Retrieval of ice cloud properties using an optimal estimation algorithm and MODIS infrared observations: 2. Retrieval evaluation
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Type of Work19 pages
Citation of Original PublicationChenxi Wang, Steven Platnick, Zhibo Zhang, Kerry Meyer, Gala Wind, Ping Yang, Retrieval of ice cloud properties using an optimal estimation algorithm and MODIS infrared observations: 2. Retrieval evaluation, Journal of Geophysical Research: Atmospheres, 121, 5827–5845, 2016, doi:10.1002/2015JD024528.
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Subjectsice cloud properties
n infrared-based optimal estimation (OE-IR)
MODerate resolution Imaging Spectroradiometer (MODIS)
High Performance Computing Facilty (HPCF)
Aqua satellite (MYD06)
Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP),
Imaging Infrared Radiometer (IIR);
An infrared-based optimal estimation ( OE-IR) algorithm for retrieving ice cloud properties is evaluated. Speciﬁcally, the implementation of the algorithm with MODerate resolution Imaging Spectroradiometer (MODIS) observations is assessed in comparison with the operational retrieval products from MODIS on the Aqua satellite (MYD06), Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and the Imaging Infrared Radiometer (IIR); the latter two instruments ﬂy on the Cloud-Aerosol Lidar and Infrared Pathﬁnder Satellite Observation (CALIPSO) satellite in the Afternoon Constellation (A-Train) with Aqua. The results show that OE-IR cloud optical thickness (τ) and effective radius (r ₑ𝒻𝒻 ) retrievals perform best for ice clouds having 0.5 < τ < 7 and r ₑ𝒻𝒻 < 50 μm. For global ice clouds, the averaged retrieval uncertainties of τ and r ₑ𝒻𝒻 are 1 9% and 33%, respectively. For optically thick ice clouds with τ larger than 10, however, the τ and r ₑ𝒻𝒻 retrieval uncertainties can exceed 30% and 50%, respectively. For ice cloud top height ( h), the averaged global uncertainty is 0.48 km. Relatively large h uncertainty (e.g., > 1 km) occurs for τ < 0.5. Analysis of 1 month of the OE-IR retrievals shows large τ and r ₑ𝒻𝒻 uncertainties in storm track regions and the southern oceans where convective clouds are frequently observed, as well as in high-latitude regions where temperature differences between the surface and cloud top are more ambiguous. Generally, comparisons between the OE-IR and the operational products show consistent τ and h retrievals. However, obvious differences between the OE-IR and the MODIS Collection 6 r ₑ𝒻𝒻 are found.