Abstract: Abnormality of summer monsoon circulation in East Asia has special impact on the precipitation in target area, and the low frequency precipitation is an important character of the monsoon. By use of the SCSMEX in situ observational precipitation data and NCEP/NCAR reanalysis data sets, the observed facts related to the abnormality of the precipitation and the related low frequency variability in 1998 are revealed, and the following results are obtained mainly. It is found that the second stage of Baiu come forth in Yangtze River area during the flood season in 1998, 10—20 d low frequency fluctuation exists universally, but 30—50 d one has a regional character. The abnormality of the precipitation in the area of Yangtze River is caused by the abnormity of the location of the west Pacific subtropical high, the abnormity of the persistence blocking high over mid latitude Eurasian land, the abnormity of upper air westerlies jet stream axis, and the second stage of monsoon surges and their interaction. The regional torrential rainfall periods include two stages, the first period is from June 12 to June 26, and the second period begins on July 17 till August 9. The division can pass the significance test for α=0.01. In 1998, the maximum entropy spectrum analysis of the summertime precipitation shows that the preferred period of more than 20 days is of only 4% of the stations during the analysis area(about 136 stations), and the preferred period of less than 10 days is of 31% of the stations, so the primary preferred period is 10—20 days near the East Asia monsoon active region. There are two high percentage areas of mean square error for 10—20 days low frequency oscillation in the target area, and two weeks fluctuation period is an important phenomenon in the flood year, so torrential rainfall cluster occurring time is a main phase of low frequency precipitation. Evidence suggests that the location of the west Pacific sub tropical high has two staggered northwards, and three times rapidly southward withdraw, whereas the location is a little southward in general. Morlet wave period analysis confirms that the sub tropical high ridge line has a low frequency oscillation character, and 10—20 days period occurs in May, and two kinds of LFO period appear from June to August. Meanwhile, the persistence blocking high over mid latitude Eurasian land is strong during 2 torrential rainfall stages, while the cold air can easily move southward, and mid high latitude circulation abnormality looks like i n 1954. Upper level westerly jet rapidly jumps northward near 50°N in early May, and one week late, the location of the jet axis withdraws southward. Since middle July, 200 hPa zonal wind axis has 5—8 latitude distance than normal years. At the same time, two times monsoon surges can be found, the θse and southerly have staggered intensities.
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图 1 1998年夏季长江流域和华南地区累积降水量分布(单位:mm)(a)5—8月,(b)7月
Fig. 1 Accumulated precipitation of Yangtze Reaches and South China in 1998 summertime(unit:mm)(a)May to August,(b)July
图 2 长江南部两个主要降水阶段分别与其前后非强降水阶段平均降水量差(单位:mm)及其t检验(阴影区为α≤0. 01)分布(a)6月12—26日,(b)7月17日—8月9日
Fig. 2 Anomaly of the main precipitation stage and its t-test(shaded region:α≤0. 01;unit:mm) (a)June 12—26,(b)July 17 to August 9
图 3 最大熵谱分析得到的优势周期(单位:d)
Fig. 3 Preponderant period in the precipitation on maximum entropy spectrum analysis(unit:d)
图 4 1998年夏季日降水低频振荡的均方差与未滤波均方差的百分比(单位:%)(a)10~20 d;(b)30~50 d
Fig. 4 Percentage of RSM of daily precipitation LFO to the unfiltered in 1998(unit:%)(a)10—20 d,(b)30—50 d
