Showing papers in "Mausam in 2021"

Thunderstorm climatology over Indian region

Abstract: Thunderstorm is a severe weather phenomenon, the impact of which is being increasingly felt by all the sectors of society. In this study attempt has been made to develop thunderstorm climatology over Indian region based on latest representative climatological data. In all, data of 450 observatories comprising of 390 IMD observatories, 50 IAF observatories, six Bangladesh observatories, two Pakistan observatories, and one each in Nepal and Sri Lanka have been analysed. Inclusion of climatological data of Indian Air Force and Bangladesh has helped in developing representative climatology over Indian region. The study has brought out higher (100-120 days) annual frequency of thunderstorm as compared to those given by earlier studies (80-100 days). The highest annual frequency (100-120 days) is observed over Assam and Sub Himalayan West Bengal in the east and Jammu region in the north. The lowest frequency (less than 5 days) is observed over Ladakh region. In the plains Gangetic West Bengal and Bangladesh record between 80 and 100 days of thunderstorm annually. Kerala records highest (80-100 days) thunderstorm frequency of thunderstorm over peninsula. Udhampur observatory (132 days) in Jammu sub-division records highest number of thunderstorms in the country followed by Kumbhigram (Silchar) observatory (129 days) in south Assam and Hasimara (123 days) in Sub Himalayan West Bengal. In the plains Saurashtra and Kutch record lowest number (less than 15 days) of thunderstorm in the country. Thunderstorms are primarily short lived mesoscale weather phenomena. Existing synoptic network of part time observatories have limitations in recording all the occurrences of thunderstorms at the observatory and adjoining areas. Inclusion of data from such observatories results in lower frequency of the event and vitiates climatology. Efforts have been made in this study to develop thunderstorm climatology by using quality data of full time current weather (Airport) observatories, class I and selected class II IMD observatories. Since number of full time observatories in most of the sub divisions is few, the study is not able to bring out finer spatial variation of thunderstorm activity with in sub-divisions. Thunderstorm is a high impact severe weather event, which affects all the sectors of the society. Therefore, both from operational and climatological point of view, there is urgent need to establish at least one full time current weather observatory in each district to ensure proper reporting of all thunderstorm occurrences and to build district level thunderstorm climatology in the country.

Long-term trends in the frequency of severe cyclones of Bay of Bengal : Observations and simulations

Abstract: The east coast of India and the coasts of Bangladesh, Myanmar and Sri Lanka are vulnerable to the incidence of tropical cyclones of the Bay of Bengal. Every year these cyclones inflict heavy loss of life and property in this region. Global climate change resulting from anthropogenic activity is likely to manifest itself in the weather and climate of the Bay of Bengal region also. The long-term trends in the frequency and intensity of tropical cyclones of the Bay of Bengal during intense cyclonic months May, October and November is one such problem which has been addressed in the present paper.Utilizing the existing data of 129 years (1877-2005) pertaining to the tropical cyclone frequency and intensity in the Bay of Bengal during May, October and November, a study was undertaken to investigate the trends in the frequency of Severe Cyclonic Storms (SCS) during past decades. The results of the trend analysis reveal that the SCS frequency over the Bay of Bengal has registered significant increasing trends in past 129 years during the intense cyclonic months. It may be emphasized that these trends are long-term trends for more than hundred years based on statistical analyses which do not necessarily imply that SCS frequency has increased continuously decade after decade. As a matter of fact there has been a slight decrease in SCS frequency after peaking in the pentad 1966-1970, but this does not alter the long-term trend much. The intensification rate during November, which accounts for highest number of intense cyclones in the north Indian Ocean, has registered a steep rise of 26% per hundred years, implying that a tropical depression forming in the Bay of Bengal during November has a high probability to reach to severe cyclone stage. A regional climate model simulation revealed the enhanced cyclogenesis in the Bay of Bengal during May, October and November as a result of increased anthropogenic emissions in the atmosphere

Numerical prediction of the Orissa super cyclone (1999) : Sensitivity to the parameterisation of convection, boundary layer and explicit moisture processes

Abstract: & ih- ,l- ;w- @ ,u- lh- ,- vkj- ,e- ,e- 5 dk mi;ksx djds mM+hlk esa 1999 esa vk, egkpOokr dh xfrfof/k;ksa vkSj mldh rhozrk ds la[;kRed iwokZuqeku dk bl 'kks/ki;u fd;k x;k gSA laogu] xzgh; ifjlhek Lrj vkSj fuf’pr ueh Ldheksa dh izkpyhdj.k ;kstukvksa dh Hkwfedk dk v/;;u djus ds fy, laosnu’khyrk iz;ksx fd, x, gSaA caxky dh [kkM+h esa 90] 30 vkSj 10 fd-eh- {kSfrt varjkyksa ds rhu ikjLifjd iz{ks=ksa ¼Mksesu½ dk irk yxkus ds fy, bl ekWMy dh ifjdYiuk dh xbZ gSA ,d va’k ds varjky ij miyC/k gq, ,u- lh- bZ- ih- ,Q- ,u- ,y- vkidM+ksa dk mi;ksx djds izkjafHkd {ks=ksa vkSj fHkUu le; ds ifjlhek ifjorhZ rFkk 12 ?kaVs ds varjky ij leqnz lrg rkieku miyC/k djk, x, gSaA laogu] xzgh; ifjlhek Lrj vkSj fuf’pr ueh izfO;kvksa ds laca/k esa pOokr ds ekxZ dk iwokZuqeku vkSj mldh rhozrk dh laosnu’khyrk dk v/;;u djus ds fy, rhu iz;ksx fd, x, gSaA blls izkIr gq, ifj.kkeksa ls pOokr ds ekxZ ds iwokZuqeku esa laoguh; izfO;kvksa dh egRoiw.kZ Hkwfedk dk irk pyk gS rFkk dSufk tk ldk gSA blds vykok ;g irk pyrk gS fd xzgh; ifjlhek Lrj izfO;k,i esyj&;eknk Ldhe ds lg;ksx ls lcls izpaMre pOokr dh rhozrk dks Kkr dj ldrh gSaA fuf’pr ueh izfO;k,i pOokr dh xfr dks fu;af=r djrh gSa tks Hkhrjh iz{ks= ¼Mksesu½ ds 10 fd-eh- ds lw{e foHksnu ds QyLo:Ik laHko gks ldrk gSA dSufeknk dh la;qDr pj.kc) ;kstuk ls pOokr ds ekxZ vkSj mldh rhozrk ds laca/kksa dks csgrj

