Recorded presentation1.8
Comparison of in situ and satellite measurements of cirrus microphysical and radiative properties
Sean M. Davis, University of Colorado at Boulder, Boulder, CO; and B. H. Kahn, Q. Yue, K. G. Meyer, Z. Zhang, K. S. Schmidt, and L. M. Avallone
During several recent NASA airborne field campaigns, a coordinated effort has been made to obtain aircraft-based in situ measurements of cirrus clouds in conjunction with satellite overpasses. Among these campaigns are CRYSTAL-FACE in 2002, the Mid-latitude Cirrus Experiment (MidCiX) in 2004, and most recently the Tropical Composition, Cloud, and Climate Coupling Experiment (TC4) in July and August of 2007.
Here, we present comparisons of the Atmospheric Infrared Sounder (AIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) cirrus retrievals with in situ cirrus cloud microphysical and radiative measurements taken from aboard the NASA WB-57F aircraft during MidCiX. Measurements of particle size/habit distributions, visible optical extinction, ice water content, water vapor, and meteorological variables (e.g. pressure, temperature, wind speed) were made from the WB-57F in a variety of cirrus types during April and May 2004. Flight patterns were coordinated with Terra and Aqua overpasses, with the WB-57F performing spiral maneuvers during or close in time to the overpasses. From these spiral maneuvers, vertically-integrated quantities such as IWP and optical depth can be estimated from in situ measurements. These quantities are compared to two retrieval methods by MODIS; the operational approach based on visible and near IR reflectances, and a second using the 1.38 micron channel. Additionally, comparisons to mid IR-based AIRS channels are made using a fast model for thin cirrus and another model that includes scattering effects. Issues such as the presence of low water cloud layers, in situ measurement uncertainty, satellite/aircraft co-location, horizontal and vertical inhomogeneities, and temporal evolution of the cloud field are examined in the context of their effect on the interpretation of in situ/satellite data comparisons. The potential to use in situ measurements for satellite retrieval sensitivity testing is also discussed via case studies that employ single-scattering models constructed from in situ measurements utilized within AIRS retrievals.
The recently completed TC4 campaign, which was based out of Costa Rica, will significantly improve the size and geographical representativeness of the data set available for comparison between in situ and satellite data. We provide a brief overview of the coordinated in situ and satellite measurements from TC4 that are relevant to these types of comparisons, focusing in particular on how these measurements will be useful for assessing satellite cirrus retrievals and expanding upon our previous work.
Session 1, Recent Field Investigations of TTL
Monday, 20 August 2007, 9:00 AM-12:30 PM, Multnomah
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