The operational Himawari-8 Cloud-top height (CTH) and cloud-top temperature (CTT) products disseminated by the Australian Bureau of Meteorology are evaluated using the active ship-borne radar-lidar observations derived from the 31-day “Clouds, Aerosols, Precipitation Radiation and atmospherIc Composition Over the southern ocean” (CAPRICORN) experiment in 2016 and one-year observations from the space-borne Cloud-Aerosol Lidar with Orthogonal Polarisation (CALIOP) cloud product over a large sector of the Southern Ocean.
Results of the comparisons show that the Himawari-8 CTH (CTT) retrievals agree reasonably well with both the ship-borne and CALIOP estimates, with the Himawari-8 CTH (CTT) generally falling between the physical CTHs observed by CALIOP and the ship-borne radar-lidar estimates. However, major systematic biases are also identified. These errors include (1) a low (warm) bias in CTH (CTT) for warm liquid cloud type, (2) a cold bias in CTT for supercooled liquid water cloud type, (3) a lack of CTH at ~3 km that does not have a corresponding gap in CTT, (4) a tendency of misclassifying some low- / mid-top clouds as cirrus and overlap cloud types, and (5) a saturation of CTH (CTT) around 10 km (-40ºC), particularly for cirrus and overlap cloud types. Various challenges that underpin these biases are also explored, including the potential of parallex bias, low-level inversion, and cloud heterogeneity.
The systematic biases in the Himawari-8 CTH and CTT retrievals identified in this study could pose further challenges in understanding the radiative effect of these clouds. Other retrieved cloud properties may also be uncertain. Further comparisons between the Himawari-8 cloud microphysical and optical products (e.g. cloud thermodynamic phase, liquid water path) and the estimates from the ship-borne observations will also be discussed.