Orissa super cyclone – A Synopsis

Abstract: lkj & 29 vDrwcj 1999] dks ikjknhi ds fudV vk, egkpOokrh; rwQku us mM+hlk dks rgl ugl dj Mkyk ftlds dkj.k ikjknhi ds fudV ,d ySUMQky cu x;k blds dkj.k van:uh {ks=ksa esa yxHkx 260 ls 270 fd-eh- izfr?kaVk dh rhozxfr ls gok,i pyus ls leqnz esa AiphAkA bl egkpOokrh; rwQku ds dkj.k yxHkx 10]000 yksxksa dks vius cgqewY; thou ls gkFk /kksuk iM+kA blds lkFkladkjh ck<+ vkus ls jkT; dk lewps ns’k ls laidZ dV x;kA bl 'kks/kikRed ekWMyksa ls bl pOokr ds mRiUu gksus vkSj mlds vkxs c<+us ds fofHkUu y{k.kksa dk foospu fd;k x;k gSA bl 'kks/ki vkSj dsUnzh; vfHkdj.kksa }kjk vkink izca/ku ds :Ik esa okLrfod le; ij fd, x, jkgr dk;ksZa ij fo’ks"k cy fn;k x;k gSA ABSTRACT. Orissa was battered by a Super Cyclonic Storm on 29 October, 1999 that made landfall near Paradip (43976). The estimated maximum wind speed reached 260-270 kmph in the core area which produced a huge storm surge that led to sea-level elevation of more than 20 feet and took away valuable lives of nearly 10,000 people. It was accompanied with exceptionally heavy rains which led to devastating floods and cut off the State from the rest of the country. An attempt is made to describe the various features of development and movement of this cyclone through radar and satellite imageries, conventional data and numerical models. Emphasis is laid on the real-time handling of this event, impacts made by the cyclone and the services rendered in relation to disaster management by the State and Central Agencies.

Variation of summer monsoon rainfall over India in El-Ninos

Abstract: . El Ninos which occurred during 1871-1990 are divided into two categories of events. The first category, EW, consists of the El Ninos in which the equatorial southeast (ESE) Pacific region (0-10° S; 80°W-180°W) experienced a Warn1ing phase as defined by suitable objective criteria, and the second category, E, consists of El Ninos in which the ESE Pacific region did not experience the warming phase. Sea surface temperature rise as well as anomaly over the Pacific region, summer monsoon rainfall over India and over its meteorological sub-divisions, in the categories EW and E are compared. Area-averaged rainfall of India for the summer monsoon season and for each of the months July and September are significantly (at 0.1 percent level) lower in EW events in comparison to those in E events. The summer monsoon rainfall of each of the 12 sub-divisions, from northwest and central India constituting about 50 per cent of the Indian plains, is significantly lower in EW events than that in E events, the highest rainfall deficiency in EW events being in the westernmost sub-divisions, i.e., West Rajasthan and Saurashtra-Kutch. Possible causes for the same have also been discussed.

Tropical cyclone track prediction by a high resolution limited area model using synthetic observations

Abstract: . Results of tropical cyclone track prediction experiments in die Indian seas by a high resolution limited area numerical weather prediction model (1° × 1° lat./long. grid) are presented. As the tropical cyclones form in data sparse regions of tropical oceans, and are, therefore, not well analysed in die initial fields, a scheme has been developed for generation of synthetic observations -based on die empirical structure of tropical cyclones, and their assimilation into the objective analysis, for preparing initial fields for running a forecast model. Experiments on track prediction have beat : conducted for die cyclones forming in the Bay of Bengal and Arabian Sea during the period 1990-95. Forecast errors of the model for 24 hr and 48 hr forecasts have been computed. A sensitivity experiment has been carried out to demonstrate the importance of initial humidity field on forecast model performance. The experiment brings out crucial important of the initial humidity field prescription in accurate track prediction by die forecast model.

Evaluation of Indian summer monsoon rainfall features using TRMM and KALPANA-1 satellite derived precipitation and rain gauge observation

Abstract: The study provides a concise and synthesized documentation of the current level of skill of the satellite (3B42RT, 3B42V-6, KALPANA-1) products over Indian regions based on the data gathered during the summer monsoon seasons of 2006, 2007 and 2008. The inter-comparison of satellite products with the rain gauge observations suggests that the TRMM 3B42V6 product could distinctly capture characteristic features of the summer monsoon, such as north–south oriented belt of heavy rainfall along the Western Ghats with sharp gradient of rainfall between the west coast heavy rain region and the rain shadow region to the east, pockets of heavy rainfall along the location of monsoon trough, over the east central parts of the country, over north-east India, along the foothills of Himalayas and over the north Bay of Bengal. The KALPANA-1 and 3B42RT products reproduce only the broadest features of mean monsoon seasonal rainfall. The near real-time products 3B42RT and KALPANA-1 underestimate the orographic heavy rainfall along the Western Ghats of India. The precipitation estimates from TRMM 3B42V6 product, when accumulated over the whole season, could reproduce the observed pattern. However, the TRMM 3B42RT and KALPANA-1 estimates are comparatively lower than the observed rainfall over most parts of the country during the season. Inter comparison reveals that the TRMM 3B42V6 product showed better skill in estimating the daily and seasonal mean rainfall over all India and also over four homogeneous regions of India.

