Indian Journal of Marine Sciences

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ISSN: 0379-5136                                                                                    CODEN: IJMNBF

VOLUME  35

NUMBER  2

JUNE 2006

 

 

Special Issue on  Air-Sea Interaction

 

Papers

 

Environmental influences on tropical cyclone structure and intensity: A review of past and present literature

Jamie R. Rhome & Sethu Raman

61-74

 

 

Seasonal variations of synoptic features over the north Indian Ocean during dipole years

     J.S.Chowdary, C.Gnanaseelan, Bijoy Thompson &P.S. Salvekar

75-86

 

 

ENSO and monsoon induced sea level changes and their impacts along the Indian coastline

O.P.Singh

87-92

 

 

The variability of Indian Ocean surface meteorological fields during summer monsoon in El Nino/La Nina years

R.Bhatala, U.C. Mohanty & P.V.S. Raju

93-103

 

 

Prediction of upper ocean mixed layer depth in the north Indian Ocean using surface fluxes from a medium range weather forecast system

       M.M.Ali & A.K.Gopalan, K.N.Babu, Rashmi Sharma & R.A.Weller

104-110

 

 

Oceanic mixed layer variations during the movement of cyclone along symmetric tracks in the Indian Ocean

A.A. Deo, D. W. Ganer & P. S. Salvekar

111-122

 

 

Simulation of the upper ocean thermal structure at the WHOI Arabian Sea mooring site

P.S. Swathi & C. Kalyani Devasena

123-131

 

 

 

Estimation of tropical cyclone heat potential in the Bay of Bengal and its role in the genesis and intensification of storms

Y. Sadhuram,T.V.Ramana Murthy & Y.K.Somayajulu

132-138

 

 

Observations and numerical simulation of the sea and land breeze circulations along the west coast of India

M.D.Simpson & S.Raman

139-152

 

 

A study on cyclone induced productivity in south-western Bay of Bengal during November-December 2000 using MODIS (SST and chlorophyll-a) and altimeter sea surface height observations

        K.H.Rao, A Smitha & M.M.Ali

153-160

 

 

Impact of satellite derived wind in mesoscale simulation of Orissa super cyclone

        M.Mandal, U.C.Mohanty & A.K.Das

161-173

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp. 61-74

 

                Environmental influences on tropical cyclone structure and intensity:
A review of past and present literature

Jamie R. Rhome* & Sethu Raman§

Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695-8208, USA

*[E-mail: jamie.r.rhome@noaa.gov ]

Received 27 December 2004, revised 12 April 2006

Tropical Cyclone (TC) track forecast skill has shown a steadily increasing trend in the north Atlantic basin over the last decade in contrast to little or no improvement in intensity forecast skill. This is attributable in part to a lack of in-situ observations to measure important inner-core processes and the inability of current operational numerical models to accurately resolve the inner-core dynamics. Consequently, much is unknown about TC intensity change, and the most skillful intensity forecasting techniques still rely upon climatology and persistence. The forecasting of rapid changes in intensity has been particularly difficult. The need for improved TC intensity forecasts has never been greater due to rapidly increasing population in coastal communities. This is the motivation for the present review, which seeks to discuss our current knowledge and highlight the most fruitful areas for future work. This is accomplished through a literature review of past and present research with emphasis on current gaps in knowledge.

[Key words: Cyclone, tropical cyclone, intensity, literature review]

 

 

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.75-86

 

                Seasonal variations of synoptic features over the north Indian Ocean
during dipole years

J. S. Chowdary, C. Gnanaseelan, Bijoy Thompson & P. S. Salvekar*

Theoretical Studies Division, Indian Institute of Tropical Meteorology, Pune - 411 008, India

*[E-mail: pss@tropmet.res.in ]

