Engineering topics
Publications and source records attributed to Salomonson, V. V..
Various techniques for reducing the satellite data to a form usable by the operational agencies were covered in mini-presentations by the operational satellite snow interpretive personnel. Similar discussions were made by operational agency stream flow forecasters on how satellite-derived snow data could be incorporated into runoff forecasting methods.
The author has identified the following significant results. The major shortcoming of the data was the loss of the infrared radiances from the S191 spectrometer. The cloud thermodynamic phase determination procedure was derived and tested with the data collected by the S192 multispectral scanner. Results of the test indicate a large fraction of the data could be classified thermodynamically. An added bonus was the inclusion of snow in the classification approach. The conclusion to be drawn from this portion of the effort is that in most cases considered ice clouds, liquid water droplet clouds, and snow fields can be spectroscopically separated to a high degree of accuracy.
The possibility that the variation in areal extent of the snow cover may be related by empirical means to the average monthly run-off in a given watershed was demonstrated by comparing run-off records from the Indus River Basin in south-east Asia with a series of snow-cover maps obtained from Nimbus-3 and 4 imagery. Similar studies using the higher spatial resolution available with ERTS-1 imagery were carried out for the Wind River Mountains watersheds in Wyoming, where it was found that the empirical relationship varied with mean elevation of the watershed. In addition, digital image enhancement techniques are shown to be useful for identifying glacier features thought to be related to extent of snow cover, moraine characteristics, debris coverage, and the like. Finally, longer wavelength observations using sensors on board the Nimbus-5 satellite are shown to be useful for indicating crystal size distributions and onset of melting on glacier snow cover.
A continuous simulation watershed model has been used to perform sensitivity analyses that provide guidance in defining remote sensing requirements for the monitoring of watershed features and processes. The results show that out of 26 input parameters having meaningful effects on simulated runoff, 6 appear to be obtainable with existing remote sensing techniques. Of these six parameters, 3 require the measurement of the areal extent of surface features (impervious areas, water bodies, and the extent of forested area), two require the descrimination of land use that can be related to overland flow roughness coefficient or the density of vegetation so as to estimate the magnitude of precipitation interception, and one parameter requires the measurement of distance to get the length over which overland flow typically occurs. Observational goals are also suggested for monitoring such fundamental watershed processes as precipitation, soil moisture, and evapotranspiration. A case study on the Patuxent River in Maryland shows that runoff simulation is improved if recent satellite land use observations are used as model inputs as opposed to less timely topographic map information.
The relation of aereal extent of snow cover to the average monthly runoff in a given watershed was investigated by comparing runoff records with a series of snowcover maps. Studies using the high spatial resolution available with ERTS-1 imagery were carried out for the Wind River Mountains watersheds in Wyoming, where it was found that the empirical relationship varied with mean elevation of the watershed. In addition, digital image enhancement techniques are shown to be useful for identifying glacier features related to extent of snowcover, moraine characteristics, and debris average. Longer wavelength observations using sensors on board the Nimbus 5 Satellite are shown to be useful for indicating crystal size distributions and onset of melting on glacier snow cover.
Consideration of the use of remote sensing technology applied from satellites to obtain information for the rapid and continuing assessment of the hydrologic cycle. A detailed account is given of the hydrological information made available through the activities of the ERTS-1 satellite, an experimental satellite entirely devoted to earth resources observations, and the NOAA-2 satellite, a high-resolution operational environmental satellite. Following a description of the satellites and their payloads, it is shown how with their aid information can be obtained regarding atmospheric moisture, surface water and snow cover, glaciers, potential flood situations, and subsurface water fluctuations. In addition, the use of the ERTS-1 and NOAA-2 satellites in watershed characterization and modeling and in monitoring water quality is discussed.
Substantial progress has been made in applying ERTS-1 data to water resources problems, nevertheless, more time and effort still appear necessary for further quantification of results, including the specification of thematic measurement accuracies. More modeling can be done very profitably. In particular, more strategy models describing the processes wherein ERTS-1 data would be acquired, analyzed, processed, and utilized in operational situations could be profitably accomplished. It is generally observed that the ERTS-1 data applicability is evident in several areas and that the next most general and substantive steps in the implementation of the data in operational situations would be greatly encouraged by the establishment of an operational earth resources satellite organization and capability. Further encouragement of this operational capability would be facilitated by all investigators striving to document their procedures as fully as possible and by providing time and cost comparisons between ERTS-1 and conventional acquisition approaches.
ERTS-1 applications in snow and ice monitoring, surface water monitoring, including monitoring of wetland areas and flood inundated area mapping, and also watershed monitoring for runoff prediction are discussed. Results also indicate that geological features can be noted which relate to ground water. ERTS-1 data can be used successfully in operational situations by water resources management agencies.
