scholarly journals Latitudinal distribution of water vapour over the Arabian Sea and Bay of Bengal using Bhaskara-II SAMIR data

MAUSAM ◽  
2021 ◽  
Vol 43 (4) ◽  
pp. 385-394
Author(s):  
P.N. PATHAK ◽  
N. GAUTAM
Keyword(s):  
Water Vapour ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Latitudinal Gradient ◽  
Southwest Monsoon ◽  
Climatological Data ◽  
Latitude Range ◽  
Uniform Value ◽  
Northern Winter ◽  
Indian Seas

The main purpose of the present work is to establish the reliability of the SAMIR-derived water vapour (WV) data over the Arabian Sea and the Bay of Bengal for the entire 18-month from January 1982 to June 1983 period of the in-orbit operation of the SAMIR system. The average latitudinal distributions of WV over the Arabian Sea and Bay of Bengal for different months, derived from the SAMJR data were found to be broadly consistent with the climatological data on WV from the coastal and island radiosonde stations.   A significant latitudinal gradient in WV has been found during the northern winter months (Dec-Feb) with the highest value of 4-5 gm/cm2 near the equator and thc lowest value of about 2 gm/cm2 at about 20oN over the Indian seas. This gradient gradually decreases during the subsequent months and almost vanishes during the southwest monsoon months (Jun-Sep) when the WV has nearly uniform value of 4-5 gm/cm2 in the entire latitude range from the equator to 20oN over the Indian seas. Finally, it has been found that WV values over the Bay of Bengal are generally higher than those over the Arabian Sea at co-latitudinal positions. The implications of this result are discussed in the light of other considerations.

scholarly journals Trends in the frequency of cyclonic disturbances and their intensification over Indian seas

MAUSAM ◽  
2021 ◽  
Vol 51 (2) ◽  
pp. 113-118
Author(s):  
A. K. SRIVASTAVA ◽  
K. C. SINHA RAY ◽  
U. S. DE
Keyword(s):  
Bay Of Bengal ◽  
Arabian Sea ◽  
Hadley Circulation ◽  
Cyclonic Activity ◽  
Recent Period ◽  
Level Of Confidence ◽  
Cyclonic Disturbances ◽  
Indian Seas

Trends in cyclonic disturbances for the period 1891-1997 were studied over Bay of Bengal and Arabian Sea. It is noticed that there is a significant decreasing trend at 99% level of confidence in the frequency of storms. The slopes of decreasing trend in cyclonic activity over Bay of Bengal and that over Arabian Sea were found to be maximum during last four decades. Weakening of Hadley circulation due to upper tropospheric warming may be one of the cause of this decreasing trend. There appears to be decrease in intensification of cyclonic disturbances in recent period.

scholarly journals Remote-Sensing-Based Estimation of Surface Nitrate and Its Variability in the Southern Peninsular Indian Waters

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
R. K. Sarangi
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Nitrate Concentration ◽  
Southwest Monsoon ◽  
Northeast Monsoon ◽  
Northern Indian Ocean ◽  
Noaa Avhrr ◽  
Nitrate Concentrations ◽  
High Nitrate Concentration

A relationship between sea surface temperature (SST) and surface nitrate concentrations has been obtained for the first time based on in situ datasets retrieved from U.S. JGOFS (1991–96) and Indian cruises (2000–2006) in the Arabian Sea, Bay of Bengal and Indian Ocean region around the southern Indian tip. The dataset includes 1537 points. A sigmoid relationship obtained with value 0.912. NOAA-AVHRR pathfinder satellite monthly averaged SST data retrieved from the PODAAC/JPL/NASA archive during July 1999–June 2004. The datasets imported in the ERDAS-Imagine software and SST images generated on monthly and seasonal scales, for latitudes 5–12°N and longitudes 75–85°E. The ocean surface nitrate images retrieved based on the established sigmoid relationship with SST. The nitrate concentrations ranged between 0.01–3.0 μM and categorized into five ranges. The significant seasonal upwelling zone around the southwest coast of India (Kerala coast, Latitude 80.10–9.30°N and Longitude 75.60–76.20°E) was identified during July–September 1999–2004 with very high nitrate concentration (~1.00 μM). Low nitrate and nitrate-depleted zones observed during summer (March–May). In the Arabian Sea and northern Indian Ocean, high nitrate concentration (~0.50 μM) observed during the southwest monsoon (SWM), whereas the Bay of Bengal was marked with high nitrate (~0.50 μM) during the northeast monsoon (NEM). SST was high (~29°C) in the Bay of Bengal and low (~26°C) in the Arabian Sea and northern Indian Ocean during SWM and vice versa during the NEM. There is a clear inverse relationship between nitrate and SST in the study area during July 1999–June 2004.

