scholarly journals Principal component analysis of monthly mean Area surface temperature over the Arabian Sea, Bay of Bengal and north Indian Ocean for two Contrasting sets of monsoon years

MAUSAM ◽  
2021 ◽  
Vol 44 (1) ◽  
pp. 69-76
Author(s):  
T. K. BALAKRISHNAN ◽  
A. K. JASWAL ◽  
S.S.. SINGH ◽  
H. N. SRIVASTAVA
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Monsoon Rainfall ◽  
Equatorial Indian Ocean ◽  
Principal Component ◽  
North Indian Ocean ◽  
Orthogonal Function ◽  
The North ◽  
Extreme North

The spatial distribution and temporal variation of the monthly mean SSTA over the Arabian Sea, Bay of Bengal and the north Indian Ocean were investigated for a set of contrasting years of monsoon over the period 1961-80 for months April through July using Empirical Orthogonal Function (EOF) technique with a view to identify regions that are significantly related to the monsoon rainfall. Over 75% of the total variance is, explained by the first mode EOF. SSTA over the north and northeast Arabian Sea during pre-monsoon months were found to be possible indicators of the ensuing monsoon activity. The higher eigen vectors in May over northeast Arabian Sea may signal good monsoon and vice versa. In June there is a marked contrast in the distribution of SST over the Arabian Sea between the two sets of the years the eastern Arabian Sea IS warmer for the deficient monsoon years while the entire Arabian Sea except over the extreme north Arabian Sea is cool during good monsoon years. There is formation of SSTA over the equatorial Indian Ocean area close to Indonesian island commencing from May which is more marked in June and is positively correlated with seasonal rainfall activity over India.  

scholarly journals An oceanic model for the prediction of southwest monsoon rainfall over India

MAUSAM ◽  
2021 ◽  
Vol 47 (1) ◽  
pp. 91-98
Author(s):  
J. P. SlNGH ◽  
D. S. PAI
Keyword(s):  
Indian Ocean ◽  
Regression Model ◽  
Summer Monsoon ◽  
Arabian Sea ◽  
Monsoon Rainfall ◽  
Principal Component ◽  
Southwest Monsoon ◽  
Summer Monsoon Rainfall ◽  
North Indian Ocean ◽  
The North

Nine new oceanic predictor for long range forecasting of Indian summer monsoon rainfall been identified utilizing  the marine meteorological data of the North Indian Ocean and the monsoon rainfall data of the period 1961-91. In order to develop a reliable regression model the principal component analysis (PCA) of original variables has been done. Five parameters having maximum influence on first principal component, which is having highest correlation with the monsoon rainfall are : wind power in the atmospheric boundary layer over the north Indian Ocean between Equator and 100 N, mean evaporation over the Arabian Sea (00 -150 N) mean sea surface temperature (SST) gradient over the Arabian Sea between 7.50 – 17.50 N, mean evaporation over Bay of Bengal between Equator and 100 N and mean sea level pressure (SLP) over the Arabian Sea, each pertaining to the month of May. A multiple regression model for all Indian rainfall of southwest monsoon season has been developed using the principal components which have got good cor-relations with the monsoon rainfall. The model was tested for all the years from 1987 to 1991 and it has been found that the predicted values of all India summer monsoon rainfall of all the years except 1989 were very close to the actual values. However, there was a substantial difference between the predicted and actual rainfall of 1989 summer monsoon.

scholarly journals Role of Rossby Waves in the Remote Effects of the North Indian Ocean Tropical Disturbances

2012 ◽  
Vol 140 (11) ◽  
pp. 3620-3633 ◽  
Author(s):  
J. V. Ratnam ◽  
S. K. Behera ◽  
Y. Masumoto ◽  
T. Yamagata
Keyword(s):  
Saudi Arabia ◽  
Indian Ocean ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Rossby Waves ◽  
Temporal Distribution ◽  
North Indian Ocean ◽  
Positive Temperature ◽  
The North ◽  
Wide Range

