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Liam E. Gumley and Michael D. King

The U.S. upper Midwest was subjected to severe flooding during the summer of 1993. Heavy rainfall in the Mississippi River basin from April through July caused flooding of many Midwest rivers, including the Mississippi, Illinois, Missouri, and Kansas Rivers. The flood crest of 15.1 m at St. Louis, Missouri, on 1 August 1993 was the highest ever measured, surpassing the previous record of 13.2 m set on 28 April 1973. Damage estimates include at least 47 flood-related deaths and a total damage cost of $12 billion.

Remotely sensed imagery of severe flooding in the U.S. Midwest was obtained under cloud-free skies on 29 July 1993 by the MODIS (Moderate Resolution Imaging Spectroradiometer) Airborne Simulator (MAS). The MAS is a newly developed scanning spectrometer with 50 spectral bands in the wavelength range 0.55–14.3 μm. By combining spectral bands centered at2.14,0.94,and0.66μm in red, green, and blue display channels, respectively, false color images were created from the MAS data obtained on 29 July 1993 that dramatically illustrate the extent of flooding near St. Louis and near Kansas City, Missouri.

Estimation of the total flooded area in the MAS scene acquired near St. Louis was accomplished by comparing the MAS scene to a Landsat-5 thematic mapper (TM) scene of the same area acquired on 14 April 1984 in nonflood conditions. For comparison, the MAS band centered at 0.94 μm and the TM band centered at 1.65 μm were selected because of the high contrast seen in these bands between land and water-covered surfaces. An estimate of the area covered by water in the MAS and TM scenes was obtained by developing land/water brightness thresholds from histograms of the MAS and TM digital image data. After applying the thresholds, the difference between the area covered by water in the MAS and TM scenes, and hence the flooded area in the MAS scene, was found to be about 396 km2, or about 153 square miles.

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Burcu Kabatas, W. Paul Menzel, Ata Bilgili, and Liam E. Gumley

Abstract

In this study of ship tracks, Moderate Resolution Imaging Spectroradiometer (MODIS) measurements from late-morning (Terra) and early-afternoon (Aqua) Earth Observing System platforms are analyzed in five separate geographically distributed cases to compare estimates of the sizes (and their changes in time) of droplets associated with ship exhaust. Ship tracks are readily detected in near-infrared imagery as bright features, especially in 2.13-μm observations. The Terra “MOD06” and Aqua “MYD06” cloud products are used to determine the effective radius of the ship-track droplets; droplet age (time in the atmosphere) is estimated as a function of the distance from the ship. Terra and Aqua MODIS estimates of droplet sizes in ship-track plumes are found to be in agreement, with a correlation greater than 0.90; for the cases studied, droplet sizes in the ship plumes are between 6 and 18 μm. Moreover, the droplets’ size growth rates inferred from the length of the ship track were found to average between 0.5 and 1.0 μm h−1.

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Tom Rink, W. Paul Menzel, Liam Gumley, and Kathy Strabala

Abstract

The Hyperspectral Data Viewer for Development of Research Applications, version 2 (HYDRA2), is a freeware-based multispectral analysis toolkit for satellite data that assists scientists in research and development, as well as education and training of remote sensing applications. HYDRA2 users can explore and visualize relationships between sensor measurements (brightness temperatures for infrared and reflectances for visible/near-infrared wavelengths) using spectral diagrams, cross sections, scatterplots, multiband combinations, and color enhancements on a pixel-by-pixel basis.

HYDRA2 can be used with direct broadcast and archived data from sensors on board the National Oceanic and Atmospheric Administration (NOAA)/National Aeronautics and Space Administration (NASA) Suomi–National Polar-Orbiting Partnership (Suomi-NPP), NASA Aqua/Terra, European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Meteorological Operational (MetOp), and Chinese Fengyun-3 platforms.

This paper describes HYDRA2 and presents some examples using data retrievals from the Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS), Cross-Track Infrared Sounder (CrIS), Advanced Technology Microwave Sounder (ATMS), and Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) instruments.