scholarly journals Climatology of Energetics of cyclones over Indian Seas

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Somenath Dutta ◽  
Geena Sandhu ◽  
Sanjay G Narkhedkar ◽  
Sunitha Devi
Keyword(s):  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Monsoon Season ◽  
Recent Decade ◽  
Reanalysis Data ◽  
Monsoon Period ◽  
Post Monsoon ◽  
Post Monsoon Season ◽  
Indian Seas

The study discusses the energetic aspects of tropical cyclones formed over Arabian Sea (AS) and Bay of Bengal (BOB) during the period from 1991 till 2013 and aims at bringing out climatology of the energetics of tropical cyclones over Indian Seas. Total 88 cyclones that developed over the Indian Seas during the recent decade of 1991-2013 have been studied. These intense systems are categorized on the basis of their formation region and season of formation. It is seen that during the study period, the frequency of formation of cyclones over BOB is twice that over AS which is consistent with the climatology of the regions. Further, it is noticed that over both the regions, they are more frequently formed in the post monsoon period compared to pre monsoon. The trend analysis of the frequency of cyclones forming over both basins, season wise shows that the overall trend for both basins is of just decreasing type. However, for Arabian Sea; the decreasing trend is more apparent in the post monsoon season, whereas in the case of the Bay of Bengal the decreasing trend is more evident in the pre monsoon season. Various energy terms, their generation and conversion terms have been computed using NCEP/NCAR reanalysis data. Day to day quantitative analysis of these parameters is studied critically during various stages of the cyclones. The composites of these categorized systems are formed and studied. The formative, intensification and dissipation stages showed variations in their energy terms.

scholarly journals A Climatology of Arabian Sea Cyclonic Storms

2011 ◽  
Vol 24 (1) ◽  
pp. 140-158 ◽  
Author(s):  
Amato T. Evan ◽  
Suzana J. Camargo
Keyword(s):  
Bay Of Bengal ◽  
Environmental Conditions ◽  
Arabian Sea ◽  
Large Scale ◽  
Late Onset ◽  
Southwest Monsoon ◽  
Reanalysis Data ◽  
Tropical Cyclogenesis ◽  
Storm Frequency ◽  
Cyclonic Storms

Abstract On average 1–2 tropical cyclones form over the Arabian Sea each year, and few of these storms are intense enough to be classified as very severe or super cyclonic storms. As such, few studies have explicitly identified the seasonal to interannual changes in environmental conditions that are associated with Arabian Sea tropical cyclogenesis. However, over the last 30 yr several intense Arabian storms did form and make landfall, with large impacts, which motivates this new study of the basin. The conclusions of earlier studies are visited by utilizing modern observational and reanalysis data to identify the large-scale features associated with Arabian tropical cyclone variability on seasonal time scales. Then year-to-year changes in environmental conditions that are related to interannual variability in Arabian storms during the pre- and postmonsoon periods are elucidated. The analysis of the relationship between large-scale environmental variables and seasonal storm frequency supports conclusions from work completed more than 40 yr prior. Investigation of the year-to-year changes in premonsoon storm frequency suggests that May (June) storms are associated with an early (late) onset of the southwest monsoon. The findings also demonstrate that November cyclones (the month when the majority of postmonsoon cyclogenesis occurs) primarily form during periods when the Bay of Bengal experiences a broad region of high sea level pressure, implying that November storms form in either the Arabian Sea or the Bay of Bengal but not in both during the same year. Finally, the analysis of changes in a genesis potential index suggests that long-term variability in the potential for a storm to form is dictated by changes in midlevel moisture.

