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International Journal of Applied Environmental Sciences
ISSN 0973-6077 Volume 12, Number 5 (2017), pp. 717-729
© Research India Publications
http://www.ripublication.com
Influence of cyclone Phailin on the Upper Ocean over
Bay of Bengal
C. Purna Chand1, M.V. Rao1, K.V.S.R. Prasad2 and K.H. Rao1
1National Remote Sensing Centre, Hyderabad, India 2 Dept. of Meteorology and Oceanography, Andhra University, Visakhapatnam, India
Abstract
The influence of cyclonic storm Phailin during October 2013 on the ocean
surface over Bay of Bengal have been studied using Earth Observation (EO)
Sensors data as well as in-situ observations including temperature and salinity
profiles from Argo float data near vicinity of the Phailin track. The Phailin
(8th to 13th October 2013) induced cooling along the cyclone track is clearly
seen with substantial cooling observed before the landfall of the cyclone. This
cooling is a result of vertical mixing induced by upwelling due to strong winds
and Ekman current during the Phailin Cyclone. The significant wave height
increase along the coast is observed in the SARAL-Altika and Jason-2
Altimeter data. The pressure drop and the increase in salinity are found during
12th October 2013 due to passage of Phailin cyclone.
Keywords: Cyclone, Argo float, phailin, upper ocean, vertical mixing.
1. INTRODUCTION
Meteorologists use the term "tropical cyclone" for a closed atmospheric circulation
that forms over a tropical or subtropical ocean. Once maximum sustained wind speed
exceeds 74 miles per hour these storms are called hurricanes in the Atlantic Ocean,
typhoons in the Pacific Ocean, and very severe cyclones (super cyclones in recent
terminology) in the Indian Ocean.
The Tropical Cyclone damages the property and lot of casualties in coastal regions
due to gale winds and heavy rains associated flooding. People realized that the oceans
play a significant role in formation, development and strengthening of Tropical
718 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
Cyclone. Aftermath of Tropical Cyclone, variation in Sea Surface Temperature, gale
winds, Sea Waves, Surface Pressure, currents and biological activity are seen. The
changes of these parameters due to Tropical Cyclone are studied independently by
several researchers. The Cyclone induced Sea Surface Temperature cooling has been
investigated by different authors, using remotely sensed data sets [Stramma et al.,
1986, Peter et al., 1995, Suetsugu et al., 2000, Rao et al., 2002, Sadhuram. Y., 2004,
and Yablonsky et al., 2013]. Space-born wind measurements and significant response
to the strong wind forcing during tropical cyclone have been noticed [Atlas et al.,
1996, Atlas and Hoffman 2000, Adams et al., 2005, 2006, Liu and Xie 2008, Shuwen
Zhang et al., 2014, C P Chand et al., 2014, 2015 and Sasamal et al., 2015]. The impact
of Scatterometer wind on tropical cyclone forecasting has been studied [Isaksen and
Stoffelen 2000]. The nutrients are efficiently replenished in euphotic layer and
phytoplankton biomass rapidly enhanced due to tropical storm passage [Shiah et al.,
2000, Subramanyam et al., 2002,Preethi et al, 2015 and Aneesh et al., 2014].
The upper ocean response to a moving storm has been an important and interesting
topic in the physical and biological oceanographic studies. Keeping this in view, a
comprehensive study during one Tropical Cyclone (Phailin) using Earth Observation
Sensors data and in-situ observations during October 8-14, 2013 has been carried out.
1.1 Very Severe Cyclonic Storms ‘Phailin’
The cyclone Phailin during October 8-14, 2013 is the category four Hurricane, out of
three very severe cyclonic storms occurred during 2013. As per India Meteorological
Department (IMD) [www.imd.gov.in] reports on 8th October 2013 the Deep
Depression upgraded to Cyclone and subsequently a cyclonic storm named it as
Phailin. It is further strengthened and formed into a very severe cyclonic storm by
10th October 2013. The Phailin is further intensified with a central pressure of 994
mb and crossed the coast near Gopalpur, Odisha, East Coast of India on 12th October
2013. The cyclone ‘Phailin’ prompted India's biggest evacuation in last 23 years with
more than 550,000 people moving up from the coastline in Odisha and Andhra
Pradesh to safer places. Forty four deaths and 696 million USD damage due to the
cyclone have been reported.