Received 27 December 2004, revised 18 January 2006

Recent studies found that the atmospheric circulation over the Indian Ocean region is highly influenced by the Indian Ocean Dipole (IOD) forcing. In the present study, we analyzed National Center for Environmental Prediction and National center for Atmospheric Research (NCEP-NCAR) reanalysis data to observe the IOD related variability at different pressure levels from surface to upper troposphere during the spring season. The study period (1982-2001) includes three positive IOD (1982, 1994 and 1997) and two negative IOD years (1992 and 1996). It is observed that during the spring season the variations in the lower tropospheric winds were stronger in the positive IOD years than the negative dipole mode years. Signals associated with IOD were weak over upper tropospheric fields. In order to strengthen the IOD events in the upcoming boreal autumn, the warming in the central and western Indian Ocean is necessary right from spring season onwards. The extreme western Indian Ocean (west of 60°E) warming and eastern cooling are not sufficient to strengthen the dipole mode structure. Although the variations in surface wind stress is small over the central Indian Ocean during spring, it has significant effect on equatorial Wyrtki Jets and the resultant variation may occur in thermal structure of equatorial Indian Ocean in the summer monsoon period. During strong dipole mode years the seasonal variability was found to be more in various fields (surface wind, sea surface temperature, outgoing long wave radiation and surface heat flux) than weaker dipole mode years.

[Key words: Indian Ocean dipole, Wyrtki Jets, monsoon, spring season, SST, surface winds, heat flux, radiation, dipole year ]

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.87-92

 

ENSO and monsoon induced sea level changes and their impacts
along the Indian coastline

O.P.Singh*

Monsoon Activity Centre , India Meteorological Department , New Delhi-110003, India

*[E-mail : op_singh54@yahoo.com ]

Recevied 27 Decmber 2004, revised 15 June 2005

For preparedness programmes aimed at combating sea level - associated disasters, it is necessary to carry out comprehensive studies on different aspects of sea level variability. On many occasions the interannual modes dominate the long term trends of mean sea level (MSL). In South Asian region El Niño-Southern Oscillation (ENSO) induced variation is an important component of sea level variability on the interannual time scale. In the present paper focus is on the ENSO and monsoon modes of interannual variability of MSL along the Indian coast. The results have revealed that good concurrent correlations exist between the Southern Oscillation Index (SOI) and the Mean Tidal Level (MTL) at Visakhapatnam during the intense cyclone period of the year, i.e. May, October and November. Also, in the end phase of the southwest monsoon (i.e. during September) MTL is significantly correlated to the SOI. During the cold phase of ENSO (i.e. positive SOI) MSL is higher over the east coast of India enhancing the hazardous potential of the Bay of Bengal tropical cyclones. ENSO seems to have relatively lesser impact on the MSL variation over the west coast of India. However, during September (southwest monsoon) the correlations between the MTL and SOI are significant, both at Mumbai and Kochi. Thus ENSO appears to influence the MSL along the west coast of India during the ending phase of the southwest monsoon. The SOI-sea level relationship has prognostic utility also. High positive correlations exist between MSL along the east coast of India during the intense cyclone period (May  , October and November) and the SOI of preceding month which can provide predictive indications of sea level one month in advance . Significant concurrent correlations have been found between monthly rainfall and MSL over the west coast of India during the southwest monsoon season. The correlation coefficients of the order of ~ +0.5 have been observed between the seasonal monsoon rainfall over Konkan and Goa coast and seasonal MSL at Mumbai; and seasonal monsoon rainfall over Kerala and seasonal MSL at Kochi. It is interesting to note that correlations between the monsoon rainfall and MSL over the east coast of India are poor, implying that the southwest monsoon rainfall has very little influence on the sea level variations over the east coast of India. It may be pointed out that southeast coast of India receives substantial amount of rainfall during the northeast monsoon season (October to December) during which northeasterly winds prevail there. The lag correlations between the southwest monsoon rainfall and sea level over the west coast and the northeast monsoon rainfall and sea level over the east coast could also be looked into for the purpose of predictability aspect of the sea level along the Indian coast.

