期刊名称：Tellus A: Dynamic Meteorology and Oceanography
电子版ISSN：1600-0870
出版年度：2020
卷号：72
期号：1
页码：1-22
DOI：10.1080/16000870.2019.1696141
摘要：Satellite data assimilation of hyperspectral Cross-track Infrared Sounder (CrIS) clear channels in regions with
but not affected by low-level clouds requires a set of height-dependent cloud emission and scattering indices
(CESIs) that are sensitive to cloud top pressures. In this study, three CESIs are generated by pairing CrIS
longwave and shortwave channels at three altitudes around 212 (CESI-5), 452 (CESI-9) and 1085 hPa (CESI19).
The training dataset for CESIs is the European Centre for Medium-Range Weather Forecasting analysis.
CESI-5 is strongly (weakly) affected by those ice clouds with cloud-top pressures (CTPs) above (below)
300 hPa; CESI-9 is strongly (weakly) affected by those ice clouds with CTPs above (below) 600 hPa; and
CESI-19 is highly correlated with the ice cloud optical depth (ICOD) obtained from the Atmospheric
Infrared Sounder (AIRS) retrieval product. CESIs have latitudinal and scan-dependent biases that need
removal. Verified with AIRS ICOD data, CESI-19 is greater than 5 K (6.5 K) if an ice cloud is present. This
5-K threshold gives a probability of correct typing of 85.3% (86.5%), a false alarm rate of 9.5% (5.1%) and a
leakage rate of 4.5% (5.0%) during the daytime (nighttime). CESI-5 (CESI-9) is greater than 3K (1 K) if
an ice cloud is present above 200 hPa (between 200 and 300 hPa). The case of Typhoon Maria (2018)
demonstrates the potential of using height-dependent CESIs to identify above-cloud CrIS clear channels.