2. DATA USED AND METHODOLOGY
In this study Level 2B wind field data from Ocean Sat-2 Scatterometer (OSCAT)
obtained during Phailin Cyclone (both descending and ascending passes, equatorial
crossing time nearly at 6:30 and 18:30 GMT respectively) from NRSC, Hyderabd.
The wind field data (both speed and direction) is available in 25 Km and 50 Km grid
size. The 25 Km wind field data has been used to estimate wind stress and wind
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 719
stress curl using standard formula [Sourabh et al., 2014]. The 50 Km wind field data
is used to compute pressure fields using University of Washington Planetary
Boundary Layer (UWPBL) Model as described by Patoux et al., [2003]. The UWPBL
model compute surface wind from the knowledge of geostrophic wind ‘Farward’ and
‘Inverse’ model calculate geostrophic wind at top of boundary layer from surface
wind. The boundary layer wind in two different models viz; two layer similarity
model for mid-latitude (60o to 10oS and 10o to 60oN) and Mixed layer model for
tropical region (20oS to 20oN) yield the pressure gradients. The absolute pressure
values can be obtained through least square fit from a priori pressures from
observations/model values and here we used buoy data from Indian National Centre
for Ocean Information Services (INCOIS) [www.incois.gov.in] as a priori pressures.
The model required input data other than wind fields on air temperature, sea surface
temperature, humidity, and horizontal temperature gradient. These inputs are taken
from the climatological data.
The Sea Surface Temperatures (SSTs) both daily and weekly were extracted from
Tropical Rainfall Measuring Mission’s (TRMM) Microwave Imager (TMI)
[www.remss.com] during the period of cyclone Phailin to study the cooling effect.
The ocean surface currents are estimated from Ekman surface current through
OSCAT wind stress component and geostrophic current through SARAL Altika
derived sea surface heights [Saurabh et al., 2014]. The chlorophyll-a estimates are
obtained from OCM-2 data during Phailin. The significant wave heights were
estimated using the Saral-Altika and Jason-2 data during Phailin Cyclone.
In addition temperature and salinity profile Argo float data near vicinity of the Phailin
track were obtained from coriolis project and programs (http://www.coriolis.eu.org)
during cyclone period. These profile data are used to compute Mixed Layer Depth
(MLD).
3. RESULTS AND DISCUSSIONS
The Tropical Cyclone ‘Phailin’ induced changes over Bay of Bengal were studied
with the help of multi sensor derived ocean parameters. Normally during the Tropical
Cyclone, the heat transfer from ocean to the atmosphere through evaporation is
enhanced by cyclone induced surface winds, which transport water vapor to the
troposphere.
Other way the cyclone induced surface winds do generate upper-ocean currents and
this process of current generation does not happen directly. The winds build up
waves at the sea surface, and some of the energy from the winds goes into growing
and propagating these waves. When the waves break, energy is transferred downward
into the ocean currents.
720 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
The cyclone-induced chl-a increase is another process accounting for a few percent of
the total chl-a increase in some areas. In oligotrophic regions, the increase in chl-a
tended to become larger as the corresponding SST decrease became larger, although
the relationship between them is opposite in mesotrophic and eutrophic regions.
3.1 Sea Surface Temperature
To compare the sea surface temperatures during cyclone period with that prior to
cyclone, SSTs from first week of October 2013 (i.e. week ending on 5th October
2013) have been chosen as reference. The SST anomaly’s estimated from the
individual day SST from 8th to 13th October, 2013 by subtracting daily SST from
weekly (week ending on 5th October 2013) SSTs. Hence the positive value indicates
cooling and negative represents warming. The colour coded SST anomaly images are
generated, have been presented in figure 1(a). The temperature anomalies during the
cyclone period along the track from 8th to 13th have been presented in figure 1(b). It is
seen from figure 1, that the cooling is observed 1.0 to 2.0 0 C from 8th to 11th and
cooling increases as it approaches to the coast, attains maximum (≈ 6.0 0C) on 13th
October 2013 near land fall point.
Figure 1. (a) Colour coded images depicting SST anomaly (weekly average for the
week ending on 5th October 2013 minus SSTs of daily from 8th to 13th October 2013),
high positive anomaly along coast indicate maximum cooling on 13th October 20113.
(b) SST anomaly all along the Phailin cyclone track is shown from 8th to 13th October
2013(Maximum cooling observed).
