Comparison of tropical convection horizontal scales between GOES-16 ABI TB observations and ERA5 all sky simulations
In this study,GOES-16 Advanced Baseline Imager Temperature Brightness(ABI TB)observations were compared with all-sky simulations of ERA5 reanalysis data.It is found that the ERA5 simulated low TB areas are nearly consistent with those of observations,and qualitatively reflect a diurnal variation from a developing to weakening process of convection.However,there are significant differences in how low TB reached.Even if the high-resolution(2 km)channel-13 TB observations are averaged to the ERA5 resolution(0.25°x0.25°),they are still lower than the ERA5 all-sky simulations.By using Principal Component Analysis(PC A)and Discrete Fourier Transform(DFT)methods,a scale analysis on the observed and simulated TB fields in two arbitrarily selected convective areas was conducted.In the area where convection is strong,the horizontal scales gradually decrease from 700 km to 150 km for principal components of TB observations from 1 to 9.However,the horizontal scales gradually decrease from 950 km to 270 km for the principal components of ERA5 all-sky simulations from 1 to 4,but hardly change from 4 to 9.In another area with weaker convection,it can also be observed that the ERA5 simulated TB significantly overestimates the horizontal characteristic scale of convection.For ERA5 simulated TB,there is an error of within two hours for the phase of each main component compared with ABI TB observations.Since the low-TB areas of the ERA5 all-sky simulations coincide highly with the areas of large ice water path,it can be speculated that the ice water path in the ERA5 reanalysis is responsible for the differences of spatial distributions and intensity changes of TBs between ERA5 all-sky simulations and ABI observations.
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