Relationship between the Indian monsoon rainfall and the tropospheric temperature over the Eurasian continent

Based on climatological data such as the all-India rainfall (AIR) for 1949- 98, air temperatures in the troposphere and at tin land surface for 1949-98 as well as precipitation and outgoing long-wave radiation (OLR) for 1979-9 8, the statistical relationship between the Indian monsoon rainfall and tro pospheric temperature (TT) over the Eurasian continent is examined by using the correlation analysis and singular value decomposition (SVD) analysis m ethods. The main results are summarized as follows. (1) The June-September (JJAS) AIR has significant positive correlations with the 200-700 hPa TT av eraged for Eurasia in JJAS. The area with the highest simultaneous correlat ion of upper TT with AIR for JJAS is located in western Eurasia. There is a lso a region with positive simultaneous correlations in the southern subtro pics covering southern Africa. The JJAS AIR also shows significant positive correlations with TT over the Eurasian continent in March-May (MAM) and wi th the TT averaged over the Tibetan Plateau in September and October. Altho ugh some precursory springtime temperature signals for the anomalous summer monsoon are found in the upper TT over Eurasia, the variation in the upper TT appears mostly independent front that of the land surface temperature. (2) The anomalies of upper TT in JJAS are closely coupled with the variatio ns in OLR related to the monsoon rainfall over tropical Asia and Africa. Th e spatial structure of the first SVD mode for OLR anomalies shows the coher ent variations in convective activity from northern tropical Africa to Indi a, while the pattern of the first SVD mode for 300 hPa temperature anomalie s shows a distribution which is nearly symmetric with respect to the equato r, with variations of the same sign over subtropical areas in both hemisphe res and variations of the opposite sign around equatorial. Africa. This pai r of coupled patterns suggests that when the monsoon rains from tropical Af rica to India become more intense, the upper troposphere from northern Afri ca to western Asia and over southern Africa becomes warmer. (3) The observe d temperature variation in the upper troposphere over the Eurasian continen t (especially western Eurasia) during the summer monsoon season is consider ed to be a result of the anomalous subsidence and thermal advection, dynami cally induced by anomalous tropical heating associated with the enhanced mo nsoon rainfall. This study suggests that tile tropical convective activity linked to the Indian monsoon rainfall has an impact on the atmospheric vari ability on a global scale.