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 721
The upwelling caused by the cyclonic storm has to be balanced by the downwelling at
the adjoining place. When the storm is closer to the coast, the downwelling might
have probably taken place to the west of the storm, which is evident from the positive
SST anomalies towards the west of the cyclonic track. The storm also has generated
coastally trapped Kelvin waves with cooler waters that propagated towards the east
coast of India. The extent of these cooled waters near the east coast of India is clearly
seen during the landfall of cyclone Phailin (figure 1(a)). The Sea Surface
Temperatures are cooled significantly along the storm track in the open ocean, but the
cooling is more prominent along the coast (figure 1(b)).
There are two possible explanations for surface cooling due to cyclones: extraction of
thermal energy from the surface due to evaporation, or wind induced vertical mixing
of the water column. This argument is based upon viewing the ocean as a two-layer
fluid; a warm upper layer, and a cold deeper layer. (The interface is referred to as the
main thermocline). The upper layer is relatively thick in October, so there must be a
great deal of vertical mixing to draw deep cold water to the surface. Along the shelf,
however, which the storm encounters as it approaches to the coast, the upper layer is
relatively thin. Therefore, with the same amount of vertical mixing, more cold water
can be drawn to the surface, and cooling is more substantial.
To substantiate the observed cooling in satellite derived SST, we have also collected
temperature and salinity profiles from Argo float data near vicinity of the Phailin
track (figure 2). There are three Argo Floats data available near vicinity of the Phailin
track with float ID Nos. 2901334, 2901335 and 2901327. Of which 2901335 is
available daily data, whereas 2901334 is once in five days starting from 07th October
2013 and 2901327 is available on 8th, 12th and 15th October 2013. The Mixed Layer
Depth (MLD) is computed based density criteria, the depth at which density is 0.125
at all three float locations and is presented in figure 2.
For all the three floats, the salinity and temperature profiles are presented in figure 3.
It is very clearly seen from all the profiles, that the surface cooling is observed on 12th
October, 2013 and at the same time the increase in surface salinity is seen on 12th,
indicating sub-surface cooled high saline waters appearing on the surface due to high
vertical mixing. It is also observed deepening of MLD on 12th October, 2013. It is
interesting to note that the surface salinity increase is quite high compared to surface
temperature cooling. Surface cooling observed is more than 2oC at Argo id 2901335
location after the passage of the storm (i.e. from 9th to 12th October 2013). The salinity
increase from 3.5 ppm, 4 ppm and 5.5 ppm at Argo id 2901334, 2901335 and
2901327 respectively during cyclone passage. From these observations (figure 3), it
is clear that the vertical mixing is dominant and observed stable mixed layer during
12th October 2013. There are fluctuation in these Argo float data due their locations
(2901335 on the track, 2901327 close to the track and 2901334 little away from the
track), as seen in figure 2, as well as coverage of data (one float, once in 5 days, one
float daily and the other on 8th, 12th and 15th October 2013).
722 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
Figure 2. The Phailin track with Argo floats Position; along with the Mixed Layer
Depth plotted against the dates for the profiles from Argo floats.
3.2 Wind, Wind Stress, Wind Stress Curl and Ekman Current
The wind, Wind Stress (WS) and Wind Stress Curl (WSC) products of the OSCAT
are studied with reference to the impact of cyclone Phailin. The wind vector and WS
are critically important for determining the large scale ocean circulation and transport.
Vector winds are needed to study the ocean and atmospheric process, like Ekman
transport, upwelling and mixed layer dynamics etc.
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 723
Figure 3. The salinity and temperature profiles for all the three Argo floats during the
cyclone Phailin period.
724 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
The high resolution (25 Km) wind velocities from OSCAT during the phailin cyclone
are studied. Though the wind speed measurement range of OSCAT is 4-24 m/s, the
wind speeds retrieved show as high as around 107 km/hr (29.6 m/s) on 12th during
landfall of Phailin. The estimated wind speeds reported by IMD are as high as 215
km/hr during landfall, which is double than the satellite estimation, and is mainly due
to saturation of the sensor. WS and WSC also increased all along the track from 8th to
12th and reached to maximum, 2.58 N/m2 and 9.86 N/m3 respectively at landfall
location on 12th October. The Tropical cyclone induced strong winds transfer the heat
from ocean to atmosphere through evaporation, which transport water vapour into the
troposphere. However, expected high evaporation may not be observed during the
cyclone due to intense cooling of surface, though strong winds are present. The
surface wind exerted stress lead to vertical mixing due to friction and generate
currents in the oceanic mixed layer. It is also known that the wind stress during
cyclone leads to move the waters away from the storm center through currents
generated over there and to maintain equilibrium cooled sub-surface waters comes up.
