23 Feb 2022
23 Feb 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Impacts of Active Satellite Sensors' Low-level Cloud Detection Limitations on Cloud Radiative Forcing

Yinghui Liu Yinghui Liu
  • Center for Satellite Applications and Research, NOAA/NESDIS, Madison, WI, USA

Abstract. Previous studies revealed that satellites sensors with the best detection capability identify 25–40 % and 0–25 % fewer clouds below 0.5 km and between 0.5–1.0 km, respectively, over the Arctic land. Quantifying the impacts of cloud detection limitations on the radiation flux are critical especially over the Arctic Ocean considering the dramatic changes in Arctic sea ice. In this study, the proxies of the space-based radar, CloudSat, and lidar, CALIPSO, cloud masks are derived based on simulated radar reflectivity and cloud optical thickness using retrieved cloud properties from surface-based radar and lidar during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. Limitations in low-level cloud detection by the space-based active sensors, and the impact of these limitations on the radiation fluxes at the surface and the top of atmosphere (TOA), are estimated. The results show that the combined CloudSat and CALIPSO product generally detects all clouds above 1 km, while detecting 25 % (9 %) fewer in absolute values below 600 m (600 m to 1 km) than surface observations. These detection limitations lead to uncertainties in the monthly mean cloud radiative forcing (CRF), with maximum absolute monthly mean values of 2.7 Wm−2 and 4.0 Wm−2 at the surface and TOA, respectively. The uncertainties for individual cases are larger – up to 30 Wm−2. Cloud information from only the CALIPSO or the CloudSat leads to larger cloud detection differences compared to the surface observations, and larger CRF uncertainties with absolute monthly means larger than 10.0 Wm−2. These uncertainties need to be considered when radiation flux products from CloudSat and CALIPSO are used in climate and weather studies.

Yinghui Liu

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Peer-Review Comment on acp-2022-140', Anonymous Referee #1, 17 Mar 2022
  • RC2: 'Comment on acp-2022-140', Anonymous Referee #2, 21 Mar 2022

Yinghui Liu


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Latest update: 27 May 2022
Short summary
The cloud detection from the state-of-art satellite radar and lidar miss low-level clouds. Using in situ observations, this study confirms this cloud detection limitation over the Arctic Ocean. Impacts of this limitation from combined satellite radar and lidar on the monthly mean radiation flux estimations at the surface and at the top of atmosphere in the Arctic are limited, but larger from only satellite radar or satellite lidar in monthly mean and instantaneous values.