ROLE OF HUMIDITY IN THE DYNAMICS OF TRANSIENT SEASONS

An atmospheric general circulation model was used to initialize a join t ''atmosphere-land'' anomaly in the fall season in a preliminary run with a fixed (surplus) atmospheric water content within the quasi-stat ionary planetary fronts. Two basic numerical experiments, control and anomalous, with the initialized joint atmosphere-land anomaly in the i nitial conditions, were each carried out for 40 days in fall. An exper iment with an initial anomaly only in the land surface fields (soil mo isture content and surface temperature) was also conducted, The initia l fields for the anomalous, run were different from those of the contr ol experiment by considerably narrowed: arid zones, by a generally coo l troposphere from the equator to the pole, by strongly deformed tropo spheric temperature fronts: over the arid regions of North America and Eurasia (as well as over the Aleutian Islands and Iceland), an by the presence of the second front in the high latitudes over the Atlantic and Europe, The numerical experiments showed that the total poleward e nergy transfer was strengthened in the anomalous case with initially c ooled troposphere and land surface and with initial surplus soil moist ure, The initial negative temperature anomaly in, the troposphere chan ged with time to positive anomalies in individual regions, thus confir ming a substantially weakened seasonal cooling rate of the atmosphere in the anomalous run, In general, the anomalies in the dynamic fields did not vanish completely during integration, However, the initial ano malies in the soil moisture virtually decayed, except for the anomaly in western Siberia, which confirms that this region is most sensitive to melioration in fall (while northern Africa, Arabia, and central Asi a were found least sensitive to melioration).