Spatial and temporal characteristics of evaporation trends over India during 1971-2000

Abstract: Evaporation and rainfall data for the period 1971-2000 for 58 well distributed stations over India were selected for this study. Trends of these two parameters for the country as a whole and for individual stations for annual (January – December), winter (December, January and February), summer (March – May), monsoon (June – September) and post-monsoon (October, November) period were analysed and tested for significance at 95% level of confidence. The analysis shows that for the country as a whole, the evaporation has significantly decreased in all seasons while there is no significant trend in rainfall. Out of 58 stations, numbers of stations having significant decrease in evaporation are 45 (annual), 30 (winter), 42 (summer) and 35 (monsoon and post monsoon seasons). Decadal analysis of trends shows that the variability of evaporation towards the decreasing trend is steadily maintained throughout the period but more in the decade 1991-2000. Spatial analysis of the seasonal trends of evaporation indicates the decreasing trends over all parts of India except northeast where it is increasing. Regions of significant decrease in evaporation viz., North, Southwest and Southeast and increase in evaporation viz., Northeast emerge from the spatial analysis of trends over the country. Spatial analysis of seasonal rainfall trends indicates the increasing trends in southern parts and decreasing trends in central and northeastern parts of the country. Evaporation trends of nearly 50% stations (mostly in southern parts of India) show complimentary relation with rainfall of the same period. Rest of the long term trends in evaporation may be due to the variation in other parameters like wind speed, cloud cover, sunshine duration etc. which needs further examination.

Current status of tropical cyclone track prediction techniques and forecast errors

Abstract: lkj & fiNys dqN n’kdksa esa HkweaMyh; m".kdfVca/kh; pOokrksa ds iwokZuqeku esa gksus okyh =qfV;ksa esa mUur vkidM+k laxzg.k rduhdksa] lrr ekWMy fodkl] mPp foHksnuksa vkSj Hkzfey fof’"Vrk ds QyLo:Ik dkQh deh vkbZ gSA ;g ns[kk x;k gS fd lewps fo’o esa iwokZuqeku dh =qfV;ksa esa izR;sd le; ds vuqHkoksa ds vk/kkj ij izfro"kZ 1 ls 2 izfr’kr rd dh deh vkbZ gS ftuds ifj.kkeLo:Ik yEch vof/k ¼48 ?kaVs ls vf/kd½ ds iwokZuqekuksa esa vR;ar rhoz xfr ls lq/kkj gks jgk gSA vVykafVd vkSj iz’kkar egklkxj tSls csfluksa esa ;|fi fofHkUu dkj.kksa ls iwokZuqeku dh =qfV;ksa esa dkQh vf/kd deh gqbZ gS rFkkfi Hkkjrh; {ks= esa ;g izo`fŸk dkQh lk/kkj.k jgh gSA bl {ks= esa iwokZuqeku dh =qfV;ksa esa deh vkus dk ,dek= dkj.k Hkkjr ekSle foKku foHkkx ¼Hkk- ekS- fo- fo-½ vkSj jk"Vah; e/;e vof/k ekSle iwokZuqeku dsUnz ¼,u- lh- ,e- vkj- MCY;w- ,Q-½ tSls izpkyukRed ,u- MCY;w- ih- dsUnzksa }kjk muds {ks=h; vkSj HkweaMyh; ekWMyksa ds fo’ys"k.k esa la’ysf"kr Hkzfeyrk dk vf/kdkf/kd iz;ksx gks jgk gSA varZjk"Vah; m".kdfVca/kh; pOokr vuqla/kku esa bl rF; ij vc vf/kd cy fn;k tk jgk gS fd fo’ks"k :Ik ls cgqr de le; esa gh vikjEifjd vkidM+ksa ds vf/kd mi;ksx] eslksLdsy fo’ys"k.kksa] Hkzfey fof’k"Vrk ds fy, la’ysf"kr vkidM+ksa ds mi;ksx ls vkSj mPp ekWMy foHksnu esa HkkSfrd izkpyhdj.k ds fu"iknu }kjk m".kdfVca/kh; pOokr ds ekxZ dk iwokZuqeku vf/kd lVhd cu ldsA pOokrksa ds ySaMQkWy ds laca/k esa igys ls py jgh gjhdsu MCY;w- vkj- ,Q- ifj;kstuk ij fo’ks"k :i ls py jgs vuqla/kku vkSj izpkyukRed dk;ksZa ls vkus okys o"kksZa esa Hkkjrh; {ks= dks ykHk gksus dh laHkkouk gSA rFkkfi] Hkkjrh; {ks= }kjk ekWMy ds fodkl ds lefUor iz;klksa ds vykok ekWMy ds fo’ys"k.k ds fy, ikjEifjd vkSj vikjEifjd vkidM+ksa dh vf/kdre miyC/krk rFkk mUur vkidM+k laxzg.k rduhd ds mi;ksx dks vf/kd izkFkfedrk nh tkuh pkfg,A Thanks to advanced data assimilation techniques, continuous model development, higher resolutions, and vortex specification, there has been considerable progress in the reduction of global tropical cyclone forecast errors during past few decades. It has been observed that world-wide rate of reduction of forecast errors was of the order of 1%-2% per year for all time horizons, with most rapid improvement at longer durations (beyond 48 hours). While other basins like Atlantic and Pacific oceans reported greater rate of decline of these errors due to various factors, the trend has been quite modest for Indian region. The only factor responsible for reduction of errors in the region was the greater use of synthetic vortex by operational NWP centres like India Meteorological Department (IMD) and National Centre for Medium Range Weather Forecasting (NCMRWF) in their Regional & Global model analyses. The current emphasis of international tropical cyclone research is to achieve greater accuracy of TC track prediction, especially in the short range, by maximizing the use of non-conventional data, meso-scale analysis, use of synthetic data for vortex specification, and the performance of physical parameterization at higher model resolution. The current research and operational emphasis of the ongoing Hurricane WRF project for land falling cyclones, is expected to benefit the Indian region in the years to come. Nevertheless, the Indian region needs to assign higher priority to the greater availability of conventional & non-conventional data and use of advanced data assimilation technique for model analysis besides its concerted efforts on model developments.