Abstract Remote effects due to the tropical disturbances in the north Indian Ocean are investigated by analyzing long-lasting (≥5 days) tropical disturbances, which reached at least the strength of tropical storms. The present analysis is carried out for both the pre- and postmonsoon periods. The spatial and temporal distribution of the outgoing longwave radiation (OLR) during the premonsoon disturbances over the Bay of Bengal reveals several interesting features. Temporal distribution of the OLR anomalies shows that the intraseasonal oscillations play an important role in the formation of those disturbances. The spatial distribution of the OLR anomalies shows a dipole with negative OLR anomalies over the bay and positive OLR anomalies over the Indonesian region. The atmospheric response to the negative OLR anomalies results in positive temperature anomalies over northwest India, Pakistan, Afghanistan, Iran, and Saudi Arabia, remote from the disturbance; and the response to the positive anomalies causes slight increase in the sea surface temperature of the Arabian Sea. Negative OLR anomalies are also seen over western Japan due to the Rossby waves generated by the heating over the Bay of Bengal besides the enhancement of the so-called “Pacific–Japan” teleconnection pattern. However, the analysis shows that the postmonsoon disturbances over the Bay of Bengal and the disturbances formed over the Arabian Sea in both pre- and postmonsoon seasons do not develop remote teleconnections associated with the above type of Rossby wave mechanism. These results are significant for the short- to medium-range weather forecast over a wide range covering Japan, Pakistan, Afghanistan, Iran, and Saudi Arabia.

scholarly journals Variability in dynamic and thermodynamic parameters in cyclogenesis over north Indian ocean

MAUSAM ◽  
2021 ◽  
Vol 60 (1) ◽  
pp. 61-72
Author(s):  
A. MUTHUCHAMI
Keyword(s):  
Indian Ocean ◽  
Thermodynamic Parameters ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Threshold Level ◽  
Reanalysis Data ◽  
North Indian Ocean ◽  
The North ◽  
Static Instability ◽  
The Difference

The two basins Arabian sea (ARS) and Bay of Bengal (BOB) of the North Indian Ocean (NIO) are having different dynamic and thermodynamic character and therefore ARS has subdued cyclone activity than BOB. In order to examine the difference between these basins in respect of various meteorological parameters, using NCEP/NCAR reanalysis data for the period 1971-2005 during the months of September to December the distribution of the dynamic and thermodynamic parameters are discussed. It is seen that sea surface temperature (SST) is not responsible for subdued activity over ARS as the SST over ARS and BOB is mostly above minimum threshold level. In respect of wind shear, during October in ARS north of 10°  N is favourable for storm formation unlike September where the whole of Arabian sea except the region north of 20° N is inert to cyclone formation. The humidity factor is more pronounced in ARS for prohibiting storm formation than shear factor. In all the months static instability at 90° E is least and so the atmosphere is neutral throughout the period and consequence of it any small trigger in the lower level will induce the system to grow further.  The BOB is more barotropic than ARS. There is a considerable difference exists in precipitation rate as a consequence of more stable atmosphere over Arabian sea than in Bay of Bengal even at the lower level.

scholarly journals Tropospheric warming over the North Indian Ocean caused by the South Asian anthropogenic aerosols: possible implications

2021 ◽  
Author(s):  
Suvarna Fadnavis ◽  
Prashant Chavan ◽  
Akash Joshi ◽  
Sunil Sonbawne ◽  
Asutosh Acharya ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
South Asia ◽  
South Asian ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
North Indian Ocean ◽  
Carbonaceous Aerosols ◽  
Anthropogenic Aerosols ◽  
The North

