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Robert Pincus, Malgorzata Szczodrak, Jiujing Gu, and Philip Austin

Abstract

The uncertainty in optical depths retrieved from satellite measurements of visible wavelength radiance at the top of the atmosphere is quantified. Techniques are briefly reviewed for the estimation of optical depth from measurements of radiance, and it is noted that these estimates are always more uncertain at greater optical depths and larger solar zenith angles. The lack of radiometric calibration for visible wavelength imagers on operational satellites dominates the uncertainty retrievals of optical depth. This is true for both single-pixel retrievals and for statistics calculated from a population of individual retrievals. For individual estimates or small samples, sensor discretization (especially for the VAS instrument) can also be significant, but the sensitivity of the retrieval to the specification of the model atmosphere is less important. The relative uncertainty in calibration affects the accuracy with which optical depth distributions measured by different sensors may be quantitatively compared, while the absolute calibration uncertainty, acting through the nonlinear mapping of radiance to optical depth, limits the degree to which distributions measured by the same sensor may be distinguished.

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Malgorzata Szczodrak, Peter J. Minnett, Nicholas R. Nalli, and Wayne F. Feltz

Abstract

Measurements of the spectra of infrared emission from the atmosphere were taken by a Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) deployed on the NOAA ship Ronald H. Brown during the Aerosol and Ocean Science Expedition (AEROSE) in the tropical Atlantic Ocean from 29 February to 26 March 2004. The spectra are used to retrieve profiles of temperature and humidity in the lower troposphere up to a height of 3000 m. The M-AERI retrievals of the atmospheric structure require an initial guess profile. In this work, retrievals obtained from four separate initializations are compared, using 1) radiosondes launched from the Ronald H. Brown, 2) NOAA/NWS/NCEP model reanalyses, 3) ECMWF model analyses, and 4) ECMWF model forecasts. The performance of the M-AERI retrievals for all four first-guess sources is then evaluated against the radiosonde measurements. The M-AERI retrievals initialized using radiosondes reproduce the radiosonde profiles quite well and capture much of the observed vertical structure as should be expected. Of the retrievals initialized with model fields, those obtained using the ECMWF data yielded results closest to the radiosonde observations and enabled detection of the Saharan air layer (SAL) evident during AEROSE. However, the NCEP reanalysis, as well as the corresponding retrievals, failed to detect the SAL. These results demonstrate the ability of the M-AERI profile retrievals to identify the anomalous humidity distributions in the lower troposphere, but underscore the need for suitable vertical resolution in the first-guess profile used in the retrievals under such conditions.

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Bingkun Luo, Peter J. Minnett, Malgorzata Szczodrak, Nicholas R. Nalli, and Vernon R. Morris

Abstract

Satellite and in situ measurements of the sea surface and the atmosphere often have inadequate sampling frequencies and often lack consistent global coverage. Because of such limitations, reanalysis model output is frequently used in atmospheric and oceanographic research endeavors to complement satellite and in situ data. The National Aeronautics and Space Administration’s (NASA’s) Goddard Earth Sciences Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) and the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) datasets provide accurate, complete fields through the assimilation of many atmospheric and surface observations. Still, the reanalysis output data must be rigorously and continuously evaluated to understand their strengths and weaknesses. To this end, this study evaluates sea surface skin temperature (SSTskin) and atmospheric temperature and humidity profiles in MERRA-2 and ERA-Interim data through comparisons with independent Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) and radiosonde data from the Aerosols and Ocean Science Expeditions (AEROSE) cruises, focusing on the representation of spatial and temporal variability. SSTskin values are generally in good agreement with corresponding M-AERI measurements, with the average differences on the order of 0.1 K. Comparisons between MERRA-2 and ERA-Interim relative humidity and air temperature profiles with a total of 553 radiosondes that have been withheld from data assimilation schemes show good correspondence below 500 hPa: the average air temperature difference is <2 K and the average relative humidity discrepancy is within 10%. These results support the use of these MERRA-2 and ERA-Interim reanalysis fields in a variety of research applications.

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Nicholas R. Nalli, Everette Joseph, Vernon R. Morris, Christopher D. Barnet, Walter W. Wolf, Daniel Wolfe, Peter J. Minnett, Malgorzata Szczodrak, Miguel A. Izaguirre, Rick Lumpkin, Hua Xie, Alexander Smirnov, Thomas S. King, and Jennifer Wei

This paper gives an overview of a unique set of ship-based atmospheric data acquired over the tropical Atlantic Ocean during boreal spring and summer as part of ongoing National Oceanic and Atmospheric Administration (NOAA) Aerosols and Ocean Science Expedition (AEROSE) field campaigns. Following the original 2004 campaign onboard the Ronald H. Brown, AEROSE has operated on a yearly basis since 2006 in collaboration with the NOAA Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) Northeast Extension (PNE). In this work, attention is given to atmospheric soundings of ozone, temperature, water vapor, pressure, and wind obtained from ozonesondes and radiosondes launched to coincide with low earth orbit environmental satellite overpasses [MetOp and the National Aeronautics and Space Administration (NASA) A-Train]. Data from the PNE/ AEROSE campaigns are unique in their range of marine meteorological phenomena germane to the satellite missions in question, including dust and smoke outflows from Africa, the Saharan air layer (SAL), and the distribution of tropical water vapor and tropical Atlantic ozone. The multiyear PNE/AEROSE sounding data are valuable as correlative data for prelaunch phase validation of the planned Joint Polar Satellite System (JPSS) and NOAA Geosynchronous Operational Environmental Satellite R series (GOES-R) systems, as well as numerous other science applications. A brief summary of these data, along with an overview of some important science highlights, including meteorological phenomena of general interest, is presented.

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