Impact of physical parameterization schemes on the numerical simulation of Orissa Super Cyclone (1999)

Abstract: & 29 vDrwcj] 1999 dks mM+hlk esa vk, egkpOokr dks izfr:fir djus ds fy, isuflyosfu;k LVsV ;wfuoflZVh ds jk"Vah; ok;qeaMyh; vuqla/kku dsUnz ds eslksLdsy ekWMy ¼,e- ,e- 5½ ds xSjnksx fd;k x;k gSA pOokr ds ekxZ vkSj mlds fodkl ij dSuf ifjlhek Lrj izkpyhdj.k ¼ih- ch- ,y-½ Ldheks ds izHkko dk v/;;u djus ds fy, iz;ksx fd, x, gSA pOokr dh xfr] U;wure nkc dk fodkl] o"kkZ dk iSVuZ vkSj rkieku ds m/okZ/kj OkWl lsD’ku ds laca/k esa laosnu’khyrk dh tkip dh xbZ gSA ,aFksld lHkh izfr:i.k vfr {kh.k ifjlapj.k ls vfr izpaM pOokrh; rwQku fodflr djus esa l{ke gSaA U;wure dsUnzh; nkc dk cuuk fofHkUu diklh Ldheksa esa vf/kd laosnu’khyrk n’kkZrk gS ftlesa lekdyu vof/k ds 4 fnuksa ds nkSjku dSufwure dsUnzh; nkc dk fodkl vkSj iouksa dh {kSfrt ,oa m/okZ/kj lajpukvksa] rkieku folaxfr;ksa vkSj jsucSaM y{k.kksa dks vPNh rjg iznf’kZr fd;k tk ldrk gSA Non-hydrostatic version of Pennsylvania State University- National Center for Atmospheric Research mesoscale model (MM5) is used to simulate the super cyclonic storm that crossed Orissa coast on 29 October, 1999. Experiments are carried out with four cumulus parameterization schemes namely; Kain-Fritsch, Betts-Miller, Grell and Anthes-Kuo and two planetary boundary layer parameterization (PBL) schemes namely; Hong-Pan and Burk-Thompson to study their impact on the movement and development of the cyclone. The sensitivity is examined in terms of movement, evolution of minimum pressure, rainfall pattern and vertical cross section of temperature. All the simulations are able to develop the very severe cyclonic storm from very weak circulation except with Anthes-Kuo scheme. The evolution of the minimum central pressure shows much sensitivity among the different cumulus schemes with Kain-Fritsch producing 966 hPa while Anthes-Kuo 1004 hPa during the 4 days of the integration period. Different cumulus parameterization schemes show significant impact on the simulated movement of the cyclone. The results reveal that the evolution of minimum central pressure and horizontal as well as vertical structures of winds, temperature anomalies and rainband characteristic to a cyclone are well brought out by the combination of Kain-Fritsch and Hong-Pan schemes.

Storm surge prediction and frequency analysis for Andhra coast of India

Abstract: Storm surges associated with severe cyclonic storms are common occurrences along the east coast of India. The coastal districts of Andhra Pradesh have experienced major surges in the past. Storm surges and the rains associated with cyclones are major causes for coastal flooding in this region. An attempt has been made, in this paper, to simulate surges along the Andhra coast that would have occurred due to severe cyclones during 1891-1996. Inland inundation due to surges is also estimated by using an empirical formula. The computed results are validated with the available observations. The comparison using post-storm survey reports, appears reasonably good to assert that the model is capable of predicting the peak surge amplitude and its location. Frequency of occurrence relationships is obtained for various zones along the coastal region for the purpose of risk analysis.

Sunshine duration climatology and trends in association with other climatic factors over India for 1970-2006

Abstract: Changes in sunshine duration in association with total cloud amount, rainy days and good visibility days over India were examined for 1970-2006. Climatologically, annual total sunshine duration over west Rajasthan and adjoining Gujarat is more than 3100 hours which is ideal for harnessing solar energy over these regions. The trend analysis indicates significant decrease in sunshine duration over the country for all months (except June) and the maximum decrease has taken place in January (-0.44 hour/decade) followed by December (-0.39 hour/decade). Seasonally, decline in sunshine hours is highest in winter and post monsoon (4% per decade) and lowest in monsoon (3% per decade). Decadal variations indicate maximum decrease in sunshine over the Indo-Gangetic plains and south peninsula during 1990-1999. Spatially, the decreasing trends in sunshine hours are highest in Indo-Gangetic plains and south peninsula while regions over Rajasthan and Gujarat have lowest decrease. Out of 40 stations under study, the maximum decrease in sunshine has occurred at New Delhi (winter at 13% per decade and post monsoon at 10% per decade) and Varanasi (summer and monsoon at 7% per decade). Correlation analysis of sunshine duration with total cloud amount, rainy days and good visibility days indicates regional and seasonal variations in factors explaining the long term trends in sunshine duration over the country.

