Charles H. Whitlock

Comparison of reflectance with backscatter and absorption parameters for turbid waters

The relation of reflectance to backscatter and absorption parameters is investigated for waters more turbid than those of previous investigations. Experimental data are examined for river waters in which beam attenuation values range from 8.9 to 18.9 m(_1) at 550 nm. Attenuation, absorption, backscatter, and irradiance reflectance spectral properties are presented for wavelengths between 450 and 800 nm. Comparisons of reflectance with backscatter to absorption ratio and backscatter with absorption plus backscatter ratio indicate that data for turbid waters do not fit linear or polynomial models which are presently available in the literature.

Criteria for the use of regression analysis for remote sensing of sediment and pollutants

Abstract An examination of limitations, requirements, and precision of the linear multiple-regression technique for quantification of marine environmental parameters is conducted. Both environmental and optical physics conditions have been defined for which an exact solution to the signal response equations is of the same form as the multiple regression equation. Various statistical parameters are examined to define a criteria for selection of an unbiased fit when upwelled radiance values contain error and are correlated with each other. Field experimental data are examined to define data smoothing requirements in order to satisfy the criteria of Daniel and Wood. Recommendations are made concerning improved selection of ground-truth locations to maximize variance and to minimize physical errors associated with the remote sensing experiment.

Surface characteristics for the alkali flats and dunes regions at White Sands Missile Range, New Mexico

Abstract Two regions at White Sands Missile Range with different surface reflectance characteristics were studied from November 1988 through December 1991. Continuous 6-min measurements of surface albedo on the alkali flats were used to produce a clear-sky surface climatology for the period. Based on the flats measurements, estimates for a dunes albedo were made using calibrated satellite data. In addition to the surface albedo history, sample bidirectional reflectance characteristics in terms of anisotropic factors for the alkali flats region are also presented. Results show that the flats region is non-Lambertian characterized by large anisotropic factors at high solar and viewing zenith angles. The flats albedo is highly influenced by surface moisture conditions. Reflectance properties of the dunes are complicated by dune shadows, surface irregularities, seasonal vegetative coverage, and soil moisture.

NASA Climatological Data for Renewable Energy Assessment

This article presents the latest parameters and delivery methods that provide global solar energy and meteorological resources on the Interuet. Over the past several years the number of parameters in the Surface meteorology and Solar Energy Data Set has tripled. The newest parameters include solar geometry, a suite of wind speed and wind direction data, diffuse, direct normal and tilted surface solar irradiance. Requests by users and recommendations by the renewable energy industry have prompted the growth.

A multiwavelength airborne radiometer scanner (ARS) for measuring surface bidirectional reflectance characteristics

Abstract The development and application of the Airborne Radiometer Scanner (ARS), a helicopter-borne multiwavelength radiometer scanner to obtain directional reflectance data over natural Earth targets, is reported. The rationale for the methodology used in the design and a detailed description of the instrument are described. Techniques used to maintain a desired heading in crosswinds without introducing unwanted pitch or roll moments into the platform are included. The system overcomes some of the limitations of previous methods used to characterize surface directional reflectance. Samples of results from a pilot experiment conducted over the alkali flats region of the white Sands Missile Range, New Mexico, are briefly reviewed.

A Global Perspective on Renewable Energy Resources: Nasa’s Prediction of Worldwide Energy Resources (Power) Project

The Prediction of the Worldwide Energy Resources (POWER) Project, initiated under the NASA Science Mission Directorate Applied Science Energy Management Program, analyzes, synthesizes and makes available data parameters on a global scale. These data have proved to be reliable and useful to the renewable energy industries, especially to the solar energy sectors. The POWER project derives its data primarily from NASA’s World Climate Research Programme (WCRP)/Global Energy and Water cycle Experiment (GEWEX) Surface Radiation Budget (SRB) project (Version 2.9) and the Global Modeling and Assimilation Office (GMAO) Goddard Earth Observing System (GEOS) assimilation model (Version 4).

Narrowband Angular Reflectance Properties of the Alkali Flats at White Sands, New Mexico

Abstract Results from helicopter measurements of the angular properties of surface reflectance for the alkali flats regions of the White Sands Missile Range are presented for the wavelength interval of 0.4 to 0.85 μm. This work was performed to allow accurate radiative transfer calculations over the region. Detailed tables and interpolation equations are given that permit other investigators to perform satellite calibrations over the alkali flats site. The effects of wavelength and soil moisture on narrowband angular reflectance are also investigated. Although there is a spectral variation in surface albedo, there is little spectral effect in Anisotropic Factor except in the forward-scattering peak at solar zenith angles greater than 60°. The magnitude of the forward-scattering peak is also sensitive to soil moisture, with wet conditions causing a larger peak. The significance of this result is that angular reflectance properties at the center of the alkali flats usually will be different than those at the flats edge because moisture differences typically exist.

Assessing the socio-economic value of NASA gridded long-term and near-term data sets for the energy sector and other uses

NASA Applied Science Program has and continues to yield significant results for nation and international programs through Science ⇒ Applications transfer; Successes include supporting renewable energy and energy efficient technology optimization and providing data from the individual user to the worldwide scale.; The value of contributions to the renewable energy show wide spread impact, but are difficult to quantify - The Brattle Group has done a preliminary assessment of benefits of the SSE web portal through RETScreen - However, specific knowledge of benefits will have to be collected - Case studies showing example benefits have to be expanded - Strategies for assessing the macro benefit are also needed.