Estimation of cloud fraction profile in shallow convection using a scanning cloud radar

Abstract

Large spatial heterogeneities in shallow convection result in uncertainties in estimations of domain‐averaged cloud fraction profiles (CFP). This issue is addressed by using large eddy simulations of shallow convection over land coupled with a radar simulator. Results indicate that zenith profiling observations are inadequate to provide reliable CFP estimates. Use of scanning cloud radar (SCR), performing a sequence of cross‐wind horizon‐to‐horizon scans, is not straightforward due to the strong dependence of radar sensitivity to target distance. An objective method for estimating domain‐averaged CFP is proposed that uses observed statistics of SCR hydrometeor detection with height to estimate optimum sampling regions. This method shows good agreement with the model CFP. Results indicate that CFP estimates require more than 35 min of SCR scans to converge on the model domain average. The proposed technique is expected to improve our ability to compare model output with cloud radar observations in shallow cumulus cloud conditions.

The Cloud-resolving model Radar SIMulator (CR-SIM) Version 3.3: description and applications of a virtual observatory

“…For example, a recent study by Oue et al (2016) has shown that zenith-pointing observations from one location are inadequate to provide reliable cloud fraction profile estimates in a cumulus field. A similar investigation on 3D wind retrievals in deep convection using multi-Doppler radar techniques highlights similar deficiencies of our current observing systems (Oue et al, 2019a). How do we best quantify the measurement uncertainty introduced by the observational strategy?…”

Cloud characteristics, thermodynamic controls and radiative impacts during the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) experiment

“…There are several limitations when designating cloud boundaries and hourly CF observations from vertically pointing cloud radars beyond the capabilities of single radar platforms or ARSCL methods (e.g., Lamer and Kollias, 2015;Oue et al, 2016). The primary limitation among these is that the WACR experiences attenuation in rain that manifests as erroneously low or missing cloud-top boundaries (e.g., Feng et al, 2009Feng et al, , 2014.…”

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

“…A scanning, S-band, radar operated by the Barbados Meteorological Service can be used for research purposes in the absence of severe weather. It will help characterize the mesoscale organization of convection, and the vertical structure of the shallow cloud cover (Nuijens et al 2009;Oue et al 2016). The deployment of a second C-Band radar, the POLDIRAD of the Institut für Physik der Atmosphäre at the Deutschen Zentrum für Luft-und Raumfahrt, is also being considered.…”

“…Another one will consist in analysing data from ground or ship-borne instruments. Ceilometers will be very useful, but a scanning radar (Oue et al 2016) on one of the research vessels or deployed on Barbados is also being considered. Yet another approach will consist of analysing observations from the SpecMACs instrument on HALO.…”