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.

scholarly journals Seasonal Nature and Trends of Tropical Cyclone Frequency and Intensity over the North Indian Ocean

2020 ◽  
Vol 15 (3) ◽  
pp. 526-534
Author(s):  
Abhisek Pal ◽  
Soumendu Chatterjee
Keyword(s):  
Time Series ◽  
Tropical Cyclone ◽  
Indian Ocean ◽  
Monsoon Season ◽  
North Indian Ocean ◽  
Post Monsoon ◽  
The North ◽  
Increasing Trend ◽  
Post Monsoon Season ◽  
Cyclone Frequency

Tropical cyclone (TC) genesis over the North Indian Ocean (NIO) region showed significant amount of both spatial and temporal variability.It was observed that the TC genesis was significantly suppressed during the monsoon (June-September) compared to pre-monsoon (March-May) and post-monsoon (October-December) season specifically in terms of severe cyclonic storms (SCS) frequency. The Bay of Bengal (BoB) was characterized by higher TC frequency but lower intensity compared to the Arabian Sea (AS). It was also observed that the TC genesis locations were shifted significantly seasonally.The movement of the TCs also portrayed some significant seasonal differences. The pre-monsoon and post-monsoon season was responsible for generating TCs with higher values of accumulated cyclone energy (ACE) compared to the monsoon. The time series of TC frequency showed a statistically significant decreasing trend whereas the time series of ACE showed astatistically significant increasing trend over the NIO.

scholarly journals Cyclonic storms and Depressions over the north Indian Ocean during 2019*

MAUSAM ◽  
2021 ◽  
Vol 71 (3) ◽  
pp. 357-376
Author(s):  
Kashyapi A ◽  
Shripad V K ◽  
Natu J C
Keyword(s):  
Arabian Sea ◽  
Monsoon Season ◽  
North Indian Ocean ◽  
Cyclonic Storm ◽  
Post Monsoon ◽  
The North ◽  
Post Monsoon Season ◽  
Severe Cyclonic Storm ◽  
Cyclonic Storms ◽  
Indian Seas

During 2019, in all 12 intense low pressure systems formed over the Indian Seas. These include; one Super cyclonic storm (KYARR), one extremely severe cyclonic storm (FANI), 4 very Severe Cyclonic Storms (VAYU, HIKAA, MAHA & BULBUL), 2 Cyclonic Storms (PABUK & PAWAN), 3 Deep Depressions and  1 Depression. Out of these 12 systems, 4 systems formed over the Bay of Bengal and 8 over the Arabian Sea. Arabian Sea remained exceptionally active in terms of cyclogenesis this year, especially in the post monsoon season. The season-wise distribution had been one cyclonic storm in winter, one in pre-monsoon season,  2 depressions and 2 very severe cyclonic storms during the monsoon season and 4 cyclonic storms and 3 depressions in Post monsoon season.

scholarly journals Analysis of rainfall and temperature trends of selected stations over North East India during last century

MAUSAM ◽  
2021 ◽  
Vol 65 (4) ◽  
pp. 497-508
Author(s):  
S.I. LASKAR ◽  
S.D. KOTAL ◽  
S.K.ROY BHOWMIK
Keyword(s):  
Monsoon Season ◽  
Maximum Temperature ◽  
Rainfall Time Series ◽  
North East India ◽  
Post Monsoon ◽  
North East ◽  
The North ◽  
Increasing Trend ◽  
Post Monsoon Season ◽  
Increasing Trends

In this study, the trends of seasonal maximum and minimum temperatures and rainfall time series were investigated for 9 selected stations in the north eastern India with the available data stretching between the years 1913-2012.During the period under study the minimum temperature has increasing trends in almost all the stations of north east India except Cherrapunji where it shows decreasing trend in all the season of the year. In case of maximum temperature Cherrapunji, Guwahati and Imphal show increasing trends during all the seasons. Agartala and Shillong show increasing trend of maximum temperature during monsoon and post monsoon season. Dibrugarh and Pasighat show decreasing trend during pre monsoon season and increasing trend during all other seasons of the year. Gangtok shows decreasing trend of maximum temperature during all the seasons where as Silchar shows no trend in maximum temperature.Out of all the selected nine stations, most of the stations show either decreasing trend or no trend of rainfall except Guwahati which shows significant increasing trend of rainfall during post monsoon season.

scholarly journals The relationship between geopotential height and movement & landfall of tropical cyclone in the Bay of Bengal region

