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IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002 
Tbs were then compared with simultaneous MSMR Tb 
measurements. Fig. 2 shows a scatter diagram of MSMR Tbs 
vs. SSM/I Tbs for 18 H channels for the periods Oct. 15-16, 
1999 and Feb. 15-16, 2000. The comparison is carried out for 
a small region in the Weddell Sea where one expects the 
ocean to be covered with sa ice, at least partially, in both the 
seasons. 
  
  
  
Dakshin Gangotri and Maitri 
L 
  
  
Fig. | - Base map of Antarctic region showing different 
sectors of the Southern Ocean. Shaded quadrangle shows the 
area over which MSMR and SSM/I data have been inter 
compared 
Oct. 15-16, 1999 
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Fig. 2 — Scatter plot of MSMR (18 GHz) vs. SSM/I (19.35 
GHz) Tb for V and H pol. for Oct. 15-16, 1999 and Feb. 15- 
16, 2000. 
411 
It is clear from the figure that there is a large scatter and 
there exists small biases due to the differences in the center 
frequency and in the incidence angle of the two sensors 
(Ulaby et al, 1982). The scatter partly results from the 
different sensitivity of MSMR 18 GHz versus SSM/I 19.35 
GHz channel to the atmospheric contribution. Nevertheless 
the scatter clearly delineates the clusters related to open 
water and sea ice with varying degree of concentration. 
In addition to a point-by-point comparison, we also 
generated Tb images over the Antarctic region from SSM/I 
data, after required interpolation and smoothing, for 
comparison with corresponding MSMR images. Fig.3 
shows a comparison of the corresponding 18H/19H Tb 
images to bring out the clear spatial correspondence 
between various sea ice and continental ice features. The 
correspondence is remarkably good for MSMR images 
obtained during the summer as well as the winter seasons. 
This gives us confidence in the use of MSMR data to study 
the variability of sea ice characteristics at seasonal scales. 
15-16 OCTOBER, 1995 
  
  
  
  
  
  
  
  
  
  
Fig. 3 — Tb images over the Antactic region from 
simultaneous MSMR (18H GHz) and SSM/ (19.35H GHz) 
channels 
4.0 DEVELOPMENT OF SEA ICE 
CONCENTRATION (SIC) ALGORITHM FROM 
MSMR DATA 
4.1 Development of SIC algorithm based on MSMR Tbs 
In addition to the observed Tbs, the SSM/I data also contain 
sea ice concentration estimates as percentages, derived from 
the Tb using the NASA Boot-strap algorithm (Comiso et al., 
1997). We have used MSMR Tbs over a few selected 
regions (indicated in Fig. 1) and attempted a multiple linear 
regression of observed MSMR Tbs with SSM/I SIC values.