Abstract
The Hyperspectral Infrared Atmospheric Sounder (HIRAS) onboard the Feng Yun-3D (FY-3D) satellite is the first Chinese hyperspectral infrared instrument. In this study, an improved cloud detection scheme using brightness temperature observations from paired HIRAS long-wave infrared (LWIR) and short-wave infrared (SWIR) channels at CO2 absorption bands (15-μm and 4.3-μm) is developed. The weighting function broadness and a set of height-dependent thresholds of cloud-sensitive-level differences are incorporated into pairing LWIR and SWIR channels. HIRAS brightness temperature observations made under clear-sky conditions during a training period are used to develop a set of linear regression equations between paired LWIR and SWIR channels. Moderate-resolution Imaging Spectroradiometer (MODIS) cloud mask data are used for selecting HIRAS clear-sky observations. Cloud Emission and Scattering Indices (CESIs) are defined as the differences in SWIR channels between HIRAS observations and regression simulations from LWIR observations. The cloud retrieval products of ice cloud optical depth and cloud-top pressure from the Atmospheric Infrared Sounder (AIRS) are used to illustrate the effectiveness of the proposed cloud detection scheme for FY-3D HIRAS observations. Results show that the distributions of modified CESIs at different altitudes can capture features in the distributions of AIRS-retrieved ice cloud optical depth and cloud-top pressure better than the CESIs obtained by the original method.
Highlights
Hyperspectral infrared instruments onboard satellites have been a fundamental part of the earth observation system (EOS) since the twenty-first century
short-wave infrared (SWIR) channels, the concept of weighting function (WF) broadness is proposed as an additional criterion to find long-wave infrared (LWIR)
When pairing LWIR and SWIR channels, the concept of WF broadness is proposed as an additional criterion to find LWIR and SWIR channels with similar WF peak altitudes
Summary
Hyperspectral infrared instruments onboard satellites have been a fundamental part of the earth observation system (EOS) since the twenty-first century. HIRAS has been onboard the FengYun-3D (FY-3D) satellite launched in November 2017 [8,9,10] Observations from these hyperspectral infrared instruments have been used worldwide for numerical weather prediction (NWP) through data assimilation and climate research using retrieval products [1,11,12]. Because CO2 is a uniformly mixed gas in the atmosphere, differences between LWIR and SWIR channels at similar altitudes provide information of cloud in addition to atmospheric temperatures at high vertical resolutions [21,22] developed a CO2 slicing technique to determine cloud-top pressure according to the ratio of observations from two channels at CO2 absorption bands (4.3-μm, 15-μm) that is suitable for cirrus cloud identification [23,24] used the CO2 slicing technique to determine the cirrus cloud occurrence, height and effective emissivity with based on HIRS (High-resolution Infrared Radiation Sounder) observations.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