Size distribution of Raindrops -Part I

Abstract: Results of measurements of the size distribution of raindrops made at Poona during the months of August, September and October 1956, are reported in the form of a table showing the number of drops received at the ground level per m2 per sec for various ranges of diameter at 0.25 nterval, for different inten sities of precipitation ranging from 0 to 40 mm hr-l. Average values have been calculated and presented in the form of a similar table. Histograms showing the number, volume of liquid water, momentum and kinetic energy of raindrops per m2 per sec, against the raindrop diameters are given for six typical intensities of precipitation. The variation of the total number N, momentum M and kinetic energy E (in joules) of raindrops per m2 per sec with intensity of precipitation is shown graphically. By the method of least squares the following relations are obtained. N=710I0.47, M=165 I, and E = 2.8x10-3 I1.13, where I is the intensity of precipitation in mm hr-1.The results are presented in a form suitable for soil erosion problems. The data are confined to general rains.

Recent trends in meteorological parameters over Jammu and Kashmir

Abstract: Annual trends of meteorological parameters temperature, rainfall, relative humidity and clouds for ten stations in Jammu and Kashmir during the period 1976-2007 were studied. Trend analysis shows that temperatures are increasing over the state with significant increase in maximum temperature in the Kashmir region (+0.04 to + 0.05° C/year) and minimum temperature in the Jammu region (+0.03 to + 0.08° C/year). The diurnal temperature range (DTR) is increasing over Kashmir region due to higher increasing trends in the maximum temperature while the strong increasing trends in the minimum temperature are contributing more towards the decrease in DTR over the Jammu region. Annual rainfall and rainy days trends are decreasing in both the regions of the state except at Jammu where rainfall trend is significantly increasing (+12.05 mm/year). Day-time relative humidity trends are mixed while total cloud amount trends are decreasing over Kashmir region and increasing over Jammu region. The effects of urbanization in the last two decades are more pronounced in Jammu region and this is strongly expressed in minimum temperature over the region. The warming trends observed over Jammu and Kashmir state during the period of study need further investigation in relation to variability of atmospheric circulation over North India.

Major advances in understanding and prediction of tropical cyclones over north Indian Ocean : A Perspective

Abstract: lkj & mRrjh fgUn egklkxj esa m".kdfVca/kh pOokrksa ij fd, x, vuqla/kku xr 150 o"kksZa esa fofHkUu pj.kksa ls xqtjs gSa vkSj vf/kd rFkk csgrj izs{k.kksa dks fodflr djus ds fy, izkS|ksfxdh ds :Ik es bldk fodkl fd;k x;k gSA 20oha 'krkCnh ds e/; rd leqnz esa bl vkinkdkjh ifj?kVuk ds cuus vkSj blds rhoz gksus dh tkudkjh iksrksa esa gh dqN gn rd fojyrk ls izkIr gksus okys izs{k.kksa ds ek/;e ls feyrh Fkh vkSj blfy, 1960 ds n’kd rd Hkkjr esa fd, x, vf/kdka’k vuqla/kku v/;;uksa esa pOokrksa ds tyok;q foKku] mudh /kjkryh; lajpuk] mudh xfr vkSj leqnz esa tgktksa dks igiqpkusa okyh {kfr dks vuns[kk djus okys fu;eksa ij vf/kd cy fn;k x;k FkkA ekSle jsMkj] mifjru ok;q ifjKkiuksa] vuqla/kku ok;q;ku losZ{k.k ekSle mixzgksa vkSj daI;wVjksa ds ek/;e ls izkIr dh xbZ ubZ ok;qeaMyh; izks|ksfxdh ds izLrqrhdj.k ls 1950 ds n’kd ls ysdj 1980 ds n’kd ds nkSjku fofHkUu ns’kksa ds m".kdfVca/kh pOokr vuqla/kku esa vk’p;Ztud :Ik ls ifjorZu vk;k gSA bl vof/k esa m".kdfVca/kh pOokrksa ds laiw.kZ mRifRr pO dk izfr:i.k djus ds fy, lS)kafrd v/;;uksa vkSj daI;wVj fun’kksaZ ds fodkl esa lq/kkj ns[kk x;k gSA bl vof/k esa m".kdfVca/kh pOokr ds ekxZ dk iwokZuqeku yxkuk Hkh vuqla/kku dk ,d {ks= cu x;k gS vkSj 1950 ds n’kd ls ysdj 1980 ds n’kd ds nkSjku tyok;q foKku] flukfIVd lkaf[;dh; vkSj xfrdh; i)fr;ksa ij vk/kkfjr rduhdksa ds izdkjksa esa fujarj fodkl gqvk gS rFkk bUgsa ekU;rk feyh gSA xr 10 o"kksZa dh vof/k ds nkSjku fodflr ns’kksa esa HkweaMyh; ifjpkyu fun’kksZa esa fufgr ifj"Nr mPp foHksnu ds fun’kksZa dk fodkl fd;k x;k gS vkSj ikjLifjd fO;kvksa dh izfO;k ds :Ik esa bl Ik)fr dk fodkl djus vkSj bldh xfr dk iwokZuqeku yxkus ds fy, budh tkip dh xbZ gSA ;s iw.kZ :i ls lgh ikbZ xbZ gSaA Hkkjr esa Hkh bl izdkj ds fodklksa dks viuk;k x;k gSA bl 'kks/ki{k izfO;kvksa ds laca/k esa fd, x, izeq[k fodklksa dh lwph miyC/k djkus dk iz;kl fd;k x;k gSA lkekU; :Ik ls HkweaMyh; vuqla/kku ds {ks= esa fd, x, iz;kl fgan egklkxj csflu esa fd, tk jgs v/;;uksa ij dsafnzr jgs gSaA mRrjh fgan egklkxj esa m".kdfVca/kh pOokrksa ds vUr% nl o"khZ; fHkUurkvksa dh tkip dh xbZ gS vkSj 1980 ds n’kd ls budh xfr;ksa esa vDlj vR;kf/kd deh ns[kh xbZ gSA fgan egklkxj csflu esa m".k@'khr bulksa dh ?kVukvksa ds e/; dksbZ laca/k ugha ik;k x;k gSA izpaM m".kdfVca/kh pOokrksa ds fodkl vkSj xfr ds fy, vko’;d o`gr eku fLFkfr;ksa dh izNfr ls lacaf/kr izs{k.kkRed vkSj lS}kafrd ekWMfyax i)fr;ksa esa daI;wVj izfr:i.kksa lfgr izs{k.kkRed vkSj lS)kafrd i)fr;ksa ls fHkUu fHkUu fopkjksa dk irk pyk gSA mRrjh fgan egklkxj csflu esa fd, x, vkSj vf/kd vuqla/kku dh vksj fo’ks"k /;ku nsus dh fn’kk esa dqN lq>ko fn, x, gSaA Research on tropical cyclones in the north Indian Ocean has passed through different phases in the last 150 years and progress was made as the technology for more and better observations evolved. Till the middle of the 20th century, the only way of knowing about the formation and intensification of this disastrous phenomenon, while out at sea, was through rather sparse ship observations and hence the climatology of the cyclones, their surface structure, movement and the rules to avoid the damage to shipping at sea were emphasized in most of the research studies in India till 1960s. Introduction of new atmospheric technologies through weather radars, upper air soundings, weather satellites and computers have brought a phenomenal change in tropical cyclone research in different countries during 1950s to 1980s. The period also witnessed break-through in theoretical studies and the development of computer models to simulate the complete genesis cycle of tropical cyclones. Predicting the track of tropical cyclone also became an area of active research in this period and a variety of techniques were increasingly developed. During the last 10 years sophisticated high resolution models embedded within global circulation models have been developed in advanced countries and tested for predicting the development and movement of the system as an interactive process. In India, too such developments have been adopted. Within the scope of global research effort in general, the focus of the article is on the studies in north Indian Ocean basin. Inter-decadal variation of tropical cyclones in the north Indian Ocean has been examined and the frequency of their formations have shown drastic decrease since 1980s. No connection is found between the warm/cold ENSO events in the Indian Ocean basin and tropical cyclone frequency in the basin. Observational and theoretical approaches with computer simulations have brought a convergence of views concerning the nature of large-scale conditions needed for development and movement of severe tropical cyclones. Some suggestions are provided for directing special attention toward further research in this area in the north Indian Ocean basin.

