2015年汛期气候预测先兆信号的综合分析

摘要

文章全面回顾了发布2015年汛期预测时考虑的先兆信号及其应用情况。2015年春夏季厄尔尼诺事件进一步发展，并由中部型向东部型转变，热带印度洋为一致偏暖模态发展；冬、春季北大西洋三极子为正位相；冬、春季北极海冰较常年略偏少，南极海冰偏多；冬季欧亚积雪增量略少，青藏高原积雪略多但气温偏高。通过诊断分析，认为2015年汛期预测的主导外强迫信号是太平洋厄尔尼诺事件和印度洋海温一致偏暖模态。同时参考动力气候模式的预测，在4月初的预报中，重点考虑了厄尔尼诺事件的强度和空间型变化对东亚夏季风环流的影响，有利于东亚夏季风偏弱，西太平洋副热带高压偏强偏西，季风季节内进程偏晚，我国降水呈南多北少型。在5月底的订正预报中，进一步考虑热带印度洋偏暖模态对副热带高压偏强偏西偏南的影响，以及南半球越赤道气流强度偏弱特征及对夏季风季节进程和强度的影响。经过综合分析，准确地预测了2015年东亚夏季风偏弱、我国夏季降水南多北少的布局，以及季节内主要气候事件的演变。最后对汛期气候预测存在的不足进行了初步分析和讨论。%The precursory signals and their application in the short-term climate prediction of the flood sea-son in 2015 are reviewed in this paper.During the winter and spring in 2015,the thermal condition of the underlying surface exhibited some anomalous features.The El Ni˜no event continued to develop and experi-enced a transition from the warm pool type to the cold tongue type.The warm sea surface temperature anomaly (SSTA)in the basin wide Indian Ocean continued to develop.The triple SSTA mode in the North Atlantic was in its positive phase.The sea ice extent was below normal in the Arctic and above normal in the Antarctic.The snow cover was below normal in Eurasia but above normal in the Tibetan Plateau. Among all the above features,the El Ni˜no event and the warm tropical Indian Ocean were considered to be the most important factor for the prediction.In early April,based on the possible impact of the El Ni˜no event and the dynamical model prediction,it was predicted that the East Asian summer monsoon would be weaker than normal and the precipitation would be more than normal in the southern part of East China and less in the northern part.In late May,a modification of the prediction was issued based on the possible impact from the warm SSTA in Indian Ocean and the weak cross-equator flow in the South Hemisphere. Based on thorough investigation and analyses,the main features of the East Asian summer monsoon,the precipitation anomaly pattern in China and the maj or rainy seasons during summer were successfully pre-dicted.Finally,this paper discusses some disadvantages of the prediction in summer 2015 as well.