MAUSAM ◽  
2022 ◽  
Vol 63 (3) ◽  
pp. 469-474
Author(s):  
G.K. DAS ◽  
S.K. MIDYA ◽  
G.C. DEBNATH ◽  
S.N. ROY
Keyword(s):  
Tropical Cyclone ◽  
Bay Of Bengal ◽  
Geopotential Height ◽  
Monsoon Season ◽  
Simple Relationship ◽  
Post Monsoon ◽  
Post Monsoon Season ◽  
The Relationship

In this paper a simple relationship is employed to investigate relative impacts on the movement and landfall of tropical cyclone in the Bay of Bengal region when geopotential height of different troposphere levels is used as an input. Five tropical cyclone during pre-monsoon and post-monsoon season over the Bay of Bengal region has been selected for the study. The RS/RW data of coastal stations namely Kolkata (Dumdum), Dhaka, Agartala, Bhubaneswar, Visakhapatnam, Machlipatnam, Chennai and Karaikal has been collected for the period of the cyclones under study. The geopotential height of different standard levels has been plotted against the time for the stations for every cyclone. The study suggests that the cyclone moves towards and cross near the station having relatively steeper decrease in geopotential height upto mid tropical level followed by increased in geopotential height.

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 Modulation of environmental conditions on the significant difference in the super cyclone formation rate during the pre- and post-monsoon seasons over the Bay of Bengal

2021 ◽  
Author(s):  
Zhi Li ◽  
Yuhuan Xue ◽  
Yue Fang ◽  
Kuiping Li
Keyword(s):  
Bay Of Bengal ◽  
Monsoon Season ◽  
Formation Rate ◽  
Specific Humidity ◽  
Global Maximum ◽  
Tropical Ocean ◽  
Post Monsoon ◽  
Significant Difference ◽  
Post Monsoon Season ◽  
Upper Level

AbstractUnlike other tropical ocean basins, the Bay of Bengal (BoB) has two tropical cyclone (TC) seasons: a pre-monsoon season (Pre-MS) and a post-monsoon season (Post-MS). More interestingly, during the period from 1981 to 2016, the global maximum and minimum formation rates of super cyclones (SCs, categories 4 and 5) occurred in the Pre-MS and Post-MS, respectively, in the BoB. Methods including Butterworth filter, box difference index analysis and quantitative diagnosis were utilized herein to detect what and how background environmental factors cause significantly different SC formation rates between the Pre- and Post-MS. Diagnosis results revealed that the vertical temperature difference (VTD) mainly determines whether TCs can develop into SCs during the Post-MS, similar to Pre-MS. It’s in agreement with previous studies demonstrating that the VTD is controlled by the low-level temperature during the Post-MS but is determined by the upper-level temperature during the Pre-MS. The results also revealed that the background sea surface temperature is much higher in the Pre-MS than in the Post-MS and forces higher 1000 hPa-level air temperature. Additionally, there is higher saturated specific humidity (qs) due to the higher temperature in the Pre-MS. The differences in the bottom-level temperature and qs cooperate to predominantly contribute to the significant difference in Vpot2, which could denote the maximum potential intensity of TC, eventually leading to the remarkably different SC formation rates between the Pre- and Post-MS in the BoB.

scholarly journals Variability of Ocean Features and their Impact on Cyclogenesis over Arabian Sea During Post Monsoon Season

2021 ◽  
Author(s):  
suchandra Aich Bhowmick ◽  
Anup Mandal
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Heat Content ◽  
North Indian Ocean ◽  
Post Monsoon ◽  
Positive Indian Ocean Dipole ◽  
South West Indian Ocean ◽  
Atmospheric Forcings

Abstract Arabian Sea (AS), the western sector of North Indian Ocean (NIO) produce smaller number of tropical cyclones as compared to Bay of Bengal. Though limited in numbers, the cyclones over Arabian sea are catastrophic by character. This make west coast of Indian subcontinent vulnerable to these hazards. The post-monsoon cyclogenesis over this region is known to be modulated by both monsoon rainfall and the El-Niño accompanied with positive Indian Ocean Dipole events. No single phenomena, however, can fully explain the variability observed in AS region. In this study, it is observed that apart from several known atmospheric forcings, inter-annual variability of ocean heat content (OHC) influence the post-monsoon AS cyclogenesis. The OHC of this region is partially modulated by the changes in salinity. Heat exchanges between the South West Indian Ocean (SWIO) and AS also modulates the OHC over AS. This remote influence is facilitated largely by the variability in the equatorial currents. Further it is seen that the recent trend of increased OHC post-2011 matches with the enhanced sea surface carbon over AS.

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.

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