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Tom Rink, W. Paul Menzel, Paolo Antonelli, Tom Whittaker, Kevin Baggett, Liam Gumley, and Allen Huang

A freeware-based multispectral data analysis tool kit for satellite data has been developed to assist research and development of remote-sensing applications as well as education and training of remote-sensing scientists; it is called HYDRA—HYper-spectral data viewer for Development of Research Applications. HYDRA provides a fast and flexible interface that allows users to explore and visualize relationships between radiances (or reflectances and brightness temperatures) and wavelength (or wavenumber) using spectra diagrams, cross sections, scatter plots, multichannel combinations, and color enhancements on a pixel-by-pixel basis with full access to the underlying metadata of location and time.

HYDRA enables interrogation of multispectral (and hyperspectral) fields of data so that a) pixel location and spectral measurement values can be easily displayed; b) spectral channels can be combined in linear functions and the resulting images displayed; c) false color images can be constructed from multiple channel combinations; d) scatter plots of spectral channel combinations can be viewed; e) pixels in images can be found in scatter plots, and vice versa; f) transects of measurements can be displayed; and g) soundings of temperature and moisture as well as spectra from selected pixels can be compared.

The World Meteorological Organization has added HYDRA to its Virtual Laboratory for Satellite Training and Data Utilization to enable research with satellite data and to enhance training capabilities. The Virtual Laboratory is designed to provide the instructors and students with a set of easy-to-use tools for creating and conducting training sessions. HYDRA is now part of this international tool kit.

This paper describes some of the procedures for displaying multispectral data using HYDRA and presents some examples with Moderate Resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) data.

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Suzanne W. Seemann, Jun Li, W. Paul Menzel, and Liam E. Gumley

Abstract

The algorithm for operational retrieval of atmospheric temperature and moisture distribution, total column ozone, and surface skin temperature from the Moderate Resolution Imaging Spectroradiometer (MODIS) longwave infrared radiances is presented. The retrieval algorithm uses clear-sky radiances measured by MODIS over land and ocean for both day and night. The algorithm employs a statistical retrieval with an option for a subsequent nonlinear physical retrieval. The synthetic regression coefficients for the statistical retrieval are derived using a fast radiative transfer model with atmospheric characteristics taken from a dataset of global radiosondes of atmospheric temperature, moisture, and ozone profiles. Evaluation of retrieved total precipitable water vapor (TPW) is performed by a comparison with retrievals from the Geostationary Operational Environmental Satellite (GOES) sounder, radiosonde observations, and data from ground-based instrumentation at the Atmospheric Radiation Measurement (ARM) Program Cloud and Radiation Test Bed (CART) in Oklahoma. Comparisons over one and one-half years show that the operational regression-based MODIS TPW agrees with the microwave radiometer (MWR) TPW at the ARM CART site in Oklahoma with an rmse of 4.1 mm. For moist cases, the physical retrieval improves the retrieval performance. For dry atmospheres (TPW less than 17 mm), both physical and regression-based retrievals from MODIS radiances tend to overestimate the moisture by 3.7 mm on average. Global maps of MODIS atmospheric-retrieved products are compared with the Special Sensor Microwave Imager (SSM/I) moisture and Total Ozone Mapping Spectrometer (TOMS) ozone products. MODIS retrievals of temperature, moisture, and ozone are in general agreement with the gradients and distributions from the other satellites, and MODIS depicts more detailed structure with its improved spatial resolution.

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W. Paul Menzel, Richard A. Frey, Hong Zhang, Donald P. Wylie, Chris C. Moeller, Robert E. Holz, Brent Maddux, Bryan A. Baum, Kathy I. Strabala, and Liam E. Gumley

