AHI-Derived Daytime Cloud Optical/Microphysical Properties and Their Evaluations With the Collection-6.1 MOD06 Product
Xiaoyong Zhuge, Xiaolei Zou, Yuan Wang
Abstract
Cloud optical/microphysical properties (COMPs) with a high spatiotemporal resolution are required for monitoring the evolution of convective clouds, studying aerosol–cloud–precipitation interactions, and evaluating cloud microphysics parameterization schemes in weather and climate models. This study applied the bispectral method, commonly used for COMP retrievals, to Advanced Himawari Imager (AHI)/Himawari-8 observations. The AHI daytime cloud optical thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau$ </tex-math></inline-formula> ) and cloud-top particle effective radius ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> ) retrievals were then evaluated with the Collection-6.1 Moderate Resolution Imaging Spectroradiometer cloud product (MOD06) for a three-month period from June 1, 2017, to August 31, 2017. Overall, the AHI-retrieved COMP results are in good agreement with the MOD06 product. The correlation coefficients of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau $ </tex-math></inline-formula> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> between the AHI retrievals and MOD06 products are 0.76–0.89 and 0.63–0.87, respectively. Overestimations are mainly observed in the 1.6- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> (Re <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> ) and ice-phase 3.9- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> (Re <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.9</sub> ) retrievals. There are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau $ </tex-math></inline-formula> dependencies in the retrieval biases of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau $ </tex-math></inline-formula> and Re <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> , as well as angular dependencies in the retrieval biases of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau $ </tex-math></inline-formula> and ice-phase Re <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.9</sub> . Moreover, the monthly mean composites for three COMP retrievals from the MOD06 and AHI algorithms are compared. Significant differences are only found between the two Re <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> products. This study also finds that AHI-retrieved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\tau $ </tex-math></inline-formula> values have a diurnal variation over land but not over oceans.