scholarly journals Modified instability index of the troposphere associated with thunderstorms / nor'westers over Bangladesh during the pre-monsoon season

MAUSAM ◽  
2021 ◽  
Vol 62 (2) ◽  
pp. 205-214
Author(s):  
SAMARENDRA KARMAKAR ◽  
MD. MAHBUB ALAM
Keyword(s):  
West Bengal ◽  
Monsoon Season ◽  
Critical Values ◽  
Spatial Distributions ◽  
Instability Index ◽  
K Index ◽  
Severe Thunderstorms ◽  
Total Index ◽  
Stability Indices ◽  
Instability Indices

The present study is an attempt to study different Modified Stability Indices in relation to the occurrence of severe thunderstorms/nor’westers in order to find out the critical values of different modified indices favorable for the formation of thunderstorms in Bangladesh. Computations have also been made for the stations in and around Bangladesh for studying the spatial distribution of the modified stability indices. The Modified Instability Indices such as Modified Cross Total Index (MCT), Modified Vertical Total Index (MVT), Modified Total Totals Index (MTT), Modified SWEAT Index (MSWI), Modified K-Index (MKI) and Modified Energy Index (MEI) show greater instability of the troposphere in the morning as compared to CT, VT, TT, SWI, KI and EI. The critical values of different modified instability indices at 0000 UTC over Dhaka are: MCT >= 20° C, MVT >= 26° C, MTT >= 46° C, MSWI > 300, MKI >= 40° C and MEI < -6 joules/gm respectively for the nor’westers to occur in Bangladesh. The spatial distributions of modified stability indices have revealed that maximum instability lies over the area of surface low pressure especially over Bihar, West Bengal and adjoining Bangladesh at 0000 UTC on the dates of occurrence of nor’westers. Nor’westers occur at theeastern end of the maximum instability. For severe nor’westers of tornadic intensity, the critical values of different modified instability indices at 0000 UTC over Dhaka are: MCT >= 20° C, MVT >= 28° C, MTT >= 50° C, MSWI >= 500, MKI >= 42° C and MEI < -8 joules/gm respectively for the nor’westers to occur in Bangladesh.

scholarly journals Interrelation among different instability indices of the troposphere over Dhaka associated with thunderstorms/nor'westers over Bangladesh during the pre-monsoon season

MAUSAM ◽  
2021 ◽  
Vol 58 (3) ◽  
pp. 361-368
Author(s):  
SAMARENDRA KARMAKAR ◽  
MD. MAHBUB ALAM
Keyword(s):  
Monsoon Season ◽  
Stability Index ◽  
Dew Point ◽  
Standard Errors ◽  
Regression Equations ◽  
K Index ◽  
Total Index ◽  
Level Of Significance ◽  
Almost All ◽  
Instability Indices

Attempts have been made to correlate different instability indices among themselves statistically. The study reveals that the Showalter Stability Index (SI) has moderate to good correlations with different instability indices except Dew-point Index (DPI), Vertical Total Index (VT), Modified Vertical Total Index (MVT) and Modified K-Index (MK). Most of the correlations co-efficient are found to be significant up to 99% level of significance except Dry Instability Index (DII), which has correlation with SI up to 95% level of significance. Lifted Index (LI) has moderate to good correlation with different instability indices except DII, K-Index (KI) and MVT. Most of the correlations co-efficient are significant up to 99% level of significance except VT, SWEAT Index (SWI) and MKI, which have correlation with LI up to 95% level of significance. Unmodified instability indices have moderate to strong correlation with the corresponding modified instability indices, having 99% level of significance. The correlation co-efficient of VT and MVT, SWI and Modified SWEAT Index (MSWI), and KI and MKI are comparatively large. Standard errors of estimate are small in almost all the cases except a few. The regression equations obtained are likely to be helpful in the computation of different instability indices.

scholarly journals A synoptic and thermodynamic analysis for forecasting of squalls at Agartala

