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Intraseasonal oscillation associated with the Indian winter monsoon
Author(s) -
Dimri A. P.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50144
Subject(s) - outgoing longwave radiation , climatology , anticyclone , madden–julian oscillation , precipitation , environmental science , monsoon , convection , atmospheric sciences , atmospheric circulation , oscillation (cell signaling) , circulation (fluid dynamics) , moisture , geology , meteorology , geography , physics , biology , genetics , thermodynamics
The Indian winter (December–February) monsoon (IWM) contributes almost one third of the annual precipitation over the western Himalayas (WH). In winter, eastward moving synoptic weather systems, or “western disturbances” (WDs), yield precipitation in either liquid or solid form. Although previous studies have examined the interannual variation (IAV) of the IWM, little is known of the intraseasonal oscillation (ISO) associated with the IWM. The present study examines the ISO and its plausible effects on the IWM using 28 years (1980–2007) of precipitation, height, wind, and outgoing longwave radiation (OLR) fields. The dominant ISO mode is found during the active IWM phase with well‐defined cyclonic circulation in the midtroposphere over the WH. The relationship between OLR and circulation indicates that this ISO mode is driven by moisture convergence. During the peak phase, a strong moisture influx from the Arabian Sea dominates. This moisture incursion adds to the precipitation over the WH. Successive growth and decay of anomalous cyclonic and anticyclonic circulation takes place within ISO periodicity. Strong convection always seems to precede anomalous cyclonic circulation. In addition, in‐phase wind and convection (over the WH region) are associated with the ISO phase.