monsoon period
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MAUSAM ◽  
2022 ◽  
Vol 53 (1) ◽  
pp. 19-30
Author(s):  
P. K. BHARGAVA

A detailed statistical analysis of monthly average wind speed data of monsoon period (June-September) for the year 1921-90  for 57 stations spread all over India have been reported. Probability densities, average wind speeds, standard deviations, kurtosis and  skewness of wind speed frequency distribution for each station have been worked out. Histograms depicting relative frequency distribution of average wind speeds have also been prepared. It is observed  that the different histograms do not exhibit any similarity among themselves indicating thereby  that no single distribution is uniformly applicable for all the stations. It is also seen that the average  wind speeds during monsoon period over major part of India  varies from 7 to 14 kmph. Further, at most of the stations average monsoon  wind speed is generally higher than average annual wind speeds. It is also noted that most of the time the wind speed exceeds 10 kmph in coastal regions of Gujarat and southern parts of the peninsular India. The information generated is of multi fold application such as (i) Identification of sites suitable for installation of Wind Energy Conversion Systems  (ii) Development of Driving Rain Index and (iii) Design of buildings for creating comfortable environment indoors.


MAUSAM ◽  
2022 ◽  
Vol 46 (3) ◽  
pp. 253-256
Author(s):  
C. K. RAJAN ◽  
BINDU G.

ABSTRACT. Rainfall data for a period of 50 years from 1931 onwards have been analysed for three west, coast stations in Kerala for the southwest monsoon period, The period is divided into two halves, the first half, i.e.June-July, providing comparatively more rainfall  and the second half, i.e. August-September, providing comparatively lesser rainfall. Rainy days, having rain amounts>6.25 cm/day, have only been utilized for this study. The lunar cycle, which is having 29.53 days, is divided into ten phases, each phase constituting of around three days. To consider the effect of solar activity, the period is divided into active and quiet sun by considering those years with sunspot number greater than the upper quartile and those with sunspot number less than the lower quartile respectively. The data were analysed using x2 test. It describes the magnitude of the discrepancy between theory and observation. Analysis has shown that there is some statistical significance between heavy rainfall and lunar cycle. The effect is more significant in active sun period which shows the effect of solar activity also.  


MAUSAM ◽  
2022 ◽  
Vol 44 (4) ◽  
pp. 329-336
Author(s):  
D LOHAR ◽  
B CHAKRAVARTY ◽  
B. Pal

  A three-dimensional hydrostatic model has been employed for the study of sea breeze circulations over south West Bengal with special reference to an inland station Kharagpur (22°.21' N, 87° 19'E). A series of sensitivity experiments have been performed to stress the Importance of differential heating on circulation over south West Bengal during pre-monsoon period. It is found that due to differential heating rate between land and sea surfaces, sea breezes can penetrate to the inland station Kharagpur and beyond even in case of moderate gradient wind. Surface observations at Kharagpur and pilot balloon observation at nearby station Kalaikunda are used to compare the model results. The onset of sea breezes, variation of the air temperature and humidity are In fairly good agreement whereas It over estimates the depth of the circulation and cannot predict the variation  of the late morning hours surface wind.


MAUSAM ◽  
2022 ◽  
Vol 64 (1) ◽  
pp. 83-88
Author(s):  
RAKESH RAKESHROY ◽  
ANIRBAN ANIRBANGUHA ◽  
BARINKUMAR BARINKUMARDE ◽  
ABHIJIT CHOUDHURY