MAUSAM ◽  
2021 ◽  
Vol 72 (4) ◽  
pp. 791-802
Author(s):  
RANJAN PHUKAN ◽  
RAKESH KUMAR ◽  
M. CHANDA ◽  
RANA DAS ◽  
D. SAHA
Keyword(s):  
Thermodynamic Analysis ◽  
Wind Direction ◽  
Monsoon Season ◽  
Critical Values ◽  
Wind Pattern ◽  
K Index ◽  
Synoptic Conditions ◽  
Stability Indices

Thunderstorms accompanied with squalls cause a serious damage in Agartala and its neighbouring areas in the pre-monsoon season. In this paper, the synoptic conditions, stability indices and lower level wind pattern associated with squalls at Agartala (23.90° N, 93.25° E) during 2011 - 2020 are analysed to obtain their percentage contributions and critical values in occurrence of the events. Five major synoptic conditions are found to have contribution to the events, with varying percentages. The critical values of Showalter Index, Lifted Index, K-Index, SWEAT Index, Total Totals Index are obtained based on their contribution for at least 80% of the events. Wind direction at 925 hPa and 850 hPa with southerly component is found to be another important precursor for occurrence of the squalls.

scholarly journals An objective method for predicting occurrence of pre-monsoon (March-May) thunderstorm events over Delhi using stability indices

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 329-338
Author(s):  
M. DURAISAMY ◽  
S.K.ROY BHOWMIK ◽  
B.K. BANDYOPADHYAY
Keyword(s):  
Free Convection ◽  
Precipitable Water ◽  
Critical Values ◽  
Objective Method ◽  
K Index ◽  
Equilibrium Level ◽  
Stability Indices

In this paper an attempt has been made to investigate different stability indices in relation to the occurrence of thunderstorms in order to determine the critical values of these indices for Delhi (28.35° N / 77.12° E) using pre monsoon data for the years 1999 - 2004. The study shows that the critical values of Showalter Index (SI), Lifted Index (LI), K Index (KI), Total Totals Index (TTI), and Sweat Index (SWI) are respectively < 2 °C, < 0 °C, > 24 °C, > 44.5 °C and > 100 for the thunderstorm to occur over Delhi. The corresponding common critical ranges of Lifted Condensation Level (LCL), Level of Free Convection (LFC), Equilibrium Level (EL) and Precipitable Water (PW) are respectively 923 hPa – 695 hPa, 856 hPa – 504 hPa, 545 hPa – 109 hPa and 18 mm – 54 mm. Testing of critical values of indices and the corresponding common critical ranges of LCL, LFC, EL and PW during pre-monsoon seasons of the years 2005 and 2006 shows that they are matching well with the respective critical values/ranges in most of the thunderstorm days.

scholarly journals Developing an index for heavy convective rainfall over a Mediterranean coastal area

2014 ◽  
Vol 2 (2) ◽  
pp. 1837-1866
Author(s):  
M. Korologou ◽  
H. Flocas ◽  
H. Michalopoulou
Keyword(s):  
Satellite Images ◽  
Local Instability ◽  
Instability Index ◽  
Synoptic Scale ◽  
Convective Rainfall ◽  
Severe Thunderstorms ◽  
Weather Stations ◽  
Synoptic Observations ◽  
Local Weather ◽  
Instability Indices

Abstract. Heavy convective rainfall incidents that occurred over western coastal Greece and led to flash floods are analyzed with respect to mesoscale analysis for the period from January 2006 to June 2011. The synoptic scale circulation is examined throughout the troposphere along with satellite images, lightning data and synoptic observations of weather stations. Well known instability indices are calculated and tested against synoptic observations. Taking into account the severity of the incidents, the performance of the indices was not as good as expected. Further detailed analysis resulted to the development of a new index that incorporates formalized experience of local weather and modeled knowledge of mechanism of severe thunderstorms. The proposed index named Local Instability Index (LII) is then evaluated and its performance is found to be quite satisfactory.

