Simulations of Infrared Radiances over a Deep Convective Cloud System Observed during TC4: Potential for Enhancing Nocturnal Ice Cloud Retrievals

Remote Sensing

Patrick Minnis⁴  Gang Hong⁹  J. Kirk Ayers⁹  William L. Smith⁴  Christopher R. Yost⁹  Andrew J. Heymsfield¹  Gerald M. Heymsfield⁵  Dennis L. Hlavka³  Michael D. King⁶  Errol Korn¹  Matthew J. McGill⁵  Henry B. Selkirk⁷  Anne M. Thompson⁸  Lin Tian² 

[1] Earth System Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA; E-Mails:;GESTAR, Morgan State University, Baltimore, MD 21251, USA; E-Mail:;Science Systems and Applications, Inc., Lanham, MD 20706, USA; E-Mail:;NASA Langley Research Center, Hampton, VA 23681, USA; E-Mail:;NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; E-Mails:;LASP, University of Colorado, Boulder, CO, USA; E-Mail:;Universities Space Research Association, Columbia, MD 21044, USA; E-Mail:;Department of Meteorology, Pennsylvania State University, State College, PA 16802, USA; E-Mail:;Science Systems and Applications, Inc., Hampton, VA 23666, USA; E-Mails:

关键词: clouds;    optical depth;    particle size;    satellite;    TC⁴;    multispectral thermal infrared;   

DOI  :  10.3390/rs4103022

来源: mdpi

【 摘 要 】

Retrievals of ice cloud properties using infrared measurements at 3.7, 6.7, 7.3, 8.5, 10.8, and 12.0 μm can provide consistent results regardless of solar illumination, but are limited to cloud optical thicknesses τ < ∼6. This paper investigates the variations in radiances at these wavelengths over a deep convective cloud system for their potential to extend retrievals of τ and ice particle size D_e to optically thick clouds. Measurements from an imager, an interferometer, the Cloud Physics Lidar (CPL), and the Cloud Radar System (CRS) aboard the NASA ER-2 aircraft during the NASA TC⁴ (Tropical Composition, Cloud and Climate Coupling) experiment flight during 5 August 2007, are used to examine the retrieval potential of infrared radiances over optically thick ice clouds. Simulations based on coincident in situ measurements and combined cloud τ from CRS and CPL measurements are comparable to the observations. They reveal that brightness temperatures at these bands and their differences (BTD) are sensitive to τ up to ∼20 and that for ice clouds having τ > 20, the 3.7–10.8 μm and 3.7–6.7 μm BTDs are the most sensitive to D_e. Satellite imagery appears to be consistent with these results suggesting that τ and D_e could be retrieved for greater optical thicknesses than previously assumed. But, because of sensitivity of the BTDs to uncertainties in the atmospheric profiles of temperature, humidity, and ice water content, and sensor noise, exploiting the small BTD signals in retrieval algorithms will be very challenging.

【 授权许可】

CC BY   
© 2012 by the authors, licensee MDPI, Basel, Switzerland.