Engineering topics

Suttles, John T.

Publications and source records attributed to Suttles, John T..

14 records

NASA NTRS1997

Finite Difference Radiative Transfer Model Calculations Compared to Measurements at the Top and Bottom of the Atmosphere

A finite difference radiative transfer program was developed to handle most anisotropic scattering and reflectance problems encountered in the Earth's atmospheric system. The model has been used to reproduce the radiance received by both satellite and ground based radiation measuring instruments. It accurately replicates the radiance measured by both narrow and wide field-of-view instruments with either narrow or broadband wavelength ranges located on the surface and at satellite altitudes. The output of the finite difference code is compared to the measurements by surface pyranometers and a spectroradiometer aboard a high flying aircraft. The program output is also compared to ERBE measurements aboard the ERBS and NOAA-9 satellites as well as the visible bands aboard the GOES-6 and GOES-7 satellites and AVHRR bands 1 and 2 of the NOAA-9 and NOAA-1 1 satellites. The model is within 0.2 % of the radiance received by pyranometers, within 0.6 % of the ERBE radiances, and within 3 % of the radiances measured by the visible bands of the GOES and NOAA AVHRR radiometers.

LeCroy, Stuart R.↗

NASA NTRS1993

An overview of the radiation component of the NASA TOGA-COARE experiment

During January and February, 1993, the Physical Climate Branch of NASA sponsored an aircraft program in support of the Tropical Ocean - Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE). The NASA program was integrated with and contributed directly to the COARE objectives, but had as its primary foci the measurement of convection and precipitation related to the Tropical Rainfall Measurement Mission (TRMM) and the measurement of the physical and radiative properties of tropical cirrus related to the International Satellite Cloud Climatology Project (ISCCP) and the First ISCCP Regional Experiment (FIRE). This brief overview will concentrate on the measurements associated with FIRE and ISCCP.

Ackerman, Thomas↗

NASA NTRS1992

Top-of-atmosphere radiative fluxes - Validation of ERBE scanner inversion algorithm using Nimbus-7 ERB data

The ERBE algorithm is applied to the Nimbus-7 earth radiation budget (ERB) scanner data for June 1979 to analyze the performance of an inversion method in deriving top-of-atmosphere albedos and longwave radiative fluxes. The performance is assessed by comparing ERBE algorithm results with appropriate results derived using the sorting-by-angular-bins (SAB) method, the ERB MATRIX algorithm, and the 'new-cloud ERB' (NCLE) algorithm. Comparisons are made for top-of-atmosphere albedos, longwave fluxes, viewing zenith-angle dependence of derived albedos and longwave fluxes, and cloud fractional coverage. Using the SAB method as a reference, the rms accuracy of monthly average ERBE-derived results are estimated to be 0.0165 (5.6 W/sq m) for albedos (shortwave fluxes) and 3.0 W/sq m for longwave fluxes. The ERBE-derived results were found to depend systematically on the viewing zenith angle, varying from near nadir to near the limb by about 10 percent for albedos and by 6-7 percent for longwave fluxes. Analyses indicated that the ERBE angular models are the most likely source of the systematic angular dependences. Comparison of the ERBE-derived cloud fractions, based on a maximum-likelihood estimation method, with results from the NCLE showed agreement within about 10 percent.

Suttles, John T.↗

NASA NTRS1991

Science requirements for a global change technology initiative architecture trade study

Science requirements for a Global Change Technology Initiative (GCTI) Architecture Trade Study were established by reviewing and synthesizing results from recent studies. A scientific rationale was adopted and used to identify a comprehensive set of measurables and their priorities. Spatial and temporal requirements for a number of measurement parameters were evaluated based on results from several working group studies. Science requirements were defined using these study results in conjunction with guidelines for investigating global changes over a time scale of decades to centuries. Requirements are given separately for global studies and regional process studies. For global studies, temporal requirements are for sampling every 1 to 12 hours for atmospheric and radiation parameters and 1 day or more for most Earth surface measurements. Therefore, the atmospheric measurables provide the most critical drivers for temporal sampling. Spatial sampling requirements vary from 1 km for land and ocean surface characteristics to 50 km for some atmospheric parameters. Thus, the land and ocean surface parameters have the more significant spatial variations and provide the most challenging spatial sampling requirements.

