No.42 2007 pp.159 166 The Relationship between Southeast Asian Summer Monsoon and Upper Atmospheric Field over Eurasia Takeshi MORI and Shuji YAMAKAWA Received September 30, 2006 Using Southeast Asian Summer Monsoon index defined by convection activity in and around the Philippine Sea from 1982 to 2005, the relationship between Southeast Asian Summer monsoon and the upper troposphere to the lower stratosphere over Asia was analyzed. In the strong monsoon years, the tropical easterly jet in the upper layer tends to become strong, and an anomaly wave track which is negative in South Asia and positive in East Asia tends to appear. The statistically significant area of easterly anomaly wind caused by its anomaly wave track reaches the easterly wind area in the stratosphere, to the south of positive geopotential height anomaly over East Asia. Besides, in the nearby upper troposphere to the tropopause, the northward divergence over the Mediterranean region of the subtropical high pressure zone affects activities of the polar jet stream and the Eurasian polar fronts, therefore a positive precipitation anomaly west of Lake Baykal may influence vorticity anomaly over East Asia. Keywords: Southeast Asian Summer Monsoon, the upper troposphere, the lower stratosphere, East Asia, geopotential height anomaly, vorticity anomaly 1 1980 1997 1997 Zhang et al. 2002 2 2 Nitta 1987 1987 20 N PJ 2004 PJ PJEnomoto et al. 2003 2005 2005 88 Niwano : 156 8550 3 3 25 40 : 156 8550 3 3 25 40 Graduate School of Integrated Basic Sciences, Nihon University: 3 25 40 Sakurajosui Setagaya ku, Tokyo, 156 8550 Japan Department of Geosystem Sciences, College of Humanities and Sciences, Nihon University: 3 25 40 Sakurajosui Setagaya ku, Tokyo, 156 8550 Japan 159 115
and Takahashi 1998 2 QBO Terao 1999 1999 2004 QBO QBO 2 NCEP/NCAR reanalysis Data P OLR 1982 2005 6 9 Wang and Fan 1999 convection index2 10 20 N 115 115 140 E 6 9 OLR 1 convection index2 0.65 0.65 Positive years0.65 Negative years Positive Negative years Negative years years OLR 2 Positive years 1984 1985 1994 1999 2000 2001 2005 1985 1994 1999 2000 2001 2005 1994 1999 2000 2001 2005 1999 2000 2001 2005 2001 2005 2005 Negative years1982 1983 1987 1993 1996 1997 1998 1983 1987 1993 1996 1997 1998 1987 1993 1996 1997 1998 1993 1996 1997 1998 1996 1997 1998 1997 1998 1998 Positive years, Negative years 6 9 95 OLR 3 2 1 0-1 -2-3 1982,Takaya and Nakamura 2001 Wave Activity Flux 3 1 convection index2 1984 1986 1988 1990 convection index2 2 OLR 1 Positive years Negative years 3 Positive years 6 9 Positive years 30 40 N 1000 15hPa 1992 1994 1996 1998 2000 2002 2004 116 160
3 Positive years 6 9 5 Positive years 6 9 10 N 4 Negative years 6 9 6 Positive years 6 9 30 N 4 Negative years 6 9 Positive years 3 30 N 750 140hPa Negative years Positive years Positive years 2 Positive years 5 Posi- tive years 6 9 10 N 6 Positive years 6 9 30 N 20 E 161 117
10 N 1000 1000 500hPa 350 85hPa 25 35 N 120 E 800 40hPa 3 7 Positive years 6 9 9 200hPa Positive years 200hPa 8 Positive years 6 9 OLR 9 Positive years 6 9 10 Positive years 6 9 300hPa P Negative years 200hPa OLR P 11 Positive years 6 9 200hPa 50 500hPa 25 N 8 Positive years 6 9 OLR 7 Positive years 6 9 200hPa 9 Positive years 6 9 118 162
70 300 hpa 12 Positive years 6 9 850 hpa 600 1000 hpa Negative years Positive years 13 Positive years 6 9 120 E Positive years 100 120 E 0 20 N 20 30 N 25hPa 200hPa 10 Positive years 6 9 300hPa P 12 Positive years 6 9 850hPa 10m/s 11 Positive years 6 9 200hPa 30m/s 13 Positive years 6 9 120 E 163 119
Positive years 20 30 N Negative years Posi- tive years Positive years20 30 N 60hPa Negative years Positive years 95 115 E 200hPa Positive years Negative years Positive years Negative years 2004 PJ Positive years PJ Positive years Negative years 14 Positive years 6 9 100hPa Wave Activity Flux 2 m 2 /s 2 10 5 15 Positive years 6 9 500hPa Wave Activity Flux 1 m 2 /s 2 10 5 PJ 4 Wave Activity Flux Takaya and Nakamura 2001 Wave Activity Flux 14 Positive years 6 9 100hPa 120 164
Wave Activity Flux 9 1 70 150 300 500hPa 150 300 500hPa 300 500hPa 500hPa 14 PJ 15 Positive years 6 9 500hPa Wave Activity Flux 4 Positive years, Negative years Positive years Negative years 2004 Positive Negative years Negative years years 200hPa Negative years Positive years Positive years Positive years Takaya and Nakamura 2001 Wave Wave Activity FluxPositive years 5 Wave Activity Flux z Positive years 165 121
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