Moisture profiles have been estimated over the region bounded by the latitudes 40~ and 40~ and longitudes 30~ to 130~ using INSAT digital infra red cloud imagery data. The representativeness of these profiles in representing moisture field associated with the development and movement of synoptic scale systems during the period September 15th, 1996 to March 31st, 1997 has been examined. It has been shown that the changes in the moisture field associated with the withdrawal of the southwest and northeast monsoons from the Indian sub-continent, development and movement of synoptic scale sytems (depressions, tropical cyclones and waves in easterlies) and equatorial troughs in the Indian Ocean could be clearly seen in humidity profiles. The initial development of tropical systems is first seen in the humidity field in the upper troposphere. These profiles could be used in monitoring the initial development and subsequent movement of tropical systems. Further the data on moisture distribution from the data gap regions of the Indian Ocean could be used as an additional source of moisture in numerical analysis and prognosis.
The present study has further confirmed the inverse relationship between the intensity of the southern hemispheric equatorial trough, (SHET) arid the activity of the southern monsoon over India. Continuous monitoring of weekly mean cloudiness in the zone of SHET may, therefore, serve as an useful tool in foreshadowing wet spells of rainfall over India during the southwest monsoon.
The second campaign of the Arabian Sea Monsoon Experiment (ARMEX-II) was conducted in two phases viz., March-April and May-June 2003. In the present work, the buoy and ocean research vessel data collected during the second phase of ARMEX-II have been analysed to bring out the characteristic features of monsoon onset. The results have shown that the thermodynamical features such as build up of lower tropospheric instability and increased height of zero degree isotherm occurred about a week before the monsoon onset over Kerala and adjoining southeast Arabian Sea. There was a sharp fall in the temperature difference between 850 and 500 hPa, and the height of zero degree isotherm about 2-3 days before the monsoon onset. The flux of sensible heat was positive (sea to air) over south Arabian Sea during the onset phase. Over the Bay of Bengal higher negative (air to sea) values of sensible flux prevailed before the monsoon onset which became less negative with the advance of monsoon over that region.The pre-onset period was characterized by large sea surface temperature (SST) gradient over the Arabian Sea with rapid decrease towards north of the warm pool region. The buoy observations have shown that SST remained close to 30.5 • C in the warm pool region during the pre-onset period in 2003 but only 2-3 degrees away (north of this region) SSTs were as low as 28.5-29 • C. An interesting aspect of sea level pressure (SLP) variability over the Indian seas during the onset phase of summer monsoon 2003 was undoubtedly, the highest SLP in the warm pool region inspite of very high SSTs.
lkj & ekulwu _rq ds nkSjku Hkkjr ds if’peh rV ij Hkkjh o"kkZ dh ?kVukvksa dk vjc lkxj ds Åij iouksa dh vf/kdre xfr ds ØksM ¼dksj½ ds lkFk ?kfu"B laca/k gSA bl 'kks/k&i= esa bZ- lh- ,e- MCY;w- ,Q- ¼;wjksih; e/;e vof/k iwokZuqeku dsUnz½ }kjk 850 gSDVkikLdy ij iwokZuqekfur 72 ?kaVs ds izokg izfr:i dk mi;ksx fd;k x;k gS ftlls if’peh rV ij Hkkjh o"kkZ dk iwokZuqeku djus ds fy, ftyk Lrjh; xfrdh; iwokZuqeku iz.kkyh dh {kerk c<+kus gsrq ek=kRed i)fr dk fodkl fd;k tk ldsA ;g ns[kk x;k gS fd if’peh rV ij o"kkZ dh ek=k dk if’peh rV ij vjc lkxj esa iou dh vf/kdre xfr ds 72 ?kaVs ds bZ- lh- ,e- MCY;w- ,Q- }kjk fd, x, iwokZuqeku ds lkFk egRoiq.kZ lglaca/k gSA if’peh rV ij Hkkjh o"kkZ ds {ks= ds v{kka’kh; foLrkj dk if’peh rV ij iou dh vf/kdre xfr ds ØksM ¼dksj½ ds lkFk egRoiw.kZ lglaca/k gSA bl 'kks/k&i= esa ;g crk;k x;k gS fd xzh"edkyhu ekulwu _rq ds nkSjku Hkkjr ds if’peh rV ij Hkkjh o"kkZ ds 72 ?kaVs dk iwokZuqeku djus ds fy, iouksa dh vf/kdre xfr ds 72 ?kaVs ds iwokZuqekfur ØksM ¼dksj½ vkSj foLrkj dh rhozrk vkSj fLFkfr dh {kerk c<+kus ds fy, laHkkfor iwoZlwpdksa ds :i esa mi;ksx fd;k tk ldrk gSA Occurrences of intense rainfall events over west coast of India during monsoon are intimately linked to the core of maximum winds over the Arabian Sea. ECMWF (Europian Centre for Medium Range Weather Forecasting ) predicted 72 hr flow pattern at 850 hPa has been used to develop a quantitative method for value addition in the district level dynamical forecast system for intense rainfall over the west coast. It has been found that the amount of rainfall over the west coast is significantly correlated to 72 hr ECMWF forecast of maximum wind speed over the Arabian Sea along the west coast. The latitudinal width of the heavy rainfall belt over the west coast has got significant correlation with the location of maximum wind core along the west coast. It has been shown that the strength and location of the 72 hr predicted core and fetch of maximum winds could be used as potential predictors in the value addition for 72 hr heavy rainfall forecast along the west coast of India during summer monsoon.
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