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We can use 19 and 22 GHz - Differential Absorption

Water Vapor. We can use 19 and 22 GHz - Differential Absorption Note the there is also little dependence on surface temperature From Case #4 T B = e s T s t + (1- e s )T a (1- t ) t + T a (1- t ) if e s = 0.4, T s = 300, T air = 270 And assume no water vapor, t = 1

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We can use 19 and 22 GHz - Differential Absorption

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  1. Water Vapor • We can use 19 and 22 GHz - Differential Absorption • Note the there is also little dependence on surface temperature • From Case #4 • TB = esTst + (1-es)Ta(1-t) t + Ta(1-t) • if es = 0.4, Ts = 300, Tair = 270 • And assume no water vapor, t = 1 • Then: TB = 0.4(300)1 + 0 + 0 = 120 K • Now add some water vapor, so thatt = 0.9 • TB = 0.4(300)0.9 + 0.6(270)0.1(.9) + 270(0.1) • = 108 + 14.6 + 27 = 149.6 • with water vapor, TB is warmer than without! • If we want to know how much water vapor (variation of t) • Ta and t unknown, (esTs=constant), need two equations • one at 19 GHz, one at 22 GHz

  2. Water Vapor Alishouse,J.C., S. Snyder, J. Vongsathorn and R.R. Ferraro, 1990: Determination of oceanic total precipitable water from the SSM/I. IEEE Trans. Geo. Rem. Sens., 28, 811-816.

  3. TB=0.4(280).9+ 0.6(260)0.1(0.9) 260(0.1) =100.8+14+26=140.8K TB=0.4(280)0+ 0.6(260)1(0) 260(1) =260K t=0.9 t=0 Ta =260K Ts =280K es =0.4 Precipitation As cloud droplets grow to precipitation size, optical depth increases. Does TB increase or decrease?  0.4

  4. Precipitation by 85 GHz scattering index http://manati.wwb.noaa.gov/doc/ssmiprecip.html Oceanic: SI85 = -174.4 + 0.715 TB19v + 2.439 TB22v - 0.00504 TB22v TB22v - TB85v Land: SI85 = 451.9 - 0.44 TB19v - 1.775 TB22v + 0.00574 TB22v TB22v - TB85v Ferraro, Ralph R. and Grody, Norman C., "Effects of Surface Conditions on Rain Identification Using the DMSP-SSM/I", Remote Sensing Reviews,11, 195-209, 1994

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