Dr. Tristan S. L'Ecuyer Profile

Dr. Tristan S. L'Ecuyer

Research Scientist at Univ of Wisconsin Madison

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Publications (5)

Proceedings Article | 1 August 2021 Presentation + Paper

Ground-based far-infrared emissivity measurements with the University of Wisconsin absolute radiance interferometer (ARI)

E. Eva Borbas, Douglas Adler, Fred Best, Robert Knuteson, Tristan L'Ecuyer, Michelle Loveless, Erik Olson, Henry Revercomb, Joseph Taylor

Proceedings Volume 11830, 1183004 (2021) https://doi.org/10.1117/12.2594834

KEYWORDS: Sensors, Calibration, Temperature metrology, Far infrared, Interferometers, Infrared radiation, Black bodies, Statistical analysis, Optical filters, Mid-IR

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Proceedings Article | 8 December 2008 Paper

Validation of rain/no-rain threshold value of cloud liquid water for microwave precipitation retrieval algorithm using CloudSat precipitation product

Satoshi Kida, Takeshi Manabe, Guosheng Liu, Tristan L'Ecuyer, Shoichi Shige

Proceedings Volume 7152, 715209 (2008) https://doi.org/10.1117/12.804924

KEYWORDS: Clouds, Liquids, Meteorology, Microwave radiation, Satellites, Radar, Profiling, Aerospace engineering, Radiometry, Scattering

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Proceedings Article | 3 December 2008 Paper

Spectral retrieval of latent heating profiles from TRMM PR data: comparisons of lookup tables from two- and three-dimensional simulations

Tristan L’Ecuyer, Shoichi Shige, Wei-Kuo Tao, Yukari Takayabu, Xiping Zeng, Satoshi Kida

Proceedings Volume 7148, 714808 (2008) https://doi.org/10.1117/12.804768

KEYWORDS: 3D modeling, Clouds, Algorithm development, Convection, Promethium, Computer simulations, Atmospheric modeling, Systems modeling, Numerical simulations, Radar

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Proceedings Article | 18 August 2005 Paper

Characterization and error analysis of an operational retrieval algorithm for estimating column ozone and aerosol properties from ground-based ultra-violet irradiance measurements

John Davis, Thomas Taylor, James Slusser, Tristan L'Ecuyer, Nick Krotkov, Christian Goering, Graeme Stephens

Proceedings Volume 5886, 58860Y (2005) https://doi.org/10.1117/12.628877

KEYWORDS: Atmospheric modeling, Error analysis, Aerosols, Ultraviolet radiation, Ozone, Radiative transfer, Climatology, Diagnostics, Algorithm development, Clouds

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Proceedings Article | 20 January 2005 Paper

On the information content of satellite radiance observations for cloud microphysical property retrievals

Tristan L'Ecuyer, Graeme Stephens, Steven Cooper, Kyle Leesman, Philip Gabriel

Proceedings Volume 5655, (2005) https://doi.org/10.1117/12.588321

KEYWORDS: Clouds, Liquids, MODIS, Atmospheric modeling, Shortwaves, Satellites, Error analysis, Crystals, Infrared radiation, Radiative transfer

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Clouds play an important role in the hydrologic cycle, influence global energy balance, and represent a significant yet poorly understood component of global climate change. As a result, quantitative global observations of liquid and ice cloud microphysical and radiative properties continue to be a focus of a growing number of satellite-based sensors each having an associated suite of retrieval algorithms. While a number of these algorithms have successfully been applied to map clouds, many can only be applied under specific conditions (eg. during the daytime) or over a limited dynamic range (eg. optically thin cirrus) often leading to unphysical discontinuities when one seeks to compile a complete picture of the global distribution of clouds. Furthermore, discrepancies exist between products of different algorithms when they are applied to the same scene by virtue of differences in the information provided by distinct combinations of measurements. This paper revisits the problem of cloud microphysical property retrievals from satellite radiance observations at solar and thermal wavelengths in an effort to quantify their information content with respect to single layer liquid and ice clouds over an oceanic background. Using the channels on the Moderate Resolution Imaging Spectroradiometer (MODIS) as an example, it will be demonstrated that an entropy-based definition of information content provides a useful metric for evaluating the utility of a set of observations in a retrieval problem. This approach is used to objectively determine the subset of wavelengths that provide the greatest amount of information for oceanic microphysical property retrievals from the MODIS instrument. The results show that the combination of a conservative and a non-conservative scattering shortwave channel in concert with a near-infrared channel, an infrared window channel, and one in the wings of the 15 m CO2 band provide the optimal channel combination for the wide variety of liquid and ice clouds examined. With an eye toward developing a coherent representation of the global distribution of cloud microphysical and radiative properties, this combination of channels may be integrated into a suitable multi-channel inversion methodology such as the optimal estimation or Bayesian techniques to provide a means of establishing a common framework for cloud retrievals under varying conditions. Under some circumstances, other channels may provide a small amount of additional information but in most cases the remaining channels only supply redundant information and do not justify the additional computation cost required to integrate them into an algorithm.

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