[Key words: Mean sea level, mean tidal level, El Nino / Southern Oscillation (ENSO), monsoon ,   southern oscillation index (SOI) , sea surface temperature, sea level, tidal level ]

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.93-103

 

The variability of Indian Ocean surface meteorological fields during summer monsoon in EL Nino/La Nina years

R. Bhatla*, U.C. Mohanty** & P.V.S. Raju***

* Department of Geophysics, Banaras Hindu University, Varanasi-221 005, India

** Centre for Atmospheric Sciences, Indian Institute of Technology-Delhi, NewDelhi-110 016, India

*** Department of Atmospheric Sciences, NTU-Taipei, Taiwan

*[E-mail: rbhatla@bhu.ac.in]

Received 27 December 2004, revised 23 March 2006

In the present study, the possible linkages between Indian summer monsoon rainfall and surface meteorological fields (basic fields and heat budget components) were investigated during El Nino years and La Nina years. For this purpose, monthly surface meteorological fields in pre-monsoon month of May and summer monsoon season (June to September) were analyzed using reanalysis data of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research). The statistical significance of the anomaly (difference) between the El Nino years and La Nina years in the surface meteorological fields was also examined. The significant negative precipitation anomalies over Indian landmass show that monsoon activity increases considerably during La Nina years. Significant positive anomalies of mean sea level pressure are observed over India during, Arabian Sea and Arabia in pre-monsoon month of May and monsoon season during El Nino years. Weaker westerlies develop in the west Arabian Sea in the month of may during El Nino years. The stronger southerlies in the monsoon months of La Nina years indicate higher northward transport of moisture. In the month of May, significant negative anomalies of cloud amount are observed over Somali coast, north Bay of Bengal and adjoining West Bengal and Bangladesh. During monsoon season, cloud amount shows negative anomalies over northwest India and Arabian Sea. There is overall reduction in the incoming shortwave radiation flux over northwest India, Arabia and north Arabian Sea during La Nina years. A significant higher magnitude of latent heat flux was also found over northwest India, central India and south Indian Ocean during La Nina years during monsoon season. The distribution of net heat flux is predominantly positive over northwest India and adjoining region, south Indian Ocean during monsoon season.

[Key words: Surface meteorological fields, monsoon, El Nino, La Nina, ENSO, Precipitation, Pressure, cloud cover, SST,   wind, temperature, radiation flux, heat flux]

 

 

 

 

 

 

 

 

 

 

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.104-110

 

Predicting upper ocean mixed layer depth in the north Indian Ocean using surface fluxes from a medium range weather forecast system

M. M. Ali1*, A.K.S. Gopalan2, K.N. Babu3, Rashmi Sharma3 & R. A. Weller4

1 Oceanography Division, National Remote Sensing Agency, Hyderabad 500037, A.P., India

2 Advanced Data Processing Research Institute, Secunderabad 500009, A.P., India

3 Space Applications Centre, Ahmedabad 380 053, India

4 Woods Hole Oceanographic Institution, Woods Hole, Massachusetts-02543, USA

*[ E-mail: mmali73@yahoo.com ]

Received 29 July 2005, revised 4 April 2006

Prediction of mixed layer depth (MLD) in the North Indian Ocean up to five days in advance was attempted using the one-dimensional numerical model of Price et al. [J. Geophys. Res. 91(1986) 8411-8427]. The model was first tested using the computed fluxes and profiles data from a moored buoy in the Arabian Sea. The forecast fields from National Centre for Medium Range Weather Forecasting (NCMRWF) were used for predicting MLD. MLD over the entire study area was computed by running the model on a 1o ´ 1o grid. The predicted MLD was compared with estimations from the in situ temperature profiles. Except at a few stations, where heat advection would have played a critical role in controlling mixed layer thermodynamics and thereby influencing the MLD, the RMS error was less than 10 m.

         [Key words: 1-D model, predictions, mixed layer depth, Ocean MLD, Indian Ocean, surface fluxes, weather forecast]

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.111-122

 

Oceanic mixed layer variations during the movement of cyclone along
symmetric tracks in the Indian Ocean

*A.A.Deo, D.W.Ganer & P.S.Salvekar

Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune 411 008, India

*[E-mail : aad@tropmet.res.in]