Suttles, John T.↗

NASA NTRS1991

Satellite orbit considerations for a global change technology architecture trade study

A study was conducted to determine satellite orbits for Earth observation missions aimed at obtaining data for assessing global climate change. A multisatellite system is required to meet the scientific requirements for temporal coverage over the globe. The best system consists of four Sun-synchronous satellites equally spaced in local time of equatorial crossing. This system can obtain data every three hours for all regions. Several other satellite systems consisting of combinations of Sun-synchronous orbits and either the Space Station Freedom or a mid-latitude equatorial satellite can provide three to six hour temporal coverage, which is sufficient for measuring many of the parameters required for the global change monitoring mission. Geosynchronous satellites are required to study atmospheric and surface processes involving variations on the order of a few minutes to an hour. Two or more geosynchronous satellites can be relocated in longitude to study processes over selected regions of Earth.

Harrison, Edwin F.↗

NASA NTRS1991

Satellite orbit considerations for a global change technology architecture trade study

A study was conducted to determine satellite orbits for earth observation missions aimed at obtaining data for assessing data global climate change. A multisatellite system is required to meet the scientific requirements for temporal coverage over the globe. The best system consists of four sun-synchronous satellites equally spaced in local time of equatorial crossing. This system can obtain data every three hours for all regions. Several other satellite systems consisting of combinations of sun-synchronous orbits and either the Space Station Freedom or a mid-altitude equatorial satellite can provide three to six hour temporal coverage, which is sufficient for measuring many of the parameters required for the global change monitoring mission. Geosynchronous satellites are required to study atmospheric and surface processes involving variations on the order of a few minutes to an hour. One or two geosynchronous satellites can be relocated in longitude to study processes over selected regions of earth.

Harrison, Edwin F.↗

NASA NTRS1991

Science requirements for a global change technology architecture trade study

Science requirements for a global change technology initiative (GCTI) Architecture Trade Study were established by reviewing and synthesizing results from recent studies. A scientific rationale was adopted and used to identify a comprehensive set of measureables and their priorities. Spatial and temporal requirements for a number of measurement parameters were evaluated based on results from several working group studies. Science requirements were defined using these study results in conjunction with the guidelines for investigating global changes over a time scale of decades to centuries. Requirements are given separately for global studies and regional process studies. For global studies, temporal requirements are for sampling every 1 to 12 hours for atmospheric and radiation parameters and 1 day or more for most earth surface measurements. Therefore, the atmospheric measureables provide the most critical drivers for temporal sampling. Spatial sampling requirements vary from 1 km for land and ocean surface characteristics to 50 km for some atmospheric parameters. Thus, the land and ocean surface parameters have the more significant spatial variations and provide the most challenging spatial sampling requirements.

Suttles, John T.↗

NASA NTRS1990

AVHRR and VISSR satellite instrument calibration results for both Cirrus and marine stratocumulus IFO periods

Accurate characterizations of some cloud parameters are dependent upon the absolute accuracy of satellite radiance measurements. Visible wavelength measurements from both the AVHRR and VISSR instruments are often used to study cloud characteristics. Both of these instruments were radiometrically calibrated prior to launch, but neither has an onboard device to monitor degradation after launch. During the FIRE/SRB cirrus Intensive Field Operation (IFO), a special effort was made to monitor calibration of these two instruments onboard the NOAA-9 and GOES-6 spacecraft. In addition, several research groups have combined their efforts to assess the long-term performance of both instruments. These results are presented, and a limited comparison is made with the ERBE calibration standard.

Whitlock, C. H.↗

NASA NTRS1990

FIRE Cirrus on October 28, 1986: LANDSAT; ER-2; King Air; theory

A simultaneous examination was conducted of cirrus clouds in the FIRE Cirrus IFO-I on 10/28/86 using a multitude of remote sensing and in-situ measurements. The focus is cirrus cloud radiative properties and their relationship to cloud microphysics. A key element is the comparison of radiative transfer model calculations and varying measured cirrus radiative properties (emissivity, reflectance vs. wavelength, reflectance vs. viewing angle). As the number of simultaneously measured cloud radiative properties and physical properties increases, more sharply focused tests of theoretical models are possible.