This process is known as storm generated ‘upwelling’. All these processes result in
cooling the sea surface all along the cyclone track and are discussed in the previous
section. The Phailin surface winds exert a stress on the ocean surface due to friction,
generating ocean currents in the oceanic mixed layer.
Under the assumption that the water currents are driven only by the transfer of
momentum from the wind, Ekman theory explains the theoretical state of circulation
and currents generated are known as Ekman Currents. Ekman motion describes the
wind-driven portion of circulation seen in the surface layer. Hence the Ekman
Currents are estimated using OSCAT wind during the Phailin cyclone. The maximum
Ekman current velocity observed was around 170 cm/s on 12th October 2013. It is
clearly seen that the waters moving away from the storm center and cooled sub-
surface waters comes up there, leading to sea surface cooling all along the cyclone
track.
3.3 Sea Level Pressure fields
The sea level pressure retrieved from OSCAT winds using UWPBL model during
Phailin Cyclone have been studied. Here we observed 10 mb pressure drop from 8th
to 13th October 2013. As per IMD, the pressure drop during the same period reported
to be 63-64 mb. Deep Depression is upgraded to Cyclone and subsequently to a
cyclonic storm named as Phailin. It is further strengthened and formed into a very
severe cyclonic storm by 10th and is further intensified with a central pressure of 994
mb and crossed the coast near Gopalpur on 12th October 2013. By nomenclature a
pressure drop of 5 to 9 mb with maximum sustained 3 minutes surface winds of
34 knots or more is called as cyclonic storm, which is clearly observed in our satellite
based pressure estimations from 8th to 10th October 2013. Though the IMD estimated
pressure values differ from satellite derived ones, the isobars maps generated are
closely matching with IMD reports during this cyclone (Figure 4). The pressure drop
at the cyclone centre is noticed to be low compared to estimated pressure drop
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 725
reported by IMD mainly due to saturation of winds (4-24 m/sec) measured by the
Oceansat Scatterometer sensor, which is input for the retrieval of pressure fields using
UWPBL model. The low pressure centers from UWPBL model derivatives are drawn
to built the cyclone track and found it is closer to the IMD track. Though the pressure
values differ from the IMD reported values, the increase in closed isobars from 8th to
12th October 2013 clearly indicate the intensity of cyclone.
Figure 4. Estimated pressures using UWPBL model from 8th to 13th October 2013 are
presented here. A low pressure system is present in north Andaman Sea with 1003 mb
pressure and for 12th October 2013, with a steep drop in pressure from surroundings
was observed and is as low as 993 mb on 12th October 2013.
726 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
3.4 Chlorophyll Concentration
The Ocean Colour Monitor (OCM) – 2 is one of the sensor onboard Oceansat-2
intended to estimate Chlorophyll-a as one of the parameters. The Chlorophyll
distribution along the cyclone track (according to IMD) has been computed before
and after the cyclone Phailin. From the analysis, it is observed that the chlorophyll-a
concentration has increased from 1.08 (before) to 7.06 mg/m3 after the cyclone
[Preethi et al., 2015].
3.5 Significant Wave Height
The significant wave heights were estimated using the SARAL-Altika and Jason-2
data during Phailin Cyclone i.e. on 12th October 2013. The Significant Wave Height
(SWH) variations against latitude during the pass of Saral-Altika-051 reveal high
SWH at 20o N latitude on 12th October, 2013 [Sasamal et al., 2015].
4. CONCLUSIONS
The cyclone induced cooling along the cyclone track is clearly seen in the satellite
derived Sea Surface Temperatures during the cyclone Phailin. Substantial cooling is
observed before the landfall of the cyclone. The cooling is a result of all the three
processes; namely evaporation, vertical mixing and upwelling. However, we observed
that the vertical mixing induced by upwelling is the dominant one.
The surface salinity increase is quite high compared to surface temperature cooling as
evident in the vertical profiles of Argo float temperature and salinity data.
