Biases in CloudSat Falling Snow Estimates Resulting from Daylight-Only Operations

Abstract

Falling snow is a key component of the Earth’s water cycle, and space-based observations provide the best current capability to evaluate it globally. The Cloud Profiling Radar (CPR) on board CloudSat is sensitive to snowfall, and other satellite missions and climatological models have used snowfall properties measured by it for evaluating and comparing against their snowfall products. Since a battery anomaly in 2011, the CPR has operated in a Daylight-Only Operations (DO-Op) mode, in which it makes measurements primarily during only the daylit portion of its orbit. This work provides estimates of biases inherent in global snowfall amounts derived from CPR measurements due to this shift to DO-Op mode. We use CloudSat’s snowfall measurements during its Full Operations (Full-Op) period prior to the battery anomaly to evaluate the impact of the DO-Op mode sampling. For multi-year global mean values, the snowfall fraction during DO-Op changes by −10.16% and the mean snowfall rate changes by −8.21% compared with Full-Op. These changes are driven by the changes in sampling in DO-Op and are very little influenced by changes in meteorology between the Full-Op and DO-Op periods. The results highlight the need to sample consistently with the CloudSat observations or to adjust snowfall estimates derived from CloudSat when using DO-Op data to evaluate other precipitation products.

Marine Cold‐Air Outbreak Snowfall in the North Atlantic: A CloudSat Perspective

“…In 2011, a battery anomaly onboard the satellite resulted in a shift to daytime‐only operations moving forward (Stephens et al., 2018). The loss of nighttime data was found to decrease global mean snowfall rate estimates by ∼8% due to pronounced latitudinal sampling issues (Milani & Wood, 2021). For this study, we used data from January 2007 to December 2010 to avoid potential high‐latitude seasonal biases from CPR daytime‐only sampling deficiencies and allow for a more robust seasonal analysis.…”

Strong Ocean/Sea‐Ice Contrasts Observed in Satellite‐Derived Ice Crystal Number Concentrations in Arctic Ice Boundary‐Layer Clouds

“…Lidar measurements originate from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP; Winker et al, 2003) on-board CALIPSO satellite, while radar measurements come from the Cloud Profiling Radar (CPR; Stephens et al, 2018) on-board CloudSat. It should be noted that since 2011, CPR has operated in a daylight-only operations mode, affecting some cloud retrieval properties, such as snowfall (Milani & Wood, 2021). The data are provided with a 1.7 km footprint and a vertical resolution of 60 m. This product has been thoroughly evaluated against recent in-situ measurements in Krämer et al (2020) and and was further used to investigate the controls on the N i by Gryspeerdt et al (2018).…”

Applications of a CloudSat-TRMM and CloudSat-GPM Satellite Coincidence Dataset

“…The operation of the CloudSat Profiling Radar (CPR) began in June 2006. Due to satellite power issues in April 2011 which temporarily suspended science data collection, CloudSat was operated in a "daytime only" (CPR operations during the ascending orbit) mode data after mid-2012, with periodic data outages since that time [10][11][12].…”