HR: 1330h
AN: A22A-1054    [PDF]
TI: Retrieval of Cloud Properties for Partially Cloud-Filled Pixels During CRYSTAL-FACE
AU: * Nguyen, L
EM: l.nguyen@nasa.gov
AF: NASA Langley Research Center, MS 420, Hampton, VA 23681 United States
AU: Minnis, P
EM: p.minnis@nasa.gov
AF: NASA Langley Research Center, MS 420, Hampton, VA 23681 United States
AU: Smith, W L
EM: w.l.smith@larc.nasa.gov
AF: NASA Langley Research Center, MS 420, Hampton, VA 23681 United States
AU: Khaiyer, M M
EM: m.m.khaiyer@larc.nasa.gov
AF: AS&M, Inc., 1 Enterprise Pkwy, Hampton, VA 23666 United States
AU: Heck, P W
EM: p.w.heck@larc.nasa.gov
AF: AS&M, Inc., 1 Enterprise Pkwy, Hampton, VA 23666 United States
AU: Sun-Mack, S
EM: s.sun-mack@larc.nasa.gov
AF: SAIC, 1 Enterprise Pkwy, Hampton, VA 23666 United States
AU: Uttal, T
EM: taneil.uttal@noaa.gov
AF: NOAA ETL, 325 Broadway, Boulder, CO 80305 United States
AU: Comstock, J
EM: jennifer.comstock@pnl.gov
AF: PNL, P.O. Box 999, MS K9-24, Richland, WA 99352 United States
AB: Partially cloud-filled pixels can be a significant problem for remote sensing of cloud properties. Generally, the optical depth and effective particle sizes are often too small or too large, respectively, when derived from radiances that are assumed to be overcast but contain radiation from both clear and cloud areas within the satellite imager field of view. This study presents a method for reducing the impact of such partially cloud field pixels by estimating the cloud fraction within each pixel using higher resolution visible (VIS, 0.65mm) imager data. Although the nominal resolution for most channels on the Geostationary Operational Environmental Satellite (GOES) imager and the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra are 4 and 1 km, respectively, both instruments also take VIS channel data at 1 km and 0.25 km, respectively. Thus, it may be possible to obtain an improved estimate of cloud fraction within the lower resolution pixels by using the information contained in the higher resolution VIS data. GOES and MODIS multi-spectral data, taken during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE), are analyzed with the algorithm used for the Atmospheric Radiation Measurement Program (ARM) and the Clouds and Earth's Radiant Energy System (CERES) to derive cloud amount, temperature, height, phase, effective particle size, optical depth, and water path. Normally, the algorithm assumes that each pixel is either entirely clear or cloudy. In this study, a threshold method is applied to the higher resolution VIS data to estimate the partial cloud fraction within each low-resolution pixel. The cloud properties are then derived from the observed low-resolution radiances using the cloud cover estimate to properly extract the radiances due only to the cloudy part of the scene. This approach is applied to both GOES and MODIS data to estimate the improvement in the retrievals for each resolution. Results are compared with the radar reflectivity techniques employed by the NOAA ETL MMCR and the PARSL 94 GHz radars located at the CRYSTAL-FACE Eastern \& Western Ground Sites, respectively. This technique is most likely to yield improvements for low and midlevel layer clouds that have little thermal variability in cloud height.
DE: 0320 Cloud physics and chemistry
DE: 0360 Transmission and scattering of radiation
DE: 3314 Convective processes
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting