Satellite Determination of Large-Scale Ice Water Path Distribution During ARM IOPs
Liu, G. and Zuiderweg, A., Florida State University
Large-scale horizontal distribution and advective tendencies of cloud water are important forcing terms in single-column models (SCMs), which are used for developing and testing physical parameterizations in general circulation models. The objective of this study is to provide large-scale distribution of cloud water, with emphasis on cloud ice water, using available high-frequency microwave satellite measurements (currently NOAA AMSU-B). Our research includes developing and evaluating satellite cloud water algorithms using ARM ground-based measurements as baseline, and producing datasets for cloud ice and liquid water path distributions and large-scale advections. The study will focus on the time periods of IOPs at ARM CART sites. Currently, we are working on the March 2000 IOP at the SGP site. The approach of the study is to expand a point measurement to an area measurement. That is, the study takes the advantage of the high quality cloud measurements (particularly cloud radar and microwave radiometer measurements) at the point of the CART sites. We use the cloud ice and liquid water characteristics derived from the point measurement to guide/constrain a satellite retrieval algorithm, then use the satellite algorithm to derive the cloud ice water and liquid water distributions within an area [currently we are doing a 10 (latitude) x 10 (longitude) area]. The current cloud ice water path retrieval algorithm is based on the Bayes Theorem, which requires a priori database. The database for the March 2000 IOP in the area surrounding SGP site is built based on the observations by millimeter-wavelength cloud radar (MMCR) and Microwave Radiometer (MWR), and atmospheric variables analyzed by M. Zhang and Colleagues. The brightness temperatures in the database are calculated using a radiative transfer model with parameterized single-scattering properties of ice particles based on discrete-dipole approximation modeling. In the poster presentation, we will show (1) the single-scattering properties of nonspherical ice particles at high microwave frequencies derived from discrete-dipole approximation, (2) ice water path retrieval algorithm based on Bayesian Theorem, (3) validation of the ice water path retrieved from AMSU-B high-frequency microwave data against MMCR retrievals, and (4) distribution and characteristics of ice water path during 2003 March SGP IOP. We are also planning to compare our retrievals to those derived from visible /infrared data of NASA Langley group.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