Abstract. Atmospheric concentrations of South Asian anthropogenic aerosols and their transport play a key role in the regional hydrological cycle. Here, we use the ECHAM6-HAMMOZ chemistry-climate model to show the structure and implications of the transport pathways of these aerosols during spring. Our simulations indicate that large amounts of anthropogenic aerosols are transported from South Asia to the North Indian Ocean (the Arabian Sea and North Bay of Bengal). These aerosols are then lifted into the upper troposphere and lower stratosphere (UTLS) by the convection over the Arabian Sea and Bay of Bengal. In the UTLS, they are further transported to the southern hemisphere (30–40° S) and downward into the troposphere by the secondary circulation induced by the aerosol changes. The carbonaceous aerosols are also transported to the Arctic and Antarctic producing local heating (0.002–0.05 K d−1). The presence of anthropogenic aerosols causes negative radiative forcing (RF) at the TOA (0.90 ± 0.089 W m−2) and surface (−5.87 ± 0.31 W m−2) and atmospheric warming (+4.96 ± 0.24 W m−2) over South Asia (60° E–90° E, 8° N–23° N), except over the Indo-Gangetic plain (75° E–83° E, 23° N–30° N) where RF at the TOA is positive (+1.27 ± 0.16 W m−2) due to large concentrations of absorbing aerosols. The carbonaceous aerosols produced in-atmospheric heating along the aerosol column extending from the boundary layer to the UTLS (0.01 to 0.3 K d−1) and in the stratosphere globally (0.002 to 0.012 K d−1). The heating of the troposphere increases water vapor concentrations, which are then transported from the highly convective region (i.e. the Arabian Sea) to the UTLS (increasing water vapor by 0.02–0.06 ppmv).

scholarly journals The association between the north Indian Ocean and summer monsoon rainfall over India

MAUSAM ◽  
2021 ◽  
Vol 49 (3) ◽  
pp. 325-330
Author(s):  
O. P. SINGH
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Arabian Sea ◽  
Monsoon Rainfall ◽  
Monsoon Season ◽  
Meteorological Data ◽  
Summer Monsoon Rainfall ◽  
North Indian Ocean ◽  
The North ◽  
The Mean

Utilizing the marine meteorological data of the period 1961-81, the sea level pressure (SLP) and sea surface temperature (SST) distributions have been obtained on a 5° grid-mesh over the north Indian Ocean area bounded by  0°- 25°N, 50°- l00°E for each individual year. It has been found that the SLP and SST fields for the month of May provide predictive indications of subsequent summer monsoon rainfall over India. Significant negative correlations have been found between the mean SLPs of May over the latitudinal belts 5°-10°, 10°- 15°, 15°-20° and 20°-25°N of Arabian Sea and Bay of Bengal and all India rainfall departures of succeeding summer monsoon season. The mean SST gradient over the Arabian Sea between 7.5°- 17 .5°N during May has been found to have significant positive correlation with all India rainfall of subsequent monsoon. The study suggests that certain functions of SLP and SST of May over the north Indian Ocean can prove to be useful predictors for subsequent summer monsoon rainfall over India.

scholarly journals Tropical cyclone frequency in the north Indian Ocean in relation to southern oscillation phenomenon

MAUSAM ◽  
2022 ◽  
Vol 52 (3) ◽  
pp. 511-514
Author(s):  
O. P. SINGH ◽  
TARIQ MASOOD ALI KHAN ◽  
MD. SAZEDUR RAHMAN
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Southern Oscillation ◽  
North Indian Ocean ◽  
Tropical Cyclone Frequency ◽  
The North ◽  
Cyclone Frequency

The present paper deals with the influence of Southern Oscillation (SO) on the frequency of tropical cyclones in the north Indian Ocean. The results show that during the negative phase of SO the frequency of tropical cyclones and depressions over the Bay of Bengal and the Arabian Sea diminishes in May which is most important pre-monsoon cyclone month. The correlation coefficient between the frequency of cyclones and depressions and the Southern Oscillation Index (SOI) is +0.3 which is significant at 99% level. Post-monsoon cyclone frequency in the Bay of Bengal during November shows a significant positive correlation with SOl implying that it also decreases during the negative phase of SO. Thus there is a reduction in the tropical cyclone frequency over the Bay of Bengal during both intense cyclone months May and November in EI-Nino/Southern Oscillation (ENSO) epochs. Therefore it would not be correct to say that ENSO has no impact on the cyclogenesis in the north Indian Ocean. It is true that ENSO has no significant impact on the frequency of cyclones in the Arabian Sea. ENSO also seems to affect the rate of intensification of depressions to cyclone stage. The rate of intensification increases in May and diminishes in November in the north Indian Ocean during ENSO. The results are based on the analysis of monthly frequencies of tropical cyclones and depressions and SOI for the 100 year period from 1891-1990.

scholarly journals Trend of shift in the area of cyclo-genesis over north Indian Ocean

