N-ESCAP, 
lication of 
getation of 
Dec 2001, 
. B, Rao, R 
tific Note, 
s Centre, 
Trivedi, C 
,Oza, SH, 
)1, Manual 
shoreline 
al Note, 
s Centre, 
rasad, K N 
monitoring 
h, Western 
nformation 
- a review. 
nitoring of 
ng satellite 
/89 Space 
A coastal 
of Canada. 
status and 
Mangroves- 
Research 
monitoring. 
ical aerial 
n (GIS) to 
uations on 
A, Aquatic 
IAPRS & SIS, Vol.34. Part 7, "Resource and Environmental Monitoring". Hyderabad, India,2002 
INTER-COMPARISON OF SIMULTANEOUS MSMR AND SSM/I OBSERVATIONS FOR 
SEA ICE ESTIMATION OVER THE ANTARCTIC REGION 
Satyendra Bhandari* , Mihir Dash and N.K. Vyas 
Space Applications Centre (ISRO), Ahmedabad — 380 015, INDIA 
and 
Amita Khanolkar, Nilay Sharma, Niloy Khare and P.C. Pandey 
National Centre for Antarctic and Ocean Research (NCAOR), Goa — 403 804, INDIA 
KEY WORDS : Polar Remote Sensing, Antarctic Sea Ice, OCEANSAT - MSMR, SSM/I, Sensor Inter-Calibration 
ABSTRACT 
With the launch of MSMR onboard OCEANSAT-1 in the polar sun-synchronous orbit, India developed the capability to 
comprehensively monitor the sea ice on a regular basis, with a repetivity of two days. In view of our direct interest, we have utilised 
MSMR data to observe and analyse, on apriority basis, the sea ice conditions over the Antarctic and Southern Polar Ocean region 
over the last few years. MSMR data have been shown to clearly delineate the presence of sea ice, and bring out its seasonal and 
long term variability in a highly consistent manner. 
In this paper, we attempt an indirect validation of the brightness temperatures (Tb) observed by MSMR with near- simultaneous 
measurements from SSM/I onboard DMSP series of satellites over the Antarctic and Southern Polar Ocean regions. for the present 
analysis, simultaneous MSMR and SSM/I data from two contrasting seasons — summer and winter, for the 1999-2000 period have 
been chosen. Analysis includes a comparison of T scatterograms to achieve confidence in the quantitative use of the T, data to 
derive various geophysical parameters e.g. sea ice extent and concentration. Additionally, the Ty images produced by the two sensors 
are compared to establish the capability of MSMR in reliable two -dimensional portrayal of all the sea and land ice features over the 
Antarctic Region. Based on a regression analysis between MSMR observed Tbs and the SSM/I derived sea ice concentration (SIC) 
values, we have developed algorithms to estimate SIC over the Southern Polar Ocean. These MSMR algorithms allow estimation of 
SIC with better than 10 96 rms error. The analysis brings out the very high level of compatibility in the measurements produced by 
the two sensors. The quantitative inter-comparison with the near-operational sea ice analyses from SSM/I paves thé way for 
continuous and reliable monitoring of polar ice with MSMR. 
  
*Corresponding Author: Dr. Satyendra Bhandari, Scientist — Remote Sensing, Email: space. scientist(g)rediffmail.com 
1.0 INTRODUCTION 
Polar regions play an important role in shaping and 
influencing Earth's climate. A vast area of several millions of 
square kilometers of polar oceans is perennially covered by 
sea ice. The seasonally expanding and contracting extent of 
sea ice profoundly impedes the ocean-atmosphere heat 
exchange because sea ice is highly insulative. The presence of 
sea ice also enhances the planetary albedo. Further, the salt 
expulsion during formation of sea ice leads to bottom water 
formation that is believed to be one of the two main sources of 
global oceanic thermohaline circulation. The climate system 
potentially involves many sea-ice climate feedbacks that are 
extremely complex and difficult to understand (King and 
Turner, 1997). This calls for detailed long term measurements 
of different characteristics of sea ice. 
Due to the all-weather and all-season synoptic coverage 
capability, space based passive microwave radiometers 
(PMRs) have played a vital and pioneering role in the study of 
mapping and monitoring of ice and sea ice conditions both in 
the Arctic and the Antarctic regions. In the microwave band 
(1-100 GHz) distinct thermal and structural properties of sa 
ice and open ocean water allow a clear delineation through the 
strong emissivity contrast. Sea ice typically has an emissivity 
of about 0.9 as compared to emissivity of ocean water of 
about 0.4 (Ulaby et al., 1982, Massom, 1991). Exploiting this, 
passive microwave sensors have been used more or less 
continuously over the last 30 years to map and study sea ice 
409 
characteristics and sea ice variability on time scales ranging 
from weekly to monthly to seasonal and inter-annual scales. 
These studies have been based on almost continuous 
monitoring of sea ice using PMR measurements from 
Nimbus-5 ESMR, Nimbus-7 SSMR and DMSP SSM/ 
(Gloersen et al., 1992, Parkinson et al., 1999, Zwally, 1984). 
Numerous investigations have been undertaken to 
understand the observed short-term and long-term regional 
and hemispheric changes in sea ice characteristics in 
relation to climate and climate change (Parkinson et al., 
1999, Hanna and Bamber, 2001). 
India launched its PMR, for the first time in a polar orbit, on 
May 26, 1999. The Multifrequency Scanning Microwave 
Radiometer (MSMR) onboard this satellite, named 
OCEANSAT-1, has provided continuous polar coverage 
every two days for a period of about three years. We have 
used the MSMR measurements to study the spatial 
distributions and seasonal variability of sea ice 
characteristics over the Southern Ocean region surrounding 
Antarctica. MSMR observed sea ice extent estimates were 
used to analyse the long term secular trend of sea ice extent 
over the southern ocean region (Dash et al, 2001). 
Interesting results on the increasing — rather than 
decreasing, sea ice extent over the last 25 years, as well as 
the possibility of recent acceleration in this increasing rate, 
were derived (Dash et al., 2001, Bhandari et al., 2002, Vyas 
et al. 2002). In contrast, sea ice extent over the Arctic region 
is known to be decreasing over the last two decades