On nature and structure of atmospheric circulation anomalies in opposite seasons

Abstract

In this paper, we consider circulation anomalies obtained in the model of atmospheric general circulation when incoming short wave radiation changes and the initial state anomalies are given. We also consider circulation differences during the years of high and low moisture content in the atmosphere, using the reanalysis data.Using the global model, we studied such winter and summer circulation anomalies that result from the attenuation of winter radiation forcing and accordingly reduction in summer radiation atmosphere heating. In the other series of experiments the joint 'atmosphere-soil'initial moisture anomalies in transitional seasons (autumn, spring) are formed by using a hemisphere model and their effects on the subsequent structure of the circulation anomalies are investigated.It turned out that these anomalous numerical experiments different both in the boundary and initial conditions model the similar anomalies. Namely, in transition in the annual variation to winter circulation (or in winter) pressure long-wave troughs and ridges are damped, in transition to summer circulation (or in summer) west-east transport at the high latitudes is attenuated by the modelled anomalies.The role of dynamics in the explanation of the normal annual variation in atmospheric circulation is due to increasing baroclinity or barotropy, the displacements of quasistationary long-wave pressure troughs near the eastern coasts of the continents as well as heating and cooling over the continents, especially over Siberia, the Plateau of Tibet, the Plateau of Iran, and the North-American plateau, to the undulatory tropical convection interactions, west-east transport at the middle latitudes.The seasonal anomalies of the annual variation in atmospheric circulation can be controlled directly by the mechanisms of variation in heat in ow to the atmosphere if (or when) they are essentially independent of atmospheric circulation.We restrict our study to those mechanisms which do not necessarily depend on the special resonances or the postulated circulation sensitivity to perturbations. We seek the causes for the seasonal anomalies of the annual variation in the heat supply anomalies beyond the direct atmosphere control.