bl 'kks/k i= esa vizSy 2009 ls vDrwcj 2009 dh vof/k ds nkSjku HkkSfrdh foHkkx] f=iqjk fo’ofo|ky; }kjk oh- ,y- ,Q- ok;qeaMyh; vFkok LQsfjDl dh vfHkyk{kf.kd fofo/krk dks pkj vyx & vyx vko`fr;ksa esa ntZ fd;k x;k gSA bl  'kks/k i= esa mRrj iwoZ Hkkjr ds 76 lfØ; xtZ ds lkFk rwQku okys vf/kdk¡’k fnuksa ds vk¡dMs+ iz;qDr fd, x,A buls izkIr ifj.kkeksa esa ekulwu ds nkSjku LQsfjDl ifjorZu esa dbZ izdkj dh fo’ks"krk,¡ n’kkZbZ xbZ gSaA bu Øfed fxjkoV] Øfed o`f) ¼th- ,Q- th- vkj-½] Øfed o`f) vpkud fxjkoV ¼th- vkj- ,l- ,Q-½] Øfed o`f) Øfed fxjkoV ¼th- vkj th- ,Q-½] Øfed fxjkoV vpkud o`f) ¼th- ,Q-,l- vkj-½] vkdfLed o`f)  Øfed fxjkoV ¼,l- vkj- th- ,Q-½] vpkud fxjkoV vpkud o`f) ¼,l- vkj- ,l- ,Q-½ vpkud fxjkoV vpkud  o`f) ¼,l- ,Q- ,l- vkj-½ vpkud fxjkoV Øfed o`f) ¼,l- ,Q- th- vkj-½ rFkk dBksj ¼Spiky½ Lo:i esa n’kkZ;k x;k gSA ekulwuh lfØ; xtZ ds lkFk rwQkuksa okys vf/kdka’k fnuksa esa lHkh izdkj ds iSVuksaZ esa ¼th- vkj th- ,Q-½ dh vko`fr vf/kdrj izdj.kksa esa ntZ gqbZ gS  ¼izR;sd vko`fr esa vkSlru yxHkx 37 izfr’kr ?kVuk,¡ ntZ gqbZ gSa½ gekjh izs{k.kkRed vof/k ds nkSjku 23&26 ebZ dh vof/k esa caxky dh [kkM+h esa ‘vkbZyk’ uked ,d rhoz m".kdfVca/kh; pØokr vkj-,l-,e-lh- inuke% ch- vks- ch- vks-2] ts- Vh- MCY;w- lh- inuke% vks- Vw- ch- vk;k FkkA 25 ebZ 2009 ds m".k ds m".kdfVca/kh; pØokr ds nkSjku lHkh izdkj ds lkekU; ekulwuh vof/k dh vfHkyk{kf.kd fo’ks"krkvksa esa ,l-vkj-,l-,Q- ¼izR;sd vko`fr esa 86 izfr’kr ds vkSlru nj ls ?kfVr½ vko`fr vf/kdrj izdj.kksa esa ns[kh xbZ gSA tc pØokr caxky dh [kkM+h ds rVksa ls Vdjk;k ml fnu ds LQsfjDl ds vyx&vyx vko`fr forj.kksa ds vuqlkj o`f) vkSj fxjkoV dk xaHkhjrk ls fo’ys"k.k fd;k x;kA ekulwuh fnuksa vkSj ‘vkbyk’ pØokr lfØ; fnol ds lHkh ds lHkh izdkj ds iSVuksaZ dk rqyukRed v/;;u fd;k x;kA gekjs fu"d"kZ ds vuqlkj izpaM pØokr ‘vkbyk’ vkSj vU; xtZ Hkjs rwQku okys ekulwuh fnuksa ds nkSjku mRrj iwoZ Hkkjr esa cknyksa dh lw{e lajpuk esa dkQh varj fn[kkA pØokrh xfrfof/k ds nkSjku LQSfjDl ds ns[ks x, cnyko dh laHkkfor O;k[;k dks xtZ Hkjs rwQku okys cknyksa dh rfM+r xfrfof/k ds vk/kkj ij le>k;k x;k gSA The present work reports the characteristic variations in VLF atmospherics or sferics at four discrete frequencies recorded at the Department of Physics, Tripura University, during the period from April 2009 to October 2009. Data from 76 active thunder days over North-East India is considered for the present investigation. Results show several types of features in the variation of sferics during the monsoon period. These are termed as gradual fall gradual rise (GFGR), gradual rise sudden fall (GRSF), gradual rise gradual fall (GRGF), gradual fall sudden rise (GFSR), sudden rise gradual fall (SRGF), sudden rise sudden fall (SRSF),  sudden fall sudden rise (SFSR), sudden fall gradual rise (SFGR) and spiky. During the Monsoon thunder active days, amongst all the patterns, GRGF occurred in most of the cases in all frequencies (average occurrence rate around 37% in each frequency). During our observational period, a severe tropical cyclonic storm named “AILA” (RSMC Designation BOB02, JTWC Designation 02B) occurred over the Bay of Bengal during 23-26 May 2009. Among several characteristic features during normal Monsoon period, SRSF (average occurrence rate around 86 % in each frequency) dominated the sferics on the 25 May, 2009, when the cyclone struck the coastal areas of the Bay of Bengal. The sferics of that day has been analyzed critically with respect to discrete frequency distribution of rise rate and fall rate of the intensity of the sferics. A comparison is made for all the patterns for the Monsoon days and the AILA cyclone active day. Our findings show substantial difference in the microstructure of clouds producing severe cyclonic storms like AILA and other thunderstorms during Monsoon seasons over North-East India. The possible interpretation of the observed variations in sferics is explained on the basis of the electrical activity that occurs inside a thunder-cloud especially during cyclonic activity.