Received 27 December 2004, revised 27 January 2006

The understanding of significant changes in the oceanic mixed layer is important for dynamical prediction of tropical cyclone. Present study aims at examining the variations in the upper ocean parameters during the movement of tropical cyclone in northern and southern Indian Ocean, by applying 1½ layer wind driven reduced gravity ocean model. Different idealized tracks in the Bay of Bengal and their mirror images in southern hemisphere are considered. The model produced mixed layer depth, temperature and currents are compared for northern and southern hemispheric cyclone cases. Also the effect of latitude for westward moving cyclones in both the hemisphere is investigated. For this, tracks in the Arabian Sea and their counter parts in the southern hemisphere are considered. The maximum cooling found in the wake of cyclone is of the order of 3 - 4°C, which is comparable with earlier studies and observations. This significant cooling can cause weakening of the storm. This can be useful for prediction especially in the event of a cyclonic storm heading towards land and likely to make land fall. Moreover it is also seen that the mixed layer is cooled more on the right (left) of the storm track in northern (southern) hemisphere. This cooling decreases for the storms translating along higher latitudes implying the sensitivity of the latitudinal location of the storm.

             [Key Words: Numerical simulation, currents, Indian Ocean, cyclone, symmetric tracks, upwelling, Arabian Sea,
                  Bay of Bengal, mixed layer]

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp. 123-131

 

Simulation of the upper ocean thermal structure at the WHOI Arabian Sea mooring site

P.S Swathi  & C. Kalyani Devasena*

Centre for Mathematical Modeling and Computer Simulation (C-MMACS), Belur Campus, Bangalore-560 037, India.

[E-mail: swathi@cmmacs.ernet.in, kalyani@cmmacs.ernet.in ]

Received 27 December 2004, revised 6 March 2006

We have forced an Ocean General Circulation Model (OGCM, MOM_4) with surface observations at the WHOI mooring site in the Arabian Sea blended with other data and compared the thermal and salinity structures of the resulting simulations with observations. The model is successful in reproducing observations during January-July 1995, but does poorly during the southwest monsoon season. We have analysed model simulations in detail to study the thermal structure and mixed layer variability and the performance of the model at the buoy location in the Arabian Sea.

[Key words: OGCM, MOM_4, Arabian Sea, WHOI buoy, mixed layer depth, thermocline variability]

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.132-138

 

Estimation of tropical cyclone heat potential in the Bay of Bengal and its role in the genesis and intensification of storms

*Y.Sadhuram & T.V.Ramana Murthy

National Institute of Oceanography, Regional centre, 176, Lawsons Bay Colony, Visakhapatnm- 530017, AP, India

and

Y.K.Somayajulu

 National Institute of Oceanography, Dona Paula, Goa- 403 004, India

* [E-mail: sadhuram@nio.og]

Received 27 December 2004, revised 31 January 2006

In the present study, cyclone heat potential (CHP) in the Bay of Bengal has been estimated for different seasons using Levitus climatology. A good association was noticed between CHP and the efficiency of intensification (i.e the ratio between severe storms to total number of storms (in 5 o ´ 5 o grid), for the period, 1877-1977. CHP has been estimated using CTD data collected along the transects 88° E (4 o -20 o N) and 11.5o N (81 o -92 o E) during 1993-96 under pre-, during and post- SW monsoon seasons. These estimates are compared with those obtained from TOPEX/Poseidon sea surface height anomalies (SSHA) and TMI (Tropical Rainfall Measuring Mission Microwave Imager) SST using a two layer gravity model. The above estimates are also compared in the Andaman Sea for the 1996 post– SW monsoon season. It appears that the later method underestimates the CHP in the regions of anti cyclonic gyre (ACG). A relation between CHP and SSHA is proposed for the Bay of Bengal which shows a high correlation of 0.79 (N= 67; significant at > 99% level) using the CTD data. 