scholarly journals Multiple variability of summer sea surface temperature (SST) and evaporation over the Indian Seas

MAUSAM ◽  
2021 ◽  
Vol 50 (4) ◽  
pp. 355-342
Author(s):  
O. P. SINGH
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Evaporation Rate ◽  
Function Analysis ◽  
Meteorological Data ◽  
North Indian Ocean ◽  
Sea Surface ◽  
Indian Seas

Utilising thirty one years' marine meteorological data from 1961-91 recorded over the north Indian Ocean the sea surface temperature (SST) and evaporation have been obtained for different regions of the Arabian Sea and the Bay of Bengal. The moving pentad averages of SST and evaporation reveal increasing tendencies of both the parameters over the Arabian Sea and that of evaporation over the Bay of Bengal during May. The changes are real and significant as revealed by the trend analysis. The spectral analysis shows that SST has a 2-3 year significant cycle and evaporation rate has a 2-5 year cycle over the Indian Seas. In addition, a significant 15-year cycle is present in the SST over the Bay of Bengal and evaporation rate over the Arabian Sea. Empirical orthogonal function analysis performed on the anomalies of SST and evaporation rate over the Arabian Sea and the Bay of Bengal reveals that the time coefficient of first EOF has an increasing tendency.

scholarly journals Study of secondary heat sources over India during southwest monsoon 2002

MAUSAM ◽  
2021 ◽  
Vol 58 (2) ◽  
pp. 213-228
Author(s):  
U. V. BHIDE ◽  
S. M. BAWISKAR ◽  
V. R. MUJUMDAR ◽  
P. V. PURANIK ◽  
S. P. GHANEKAR ◽  
...  
Keyword(s):  
Heat Source ◽  
Bay Of Bengal ◽  
Seasonal Variations ◽  
Seasonal Variability ◽  
Arabian Sea ◽  
Southwest Monsoon ◽  
Monsoon Circulation ◽  
Heat Sources ◽  
Drying Rates ◽  
The Impact

The southwest monsoon of 2002 has three unusual features viz., (i) delay in advance over westernmost parts of India by one month, (ii) absence of depressions/storms over Bay of Bengal and Arabian Sea and (iii) -51% departure of all India rainfall in July. These features of intra-seasonal variability have been studied in this paper. Apparent heat source (Q1) and apparent moisture sink (Q2) over Indian region have been estimated using daily NCEP-reanalysis data, for June - September 2002 to study the intra-seasonal variations of the secondary heat sources in relation to observed intra-seasonal variations of circulation and rainfall over India.The intensities of vertically integrated heat source < Q1 > and moisture sink < Q2 > are found to coincide with the excess rainfall zone over India in June 2002, whereas the intensities of < Q1 > and < Q2 > over central parts of the country in July 2002 are not comparable. This indicates absence of convective rainfall and increased sensible heating over India in July. The x-t diagram of heating and drying rates at 500 hPa along 22.5° N shows large positive heating and drying rates of the order of 16° C per day over the western trough region around 26 June. Following this event, low positive or negative values are observed over central India in July.The y-t diagram of vertical velocity at 500 hPa shows strong subsidence near the foot hills of Himalayas during the season. This has affected the formation of depressions or storms over Bay of Bengal and Arabian Sea. Adiabatic and diabatic heating as well as drying in the troposphere has led to the break-like situation over India in July 2002 and weaker monsoon circulation during August and September. The analysis has brought out the impact of northern hemispheric mid-latitude circulation on intra-seasonal variability of southwest monsoon 2002 more clearly. 

Cyclogenesis in the Bay of Bengal and the Arabian Sea

Tellus ◽  
1970 ◽  
Vol 22 (6) ◽  
pp. 716-718
Author(s):  
K. G. Mowla
Keyword(s):  
Bay Of Bengal ◽  
Arabian Sea
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