Retrieval of atmospheric and ocean surface parameters from ADEOS‐II Advanced Microwave Scanning Radiometer (AMSR) data: Comparison of errors of global and regional algorithms

Abstract

Retrieval of the sea surface temperature ts, wind speed W, total atmospheric water vapor content V, and total cloud liquid water content Q over the ocean from the simulated ADEOS‐II AMSR data in the absence of precipitation is considered. The brightness temperatures (TB) with the vertical (V) and horizontal (H) polarizations at the AMSR frequencies ν = 6.9, 10.7, 18.7, 23.8, and 36.5 GHz were computed for the radiosonde and relevant data collected by research vessels. V and Q were retrieved from TB(23.8V) and TB(36.5V) with the physically based “global” (−1.6 < ts ≤ 31°C), “polar” (ts ≤ 15°C), and “tropical” (ts ≥ 24°C) algorithms under the assumption that ts values were derived from the measurements at 6.9 and 10.7 GHz with an error σts. The errors σV and σQ were estimated at several combinations of the difference ΔT36 = TB(36.5V) ‐ TB(36.5H), radiometer noises ΔT and σts. At ΔT36 = 35 K, ΔT = 0.3 K, and σts = 1°C, σV = 1.5 kg/m2 and σQ = 0.029 kg/m2 for a global algorithm. Standard regression techniques were applied to retrieve ts and W from the simulated brightness temperatures for the cases TB(10.7V) ≤ 185 K. For a global data base, three‐channel algorithm (6.9V, 6.9H, 10.7V or 10.7V) yields the ts and W errors equal to 0.40 and 0.58°C and 0.66 and 0.85 m/s as radiometer noises increase from 0.1 to 0.2 K at ν = 6.9 GHz and from 0.13 to 0.27 K at ν = 10.7 GHz.