East Asian Monsoon Monitoring Bulletin
（No. 26）
October 16, 2014
The SCSSM Ended in the 6th Pentad of September
Abstract: The latest monitoring showed that the South China Sea Summer Monsoon (SCSSM) ended in the 6th pentad of September in 2014, with the same date as normal. The intensity of the SCSSM was a bit weaker than normal. The intensity of the East Asian subtropical summer monsoon (June-August) was also slightly weaker than normal. During the rainy season of 2014, total precipitation over eastern China showed “more in South and less in North” feature.
The latest monitoring in the Beijing Climate Center (BCC) showed that during the 6th pentad of September in 2014, the westerly wind at 850 hPa over the monitoring region for SCS weakened greatly , and the θse (pseudo-equivalent potential temperature) dropped to below threshold (340°K, Fig.1). During the 6th pentad of September and 1st pentad of October, the westerly wind changed into easterly wind and the θse index was stably below 340K. Based on the above mentioned, the SCS summer monsoon ended in the 6th pentad of September, with the same date as normal.
Fig.1 Pentad variations of zonal wind (unit: m/s) and pseudo-equivalent potential temperature
(unit: K) over the monitoring region (10º-20ºN, 110º-120ºE）
The SCS summer monsoon intensity index was -0.29 in 2014, which revealed that the SCS summer monsoon was a bit weaker than normal (Fig. 2). The pentad evolution of the intensity index indicated that the SCS summer monsoon was stronger from 2nd pentad of June to 3rd pentad of August, while extremely weaker during 4th pentad of August and 1st pentad of September, then became slightly strong from 3rd to 5th pentad of September.
Fig.2 Variations of the SCS summer monsoon intensity from 1951 to 2014
During the summer (JJA) of 2014, the intensity of the East Asia subtropical Summer Monsoon (Zhang Q., 2003，Fig.3) was slightly weaker than normal. For the rainy season of 2014, the total precipitation over eastern China showed “more in South and less in South ” feature, namely more than normal in southern China, while less than normal in the middle and lower reaches of the Yangtze River and North China (Table 1).
Fig.3 Variations of the East Asian subtropical summer monsoon intensity from 1951 to 2014
Table 1 Summary of China Rainy Seasons in 2014
Region / Start date / End date(mon/day) / Period
（day） / Total precipitation(mm) and anomaly percentage（%）
Pre-summer rainy period in South China / 30 March / 7 July / 99 / 831.9
(+13.7%）
Meiyu
（ middle and lower reaches of the Yangtze River） / 16 June / 20 July / 34 / 318.6
(-7.2%）
Rainy season
in North China / — / — / — / No significant PCP
Rainy season in southwestern China / 7 June / 8 October / 123 / 754.6(-11.1%)
Autumn rain
in western China / 9 September / Not yet over / — / 156
Editor: Wang Pengling Technical assistant: Hao Xin Chief Editor: Liu Yanju Zhou Bing
BCC’s East Asian Monsoon monitoring website: http://bcc.cma.gov.cn/influ/monsoon.php
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