Wielicki, Bruce A.↗

NASA NTRS1990

Angular dependence models for radiance to flux conversion

Angular dependence models (ADM) used for converting the measured radiance to flux at the top of the atmosphere are reviewed, and emphasis is placed on the measure of their effectiveness and the implications of requiring the ADMs to satisfy reciprocity. The overall significance of the ADMs is figured out by analyzing the same satellite data with a single Lambertian model, single mean model, and the 12 Earth Radiation Budget Experiment (ERBE) ADMs. It is shown that the Lambertian ADM is inadequate, while the mean ADM results in nearly unbiased fluxes but creates substantial differences for individual pixel fluxes. The standard ERBE ADM works well except for a 10-pct to 15-pct albedo growth across the scan; a modified ADM based on the standard ERBE ADM but forced to satisfy the principle of reciprocity increases the limb brightening and reduces the albedo growth but does not improve the scanner and nonscanner intercomparison.

Green, Richard N.↗

NASA NTRS1990

Satellite derived cirrus particle size - Tropical clouds

The present study extends the earlier work of Wielicki et al. (1990) to examine several cases of tropical cirrus clouds. Particle effective radius is estimated and compared to other studies of cirrus clouds. Particle size and phase are estimated by comparing reflectance observations by the Landsat satellite with theoretical calculations for a range of possible water and ice particle sizes. An examination of effective particle radius for six cases of tropical cirrus clouds over the eastern Pacific Ocean found typical radii of 60 microns. This value is similar to that derived for a case of midlatitude cirrus during the FIRE experiment in October 1986. Particle size is found to increase with decreasing cloud optical depth.

Wielicki, Bruce A.↗

NASA NTRS1990

Performance of scene dependent angular models in deriving top-of-atmosphere radiative fluxes from satellite radiance measurements

The ERB experiment algorithm is applied to the Nimbus-7 scanner data for June 1979 to analyze the performance of scene-dependent angular models. The ERBE-derived albedo and LW flux are compared to results from the sorting-into-angular-bins (SAB) method described by Arking and Vemury (1984) and the ERB Matrix algorithm described by Jacobowitz et al. (1984). Results are given for the variation of ERBE-derived flux with viewing zenith angle. Comparing results derived from the ERBE algorithm and from the SAB method, zonal mean differences for the month were less than 0.01 for albedo and 2 W/ sq m for longwave flux. When compared to the ERB matrix algorithm, the ERBE algorithm gives less dependence on viewing zenith angle for SW fluxes, but more for LW fluxes. Cloud results from the ERBE method using broadband Nimbus-7 ERB radiances are compared with the new cloud ERB data results of Stowe et al. (1988). Agreement typically within 0.10 was found.

Suttles, John T.↗

NASA NTRS1990

Validation of Earth Radiation Budget Experiment scanning radiometer data inversion procedures

Validation techniques were implemented in the inversion of scanner radiometer data to assess the accuracy of the top of atmosphere radiant fluxes. An evaluation of SW radiant flux standard deviations for the same scene type shows that they contribute about 6.0 W/sq m for viewing zenith angles less than 55 deg and can reach values of up to 17.6 W/sq m for larger zenith angles in the backward scanning position. Three-channel intercomparison results, presented as color graphic displays and histograms, effectively validate the radiance measurements and the spectral factors. Along-track data were used to validate limb-darkening models and showed good agreement with current ERBE models. These validation techniques were found to be very effective in assessing the quality of the radiant fluxes generated by the ERBE inversion algorithm.

Manalo, Natividad D.↗

NASA NTRS1989

Limb-darkening functions as derived from along-track operation of the ERBE scanning radiometer for January 1985

During January 1985, the scanning radiometer aboard the Earth Radiation Budget Satellite was operated to scan along-track. These data have been analyzed to produce limb-darkening functions for Earth emitted radiation, which relate the radiance in any given direction to the radiant exitance. Limb-darkening functions are presented in tabular form and shown as figures for 10 day cases and 12 night cases, corresponding to various scene types and latitude zones. The scene types were computed using measurements within 10 deg of zenith. The limb-darkening functions have values of 1.03 to 1.09 at zenith, with 1.06 being typical. It is found that latitude causes a variation on the order of 1 percent, except for zenith angles greater than 70 deg. These limb-darkening models are about 2 percent higher at zenith than the models derived from Nimbus 7 data.

Smith, G. Louis↗