Variability and trends of rainfall using non-parametric approaches: A case study of semi-arid area

Abstract: The analysis of variability and trends of rainfall can be used to assist better decision for climate risk and agricultural water management. This study makes an attempt to evaluate the trend and variability of annual, seasonal and monthly rainfall of 19 stations of Ajmer district, Rajasthan based on 44 year’s monthly rainfall data (1973-2016). Non-parametric Mann-Kendall (MK), Modified Mann-Kendall (mMK) and Spearman’s rho (SR) tests were used to achieve if there was an increasing or decreasing trend in the time series and the Sen’s slope (Q) estimator was applied to identify the quantity of the trend. From the results, it was found that annual and monsoon rainfall both showed an increasing trend at three stations, located in the central part and a decreasing trend at two stations, located in the north-western and south-western part of the study area. The magnitude of maximum increasing trends in both annual and monsoon rainfall was observed at Goela (Q=+10.17 mm/year and+9.50 mm/year) while Jawaja (Q = - 6.76 mm/year and -5.21 mm/year) appeared with the maximum decreasing trends. On a monthly scale February showed an increasing trend at maximum number of stations (seven) and July showed a decreasing trend at maximum number of stations (seven). The information gathered from our study will help in future to estimate hydraulic procedures as well as to make sustainable water resource planning and management in this region.

Advance forecasting of cyclone track over north Indian Ocean using a global circulation model

Abstract: & m".kdfVca/kh; pOokr lewps fo’o esa vf/kdka’k rVorhZ {ks=ksa esa xaHkhj vkSj fodjky Mj mRiUu djrs jgrs gSaA blfy, m".kdfVca/kh; pOokrksa ds laca/k esa vf/kd lVhd vkSj yEch vof/k ds iwokZuqeku dh ekix c<+rh tk jgh gSA ;|fi dkQh le; ls lhfer {ks= fun’kZ ¼,y- ,- ,e-½ m".kdfVca/kh; pOokrksa ds xfrdh; iwokZuqeku ds fy, ijEijkxr lk/ku jgs gSa fQj Hkh bl ckr ls Hkh badkj ugh fd;k tk ldrk gS fd pOokrksa dh xfrdh; izNfr ds izLrqrhdj.k esa HkweaMyh; ifjlapj.k fun’kkZsa ¼th- lh- ,e-½ ds mi;ksx ds Qy Lo:Ik dkQh lq/kkj vk;k gSA mnkgj.k ds fy, caxky dh [kkM+h ds dqN pOokr rks caxky dh [kkM+h esa gh fodflr gksrs gSa fdarq cgqr ls pOokr [kkM+h ds iwoZ dh rjQ cus fuEu nkc {ks= ds l?ku gksus vkSj [kkM+h dh vksj c<+us ds dkj.k curs gSa ftlls ;g Li"V gS fd pOokr ds iwokZuqeku ds fy, pOokr ds mRiUu gksus ds foLr`r {ks= dks 'kkfey djus dh vko’;drk gSA bl 'kks/kik gS fd ,y- ,- ,e- vkSj th- lh- ,e- dh la;qDr fo’ks"krk rqyukRed :Ik ls uohu Js.kh ds HkweaMyh; ekWMyksa ¼th- lh- ,e-½ ls pOokr ds ekxZ vkSj mldh rhozrk tSls dqN vR;ar egRoiw.kZ y{k.kksa ds laca/k eas yEch vof/k ds vkSj vf/kd lVhd rjg ds iwokZuqeku nksuksa miyC/k djk ldrs gSaA lkr pOokrksa ls lacaf/kr fofHkUu LFkkuksa] _rqvksa] o"kZ vkSj mudh rhozrk] izfr:fir ekxksZa vkSj pOokrksa ds ySaMQky ds LFkyksa ds ikip fnuksa ls Hkh vf/kd le; igys dh mudh vkjafHkd voLFkkvksa vkSj muds laca/k esa leqnz lrg rkieku ¼,l- ,l- Vh-½ ds ekfld tyok;q foKku ds 48 ?kaVs igys tkjh fd, x, gSaA buesa rkRdkfyd izpkyukRed iwokZuqeku ds leku gh =qfV;ki ikbZ xbZ gSaA Tropical cyclones pose a serious and growing threat to many coastal areas world over; there is increasing demand for better accuracy as well as longer range for tropical cyclone forecasts. While the traditional tool for dynamical forecasting of tropical cyclones has been Limited Area Models (LAM), there are reasons to believe that use of Global Circulation Models (GCM) may result in improved representation of cyclone dynamics. Over Bay of Bengal, for example, while some cyclones develop in situ, many result from intensification of low pressure system that travel from the east, implying need for consideration of a large domain. We show here that a relatively new class of Global Circulation Models (GCM), combining the advantages of LAMs and GCMs, can provide both longer range and better accuracy for such critical parameters like track and intensity. For seven cyclones representing different locations, seasons, years and strength, simulated tracks and land-fall locations show, with initial condition more than 5 days ahead and only monthly climatology of sea surface temperature (SST), errors comparable to those from current operational forecast 48 hours in advance.