The OSCAT winds, wind stress and wind stress curl impact is reflected in the ocean
surface by indicating intensive mixing to deeper waters.
It is clearly seen from the Ekman current that the waters are moving away from the
storm center leading upwelling to happen at the storm center.
The UWPBL model derived pressure fields are found useful in the construction of
cyclone track and intensity, through numerically they are underestimated due to
saturation of winds during cyclone.
Though, the evaporation rates are expected to be high during cyclone due to high
surface winds, but it is not as high as expected due to sudden surface cooling.
Finally, the winds are the major cause for upper ocean response to a moving storm.
Vertical mixing occurs because the cyclone’s surface winds exert a stress on the ocean
surface due to friction, generating ocean currents in the oceanic mixed layer which is
reflected in surface cooling, increase in surface salinity and high chlorophyll
concentration observed in passage of Phailin cyclone.
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 727
5. ACKNOWLEDGEMENTS
We express our gratitude to J. Patoux, PBL Research Group, Department of
Atmospheric Sciences, University of Washington, USA for his support rendered
during the execution of UWPBL model at NRSC and also his valuable suggestions.
Our sincere thanks to Saurabh Bansal former Scientist in OSG/ECSA/NRSC for his
continuous support. This work was carried out at National Remote Sensing Centre
(NRSC), as a part of Oceansat-II utilisation and NICES program. The Argo data were
collected and made freely available by the Coriolis project and programmes that
contribute to this study. TMI data are produced by Remote Sensing Systems and
sponsored by the NASA Earth Sciences Program is used in this study.
REFERENCES
[1] Adams, I. S., W. L. Jones, S. Vasudevan, and S. Soisuvarn (2005), Hurricane
wind retrievals using the SeaWinds scatterometer on QuikSCAT. Proc. Of
MTS/IEEE OCEANS 2005, Washington, D.C., Marine Technology Society and
the Oceanic Engineering Society of the IEEE, pp.2148-2150.
[2] Adams, I.S., C.C. Hennon, W. L. Jones, and K. A. Ahmad (2006), Evaluation
of hurricane ocean vector winds from WindSat. IEEE Trans. Geosci. Rem.
Sens., 44, pp.656 – 667.
[3] Aneesh, A. Lotliker, T. Srinivasa Kumar, Venkat Shesu Reddem and Shailesh
Nayak (2014), Cyclone Phailin enhanced the productivity following its
passage: evidence from satellite data. Current Sci., 106(3), pp.360-361
[4] Atlas, R. M., R. N. Hoffman, S. C. Bloom, J. C. Jusem, and J. Ardizzone
(1996), A multiyear global surface wind velocity dataset using SSM/I wind
observations. Bull. Amer. Meteor. Soc., 77, pp.869-882.
[5] Atlas, R., and R.N. Hoffman (2000), The use of satellite surface wind data to
improve weather analysis and forecasting at the NASA Data Assimilation
Office. Satellites, Oceanography and Society, Halpern, D., Elsevier
Oceanography Series,
[6] Isaksen, L., and A. Stoffelen (2000), ERS-Scatterometer wind data impact on
ECMWF's tropical cyclone forecasts. IEEE Trans. Geosci. Rem. Sens., 38,
pp.1885-1892.
[7] Liu, W. T. and X. Xie (2008), Ocean-atmosphere momentum coupling in the
Kuroshio Extension observed from space. J. Oceanogr., 64, pp.631-637.
[8] Peter, G. Black, and L.K. Shay (1995). Observed sea surface temperature
variability in tropical cyclones: Implications for structure and intensity change.
Preprints, 21st Conference on Hurricanes and Tropical Meteorology, Miami,
FL, April 24-28, 1995. American Meteorological Society, Boston, 603-604.
[9] Patoux, J., R. C. Foster, and R. A. Brown (2003), Global Pressure Fields from
Scatterometer Winds. Journal of Applied Meteorology, 42, 813-826
728 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao
[10] Preethi Latha, T., K. H. Rao, P. V. Nagamani, E. Amminedu, S. B.
Choudhury, C. B. S. Dutt, V. K. Dadhwal (2015), Impact of Super Cyclone
PHAILIN on chlorophyll-a concentration and productivity in the Bay of
Bengal. International Journal of Geoscience, Vol. 6(5), pp.473-480.
