Possible Effects Of Eurasian Snow Anomaly On Northern Pacific Storm Track During Winter

By using the observation data for the depth of perpetual snow, Eurasian snowarea index in winter is elucidated. It was found that the area of Eurasian snow notonly have a significant interarmual change but also being gradually shrinking inwinter during the period from 1980 to 2002. The snowy winters as well as snow-lesswinters over Eurasian continent are picked out on the basis of the index for the areaof Eurasian snow.The effects of Eurasian snow anomaly on the north Pacific storm track is studiedthrough singular value decomposition(SVD), correlation analysis and compositeanalysis on 23 winters' 500hPa filtered geopotential height variance over the northPacific storm track and Eurasian snow. It illustrates that the positive anomaly ofEurasian snow area anomaly is associated with the southward shifting of Pacificstorm track and the intensity decrease of the storm track center. Vice versa.The possible physical process of the influence that Eurasian snow exerts on thenorth Pacific storm track is studied through the further composite analysis. Theresults indicate that when the Eurasian snow area is abnormally large, cooling effectbecome stronger, which leads to the noticeable decrease of upper air temperature andsubsequent height depress over Eurasian continent and Pacific ocean. Then, beyondthose region the temperature and pressure gradient chang: decrease in themid-and-high latitude and increase in the low latitude. Therefore, on one hand, themeridional heat transportation and the wind become weaker in the mid-and-highlatitude, on the other hand, they become stronger in the low latitude. Then, jet streammoves southward and its intensity decrease in the mid-and-high latitude and increasein the low latitude. So the development of baroclinic wave is restrained in themid-and-high latitude. Then, the baroclinicity in the upstream of the storm track to beweaker and the energy of baroclinic-instable which could be converted transform to disturbance energy to decrease in the mid-and-high latitude. And vice versa in thelow latitude. Finally, the intensity of storm track get weaker in the mid-and-highlatitude while become stronger in the low latitud. The general result is the southwardmovement and the decrease of its center intensity for the storm track.