Determining AHI Cloud-Top Phase and Intercomparisons with MODIS Products over North Pacific

Abstract

Developed here is an algorithm for determining the infrared (IR) cloud-top phase for advanced Himawari imager (AHI) measurements from the Japanese geostationary satellite Himawari-8. The tests and decision tree used in the AHI algorithm are different from those in the Moderate Resolution Imaging Spectroradiometer (MODIS) Level-2 cloud product algorithm. Verification of AHI cloud-top phase results with the Cloud-Aerosol Lidar with orthogonal polarization product over a four-month period from March to June of 2017 over the North Pacific gives hit rates of 80.20% (66.33%) and 86.51% (80.61%) for liquid-water and randomly oriented-ice cloud tops, respectively, if clear-sky pixels are excluded (included) from the statistics. Also made are intercomparisons between AHI and MODIS IR cloud-top phase products over the North Pacific in June 2017. AHI liquid-water-phase determinations agree with MODIS liquid-water-phase determinations at an agreement rate of 83.68%, showing a dependence on MODIS zenith angles. The agreement rate of ice phase classifications between AHI and MODIS is 93.54%. The MODIS IR product contains some unreasonable ice-phase pixels over oceans, as well as uncertain-phase pixels over land, and has limitations for daytime liquid-water-phase identifications over the Indo-China Peninsula. Limitations of the AHI cloud-top phase algorithm are mainly caused by difficulties in identifying liquid-water-phase clouds over sun-glint regions and during twilight.