[11] Purnachand, Ch., M. V. Rao, I. V. Ramana, M. M. Ali, J. Patoux, and
M.A.Bourassa (2014), Estimation of Sea-Level Pressure Fields during
Cyclone Nilam from Oceansat-2 Scatterometer Winds. Atmos. Sci. Let. 15,
pp.65-71.
[12] Purnachand, Ch., I. V. Ramana, M. M. Ali, K. H. Rao, P. N. Sridhar, C. B. S.
Dutt and M. V. Rao (2015), Retrieval and Validation of Pressure Fields from
Scatterometer Winds. Tech. Rep. No. NRSC – ECSA – OSG – NOV – 2014 –
TR – 667, NRSC, Hyderabad, pp. 27.
[13] Rao, M. V., B. Jena, I. V. Ramana and M. M. Ali (2002), Remote Sensing of
Sea Surface cooling by a Tropical Cyclone. In: Proc. of International
conference of ISPRS held during Dec. 3rd-6th at Hyderabad, India, 34(7),
pp.63-68.
[14] Sadhuram, Y. (2004), Record decrease of sea surface temperature following
the passage of a super cyclone over the Bay of Bengal, Current Sci., 86( 3),
pp.383-384.
[15] Sasamal, S. K., B. Sourabh, K. H. Rao, C. B. S. Dutt, and V. K. Dadhwal
(2015). OSCAT Wind Stress and Wind Stress Curl during the Bay of Bengal
Tropical Cyclone ‘Mahasen’, International Journal of Engineering Science
and Innovative Technology, 4(2), pp.152-162.
[16] Sasamal, S. K., Sourabh Bansal, C. B. S. Dutt, V. K. Dadhwal (2015), Use of
SARAL AltiKa geophysical products towards the study of ‘Phailin’.
International Journal of Engineering Science and Innovative Technology, Vol.
4(2), pp. 125-134.
[17] Sourabh, B., S. K. Sasamal, K. H. Rao, C. B. S. Dutt, (2014). Indian Ocean
Surface Currents using OSCAT and Saral-Altika. Tech. Rep. No. NRSC –
ECSA – OSG – NOV – 2014 – TR – 659, NRSC, Hyderabad, pp. 21.
[18] Sourabh, B., S. K. Sasamal, Chiranjivi Jayaram, T.V.S. Udaya Bhaskar, D.
Swain (2014), OSCAT Wind Stress and Wind Stress Curl Products. Tech.
Rep. No. NRSC – ECSA – OSG – NOV – 2014 – TR – 661, NRSC, Hyderabad,
pp. 18.
[19] Shiah, F. K., S.W. Chung, S.J. Kao, G. C. Gong, K. K. Liu (2000),
Biological and hydrographical responses to tropical cyclones (typhoons) in the
continental shelf of the Taiwan Strait. Cont. Shelf Res. 20, pp.2029–2044.
[20] Shuwen Zhang, Lingling Xie , Yijun Hou, Hui Zhao, Yiquan Qi, and Xiaofei
Yi (2014). Tropical storm-induced turbulent mixing and chlorophyll-a
enhancement in the continental shelf southeast of Hainan Island, Journal of
Marine Systems, 129, pp.405-414.
Influence of cyclone Phailin on the Upper Ocean over Bay of Bengal 729
[21] Stramma, L., P. Cornillon (1986), Satellite observation of Sea Surface Cooling
by Hurricanes, J. Geophys. Res., 91, pp.5031-5035.
[22] Subramanyam Bulusu, K. H. Rao, N. Srinivasa Rao, V. S. N. Murthy, and
Ryan J. Sharp (2002), Influence of a tropical Cyclone on Chlorophyll-a
concentration in the Arabian Sea, Geophysical Research Letters, 29(22),
pp.2051-2065.
[23] Suetsugu, M. Kawamura, H., and Nishihama, S (2000), Sea Surface cooling
caused by typhoons in the Western North Pacific Ocean. PORSEC
Proceedings, Goa, India, 1, pp.258-262.
[24] Yablonsky, R. M., and I. Ginis (2013), Impact of a warm ocean eddy's
circulation on hurricane-induced sea surface cooling with implications for
hurricane intensity, Monthly Weather Review, 141(3), pp. 997-1021.
730 C. Purna Chand, M.V. Rao, K.V.S.R. Prasad and K.H. Rao