图 5 1998年5—8月副热带高压脊线(110°~130°E平均, 实线)和气候平均(虚线)位置及其距平(直方图)
Fig. 5 The mean location(110°—130°E)of subtropical high ridge line(solid line)and climatic value(dashed line)as well as the anomaly histogram
图 6 1998年5—8月副热带高压脊线位置小波分析
(小波系数×100)
Fig. 6 Morlet wave period of subtropical high ridge in 1998 summertime
(wave coefficient enlarged by 100 times)
图 7 1998年500 hPa高度场(等值线)及其距平(阴影区, 单位:gpm) (a)第1暴雨期,(b)第2暴雨期
Fig. 7 500 hPa height field(isolines)and its anomaly(shaded region, unit:gpm)in 1998(a)the 1st heavy rain stage,(b)the 2nd heavy rain stage
图 8 1998年5—8月110°~150°E平均的200 hPa纬向风时间-经向剖面图(单位:m·s-1)
Fig. 8 Time-meridian section of 200 hPa mean zonal wind(110°—130°E)in 1998 summertime(unit:m·s-1)
图 9 1998年5—8月105°~135°E 200 hPa平均纬向风随纬度变化
(单位:m·s-1; 其中细实线为1998年7月, 点线为气候平均, 长断线和粗实线分别为第1, 2暴雨期)
Fig. 9 200 hPa mean max westerlies variation near 40°N(105°—135°E)with the latitude
(unit:m·s-1; thin solid line denotes July 1998, dotted line denotes climatic mean, long dotted line denotes the 1st heavy rain stage, thick solid line denotes the 2nd heavy rain stage)
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[1] Krishnamurti T N, Subrahmanyan D.The 30~50 day mode at 850 mb during MONEX.J Atmos Sci, 1982, 39:2080-2095. https://www.researchgate.net/publication/234335597_The_30-50_day_mode_at_850_mb_during_MONEX [2] Lau K M, Yang G J, Shen S H, Seasonal and intraseasonal climatology of monsoon rainfall over East Asia.Mon Wea Rev, 1988:116, 18-37 doi: 10.1175/1520-0493(1988)116<0018:SAICOS>2.0.CO;2 [3] 陈隆勋. 夏季东亚季风系统中二个半球环流的相互作用∥东亚夏季风学术会议文集. 昆明:云南人民出版社, 1982:204-217. [4] 缪锦海, 刘家铭.东亚夏季风降水中3060天低频振荡.大气科学, 1991, 15(5):65-71. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK199105007.htm [5] 何金海, 陈丽臻.南北半球环流的准40天振荡与夏季风降水预报的可能途径.低纬高原天气, 1988, 1:38-49. [6] 陈隆勋, 朱乾根, 罗会邦, 等.东亚季风.北京:气象出版社, 1991:102-161. [7] 丁一汇.1991年江淮流域持续性特大暴雨研究.北京:气象出版社, 1993:47-68. [8] 陶诗言, 徐予红. 东亚季风的年际变化与长江淮河流域的夏季降水. 海峡两岸天气与气候学术研讨会论文集, 台北, 1994:1. [9] 陶诗言, 朱文妹, 赵卫.论梅雨的年际变率.大气科学, 1988, 12(特刊):13-21. [10] 潘琦, 王作台.东亚夏季风年际变化:江淮及台湾地区观点之探讨.大气科学(台湾), 1996, 24(2):89-122. [11] Lau K M, Yang G J, Shen S H.Seasonal and intraseasonal climatology of summer monsoon rainfalls over East Asia.Mon Wea Rev, 1988, 116:18-37. doi: 10.1175/1520-0493(1988)116<0018:SAICOS>2.0.CO;2 [12] 孙照渤, 李云康, 章基嘉.夏半年青藏高原及附近地区3060天振荡的分布特征.南京气象学院学报, 1991, 14(4):497-502. http://www.cnki.com.cn/Article/CJFDTOTAL-NJQX199104000.htm [13] 丁一汇.高等天气学(第二版).北京:气象出版社, 2005:435-437. [14] 陆尔, 丁一汇, 李月洪.1991年江淮特大暴雨的位涡分析与冷空气活动.应用气象学报, 1994, 5(3):266-274. http://qikan.camscma.cn/jams/ch/reader/view_abstract.aspx?file_no=19940349&flag=1 [15] 毕慕莹, 丁一汇.1980年华北干旱时期东亚阻塞形势的位涡分析.应用气象学报, 1992, 3(2):145-156. http://qikan.camscma.cn/jams/ch/reader/view_abstract.aspx?file_no=19920228&flag=1 [16] 陈汉耀.1954年长江淮河流域洪水时期的环流特征.气象学报, 1957, 28:1-12. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB195701000.htm [17] Suda K, Asakura T.A study on the unusual "Baiu" season in 1954 by means of Northern Hemisphere upper sir mean charts.J Meteor Soc Japan, 1955, 33(6):1-12. [18] 涂长望, 黄士松.中国夏季风之进退.气象学报, 1944, 18:81-92. [19] Tao S Y, Chen L X.A Review of Recent Research on the Summer Monsoon China∥Chang C P, Krishnamurti T N.Monsoon Meteorology.Britain:Oxford University Press, 1987:60-92. [20] 陆尔, 丁一汇.1991年江淮持续性特大暴雨的夏季风活动分析.应用气象学报, 1997, 8(3):316-324. http://qikan.camscma.cn/jams/ch/reader/view_abstract.aspx?file_no=19970345&flag=1 [21] 丁一汇, 薛纪善, 王守荣, 等. 1998年亚洲季风活动与中国的暴雨/洪涝∥丁一汇, 李崇银. 南海季风爆发和演变及其与海洋的相互作用. 北京:气象出版社, 1999:1-4. -
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