EAST ASIAN SUMMER MONSOON AND THE RAINFALL IN EAST CHINA - Advances in Geosciences - page 41

EAST ASIAN SUMMER MONSOON
AND THE RAINFALL IN EAST CHINA

LU XINYAN ∗ , † , ‡ , ZHANG XIUZHI § and CHEN JINNIAN ∗
∗ Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
‡ [e-mail]
† Graduate School of the Chinese Academy of Sciences,
Beijing 100049, China
§ Beijing Climate Center, Beijing 100081, China

Using daily rainfall measurements from 740 stations across China and
European Center for Medium-Range Weather Forecasts (ECMWF) upper
air reanalysis daily data (1958-2001), we give out climatically characters of
East Asian Summer Monsoon's (EASM) movement with the definition of the
EASM's front, finding out that the transfer of the rain belt over East China
is consistent with the advance and retreat of the EASM. By the empirical
orthogonal function (EOF) analysis of the gridded EASM's index (average for
the 28th-45th pentad) from 1958 to 2001 in the area (105 ◦ E-150 ◦ E, 15 ◦ N-
55 ◦ N), it is founded that, the second mode of the EOF analysis exhibits
interdecadal variations and indicate that the movement of EASM has three
interdecadal abrupt changes in 1965, 1980, and 1994, respectively. Therefore,
the three interdecadal abrupt changes bring the different processes of the
EASM's movement and lead to the obvious change of the spatial distribution
pattern of summer rainfall in East China directly, especially prior to 1965,
the rainfall in the mid-lower reaches of the Yangtze River is much less than
normal, while the precipitation is much more in South China, North China,
and Northeast China but decreasing continuously since 1965. However, the
rainfall in the mid-lower Yangtze Valley increases continually from 1980,
especially from 1994 the rainfall in South China and the Yangtze Valley
increases rapidly while the precipitation over North China was much less than
normal. Therefore, East China underwent from the pattern of south-drought
and northern-waterlog before 1979 to south-waterlog and north-drought.

1. Introduction

China is in a typical monsoon zone and the East Asian Summer Monsoon
(EASM) controls the distribution of most rainfall over China from June to

‡ Corresponding author.

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