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广东2月“冷干”和“暖干”年代际特征对比及其与海温异常的联系
胡蓓蓓1, 胡娅敏2
1.中国人民解放军92682部队,广东 湛江 524001;2.广东省气候中心,广东 广州 510641
摘要:
根据1961—2019年广东86个站点的降水和气温以及大气环流和海温资料,采用统计分析方法,研究广东2月降水和气温的时空分布特征及其相应的大气环流与海温特征。结果表明:近59年广东2月有两个年代际降水偏少时段,但对应的气温特征显著不同,分别是1961—1981年“冷干”和1999—2019年“暖干”,其对应的大气环流特征表明,第一时段1961—1981年(第二时段1999—2019年)500 hPa高度场以经向(纬向)环流为主,东亚大槽偏强(弱),东亚冬季风偏强(弱),低层受异常北(南)风控制,地面冷高压偏强(弱),偏强的冷空气阻碍了来自海上的水汽输送(偏弱的冷空气不能南下至广东),使得广东处于水汽辐散区(青藏高原表现为反气旋式环流,南支系统不活跃,对广东地区水汽输送不足),最终导致广东2月低温少雨(高温少雨)。进一步的分析表明,热带东太平洋和北太平洋中部海温异常是影响广东2月降水的重要外强迫因子,其中第一时段1961—1981年(第二时段1999—2019年)是热带东太平洋(北太平洋中部)海温异常偏冷(暖)通过850 hPa经向风切变偏弱(北太平洋中部异常反气旋环流)来影响广东降水。热带印度洋全区一致型、西太平洋暖池区和北太平洋中部海温异常是影响广东2月气温的外强迫因子,其中前两者主要通过东亚大槽这一环流影响广东气温,而北太平洋中部海温仅影响“暖干”期下广东2月的气温。
关键词:  冷干  暖干  年代际变化  大气环流  海温
DOI:10.16032/j.issn.1004-4965.2021.006
分类号:
基金项目:
COMPARISON OF INTER-DECADAL CHARACTERISTICS OF ‘COLD-DRY’ AND ‘WARM-DRY’ PERIOD AND THEIR RELATIONSHIP WITH SEA SURFACE TEMPERATURE ANOMALIES IN GUANGDONG
HU Bei-bei1, HU Ya-min2
1.92682 Troops of the Chinese People's Liberation Army, Zhanjiang, Guangdong 524001, China;2.Guangdong Climate Center, Guangzhou 510641, China
Abstract:
The long-term change in the February precipitation and temperature and associated large-scale circulation and sea surface temperature (SST) features are examined by using the dataset from 86 surface stations for recent 59 years (1961—2019) in Guangdong. The following features are identified. The February precipitation periods during 1961—1981 and 1999—2019 were two typical rain-deficient periods with significantly different temperature in Guangdong, corresponding to ‘cold-dry’ and ‘warm-dry’ phase, respectively. Accompanying the afore-described precipitation and temperature changes, the general circulation and moisture transport between the two rain-deficient episodes presented opposite features. In the ‘cold-dry’ phase (1961—1981), meridional distribution prevailed over 500 hPa geopotential height with strong East Asian Trough (EAT) and the East Asian Winter Monsoon (EAWM). In addition, under the control of the surface cold high pressure, the northward cold surge was so strong that the warm moisture air mass from sea couldn’t arrive at Guangdong, the place where the moisture divergence field was; thus the precipitation was less and the temperature was lower than normal. However, in the ‘warm-dry’ phase (1999—2019), zonal circulation pattern with weak EAT and EAWM dominated over the Asian mid- and high latitudes region. The airflow from the cold high pressure was too weak to affect Guangdong, while southerly flow was significantly stronger than normal. Meanwhile, owing to an anti-cyclonic circulation anomaly over the Qinghai-Tibet Plateau, the inactive south branch westerlies were not favorable for moisture transport to Guangdong, leading to much deficient moisture supply for precipitation and higher temperature over Guangdong in February. Further analysis shows that the SST over the tropical Eastern Pacific and central North Pacific played an important role in the precipitation anomaly between the two different stages, respectively. In the first phase, anomalous cold SST of the tropical Eastern Pacific had an influence on February precipitation owing to the weak meridional wind shear at 850hPa. However, in the second stage, anomalous warm SST of the central North Pacific influenced the monthly rainfall based on anomalous anticyclone circulation in the central North Pacific. The uniform pattern of the tropical Indian Ocean, the western Pacific warm pool area and the central North Pacific SST anomalies were external forcing factors that affect Guangdong’s February temperature. The first two mainly affected the temperature in Guangdong through the circulation of the EAT during 1961—2019, while the SST in the central North Pacific only affected the temperature in Guangdong in February during the ‘warm-dry’ period.
Key words:  cold-dry  warm-dry  inter-decadal change  Guangdong  February  atmospheric circulation  sea surface temperature
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