Radiation fog over north India during winter from 1989-2004

Abstract: Lkkj & bl 'kks/k-i= esa rsjg gokbZ vM~Mksa ds orZeku ekSle laca/kh vkidMksa dk mi;ksx djrs gq, mUkjh Hkkjr esa fofdj.k ;qDr dksgjs dk v/;;u fd;k x;k gSA gky gh ds o"kksZa esa Hkkjr ds mUkjh Hkkxksa esa dksgjs dh mRifUk esa cgqr vf/kd o`f) ik;h xbZ gSA pwifd bafnjk xki/kh vUrjjk"Vah; ¼vkbZ- th- vkbZ-½ gokbZ vM~Ms dh o"kZ 1997&1998] 1998&1999] 1999&2000] 2000&2001] 2001&2002] 2002&2003 vkSj 2003&2004 ds nkSjku dqy 900 mM+kuksa ds ekxZ cnys x,A blfy, bl gokbZ vM~Ms ds oSekfudh izpkyuksa ij iM+s dksgjs ds izfrdwy izHkko dk v/;;u fd;k x;k gSA bafnjk xki/kh gokbZ vM~Ms ij dSVId vR;f/kd l{ke midj.k iz.kkyh vkbZ- ,y- ,l- miyC/k djkbZ xbZ gSA bl 'kks/kirk okys izpkyuksa ds fy, vko’;d juos dh n`’; jsatksa vkj- oh- vkj- dh mi;ksfxrk ij fopkjfk x;k gSA mixzg }kjk dksgjs ij fd, x, izs{k.kksa dk /kjkryh; izs{k.kksa ds lkFk lgh rkyesy ik;k x;k gSA mixzg ls izkIr gq, fp= bl ckr dk izek.k gSa fd o"kZ 1998&1999 ds nkSjku mŸkjh Hkkjr esa vR;f/kd l?ku dksgjk vjc lkxj esa cus izpaM pOokr ls vR;f/kd ek=k esa vknzZrk ds izokg ds dkj.k cuk FkkA bl 'kks/k-i= esa bafnjk xki/kh gokbZ vM~Mk] y[kuA gokbZ vM~Mk] okjk.klh gokbZ vM~Mk vkSj ve`rlj gokbZ vM~Mk ij dksgjs ds nkSjku vf/kdre rkieku vkSj lkisf{kd vknzZrk dh folaxfr;ksa ds e/; laca/k dk irk yxkus dk Hkh iz;kl fd;k x;k gSA Radiation fog over north India has been studied using current weather data of thirteen airports. There has been a tremendous increase in the fog formation over northern parts of India in recent years. An attempt has been made to study the adverse impact of fog on aeronautical operations at Indira Gandhi International (I.G.I.) airport as total number of flights diverted during 1997-98, 1998-99, 1999-2000, 2000-01, 2001-02, 2002-03 and 2003-04 were about 900. I.G.I. airport is provided with a very efficient Instrument Landing System (ILS) for Cat-I, Cat-II and Cat-III operations. The utility of Runway Visual Ranges (RVRs) required for low visibility operations, calculated from skopographs, for the last fifteen years, has been discussed. Satellite observations on fog have been found to be in fair agreement with the surface observations. Most catastrophic fog formations, which occurred over north India during 1998-99, were found to be due to the enormous amount moisture flow from a severe cyclone formed in the Arabian Sea as evidenced in satellite imagery. An attempt has also been made to establish a relation of maximum temperature and Relative Humidity anomaly with the duration of fog at I.G.I. airport, Lucknow airport, Varanasi airport and Amritsar airport.