2021 ◽  
Vol 34 (4) ◽  
Author(s):  
ALANKARAGE PUBUDINI RANAHANSIKA SILVA ◽  
◽  
RANKIRI PATHIRANNAHELAGE PRABATH KRISHANTHA JAYASINGHE ◽  
MAHADURAGE ISHARA GIMHAN RATHNASURIYA ◽  
KAHAWE PALLIYA GURUGE KSHANIKA PIYUMI GURUGE ◽  
...  

Fundamental understanding of fish resources has become a crucial need in Sri Lanka for the sustainable management of fish stocks. Knowledge of ichthyoplankton essential in identifying the spawning dynamics of fish is scarce in this region of the Indian Ocean. A survey was conducted in 2018 covering different monsoon seasons to monitor the abundance, distribution, and diversity of ichthyoplankton along the west coast of Sri Lanka. Samples collected using vertical and horizontal WP2 hauls showed a total of 4095 fish eggs, with identification possible only to 3 families: Clupeidae, Engraulidae, and Cynoglossidae and 465 larval fish belonging to 23 families. The most dominant families recorded were the Siganidae, Blenniidae, Clupeidae, Gobiidae, and Engraulidae, which highlight the importance of pelagic and demersal fish along the west coast. A significant temporal pattern in egg abundance was observed with the highest abundance in March (535 10 m-3) in vertical WP2 net hauls. Furthermore, significant differences in spatial patterns of larval abundance were seen in vertical and horizontal samples. High larval fish abundances were recorded in March and during September - November, with northern regions generally having the highest abundances (~36 larvae 10 m-3). The spawning coincides with the productive southwest monsoon period (May to September). The high diversity and abundance of eggs and larvae recorded in this study indicate that the west coast is likely an important spawning and nursery ground for demersal and pelagic fish.


2021 ◽  
Author(s):  
Soumyajyoti Jana ◽  
Gargi Rakshit ◽  
Animesh Maitra

Abstract The elevated layer of heat-absorbing pollutant aerosols causes temperature perturbations in the pre-monsoon period above the boundary layer height (1.6-4 km) as observed over a polluted tropical urban location Kolkata (22°34' N, 88°22' E) during 2007-2016. Satellite observations of different types of aerosols show an increase in aerosol extinction coefficient around 1.6-4 km altitude, enhancing the perturbations in both temperature and wind profiles at that height. The opposing air mass movement within and above the boundary layer, which is strengthened by elevated heat-absorbing aerosols, is illustrated by height profiles of atmospheric vorticity and divergence. This results in higher Brunt-Vaisala frequencies indicating increased atmospheric oscillations. Consequently, atmospheric gravity waves, which manifest the temperature and wind profile perturbations, have enhanced energy in the upper troposphere (6-10 km). Based on multi- technique observations consisting of radiosonde, space-borne lidar and model data, this study reveals the interactions between aerosol and other atmospheric processes such as temperature variations and wind perturbations, which affect the atmospheric instability and increase gravity wave activities during the pre-monsoon period over a tropical metropolis.


