Abstract
Abstract. In this paper, interannual variability of tropospheric air temperatures over the Asian summer monsoon region during the pre-monsoon months is examined in relation to Indian summer monsoon rainfall (ISMR; June to September total rainfall). For this purpose, monthly grid-point temperatures in the entire troposphere over the Asian summer monsoon region and ISMR data for the period 1949–2012 have been used. Spatial correlation patterns are investigated between the temperature field in the lower tropospheric levels during May over the Asian summer monsoon region and ISMR. The results indicate a strong and significant northwest–southeast dipole structure in the spatial correlations over the Indian region, with highly significant positive (negative) correlations over the regions of north India and the western Tibetan Plateau region – region R1 (north Bay of Bengal: region R2). The observed dipole is seen significantly up to a level of 850 hPa and eventually disappears at 700 hPa. Thermal indices evaluated at 850 hPa level, based on average air temperatures over the north India and western Tibetan Plateau region (TI1) and the north Bay of Bengal region (TI2) during May, show a strong, significant relationship with the ISMR. The results are found to be consistent and robust, especially in the case of TI1 during the period of analysis. A physical mechanism for the relationship between these indices and ISMR is proposed. Finally the composite annual cycle of tropospheric air temperature over R1 during flood/drought years of ISMR is examined. The study brings out the importance of the TI1 in the prediction of flood/drought conditions over the Indian subcontinent.
Highlights
The Asian summer monsoon (ASM), a part of the global monsoon system, is considered to be an atmospheric response to seasonal changes in a land–sea thermal contrast, induced by the annual cycle of the solar zenith angle
To explore the air temperature–Indian summer monsoon rainfall (ISMR) relationship during pre-monsoon months, we have computed the spatial correlation between the thermal field over the ASM region for each month of the pre-monsoon season (March through May) at standard levels in the troposphere and ISMR
It was noticed that the spatial correlation coefficients (CC) between air temperature field and ISMR were weak and insignificant during March to April for all the levels, while for the month of May, CC is found to be significant for lower tropospheric levels and only these results are presented
Summary
The Asian summer monsoon (ASM), a part of the global monsoon system, is considered to be an atmospheric response to seasonal changes in a land–sea thermal contrast, induced by the annual cycle of the solar zenith angle. Bansod et al.: Pre-monsoon thermal field over north India and the western Tibetan Plateau ley and Paolino (1988) examined the relationship between the monthly surface thermal field over India during the premonsoon months and summer monsoon rainfall. They reported that the mean minimum temperature in the month of May over the south Gujarat region showed a highly significant positive correlation with subsequent monsoon rainfall. Using conventional data (station observations) over the Indian region, Parthasarathy et al (1990) showed that upper air temperature during the pre-monsoon season over west central India can be useful in the prediction of ISMR.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