           [Key words: Cyclones, Bay of Bengal, cyclone heat potential, sea surface height, SST, storms, heat potential]

 

 

 

 

 

 

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.139-152

 

Observations and numerical simulation of the sea and land breeze circulations along the west coast of India

M. D. Simpson & S. Raman*

Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695-8208, USA

*(E-mail: sraman@ncsu.edu)

Received 27 December 2004, revised 7 April 2006

Sea breeze circulation along the west coast of India during the Indian Ocean Experiment (1999) is investigated. Pilot balloon sounding data from Mumbai, Goa, and Trivandrum, India show a diurnal variation in wind direction caused by land and sea breeze circulations along the west coast of India. Rawinsonde wind profiles taken from R/V Sagar Kanya 130 km offshore from the west coast of India show the presence of sea and land breeze circulations. Infrared satellite images show the furthest extent of the sea breeze circulation over the Arabian Sea to be around 200 km. Constant level balloons released from Goa, India also showed the extent of the sea breeze over the ocean to be 200 km. A mesoscale numerical model was used to further investigate the sea breeze circulation and its horizontal extent over the ocean. Simulated cross sections along the west coast of India show the horizontal extent of the afternoon sea breeze over the ocean to vary from around 130 to 260 km. Vertical velocities of about 0.25 ms-1 were simulated inland as the sea breeze interacted with the mountains along India’s west coast.

[Key words: INDOEX, sea breeze, air-sea interaction, sea breeze front, inland penetration, SST, boundary layer meteorology, Arabian Sea]

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp. 153-160

 

A study on cyclone induced productivity in south-western Bay of Bengal during November-December 2000 using MODIS (SST and chlorophyll-a)
and altimeter sea surface height observations

K. H. Rao*, A. Smitha & M. M. Ali

Oceanography Division, National Remote Sensing Agency, Balanagar, Hyderabad 500 037, India

*[E-mail: rao_kh@yahoo.com]

Received 27 December 2004, revised 10 April 2006

MODIS (Moderate Resolution Imaging Spectroradiometer) on board TERRA weekly composite mean products of sea surface temperature (SST) and chlorophyll-a, and modeled ocean net primary productivity with a spatial resolution of 4.63 km and altimeter derived sea surface height (SSH) data are used to study the changes in the primary productivity (PP) induced by the November-December 2000 tropical cyclone in the Bay of Bengal. A maximum SST drop of 2oC, a sea surface depression of 10 cm compared to the periphery, increase in chlorophyll-a by 1.5 mg/m3 and enhanced average mixed PP of 964 gC/m2/y were observed around 11.0oN and 81.0oE after the passage of the cyclonic storm. The enhanced PP after the passage of the cyclone supports the base of the pelagic marine food web, directly affecting the fishery productivity.

[Key words: Tropical cyclone, chlorophyll-a, sea surface temperature, mixed layer depth, primary productivity]

 

 

 

 

 

 

 

Indian Journal of Marine Sciences

Vol. 35(2), June 2006, pp.161-173

 

Impact of satellite derived wind in mesoscale simulation of Orissa super cyclone

M. Mandal & U. C. Mohanty*

Centre for Atmospheric Sciences, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi -110 016, India

and

A. K. Das

India Meteorological Department, Mausam Bhavan, Lodi Road, New Delhi - 110 003, India

*[E-mail: mohanty@cas.iitd.ernet.in]

Received 12 July 2005, revised 26 April 2006

Prediction of track and intensity of tropical cyclones is one of the most challenging problems in numerical weather prediction (NWP). Providing reasonably accurate initial condition to tropical cyclone forecast models has always been a problem to numerical weather forecasters. Recent advancements in spatial resolution and radiometric sensitivity have significantly improved the accuracy and density of satellite derived wind. The objective of the present study is to examine the impact of satellite derived winds in improving model initial condition and hence in mesoscale simulation of cyclonic storm. In this study, PSU/NCAR mesoscale model MM5 is used to produce 5-day simulation of the super cyclone that crossed Orissa coast on 29 October 1999. Winds derived from QSCAT, SSM/I, MSMR and METEOSAT-5 satellites are used in preparation of high-resolution reanalysis (HRR) and improving model initial condition. The strength of the southwesterly wind (over ocean) converging to the storm is found to be stronger both in the HRR and improved model initial condition compared to that in the NCEP/NCAR reanalysis. The strength of the cyclonic vortex is also better represented in the HRR and improved model initial condition. Improvement in model initial condition has resulted in consistent and significant improvement (35% in average) in prediction of the track of the storm.

[Key words: Cyclone, mesoscale, satellite derived wind, high-resolution reanalysis, super cyclone, Orissa cyclone]