2000/2001年冬季北欧异常流型形成机理及其对我国北方天气的影响

从Rossby波能量的频散和瞬变斜压扰动的正压反馈角度,探讨了2000/2001年冬季盛行的斯堪的纳维亚环流型(正位相)的维持机理,并讨论了其对我国北方地区天气气候的影响。该环流型上游部分,即北大西洋和斯堪的纳维亚半岛的两个活动中心主要由瞬变斜压扰动的正压反馈所形成,部分由Rossby波能量频散所维持。而下游部分,即贝加尔湖附近的气旋式环流异常主要由Rossby波能量从上游频散所形成和维持。与该环流型对应,冷空气在西、中西伯利亚堆积,并在其南侧的西风气流区中平流,使得我国华北部分地区和东北地区比常年冷。该环流型导致新疆北部地区、内蒙古东部及东北地区降雪量显著增强。大西洋急流的东伸及对应斜压扰动的显著加强是预报北疆和内蒙古东部及东北地区多雪的一个重要前兆因子。

Maintenance Mechanism of the Scandinavian Pattern in Its Positive Phase during2000/2001 Winter and Its Influence on the Weather over the Northern Part of China

The maintenance mechanism of the Scandinavian pattern(SCA) in its positive phase,which prevailed in 2000/2001 winter,is investigated in terms of the energy dispersion of Rossby wave and barotropic feedback forcing due solely to high-frequency transient eddies.The possible impact of this pattern on the weather and climate of the northern part of China is analyzed as well.The upstream portion of this pattern,which covers the region extending from the North Atlantic to the Scandinavian peninsula,is primarily driven and maintained by high-frequency transient eddies and partly sustained by the energy dispersion in association with the Rossby wave propagation. The downstream part,which locates near Lake Baikal,manifests itself as a result of an almost pure downstream propagation of the Rossby wave packet.The maintenance of this pattern causes a cold air accumulation over the west and central Siberia and,a cold advection in the westerly to the south.Consequently,the northeastern China and part of North China suffered from the cold weather.It also causes an abundant snowfall over North Xinjiang,eastern part of Inner Mongolia and northeastern China.The eastward extension of the Atlantic jet and the associated enhancement of the baroclinic eddies may be regarded as a precusory signal of the strong snowfall event of North Xinjiang,eastern part of Inner Mongolia and northeastern China.