A Simulation Study On The Millimeter-wave Attenuation Correction Of Water Cloud Using SimRAD

Weather radar, which as a new detection tools, has played an irreplaceable role in the severe weather system monitoring and forecasting, quantitatively estimating of a wide range of precipitation and cloud observations. In the use of relatively short wavelengths band weather radar detect precipitation or microscopic cloud area, its radar reflectivity is serious by attenuation. So before using the reflectivity or other millimeter radar child products, attenuation correction must be made to ensure its accuracy. This paper aiming at relatively short wavelengths W band millimeter wave, based on the radiative transfer characteristics of the electromagnetic waves in atmospheric, cloud and precipitation, studies of the characteristics of the radar reflectivity attenuation and attenuation calculation formula have been done.According to the characteristics of the radar reflectivity which attenuated by atmosphere, cloud and rain, the paper correct the radar reflectivity by atmospheric absorption firstly. Then it corrects the radar reflectivity attenuation by cloud and rain with the method of HB,iteration,bin-by-bin algorithm,approximated bin-by-bin algorithms respectively. In the end, we apply a simulation platform of SimRAD (Simulating airborne Radar detection and Data processing), making to simulate the attenuation correct tests. The simulation result shows that these Attenuation Correction Algorithms are all suitable for stratus which has low base height and little moisture content. HB methods and the Meneghini's iteration are better than the bin-by-bin algorithm and approximated bin-by-bin algorithms for correcting the bottom of the cloud, but worse than those for correcting the top of the cloud; When we correct the whole cloud, HB methods and the Meneghini's iteration are better than the bin-by-bin algorithm and approximated bin-by-bin algorithms for correcting nimbostratus. The attenuation correction algorithms are all suitable for the bottom of cumulus. Because of the severe attenuation, the algorithms have their own disadvantages for the middle and top of cumulus on the different height. However, using the method of iteration and HB are better than bin-by-bin algorithm and approximated bin-by-bin algorithms. The results show that, methods of iteration and HB are suitable for the severe attenuated cumulus; As to the little moisture content and low base height stratocumulus, all the attenuation correction algorithms are appropriate. In order to verify the influence of the atmospheric attenuation to the total attenuation amount of millimeter wave radar, we also choose four different kind of stratus with different base height and moisture content and carry out four contrast tests for the atmospheric attenuation. The simulation result shows that the atmospheric Attenuation is necessary.In the conclusion, as the atmospheric attenuation is inevitable, atmospheric attenuation correction plays an important role for the millimeter wave radar. We should choose the suitable algorithm for different kind of cloud.