SENSITIVITY OF A SUMMER ATMOSPHERIC CIRCU LATION MODEL TO THE LAND-SURFACE CONDITIONS IN SPRING AND SEA-SURFACE TEMPERATURE IN SUMMER

A series of numerical experiments with different initial land surface conditions and different initial sea surface temperatures was performe d to determine the sensitivity of a summer atmospheric circulation mod el to these two factors. It was shown that a snow cover anomaly in spr ing on some territories led to a noticeable change of the territory su rface temperature up to June-July; however, this change was several ti mes less than the natural interannual variability. For this reason, it was almost impossible to observe a significant influence of the snow cover anomalies on the Indian summer monsoon, A study of the influence of sea surface temperature anomalies on circulation showed that the m odel could reproduce a local response of tropical circulation to the s ea surface temperature but could hardly reproduce a remote one, for ex ample, the relationship between the Indian monsoon and the El Nino pha se. It was suggested that a low reproducibility of tropical circulatio n anomalies was caused by an overestimated horizontal diffusion in the tropics resulting in the shift of the spatial and temporal scales of condensation and low-frequency variability in general.