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 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 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 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 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 Understanding differences in tropical cyclone activity over the Arabian Sea and Bay of Bengal

MAUSAM ◽  
2021 ◽  
Vol 72 (1) ◽  
pp. 187-198
Author(s):  
IRIS C. LIU ◽  
SUZANA J. CAMARGO ◽  
ADAM H. SOBEL
Keyword(s):  
Tropical Cyclone ◽  
Bay Of Bengal ◽  
Arabian Sea ◽  
Ocean Basin ◽  
North Indian Ocean ◽  
Tropical Cyclone Genesis ◽  
The North ◽  
The Difference ◽  
Cyclone Genesis ◽  
The Individual

Within the North Indian Ocean basin, tropical cyclone (TC) activity over the Bay of Bengal (BoB) is substantially greater than over the Arabian Sea (AS). The authors attempt to quantify the roles of specific environmental factors in order to understand the reasons for this difference between the two basins. Environmental variables are considered in the basin as a whole and in the immediate times and places at which cyclogenesis and storm intensification occur.The results for the two sub-basins are compared to determine  which environmental variablessignificantly between the sub-basins. A tropical cyclone genesis index (TCGI) is also examined to determine whether the AS- differedBased on that partial success, climatologies of the individual factors that comprise the index are examined to determine which ones are most important in the difference  

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.

scholarly journals Demonstration of the Temporal Evolution of Tropical Cyclone “Phailin” Using Gray-Zone Simulations and Decadal Variability of Cyclones over the Bay of Bengal in a Warming Climate

Oceans ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 648-674
Author(s):  
Prabodha Kumar Pradhan ◽  
Vinay Kumar ◽  
Sunilkumar Khadgarai ◽  
S. Vijaya Bhaskara Rao ◽  
Tushar Sinha ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
North Indian Ocean ◽  
Strong Wind ◽  
Cyclonic Storm ◽  
Parameterization Schemes ◽  
The North ◽  
Single Moment ◽  
Double Moment ◽  
Microphysical Parameterization

The intensity and frequency variability of cyclones in the North Indian Ocean (NIO) have been amplified over the last few decades. The number of very severe cyclonic storms (VSCSs) over the North Indian Ocean has increased over recent decades. “Phailin”, an extreme severe cyclonic storm (ESCS), occurred during 8–13 October 2013 over the Bay of Bengal and made landfall near the Gopalpur coast of Odisha at 12 UTC on 12 October. It caused severe damage here, as well as in the coastal Odisha, Andhra Pradesh, and adjoining regions due to strong wind gusts (~115 knot/h), heavy precipitation, and devastating storm surges. The fidelity of the WRF model in simulating the track and intensity of tropical cyclones depends on different cloud microphysical parameterization schemes. Thus, four sensitivity simulations were conducted for Phailin using double-moment and single-moment microphysical (MP) parameterization schemes. The experiments were conducted to quantify and characterize the performance of such MP schemes for Phailin. The simulations were performed by the advanced weather research and forecasting (WRF-ARW) model. The model has two interactive domains covering the entire Bay of Bengal and adjoining coastal Odisha on 25 km and 8.333 km resolutions. Milbrandt–Yau (MY) double-moment and WRF single-moment microphysical schemes, with 6, 5, and 3 classes of hydrometeors, i.e., WSM6, WSM5, and WSM3, were used for the simulation. Experiments for Phailin were conducted for 126 h, starting from 00 UTC 08 October to 06 UTC 13 October 2013. It was found that the track, intensity, and structure of Phailin are highly sensitive to the different microphysical parameterization schemes. Further, the precipitation and cloud distribution were studied during the ESCS stage of Phailin. The microphysics schemes (MY, WSM3, WSM5, WSM6), along with Grell–Devenyi ensemble convection scheme predicted landfall of Phailin over the Odisha coast with significant track errors. Supply of moisture remains a more crucial component than SST and wind shear for rapid intensification of the Phailin 12 h before landfall over the Bay of Bengal. Finally, the comparison of cyclone formation between two decades 2001–2010 and 2011–2020 over the Bay of Bengal inferred that the increased numbers of VSCS are attributed to the supply of abundant moisture at low levels in the recent decade 2011–2020.

scholarly journals Modulation of cyclonic disturbances over the north Indian Ocean by Madden - Julian oscillation

MAUSAM ◽  
2021 ◽  
Vol 62 (3) ◽  
pp. 375-390
Author(s):  
M. MOHAPATRA ◽  
S. ADHIKARY
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Phase 1 ◽  
North Indian Ocean ◽  
Maritime Continent ◽  
Phase 3 ◽  
Post Monsoon ◽  
The North ◽  
Post Monsoon Season

The relationship of genesis and intensity of cyclonic disturbances (CDs) over the north Indian Ocean with the Madden – Julian Oscillation (MJO) has been examined using 33 years (1975 - 2007) data of MJO index and best track of (CDs) developed by India Meteorological Department (IMD). The MJO index based on outgoing long wave radiation (OLR) and zonal wind in upper (200 hPa) and lower (850 hPa) troposphere (Wheeler and Hendon, 2004) has been used for this purpose. The MJO strongly modulates the genesis and intensity of CDs over the north Indian Ocean. However there are other factors contributing to cyclogenesis over the north Indian Ocean, as about 60% of cyclogenesis during monsoon and post-monsoon seasons are not significantly related with MJO. While the probability of cyclogenesis during monsoon season is higher with MJO in phase 4 and 5 (Maritime Continent), that during post-monsoon season is higher with MJO in phase 3 and 4 (east Indian Ocean and adjoining Maritime Continent). It indicates that while possibility of genesis during monsoon season is significantly suppressed with active MJO at phase 1, 7 and 8 (Africa, western Hemisphere and adjoining Pacific Ocean), there is no significant relationship between genesis and active MJO at phase 1, 7 and 8 during post-monsoon season. The anomalous cyclonic circulation at lower levels over central and north Bay of Bengal in association with MJO at phase 4 and 5 favours enhanced probability of cyclogenesis over the Bay of Bengal during monsoon season. The anomalous easterlies in association with MJO at phase 1 and development of anomalous ridge over south India in association with MJO at phase 7 and 8 which are weak monsoon features lead to suppressed cyclogenesis over north Indian Ocean during this season. The anomalous north-south trough in easterlies embedded with cyclonic circulation over the south west/west central Bay of Bengal in association with southerly surge over the region during active MJO in phase 3 and 4 most favourably influences the convection and enhances the probability of cyclogenesis over the north Indian Ocean during post-monsoon season. The genesis of CDs is more sensitive to phase than the amplitude while the intensification of CDs is more dependent on the amplitude of MJO. Comparing monsoon and post-monsoon seasons, the modulation of genesis, intensification and duration of CDs by the MJO is more during the monsoon season than the post-monsoon season.

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