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Earth Observing System (EOS) Terra and Aqua platforms provides unique measurements for deriving global and regional cloud properties. MODIS has spectral coverage combined with spatial resolution in key atmospheric bands, which is not available on previous imagers and sounders. This increased spectral coverage/spatial resolution, along with improved onboard calibration, enhances the capability for global cloud property retrievals. MODIS operational cloud products are derived globally at spatial resolutions of 5 km (referred to as level-2 products) and are aggregated to a 1° equal-angle grid (referred to as level-3 product), available for daily, 8-day, and monthly time periods. The MODIS cloud algorithm produces cloud-top pressures that are found to be within 50 hPa of lidar determinations in single-layer cloud situations. In multilayer clouds, where the upper-layer cloud is semitransparent, the MODIS cloud pressure is representative of the radiative mean between the two cloud layers. In atmospheres prone to temperature inversions, the MODIS cloud algorithm places the cloud above the inversion and hence is as much as 200 hPa off its true location. The wealth of new information available from the MODIS operational cloud products offers the promise of improved cloud climatologies. This paper 1) describes the cloud-top pressure and amount algorithm that has evolved through collection 5 as experience has been gained with in-flight data from NASA Terra and Aqua platforms; 2) compares the MODIS cloud-top pressures, converted to cloud-top heights, with similar measurements from airborne and space-based lidars; and 3) introduces global maps of MODIS and High Resolution Infrared Sounder (HIRS) cloud-top products.

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Jassim Al-Saadi, James Szykman, R. Bradley Pierce, Chieko Kittaka, Doreen Neil, D. Allen Chu, Lorraine Remer, Liam Gumley, Elaine Prins, Lewis Weinstock, Clinton MacDonald, Richard Wayland, Fred Dimmick, and Jack Fishman

Accurate air quality forecasts can allow for mitigation of the health risks associated with high levels of air pollution. During September 2003, a team of NASA, NOAA, and EPA researchers demonstrated a prototype tool for improving fine particulate matter (PM2.5) air quality forecasts using satellite aerosol observations. Daily forecast products were generated from a near-real-time fusion of multiple input data products, including aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS)/Earth Observing System (EOS) instrument on the NASA Terra satellite, PM2.5 concentration from over 300 state/local/national surface monitoring stations, meteorological fields from the NOAA/NCEP Eta Model, and fire locations from the NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) Geostationary Operational Environmental Satellite (GOES) Wildfire Automated Biomass Burning Algorithm (WF_ABBA) product. The products were disseminated via a Web interface to a small group of forecasters representing state and local air management agencies and the EPA. The MODIS data improved forecaster knowledge of synoptic-scale air pollution events, particularly over oceans and in regions devoid of surface monitors. Forecast trajectories initialized in regions of high AOD offered guidance for identifying potential episodes of poor air quality. The capability of this approach was illustrated with a case study showing that aerosol resulting from wildfires in the northwestern United States and southwestern Canada is transported across the continent to influence air quality in the Great Lakes region a few days later. The timing of this demonstration was selected to help improve the accuracy of the EPA's AIRNow (www.epa.gov/airnow/) next-day PM2.5 air quality index forecast, which began on 1 October 2003. Based on the positive response from air quality managers and forecasters, this prototype was expanded and transitioned to an operational provider during the summer of 2004.

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Michael D. King, W. Paul Menzel, Patrick S. Grant, Jeffrey S. Myers, G. Thomas Arnold, Steven E. Platnick, Liam E. Gumley, Si-Chee Tsay, Christopher C. Moeller, Michael Fitzgerald, Kenneth S. Brown, and Fred G. Osterwisch

Abstract

An airborne scanning spectrometer was developed for measuring reflected solar and emitted thermal radiation in 50 narrowband channels between 0.55 and 14.2 µm. The instrument provides multispectral images of outgoing radiation for purposes of developing and validating algorithms for the remote sensing of cloud, aerosol, water vapor, and surface properties from space. The spectrometer scans a swath width of 37 km, perpendicular to the aircraft flight track, with a 2.5-mrad instantaneous field of view. Images are thereby produced with a spatial resolution of 50 m at nadir from a nominal aircraft altitude of 20 km. Nineteen of the spectral bands correspond closely to comparable bands on the Moderate Resolution Imaging Spectroradiometer (MODIS), a facility instrument being developed for the Earth Observing System to be launched in the late 1990s. This paper describes the optical, mechanical, electrical, and data acquisition system design of the MODIS Airborne Simulator and presents some early results obtained from measurements acquired aboard the National Aeronautics and Space Administration ER-2 aircraft that illustrate the performance and quality of the data produced by this instrument.

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