辽宁春末霜冻年代际变化特征及其与海温的关系

Interdecadal Variation of Late Spring Frost and the Relationshipwith SST in Liaoning

中国东北位于高纬度地区,春季霜冻天气频繁发生,对农业生产有严重威胁,分析东北春末霜冻的气候特征及影响因子可为中长期预测提供可靠科学依据。以辽宁省为例,利用近60年气象台站观测资料和气象再分析资料,采用诊断分析方法,结合辽宁作物生育期,统计历年4月20日—5月31日辽宁省春末发生霜冻的范围并定义为春末霜冻指数(LSFI),研究其年代际尺度变化特征及对应的大尺度环流和前期海温关键区。结果表明:LSFI存在周期为14.25 a的年代际变化。辽宁地区春末霜冻事件在年代际尺度上增强对应大气环流特征为中高纬度有明显波列,东北亚上空为深厚气旋性异常,东北冷涡偏强,与西伯利亚附近的反气旋性异常结合,伴随副热带高压偏南,有利于冷空气持续影响辽宁。此外,LSFI的年代际变化与海温显著相关,相关联的海温关键区在1997年前后出现变化,1997年以前与春季(3、4月)北大西洋“三极子”海温模态显著相关,而1997年之后则与前冬北太平洋年代际振荡(Pacific Decadal Oscillation,PDO)联系密切,转变原因可能为海温模态的年代际转变。

Northeast China is located in high latitudes,spring frost weather occurs frequently,which poses a serious threat to agricultural production.To clarify the characteristics of spring frost events in northeast China and provide reliable predictor is very important.Taking Liaoning province as an example,based on the meteorological observation data and meteorological reanalysis data in recent 60 years,the late spring frost index(LSFI)in Liaoning province is defined,the relationship with the temporal characteristics of LSFI and the related large-scale circulation and the sea surface temperature(SST)is investigated.The results show that:LSFI has an interdecadal variation witha period of 14.25 a.The interdecadal enhancement is corresponding toa“Silk Road”pattern at middle latitudes,with anomalous cyclones over northeast Asia,which is beneficial to the transport of cold air.Meanwhile,there is a strong cyclonic anomaly over the Okhotsk Sea,which makes the cold air invaded at high latitudes affecting Liaoning province.And the southerly subtropical high is disadvantage to warm and humid air to north.In addition.SST also has important effects on late spring frost events.And there is a shift between the interdecadal variation of LSFI and SST around 1997.Before 1997,it is significant correlated with the North Atlantic“+-+”triple mode of SST in the early spring(March and April).The wave energy originates from the North Atlantic converged in northeast Asia,which strengthens the cyclone anomaly.After 1997,it is positively correlated with the Pacific Decadal Oscillation(PDO)in the previous winter.The wave activity flux mainly originates from the Pacific Ocean and spreads eastward to northeast Asia via the North Atlantic.