The operational cloud retrieval algorithms from TROPOMI on board Sentinel-5 Precursor
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.