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 49-58
Author(s):  
CHARAN SINGH ◽  
B. R. LOE
Keyword(s):  
Standard Deviation ◽  
Indian Ocean ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
North Indian Ocean

ABSTRACT. Cyclo-genesis over north Indian Ocean (Bay of Bengal and the Arabian Sea) has been studied with reference to the formation and shift of cyclo-genesis area. The frequency of formation of cyclones during a particular month and year for the period of study has been presented. The study has shown that the maximum number of cyclo-genesis occurred during the month of July followed by August and September. Cyclo-genesis was about three times more in the Bay of Bengal as compared to that in the Arabian Sea. Areas favourable for cyclo-genesis were found between Lat. 15.0° N to 22.5° N and Long. 86.0° E to 92.0° E over the Bay of Bengal and Lat. 7.0° N to 12.5° N and 60.0° E to 74.0° E over the Arabian sea while meander over north Indian ocean, some times its shift significantly. Standard deviation of number of cyclones has been computed for the decades from 1891-2000. It was found that it was maximum (1.96) during 1941-1950 followed by 1981-1990 (1.92).

Enhanced double-diffusive salt flux from the high-salinity core of Arabian Sea origin waters to the Bay of Bengal

2020 ◽  
Author(s):  
Jenson V. George ◽  
P.N. Vinayachandran ◽  
Anoop A. Nayak
Keyword(s):  
Bay Of Bengal ◽  
Arabian Sea ◽  
High Salinity ◽  
Saline Water ◽  
North Indian Ocean ◽  
Salt Flux ◽  
High Salinity Water ◽  
The North ◽  
Salt Fingering ◽  
Double Diffusive

AbstractThe inflow of high saline water from the Arabian Sea (AS) into the Bay of Bengal (BoB) and its subsequent mixing with the relatively fresh BoB water is vital for the North Indian Ocean salt budget. During June–September, Summer Monsoon Current carries high salinity water from the AS to the BoB. A time series of microstructure and hydrographic data collected from 4–14 July 2016 in the Southern BoB (8°N, 89°E) showed the presence of subsurface (60–150 m) high-salinity core. The high-salinity core was comprised of relatively warm and saline AS water overlying the relatively cold and fresh BoB water. Lower part of the high-salinity core showed double-diffusive salt fingering instability. Salt fingering staircases with varying thickness (up to 10 m) in the temperature and salinity profiles were also observed at the base of high-salinity core at approximately 75–150 m depth. The average downward diapycnal salt flux out of the high salinity core due to the effect of salt fingering was 2.8×10−7 kg m−2 s−1; approximately one order of magnitude higher than the flux if salt fingering were neglected.

MEASURING POLICY BENEFITS OF THE CYCLONE SHELTER PROGRAM IN THE NORTH INDIAN OCEAN: PROTECTION FROM INTENSE WINDS OR HIGH STORM SURGES?

2017 ◽  
Vol 08 (04) ◽  
pp. 1750011 ◽  
Author(s):  
S. NIGGOL SEO
Keyword(s):  
Indian Ocean ◽  
Low Income ◽  
Arabian Sea ◽  
Negative Binomial ◽  
Storm Surges ◽  
North Indian Ocean ◽  
High Population Density ◽  
Cyclone Intensity ◽  
The North ◽  
Cyclone Shelter

This paper provides a quantitative estimate of the policy benefit of the cyclone shelter program (CSP) implemented in Bangladesh. The present author examines all cyclones that were generated in the North Indian Ocean, both the Bay of Bengal and the Arabian Sea, from 1990 to 2015. A negative binomial (NB) model of cyclone fatalities against cyclone intensity finds that the CSP does little in protecting people’s lives against the high storm intensity. In contrast, a two-stage NB model of cyclone fatalities against the level of surges reveals that the CSP is vastly effective against storm surges. The number of fatalities is, on average, 75% smaller in the areas where the shelter program has been implemented against the areas without the program in response to the same level of storm surges. A set of Probit adoption models of adaptation options in response to cyclone surges and intensity reveals that the CSP has been directed to a low-income area with high population density, which is in contrast to the other strategies which have been increasingly adopted with higher income, e.g., cyclone trajectory projection technologies.

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