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.

Extended Prediction of North Indian Ocean Tropical Cyclones

2012 ◽  
Vol 27 (3) ◽  
pp. 757-769 ◽  
Author(s):  
James I. Belanger ◽  
Peter J. Webster ◽  
Judith A. Curry ◽  
Mark T. Jelinek
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
North Indian Ocean ◽  
Ensemble Prediction ◽  
Tropical Cyclone Genesis ◽  
Lead Times ◽  
Prediction System ◽  
Ensemble Prediction System ◽  
The North

Abstract This analysis examines the predictability of several key forecasting parameters using the ECMWF Variable Ensemble Prediction System (VarEPS) for tropical cyclones (TCs) in the North Indian Ocean (NIO) including tropical cyclone genesis, pregenesis and postgenesis track and intensity projections, and regional outlooks of tropical cyclone activity for the Arabian Sea and the Bay of Bengal. Based on the evaluation period from 2007 to 2010, the VarEPS TC genesis forecasts demonstrate low false-alarm rates and moderate to high probabilities of detection for lead times of 1–7 days. In addition, VarEPS pregenesis track forecasts on average perform better than VarEPS postgenesis forecasts through 120 h and feature a total track error growth of 41 n mi day−1. VarEPS provides superior postgenesis track forecasts for lead times greater than 12 h compared to other models, including the Met Office global model (UKMET), the Navy Operational Global Atmospheric Prediction System (NOGAPS), and the Global Forecasting System (GFS), and slightly lower track errors than the Joint Typhoon Warning Center. This paper concludes with a discussion of how VarEPS can provide much of this extended predictability within a probabilistic framework for the region.

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 Pacific Decadal Oscillation Causes Fewer Near-Equatorial Cyclones in North Indian Ocean

2021 ◽  
Author(s):  
Shinto Roose ◽  
Ajayamohan Ravindran ◽  
Pallav Ray ◽  
Shang-Ping Xie ◽  
Cherumadanakadan Thelliyil Sabeerali ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Tropical Cyclones ◽  
Pacific Decadal Oscillation ◽  
North Indian Ocean ◽  
Mitigation Strategies ◽  
The Past ◽  
The North ◽  
The Pacific ◽  
Low Latitudes ◽  
Cyclone Frequency

Abstract Tropical cyclones do not form easily near the equator but can intensify rapidly, leaving little time for preparation. We investigated the number of near-equatorial (originating between 5°N and 11°N) tropical cyclones over the north Indian Ocean during post-monsoon seasons (October to December) over the past 60 years. A marked 43% decline in the number of such cyclones was detected in recent decades (1981-2010) compared to earlier (1951-1980). This decline in tropical cyclone frequency is primarily due to the weakened low-level vorticity modulated by the Pacific Decadal Oscillation (PDO). In the presence of basin-wide warming at low latitudes, and a favorable phase of the PDO, both the intensity and frequency of such cyclones is expected to increase. Such dramatic and unique changes in tropical cyclonic activity due to the interplay between natural variability and climate change call for appropriate planning and mitigation strategies.

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 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 On tropical cyclone frequency and the warm pool area

2009 ◽  
Vol 9 (2) ◽  
pp. 635-645 ◽  
Author(s):  
R. E. Benestad
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
Warm Pool ◽  
North Indian Ocean ◽  
North West ◽  
The North ◽  
The North Atlantic ◽  
Pool Area

Abstract. The proposition that the rate of tropical cyclogenesis increases with the size of the "warm pool" is tested by comparing the seasonal variation of the warm pool area with the seasonality of the number of tropical cyclones. An analysis based on empirical data from the Northern Hemisphere is presented, where the warm pool associated with tropical cyclone activity is defined as the area, A, enclosed by the 26.5°C SST isotherm. Similar analysis was applied to the temperature weighted area AT with similar results. An intriguing non-linear relationship of high statistical significance was found between the temperature weighted area in the North Atlantic and the North-West Pacific on the one hand and the number of cyclones, N, in the same ocean basin on the other, but this pattern was not found over the North Indian Ocean. A simple statistical model was developed, based on the historical relationship between N and A. The simple model was then validated against independent inter-annual variations in the seasonal cyclone counts in the North Atlantic, but the correlation was not statistically significant in the North-West Pacific. No correlation, however, was found between N and A in the North Indian Ocean. A non-linear relationship between the cyclone number and temperature weighted area may in some ocean basins explain both why there has not been any linear trend in the number of cyclones over time as well as the recent upturn in the number of Atlantic hurricanes. The results also suggest that the notion of the number of tropical cyclones being insensitive to the area A is a misconception.

scholarly journals Generating reliable estimates of tropical cyclone induced coastal hazards along the Bay of Bengal for current and future climates using synthetic tracks

2021 ◽  
Author(s):  
Tim Willem Bart Leijnse ◽  
Alessio Giardino ◽  
Kees Nederhoff ◽  
Sofia Caires
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Storm Surge ◽  
Bay Of Bengal ◽  
Coastal Hazards ◽  
Wind Fields ◽  
Tropical Cyclone Frequency ◽  
Wind Speeds ◽  
Wave Heights ◽  
Cyclone Frequency

Abstract. Deriving reliable estimates of design water levels and wave conditions resulting from tropical cyclones is a challenging problem of high relevance for, among others, coastal and offshore engineering projects and risk assessment studies. Tropical cyclone geometry and wind speeds have been recorded for the past few decades only, therefore resulting in poorly reliable estimates of the extremes, especially at regions characterized by a low number of past tropical cyclone events. In this paper, this challenge is overcome by using synthetic tropical cyclone tracks and wind fields generated by the open source tool TCWiSE (Tropical Cyclone Wind Statistical Estimation), to create thousands of realizations representative for 1,000 years of tropical cyclone activity for the Bay of Bengal. Each of these realizations is used to force coupled storm surge and wave simulations by means of the processed-based Delft3D Flexible Mesh Suite. It is shown that the use of synthetic tracks provides reliable estimates of the statistics of the first-order hazard (i.e. wind speed) compared to the statistics derived for historical tropical cyclones. Based on estimated wind fields, second-order hazards (i.e. storm surge and waves) are computed. The estimates of the extreme values derived for wind speed, wave height and storm surge are shown to converge within the 1,000 years of simulated cyclone tracks. Comparing second-order hazard estimates based on historical and synthetic tracks show that, for this case study, the use of historical tracks (a deterministic approach) leads to an underestimation of the mean computed storm surge up to −30 %. Differences between the use of synthetic versus historical tracks are characterized by a large spatial variability along the Bay of Bengal, where regions with a lower probability of occurrence of tropical cyclones show the largest difference in predicted storm surge and wave heights. In addition, the use of historical tracks leads to much larger uncertainty bands in the estimation of both storm surges and wave heights, with confidence intervals being +80 % larger compared to those estimated by using synthetic tracks (probabilistic approach). Based on the same tropical cyclone realizations, the effect that changes in tropical cyclone frequency and intensity, possibly resulting from climate change, may have on modelled storm surge and wave heights were computed. An increase in tropical cyclone frequency of +25.6 % and wind intensity of +1.6 %, based on literature values, could result in an increase of storm surge and wave heights of +11 % and +9 % respectively. This suggest that climate change could increase tropical cyclone induced coastal hazards more than just the actual increase in maximum wind speeds.

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