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IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring", Hyderabad, India, 2002
2. METHODOLOGY, DATA AND ANALYSIS:
Indian Remote Sensing Satellite — P4 (IRS-P4)/Multi-
frequency Scanning Microwave Radiometer (MSMR):
The Indian Remote Sensing Satellite — P4, IRS-P4 (Oceansat-
1) is the first in the series of the Indian satellites to address the
oceanographic applications in a more concentrated manner.
Oceansat-l, was launched from Sriharikota (SHAR) range
using the indigenous Polar Satellite Launch Vehicle (PSLV)
during May 29, 1999, carries two payloads Viz; an Ocean
Colour Monitor (OCM) and a Multi-frequency Scanning
Microwave Radiometer (MSMR) to study both the biological
and physical parameters of oceans. The primary mission
objectives of IRS-P4 are to gather systematic data for
oceanographic, coastal and atmospheric applications. The
satellite is placed in a near circular, sun-synchronous orbit at an
altitude of 720 Km with the local time of equatorial crossing in
the descending node at 1200 hrs + 10 minutes.
Multi-frequency Scanning Microwave Radiometer works
on the principle of collecting radiation from earth in
microwave range of electromagnetic spectrum. MSMR is
configured as an eight-channel radiometer with both
vertical and horizontal polarizations in four frequencies.
The brightness temperature is computed from the
radiometric measurement at frequencies of 6.6(GHz),
10.65(GHz), 18(GHz) and 21(GHz) for both horizontal
and vertical polarizations. For the ice and land
application studies, the brightness temperature data’s are
used directly, where as for ocean application the
geophysical parameters like Sea surface temperature
(SST), Sea surface wind speed (SSWS), Water vapor
(WV), Cloud liquid water (CLW) are retrieved from
brightness temperature corresponding to a specific grid
size of brightness temperature data sets. The sensor
specification and retrievable parameters are provided in
Table 1. The weekly averaged SST data for 1.5 deg. X
1.5 deg. Grid has been created for the study area.
Table 1 - Geophysical Parameters from MSMR
GRID FREQUENCY PARAMETERS
(GHz)
1(150Kms) | 6.6,10.6,18,21 SST, SSWS, IWV,
CLW
2(75Kms) 10.65,18,21 SSWS, IWV, CLW
3(50Kms) 18,21 IWV, CLW
Tropical Rainfall Measuring Mission’s (TRMM)
Microwave Imager (TMI):
The Tropical Rainfall Measuring Mission’s (TRMM)
Microwave Imager (TMI) is a passive microwave sensor
designed to provide quantitative rainfall information and other
oceanographic parameters over a wide swath under the TRMM
satellite. By carefully measuring the minute amounts of
microwave energy emitted by the Earth and its atmosphere,
TMI will be able to quantify the water vapor, the cloud water,
Sea Surface Temperature and the rainfall intensity in the
atmosphere. TMI is not a new instrument. It is based on the
design of the highly successful Special Sensor
399
Microwave/Imager (SSM/I), which has been flying
continuously on Defense Meteorological Satellites since 1987.
The TMI measures the intensity of radiation at five separate
frequencies: 10.7, 19.4, 21.3, 37, 85.5 GHz. These frequencies
are similar to those of the SSM/I, except that TMI has the
additional 10.7 GHz channel designed to provide a more-linear
response for the high rainfall rates common in tropical rainfall
and also to measure the sea surface temperatures. The other
main improvement that is expected from TMI is due to the
improved ground resolution. This improvement, however, is
not the result of any instrument improvements, but rather a
function of the lower altitude of TRMM 218 miles (350
kilometers) compared to 537 miles (860 kilometers) of SSM/I).
TMI has a 487 mile (780-kilometer) wide swath on the surface.
The higher resolution of TMI on TRMM, as well as the
additional 10.7 GHz frequency, has made TMI a better
instrument than its predecessors.
The measurement of sea-surface temperature (SST) through
clouds by satellite microwave radiometers has been an elusive
goal for many years. The early radiometers in the 1980's (i.e.,
SMMR) were poorly calibrated, and the later radiometers (i.e.,
SSM/I) lacked the low frequency channels needed by the
retrieval algorithm. Finally, in November 1997, the TMI
radiometer with a 10.7 GHz channel was launched aboard the
TRMM satellite. The important feature of microwave
retrievals is that SST can be measured through clouds, which
are nearly transparent at 10.7 GHz. This is a distinct advantage
over the traditional infrared SST observations that require a
cloud-free field of view. Ocean areas with persistent cloud
coverage can now be viewed on a daily basis. Furthermore,
microwave retrievals are not affected by aerosols and are
insensitive to atmospheric water vapor. However, the
microwave retrievals are sensitive to sea-surface roughness,
while the infrared retrievals are not. A primary function of the
TRMM SST retrieval algorithm is the removal of surface
roughness effects. The microwave and infrared SST retrievals
are very complementary and can be combined to obtain a
reliable global data set. The weekly SST in binary format
retrieved from TMI data have been obtained from net which is
now available as part of the 6 parameter binary data file. The
data for study area have been extracted from this global data
set. :
3. RESULTS AND DISCUSSION:
A well-marked low-pressure area lay over Gulf of Siam and
neighborhood on 24" October 1999, It formed into a
depression over North Andaman sea and neighborhood at 1200
UTC of 25" and lay near latitude 12.5°N/Long.98.0°E The
depression area further moved into a west northwestly direction
and intensify into a cyclonic storm and lay centered at 0300
UTC of 26" near lat.13.5°N/long.95.5°E. The whole system,
further intensified into a severe cyclonic storm at 0300 UTC of
277" and lay centered nearer lat.16.0°N/long.92.0°E about 750
Km southwest of paradeep. The cyclone further intensified into
a severe cyclonic storm at 1500 UTC of 27” near
1at.17.2°N/long.90.3°E. At 0300 UTC of 28" October, the
system was centered near lat.18.0°N/long.89.0°E. At 1200
UTC of 28" the system moved near lat.18.5?N/long.88.0?E
with the maximum surface wind of 135Kts (1 minute average).
The system intensified into super cyclonic storm at 1800 UTC
on 28" near lat.19.3°N/lon.87.2°E with the maximum surface
wind of 140Kts. On 29" October, the whole system centered
near lat.19.9°N & long. 86.7? E at 0300 UTC. It crossed
