A computer program performs level-2 processing of thermal- microwave-radiance data from observations of the limb of the Earth by the Earth Observing System (EOS) Microwave Limb Sounder (MLS). The purpose of the processing is to estimate the composition and temperature of the atmosphere versus altitude from ≈8 to ≈90 km. "Level-2" as used here is a specialists' term signifying both vertical profiles of geophysical parameters along the measurement track of the instrument and processing performed by this or other software to generate such profiles. Designed to be flexible, the program is controlled via a configuration file that defines all aspects of processing, including contents of state and measurement vectors, configurations of forward models, measurement and calibration data to be read, and the manner of inverting the models to obtain the desired estimates. The program can operate in a parallel form in which one instance of the program acts a master, coordinating the work of multiple slave instances on a cluster of computers, each slave operating on a portion of the data. Optionally, the configuration file can be made to instruct the software to produce files of simulated radiances based on state vectors formed from sets of geophysical data-product files taken as input.

This work was done by W. Van Snyder, Dong Wu, William Read, Jonathan Jiang, Paul Wagner, Nathaniel Livesey, Michael Schwartz, Mark Filipiak, Hugh Pumphrey, and Zvi Shippony of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Software category.

This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (818) 393-2827. Refer to NPO-35188.

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Calibration Computer software and hardware Logistics Software
This Brief includes a Technical Support Package (TSP).
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Processing EOS MLS Level-2 Data

(reference NPO-35188) is currently available for download from the TSP library.

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NASA Tech Briefs Magazine

This article first appeared in the March, 2006 issue of NASA Tech Briefs Magazine (Vol. 30 No. 3).

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Overview

The document is a Technical Support Package for Processing EOS MLS Level-2 Data, detailing the algorithms and methodologies used by the EOS Microwave Limb Sounder (MLS) to retrieve atmospheric data. The MLS, launched on July 15, 2004, is designed to measure various atmospheric constituents, including water vapor, ozone, and other gases, from altitudes ranging from approximately 8 km to 90 km.

The paper discusses the retrieval algorithms implemented for the MLS instrument, emphasizing the importance of a cumulative approach to retrieval phasing. This method was found to be preferable in many cases, although it was noted that certain species, particularly tropospheric water, exhibited nonlinear impacts on MLS radiances, leading to potential instabilities. As a result, retrievals of such species are constrained in later phases to ensure stability and accuracy.

The document also highlights the challenges posed by thick clouds, which can significantly affect microwave signals and, consequently, the measurements of gas phase composition. The Level 2 software is designed to identify and appropriately handle these cloud radiances, which can also provide insights into cloud characteristics.

Future plans for the MLS include improving the vertical resolution of water vapor retrievals, aiming for twelve surfaces per decade change in pressure in the tropopause region, compared to the standard six. While this enhancement will improve vertical resolution, it may come at the cost of precision. Additionally, advancements in forward model efficiency are anticipated, which will allow for the use of a more comprehensive non-linear forward model without prohibitive computational demands.

The document concludes by summarizing the performance of the retrieval algorithms, which are yielding results consistent with pre-launch expectations. It serves as a reference for understanding the EOS MLS measurement system and offers guidance for those implementing retrieval schemes for other instruments. Overall, the paper underscores the significance of the MLS in atmospheric research and the continuous efforts to enhance its data quality and retrieval capabilities.