Some climatological aspects of thunderstorms and squalls over Guwahati Airport

Abstract: Lkkj & xqokgkVh gokbZ vM~Ms ij vk, paMokr ls tqM+s okf"kZd vkSj ekfld ckjEckjrk dk forj.k] xtZ ds lkFk vk, rwQkuksa vkSj paMokrksa ds vkjEHk gksus dk le; vkSj mudh vof/k rFkk i;kZoj.kh; ifjorZuksa dk fo’ys"k.k fd;k x;k gSA rwQku vkSj paMokr lcls T;knk ebZ ds eghusa esa vkrs gSa vkSj mlds ckn viSzy ds eghus esa vkrs gSaA rwQkuksa vkSj paMokrksa dh vko`fr;ki lcls T;knk ebZ ds eghusa esa gksrh gSa vkSj mlds ckn vizSy ds eghus esa gksrh gSaA vf/kdki’k rwQku ekulwu _rq ls iwoZ vkSj ekulwu _rq ds nkSjku vkrs gSa rFkk paMokr Qjojh ls ebZ ds eghuksa ds nkSjku vkrs gSaA ekulwu _rq ls iwoZ vkus okys vf/kdki’k rwQku e/; jkf= ls ysdj rM+ds lqcg ds le; esa vkrs gSa tcfd ekulwu _rq ds nkSjku vkus okys rwQku 0600&1200 ;w- Vh- lh- ds chp vk;k djrs gSa vf/kdki’k rwQkuksa dh vof/k rhu ?kaVksa ls Hkh de dh gksrh gSA vf/kdki’k paMokrksa dh vof/k pkj feuVksa ls Hkh de dh gksrh gS] fn’kk mUkj if’pe vkSj ;s 0900&2100 ;w- Vh- lh- ds le; vkrs gSaA xqokgkVh gokbZ vM~Ms ij paMokr ds vkus ls i;kZoj.kh; rkieku vkSlru 2-2° lsa- rd fxj tkrk gS] lkisf{kd vknzZrk 8-5 izfr’kr rd c<+ tkrh gS vkSj nkc 1-6 gSDVkikLdy rd c<+ tkrk gSA xqokgkVh gokbZ vM~Ms ij paMokr ds vkus ls vf/kdre iou xfr vkSlru yxHkx 39 ukWV~l gksrh gSA fiNys v/;;uksa ls rqyuk djus ij ;g irk pyrk gS fd fiNys dqN o"kksZa esa rQkuksa vkSj paMokrksa ds y{k.kksa esa fo’ks"k ifjorZu ugha vk;k gSA The annual and monthly frequency distribution, time of commencement and duration of thunderstorms & squalls and environmental changes associated with occurrence of squall at Guwahati Airport have been analyzed. The frequencies of thunderstorms and squalls are maximum in the month of May followed by April. Most of the thunderstorms occur during premonsoon and monsoon season and squalls occur during Feb-May. Most of the premonsoon thunderstorms commence during midnight to early morning while the thunderstorms during monsoon season have preference to commence between 0600-1200 UTC. Majority of thunderstorms is of the duration of less than three hours. Majority of squalls have the duration of less than four minutes, direction as northwesterly and occur during 0900-2100 UTC. On the average, environmental temperature falls by 2.2° C, the relative humidity rises by 8.5%, and the pressure increases by 1.6 hPa due to squall over Guwahati Airport. The average maximum wind speed associated with a squall over Guwahati Airport is about 39 knots. Comparison with the past studies indicates that characteristics of thunderstorms and squalls have not changed significantly over the years.

Comparison of different artificial neural network (ANN) training algorithms to predict the atmospheric temperature in Tabuk, Saudi Arabia

Abstract: Use of Artificial neural network (ANN) models to predict weather parameters has become important over the years. ANN models give more accurate results in weather and climate forecasting among many other methods. However, different models require different data and these data have to be handled accordingly, but carefully. In addition, most of these data are from non-linear processes and therefore, the prediction models are usually complex. Nevertheless, neural networks perform well for non-linear data and produce well acceptable results. Therefore, this study was carried out to compare different ANN models to predict the minimum atmospheric temperature and maximum atmospheric temperature in Tabuk, Saudi Arabia. ANN models were trained using eight different training algorithms. BFGS Quasi Newton (BFG), Conjugate gradient with Powell-Beale restarts (CGB), Levenberg-Marquadt (LM), Scaled Conjugate Gradient (SCG), Fletcher-Reeves update Conjugate Gradient algorithm (CGF), One Step Secant (OSS), Polak-Ribiere update Conjugate Gradient (CGP) and Resilient Back-Propagation (RP) training algorithms were fed to the climatic data in Tabuk, Saudi Arabia. The performance of the different training algorithms to train ANN models were evaluated using Mean Squared Error (MSE) and correlation coefficient (R). The evaluation shows that training algorithms BFG, LM and SCG have outperformed others while OSS training algorithm has the lowest performance in comparison to other algorithms used.

A review of Nowcasting of convective weather over the Indian region

Abstract: In recent years, with the improvement of observation and computation networks, prediction techniques as well as communication channels, there is an increasing public demand for location specific accurate forecast of weather. This need is especially felt for short duration mesoscale weather systems, for which there is less time for taking safety measures. The present article is a brief review of the recent developments in the field of operational thunderstorm prediction over India in the short to very short time scale. The article first briefly discusses the climatology of thunderstorms over the Indian region, its seasonal, spatial and diurnal variability. It then discusses the new observation resources that are now becoming available for operational thunderstorm forecasting including the current generation of satellites, Doppler radars, lightning detection network, as well as the surface and upper air network of observatories. This is followed by a discussion of numerical techniques available worldwide for very short range to nowcast scale forecasting of convective weather. The models that have been operationally implemented in India are discussed in greater detail along with brief mention of the results from the verification of these softwares. The next section details the current procedure of operational nowcasting in India Meteorological Department (IMD) including the recent efforts undertaken to improve the nowcast mechanism. The verification results bear out the fact that these measures have been successfully implemented and there has been significant improvement in operational forecasting of thunderstorms over the Indian region. The final section details the initiatives taken by various government and private agencies to improve the forecasting of thunderstorms and associated weather and impact assessment of thunderstorms. The present challenges before the community of thunderstorm forecasters is also detailed in this section.