scholarly journals Studies on fish diversity concerning Hydro-ecology of Kangsabasti river in Purulia district, West Bengal, India

2020 ◽  
Vol 26 (2) ◽  
Author(s):  
Manab Kumar Saha
Keyword(s):  
Fish Species ◽  
Physicochemical Parameters ◽  
West Bengal ◽  
Monsoon Season ◽  
Fish Diversity ◽  
Riverine Ecosystem ◽  
Post Monsoon ◽  
Fish Catch ◽  
Purulia District

Fish diversity depends both on various physicochemical parameters and the biological components of the riverine ecosystem. During the study period from January 2017 to December 2019 the highest fish diversity and density were observed in post-monsoon and lowest in pre-monsoon season in the Kangsabati River, Purulia District of West Bengal. Twenty five fish species, associated with 19 genera, 10 families and 5 orders have been identified. It was recorded that the Cyprinidae was the predominant family, which represented 56% of the entire fish catch.

scholarly journals MENGINTIP KONDISI CUACA PENYEBAB BANJIR BESAR DI DKI JAKARTA TANGGAL 25 OKTOBER 2010

2011 ◽  
Vol 12 (2) ◽  
pp. 43
Author(s):  
Mimin Karmini ◽  
Findy Renggono
Keyword(s):  
Rainfall Intensity ◽  
Heavy Rain ◽  
Rainfall Amount ◽  
Western Region ◽  
Convective Activity ◽  
Stagnant Water ◽  
Standing Water ◽  
K Index ◽  
Convective Process ◽  
Stability Indices

DKI Jakarta dikejutkan dengan hujan deras pada jam 16:00 WIB. Genangan airlangsung terjadi akibat derasnya hujan. Hujan berlangsung sampai sekitar jam 20:00WIB. Dari data AWS di Jatiwaringin, curah hujan tertinggi sebesar 230 mm tercatatpada jam 16:00 WIB. Curah hujan sampai jam 19:00 WIB tercatat sebesar 650.60 mmatau intensitas 216.87 mm/jam untuk periode jam 16:00 s.d. 19:00 WIB. Beberapaindeks stabilitas, yang dihitung dari data rawinsonde jam 07:00 WIB, menunjukanpotensi terjadinya aktivitas konvektif yang bisa menghasilkan hujan deras. Beberapaindeks stabilitas yang menunjukan potensi terjadinya proses konvektif kuat adalah: LI(Lifted Index) = - 06; SI (Showalter Index) = - 0.7; K Index = 36.7; TT (Total Totals) =43.9. Kejadian hujan paling deras di kawasan barat DKI Jakarta sampai Tangerang.Genangan air hampir merata di DKI Jakarta dan Tangerang dengan ketinggian yangbervariasi antara 20 cm – 100 cm.Jakarta was struck by torrential rain at 16:00 pm. Standing water caused by heavy rainoccured immediately. The rain lasted until around 20:00 pm. From the AWS measurement at Jatiwaringin, highest rainfall of 230 mm was recorded at 16:00 pm. Rainfall amount until 19:00 pm was recorded of about 650.60 mm, in other words rainfall intensity was about 216.87 mm/hour for the period of 16:00 – 19:00 pm. Some stability indices, which is calculated from rawinsonde at 07:00 am showed the potential for convective activity which could produce heavy rain. Some stability indices that show strong potential for convective process are: LI (Lifted Index) = - 06; SI (Showalter Index) = - 0.7; K Index = 36.7; TT (Total Totals) = 43.9. The heaviest rainfall occured in the western region of Jakarta until Tangerang. Stagnant water is almost evenly in Jakarta and Tangerang with varying heights between 20 cm - 100 cm.

