Comparing the FAA Cloud Top Height product and the NESDIS/CIMSS Cloud Top Pressure product in oceanic regions

As part of an effort to assess the quality of the Cloud Top Height (CTOP) product recently developed by the Oceanic Weather Product Development Team (OW PDT) of the Federal Aviation Administration Aviation Weather Research Program (FAA/AWRP), an intercomparison of CTOP and the NESDIS/CIMSS Cloud Top Pressure (NCTP) product was performed. This study summarizes the comparison of CTOP and NCTP during two periods, 12 February–23 April and 15 August–15 September 2004, for the Pacific, North Pacific, and Gulf of Mexico oceanic domains, as defined by the OW PDT.

The CTOP product, according to the concept of use, employs the IR Window technique to provide a depiction of the current locations of aviation hazards related to convection in remote oceanic regions. NCTP, in contrast, utilizes a hybrid algorithm including both the IR Window as well as the CO2 Slicing approach to determine the heights of clouds with a wide range of transparency. The analysis accounts for these underlying differences by stratifying the results by the transparency of the clouds. In an attempt to delineate the different cloud regimes (i.e., hazardous versus nonhazardous), the comparison utilizes a threshold of the NESDIS/CIMSS effective cloud amount (ECA) as a proxy for the presence of convection.

In addition to the detailed comparison statistics, this paper presents the results of an analysis to justify the overall comparison mechanics, which were designed to account for the temporal and spatial differences between the products. The findings of the satellite product comparison demonstrate very good agreement, with respect to values established by other cloud top height validation studies, between CTOP and NCTP for opaque and thick clouds, particularly at upper levels. The statistics for the thin cloud comparison show significant disagreement, an expected result given the theoretical strengths and weaknesses of the products.