MAUSAM ◽  
2021 ◽  
Vol 42 (4) ◽  
pp. 393-400
Author(s):  
N. PANDHARINATH

For agricultural planning, it is important to know the sequence of dry, wet periods. For this purpose a week period may be taken as the optimum length of time. The success or failure of crops particularly under rainfed conditions is closely linked with the rainfall patterns. In this study the Markov chain model method has been applied to know the probability of having a dry or a wet week and consecutive dry or wet periods of 2 or 3 weeks during monsoon period over Andhra Pradesh.    


MAUSAM ◽  
2021 ◽  
Vol 52 (2) ◽  
pp. 371-378
Author(s):  
G. C. BASU ◽  
SANJIB KUMAR BASU

One-step transitional probability matrices are obtained by Markovian model from one transitional state to other for different rainfall characteristics (such as, non-rainy days, light rains, moderate rains, heavy rains and very heavy rains) at Calcutta (Alipore) for different monsoon months. The disorderness (unvertainty) of the transitional system of the monsoon rainfall characteristics are studied by Shannon’s model. The favourable or unfavourable condition of different states are also studied by redundancy test during monsoon period at Caluctta. A Long-run probability vectors of such rainfall characteristics are found out from probability matrices. A trend in rainfall amounts during monsoon period at Calcutta for each of the monsoon month, June to September, has also been studied here.


MAUSAM ◽  
2021 ◽  
Vol 65 (1) ◽  
pp. 67-72
Author(s):  
PRAGYAN KUMARI ◽  
RAJAN KUMAROJHA ◽  
AWADOOD WADOOD ◽  
RAMESH KUMAR

Daily rainfall data of 56 years (1956-2011) of Palamau district of Jharkhand have been considered to analyse the long term average and its temporal variability on weekly, monthly, seasonal and annual basis. The average annual rainfall at Palamau was 1138 mm with 34 per cent coefficient of variation indicating thereby that the rainfall was not much stable over the years. July was the highest rainfall recipient month (332 mm) followed by August (310 mm) during the monsoon period. Trend analysis on rainfall of past 56 years exhibited a decreasing pattern of 8.33 mm and 7.04 mm per year in annual and kharif season rainfall, respectively. Agricultural drought was most frequently observed in early (23-26 SMW) as well as late (37-40 SMW) stages of kharif crops. Meteorological droughts of different intensities, viz., mild, moderate and severe over the observed periods showed that station is prone to mild-moderate type of drought. Short duration, low water requiring but high value crops like maize, pulses, oilseeds and some vegetables can be opted for this region to minimize the production risk.


2021 ◽  
Author(s):  
ATEETH SHETTY ◽  
R. S. KANKARA ◽  
DHANALAKSHMI S. ◽  
BUCKLE S. ◽  
SUBBURAJ S.

Abstract The study examines the shoreline (1990-2019) and nearshore morphological changes (seasonal) to understand the littoral drift and sediment budget variability. Shoreline change rate depicts erosion (-0.06 m/yr) in the northern sector and accretion (+0.12 m/yr) in the southern sector. Seasonal nearshore morphological changes from non-monsoon to monsoon period signifies net erosion (-1.8x10^4 m^3 ) in northern sector and net accretion (+2.5x10^4 m^3) in the southern sector. Although the lost sediment during monsoon is regained in non-monsoon period, the quantity of sediment gain is reduced in areas with human interventions. The results of the investigation depict the dominance of littoral drift towards north from February to October, when wave approach from east-southeast to south-southeast direction and southwards from November to January when the wave direction was from east-northeast to east-southeast. The net longshore sediment transport rate estimated during the study period was 2.6x10^5 m^3/year in the northern sector and 1.5x10^5 m^3/year in the southern sector with higher rate attributed to monsoon than the non-monsoon. Sediment budget results in deciphering the causes of erosion (-1.27×10^4 m^3/yr) in northern sector and accretion (3.91×10^4 m^3/yr) in southern sector in the wave-dominated Chennai beach.


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