Recent extraordinary cool and hot summers in East Asia simulated by an ensemble climate experiment
Recent extraordinary cool and hot summers in East Asia simulated by an ensemble climate experiment
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集合气候实验模拟了东亚最近异常凉爽和炎热的夏季
DOI：
10.2151/jmsj1965.76.4_597
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发表时间：
1998
影响因子：
3.1
通讯作者：
N. Sato
中科院分区：
文献类型：
--
作者：
R. Kawamura;M. Sugi;T. Kayahara;N. Sato
使用日本气象厅全球模型的 T42 AGCM 版本进行了三个 40 年平行模拟的集合，以回答为什么东亚，特别是日本和韩国近年来从 1970 年代末到 90 年代初往往非常频繁地出现异常凉爽炎热的夏季的问题。 1955 年 1 月至 1994 年 12 月期间的三次独立长期积分是由全球范围内观察到的相同海温边界条件所迫使的。我们的 AGCM 模拟采用规定的观测到的海温，成功地再现了温带环流异常，这种异常导致了日本附近夏季平均气温的年代际变化的十年尺度振幅调制。 20世纪80年代初至90年代初，南海与菲律宾东部热带西太平洋夏季海温异常东西梯度年际变化明显较大，并伴有菲律宾周边积云对流异常，其相位与模式模拟的日本附近对流层低层位势高度变化吻合较好。对流加热异常通过PJ遥相关图激发的动态过程对东亚地区夏季对流层低层环流异常产生重大影响(Nitta，1987)。来自热带的异常海温强迫是造成 20 世纪 70 年代末至 90 年代初日本和韩国频繁出现极端凉爽和炎热夏季的主要原因。菲律宾各地出现较强的东西向海温异常梯度主要是由于南亚夏季风弱（强）与ENSO暖（冷）事件的显着耦合所致。 1970年代末至90年代初发生的温暖事件在季节演变方面与Rasmusson和Carpenter（1982）所例证的典型厄尔尼诺事件模型明显不同。预计从前一个冬季到夏季异常持续的 ENSO 信号以及相关的南亚夏季季风活动都会强烈调节北半球夏季菲律宾附近东西向海温梯度的形成。
An ensemble of three 40-year parallel simulations was performed using a T42 AGCM version of the Japan Meteorological Agency global model to answer the question why extraordinary cool anti hot summers in East Asia, especially Japan and Korea, tend to occur very frequently in recent years from the late 1970s to the early 1990s. Three independent long-term integrations from January 1955 to December 1994 were forced by the same SST boundary condition observed on the global scale. Our AGCM simulations employing prescribed observed SSTs were successful in reproducing extratropical circulation anomalies that bring about the decadal-scale amplitude modulation of interannual variations of summer mean temperatures in the vicinity of Japan. During the period from the beginning of 1980s to the early 1990s, the interannual variability of the east-west gradient of summertime SST anomalies between the South China Sea and the tropical western Pacific east of the Philippines became appreciably large, was accompanied by anomalous cumulus convection around the Philippines, and its phases coincided quite well with those of model-simulated lower-tropospheric geopotential height variations near Japan. The anomalous convective heating substantially affected summertime lower tropospheric circulation anomalies in East Asia through the dynamic process of the excitation of PJ teleconnection pattern (Nitta, 1987). The anomalous SST forcing from the tropics is crucially responsible for the frequent occurrence of extreme cool and hot summers in Japan and Korea from the late 1970s to the early 1990s. The presence of strong east-west gradient of SST anomalies across the Philippines is primarily attributed to the significant coupling of weak (strong) South Asian summer monsoon and the warm (cold) episode of ENSO. The warm episodes that occurred during the period from the late 1970s to the early 1990s are appreciably different from a typical model of El Nino event exemplified by Rasmusson and Carpenter (1982) in terms of seasonal evolution. It is anticipated that both unusually persistent ENSO signals from the preceding winter until summer and the associated South Asian summer monsoon activity strongly regulate the formation of the east-west SST gradient near the Philippines in boreal summer.