Abstract
Abstract. This paper presents the operational cloud retrieval algorithms for the TROPOspheric Monitoring Instrument (TROPOMI) on board the European Space Agency Sentinel-5 Precursor (S5P) mission scheduled for launch in 2017. Two algorithms working in tandem are used for retrieving cloud properties: OCRA (Optical Cloud Recognition Algorithm) and ROCINN (Retrieval of Cloud Information using Neural Networks). OCRA retrieves the cloud fraction using TROPOMI measurements in the ultraviolet (UV) and visible (VIS) spectral regions, and ROCINN retrieves the cloud top height (pressure) and optical thickness (albedo) using TROPOMI measurements in and around the oxygen A-band in the near infrared (NIR). Cloud parameters from TROPOMI/S5P will be used not only for enhancing the accuracy of trace gas retrievals but also for extending the satellite data record of cloud information derived from oxygen A-band measurements, a record initiated with the Global Ozone Monitoring Experiment (GOME) on board the second European Remote-Sensing Satellite (ERS-2) over 20 years ago. The OCRA and ROCINN algorithms are integrated in the S5P operational processor UPAS (Universal Processor for UV/VIS/NIR Atmospheric Spectrometers), and we present here UPAS cloud results using the Ozone Monitoring Instrument (OMI) and GOME-2 measurements. In addition, we examine anticipated challenges for the TROPOMI/S5P cloud retrieval algorithms, and we discuss the future validation needs for OCRA and ROCINN.
Highlights
Clouds are an important component of the hydrological cycle and play a major role in the Earth’s climate system through their strong impact on radiation processes
The Optical Cloud Recognition Algorithm (OCRA) and Retrieval of Cloud Information using Neural Networks (ROCINN) algorithms are integrated in the Sentinel5 Precursor (S5P) operational processor UPAS (Universal Processor for UV/VIS/near infrared (NIR) Atmospheric Spectrometers), and we present here UPAS cloud results using the Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment (GOME)-2 measurements
We have presented the latest versions of the retrieval algorithms OCRA and ROCINN to be used for the generation of the operational TROPOspheric Monitoring Instrument (TROPOMI)/S5P cloud products: cloud fraction, cloud top height, and optical thickness
Summary
Clouds are an important component of the hydrological cycle and play a major role in the Earth’s climate system through their strong impact on radiation processes. Loyola et al.: The operational cloud retrieval algorithms from TROPOMI trieval of trace gas columns (Liu et al, 2004; Ahmad et al, 2004; Boersma et al, 2004; Van Roozendael et al, 2006; Kokhanovsky et al, 2007; du Piesanie et al, 2013; Doicu et al, 2014). These studies have shown that cloud fraction, cloud optical thickness (albedo), and cloud top pressure (height) are the most important quantities determining cloud correction of satellite trace gas retrievals.
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