(a) for Horizontal and Vertical Polarizations H and V


(b) for Horizontal/Vertical Polarization ratio H/V

Figure 2. Monthly Variation for October 2000 of Brightness temperature for location near latitude 75° N and longitude 135oE for frequencies 18 and 21 GHz

In order to verify the extent of this phenomenon and to eliminate any flaws, if present, a temperature brightness map was made for the dates 5-6 October 2000 and 21-22 October 2000 for which this sharp increase was found to have occurred. It was found that this was not local but extending from latitudes 73°N to 78°N and longitudes 115°E to 145°E [Figure 3a and 3b]. Also, a map made for dates 21-22 September 2001 showed that this phenomenon is recurring and not a permanent change. [Figure 3c]


(a) Brightness Temperature Tb (18V) on 5-6 October 2000


(b) Brightness Temperature Tb (18V) on 21-22 October 2000

(c) Brightness Temperature Tb (18V) on 21-22 September 2001

Figure 3. Brightness Temperature Map for area extending from latitude 73°N to 78°N and longitude 115°E to 145°E
After noticing that this phenomenon is taking place in a large region, the polar map of the Northern Hemisphere up to latitude 68oN for brightness temperature (18V) was made using data for Grid-1 (150km resolution) and it was found to be extending to some other regions. [Figure 4]


(a) 5-6 October 2000


(b) 21-22 October 2000


(c) 21-22 September 2001

Figure 4. Polar Brightness Temperature map of Tb (18V) up to latitude 68oN

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