• D A Mooley

      Articles written in Journal of Earth System Science

    • Relationship between all-India summer monsoon rainfall and southern oscillation/eastern equatorial Pacific sea surface temperature

      D A Mooley B Parthasarathy N A Sontakke

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      The interannual variability of all-India summer monsoon (June to September) rainfall and its teleconnections with the southern oscillation index (SOI) and sea surface temperature (SST) anomaly of the eastern equatorial Pacific ocean have been examined for the period 1871–1978 for different seasons (i.e., winter, spring, summer and autumn). The relationship (correlation coefficient) between all-India summer monsoon rainfall andSOI for different seasons is positive and highly significant. Further examination of 10-, 20- and 30-year sliding window lengths’ correlations, brings out the highly consistent and significant character of the relationships. The relationship between all-India monsoon rainfall andSST for different seasons is negative and is significant at 1 % level or above. Drought years are characterised by negative anomalies ofSOI and positive anomalies ofSST and vice versa with flood years. The relationship betweenSOI andSST is negative and significant at 0.1 % level.

      The relationships between all-India summer monsoon rainfall,SOI and sst are expected to improve our understanding of the interannual variability of the summer monsoon.

    • Variation in the relationship of the Indian summer monsoon with global factors

      D A Mooley A A Munot

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      Utilizing data for the long period 1871–1990, variation in the relationships between Indian monsoon rainfall (IMR) and tendencies of the global factors. Southern Oscillation Index (SOI) and the sea surface temperature (SST) over eastern equatorial Pacific Ocean has been explored. The periods for which relationships exist have been identified. Tendencies from the season SON (Sept-Oct-Nov) to season DJF (Dec-Jan-Feb) and from DJF to MAM (Mar-Apr-May) before the Indian summer monsoon are indicated respectively by SOIT-2/SSTT-2 and SOIT-l/SSTT-1, current tendency from JJA (June-July-Aug) to SON, by SOIT0/SSTT0, tendencies from SON to DJF and DJF to MAM following monsoon, by SOIT1/SSTT1 and SOIT2/SSTT2 respectively.

      It is observed that while the relationships of IMR with SSTT-1, SSTT0 and SSTT2 exist almost throughout the whole period, that with SOIT-1 exists for 1942–1990, with SOIT0 for 1871–1921 and 1957–1990 and with SOIT2, for 1871–1921 only. The relationships that exist with SOIT-1, SOIT2, SSTT-1, SSTT2 and with SSTT0 (for period 1931–1990) are found to be very good and those that exist with SOIT0 for periods 1871–1921 and 1957–90 and for SSTT0 for the period 1871–1930 are good. It is thus seen that the relationships of SOIT-1, SOIT0 and SOIT2 with IMR do not correspond well with those of SSTT-1, SSTT0 and SSTT2 with IMR respectively, even though SOI and SST are closely related to each other for all the seasons. SOIT-1 and SSTT-1 can continue to be used as predictors for IMRDuring the whole period, IMR is found to play a passive, i.e. of being influenced or anticipated by SSTT-1 as well as an active role, i.e. of influencing or anticipating SSTT2. This implies a complex and perhaps non-linear interaction between IMR and SST tendency from DJF to MAM. Possibly, this is a part of the larger interaction between Asian monsoon rainfall and the tropical Pacific. A possible physical mechanism for the interaction is indicated.

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