Thomas J. Kleespies

Retrieval of Precipitable Water from Observations in the Split Window over Varying Surface Temperatures

Abstract The split window technique makes use of two differentially absorbing channels in the 11 μm region to remove the attenuating effects of atmospheric absorption so as to achieve a better estimate of the underlying skin temperature than could be produced by a single channel measurement. Since the primary absorber in this region is water vapor, it follows that split window measurements should be able to produce bulk water vapor retrievals as well. When observations are made with split window channels under conditions where the surface contribution to measured radiance changes, but the atmospheric contribution does not, it is possible to estimate the ratio of the transmittance of the two split window channels. This transmittance ratio is inversely related to precipitable water. This paper applies this technique to observations from the Advanced Very High Resolution Radiometer, and the VISSR Atmospheric Sounder, and demonstrates the capability of both instruments to determine precipitable water under tw...

Atmospheric transmittance of an absorbing gas. 6. OPTRAN status report and introduction to the NESDIS/NCEP community radiative transfer model

Since the publication of the Optical Path Transmittance (OPTRAN) algorithm [Appl. Opt. 34, 8396 (1995)], much of the code and implementation has been refined and improved. The predictor set has been expanded, an objective method to select optimal predictors has been established, and the two-interpolation method has been discarded for a single-interpolation method. The OPTRAN coefficients have been generated for a wide range of satellites and instruments. The most significant new development is the Jacobian-K-matrix version of OPTRAN, which is currently used for operational direct radiance assimilation in both the Global Data Analysis System and the ETA Data Analysis System at the National Oceanographic and Atmospheric Administration, National Weather Service, National Centers for Environmental Prediction Environmental Modeling Center. This paper documents these improvements and serves as a record of the current status of the operational OPTRAN code.

The Retrieval of Marine Stratiform Cloud Properties from Multiple Observations in the 3.9-µm Window under Conditions of Varying Solar Illumination

Abstract Radiometric observations in the 3.9-µm region have been used by a number of investigators for the determination of cloud parameters or sea surface temperature at night. Only a few attempts have been made to perform quantitative assessments of cloud and surface properties during the daytime because of the inability to distinguish between the thermal and solar components of the satellite-sensed radiances. This paper presents a new method of separating the thermal and solar components of upwelling 3.9-µm radiances. Two collocated satellite observations are made under conditions where the solar illumination angle changes but the thermal structure of the cloud and atmosphere, as well as the cloud microphysics change very little. These conditions can easily be met by observing the same cloud from geosynchoronous orbit over a short time interval during the morning hours. When the radiances are differenced under these constraints, the thermal components cancel, and the difference in the radiances is simp...