Variability of cloud microphysical and optical parameters obtained from aircraft and satellite remote sensing measurements during RACE

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Abstract
Observations of low stratiform clouds made during the Radiation, Aerosol and Cloud Experiment (RACE) over the Bay of Fundy, Nova Scotia, on 15 August 1995, and central Ontario on 4 October 1995 were used in this study. Aircraft, LAND Resources SATellite System (LANDSAT) and the Center for Atmospheric Research Experiments (CARE) lidar observations are used to obtain effective radius (reff), droplet number concentration (Nd) and cloud optical thickness (τ). Radiation observations with 28.5 m resolution from the Thematic Mapper (TM) on LANDSAT were used. The 10.4–12.5 µm infrared channel with a field of view of 114 m was used for the blackbody temperature calculation. Comparisons are made between clouds over the Ontario region, representing clouds over the land and over the Bay of Fundy, representing clouds over the ocean. Results of the aircraft observations show that the leg averaged Nd, liquid water content (LWC) and reff over land were about 147±73 cm−3, 0.21±0.11 g m−3 and 7.7±1.7 µm, respectively. Corresponding parameters for the clouds over the ocean were approximately 61±34 cm−3, 0.12±0.07 g m−3 and 13.8±3 µm, respectively. The mean measured visible extinction coefficient (σext) was about 55±15 km−1 for all cases, and it was a strong function of both LWC and Nd. The horizontal variability in both aircraft and LANDSAT observations indicate the need to address inhomogeneity in the sub‐grid scales of models. Copyright © 2001 Royal Meteorological Society