scholarly journals Prospect of double cropping of rainfed rice in West Bengal

MAUSAM ◽  
2021 ◽  
Vol 49 (1) ◽  
pp. 121-126
Author(s):  
H. P. DAS ◽  
S. V. DATAR
Keyword(s):  
Markov Chain ◽  
West Bengal ◽  
Monsoon Season ◽  
Growing Season ◽  
Threshold Value ◽  
Rainfall Data ◽  
Ranking Method ◽  
Growing Period ◽  
Rainfed Rice ◽  
Double Cropping

The prospect of double cropping of rain fed rice in West Bengal has been studied in two agroecological conditions (Canning, located in coastal saline region and Nagri, located in Red lateritic region) by identifying growing season through the analysis of rainfall data. The rainfall data of these locations have been analysed for dry and wet weeks by assuming a dry threshold value of 20 mm per week. Wet and dry weeks have been subjected to Markov Chain probability analysis and periods of ideal sowing have been determined. Rainfall data has also been accumulated from 1st  week (1- 7 Jan) onwards, and 52nd week (24- 31 Dec) backwards and by subjecting it to ranking method, growth periods of dry and wet crops have been determined. The study reveals that generally from 24th to 37th week (11 Jun-16 Sep) the probability of getting wet weeks exceeds 15% and probability of two consecutive dry weeks is negligible from 20th to 38th week (14 May - 23 September) for both the statistics. It is also found that harvesting two rice crops of shorter duration is feasible during the growing period covering pre-monsoon and monsoon season.

scholarly journals Nor’wester over West Bengal and comfortability

MAUSAM ◽  
2021 ◽  
Vol 58 (2) ◽  
pp. 177-188
Author(s):  
K. K. CHAKRABARTY ◽  
A. K. NATH ◽  
S. SENGUPTA
Keyword(s):  
Relative Humidity ◽  
West Bengal ◽  
Monsoon Season ◽  
Early Morning ◽  
Positive Aspect ◽  
Weather Factors ◽  
Thermal Index ◽  
The People ◽  
Tropical Areas ◽  
Weather Parameters

During the pre-monsoon months of March, April and May the weather over Kolkata is generally very uncomfortable due to high temperature and relative humidity. During this season Kolkata is affected by the nor’wester activity. Generally the nor’wester activity is defined as a disastrous weather activity and is locally called as ‘Kaalbaisakhi’ as it is ‘kaal’ or destruction during Bengali Baishakh (April-May) month over Bengal. However the downdraft associated with the nor’wester brings cool air and temperature sometimes drops by as much as 8 to 9 degree Celsius and the atmosphere becomes comfortable for some period. This is an entirely different and positive aspect of nor’wester.The human comfortability depends upon many weather parameters apart from human physiological parameters. However the primary weather factors are air temperature and relative humidity especially for tropical areas. Many authors have worked on this and the well accepted formula for thermal index THI or Discomfort Index DI is taken from Thom (1957,1958) which is a function of dry bulb and wet bulb temperature i.e., THI or DI = 0.4 (Ta + Tw) + 15 where temperature is in ºF and is 0.72 (Ta + Tw) + 40.6 where temperature is in ºC. Various stages of comfortability are classified viz., (i) Discomfortable (ii) Partial discomfortable and (iii) Comfortable. Neglecting the effect of wind and further simplifying the equation for DI as a function of (Ta + Tw) the range varies from 27 to 55 in increasing order of temperature.During the pre-monsoon months when the climate over Kolkata is very sultry and uncomfortable, people generally desire the onset of nor’wester for some temporary relief although it results into destruction. The nor’wester makes the weather comfortable after its occurrence and remains comfortable for 10 to 12 hours and some time even for a day. The present study is made taking six years data over Kolkata, both Alipore and Dum Dum. It is seen that except early morning of March the remaining period of pre-monsoon season is found to be uncomfortable climatologically. In the present study there were 91 occasions of squalls and it is found that most of the squalls occurred during the month of April and May and on most of the occasions nor’wester made the weather comfortable for a large part of the day in the month of April. By the end of May nor’wester activity also brought relief but not to that extent as in March and April to the people of Kolkata and neighbourhood.

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