The Nimbus 4 infrared interferometer spectrometer (IRIS) measured the thermal emission of the earth's atmosphere and surface from 400-1600 wavelengths/cm with an apodized spectral resolution of 2.8 wavelengths/cm. A comparison of theoretical radiances, computed from in situ measurements and using a direct integration slant path atmospheric transmittance model, with the observed IRIS radiances has been made to verify the radiometric and spectral performance of the instrument and to assess the accuracy of the atmospheric transmittances. The radiance comparison has indicated a relatively constant difference of less than 5% in the water vapor continuum in the 425 to 550 wavelengths/cm and 750 to 1200 wavelengths/cm atmospheric 'window' regions, whereas in the 667 wavelengths/cm CO2 band the difference was 5-10%.
Nimbus-5 observations indicate that over the oceans the total precipitable water in a column of atmosphere can be estimated to within + or - 10%, the liquid water content of clouds can be estimated to within + or - 25%, areas of precipitation can be delineated, and broad estimates of the precipitation rate obtained. ERTS-1 observations permit the measurement of snow covered area to within a few percent of drainage basin area and snowline altitudes can be estimated to within 60 meters. Surface water areas as small as 1 hectare can be inventoried over large regions such as playa lakes region of West Texas and Eastern New Mexico. In addition, changes in land use on water-sheds occurring as a result of forest fires, urban development, clear cutting, or strip mining can be rapidly obtained.
Some ERTS-1 observations of snowcover, turbidity variations in the major lakes, surface water area changes, land use features, and phenomena associated with industrial emissions are described. Turbidity patterns in the major water bodies can be observed that appear to be related to the general wind flow, or to lake circulation patterns, and the chemical or biological constituents in the water. Monthly, seasonal, and annual changes in surface water extent can be monitored and serve as indicators of water availability. Time and space variations in snowcover that are a function of exposure or time of year were observed in some regions. Specific measurements of snowline altitude during the major snowmelt period of 1973 were obtained. The existence and effect of industrial emission on vegetation were found to be detectable.
In order to determine if a quantifiable relationship exists between the 6.7 micron radiometric patterns observed by the Nimbus-4 temperature-humidity infrared radiometer (THIR) and tropospheric dynamics, a 10-level diagnostic model is employed. The model is used to show the spatial and temporal relationships existing between radiometrically observed water vapor patterns and conventionally derived water vapor patterns, and to examine the upper and middle tropospheric water vapor budget and associated dynamics in order to assess the causes behind the spatially- and temporally-varying water vapor radiometric patterns. A particular situation involving a confluent trough located to the lee of the Rockies over the Central United States is examined.
The Nimbus 4 infrared interferometer spectrometer (IRIS) measured the thermal emission of the earth's atmosphere and surface from 400-1600/cm with an apodized spectral resolution of 2.8/cm. A comparison of theoretical radiances, computed from in-situ measurements and using a direct integration slant path atmospheric transmittance model, with the observed IRIS radiances has been made to verify the radiometeric and spectral performance of the instrument and to assess the accuracy of the atmospheric transmittances. The radiance comparison has indicated a relatively constant difference of less than 5% in the water vapor continuum in the 425-550/cm and 750-1200/cm atmospheric window regions while in the 667/cm CO2 band the difference was 5-10%. The absolute accuracy was found to be approximately 5-10% for each of the parameters; measured radiances, in-situ measurements, and the atmospheric transmittances, thus it is not possible to uniquely specify the degree of error arising from each parameter in the total resultant difference.
After having been in orbit for less than one year, the Earth Resources Technology Satellite (ERTS-1) has shown that it provides very applicable data for more effective monitoring and management of surface water features over the globe. Mapping flooded areas, snowcover, and wetlands and surveying the size, type, and response of glaciers to climate are among the specific areas where ERTS-1 data were applied. In addition the data collection system has proven to be a reliable tool for gathering hydrologic data from remote regions. Turbidity variations in lakes and rivers were also observed and related to shoreline erosion, industrial plant effluent, and overall water quality.
The application of ERTS-1 imagery to the conservation and control of water resources is discussed. The effects of exisiting geology and land use in the water shed area on the hydrologic cycle and the general characteristics of runoff are described. The effects of floods, snowcover, and glaciers are analyzed. The use of ERTS-1 imagery to map surface water and wetland areas to provide rapid inventorying over large regions of water bodies is reported.
Uses of ERTS-1 imagery and data for water resources surveys and management are summarized. Areas discussed are: (1) land use and geology; (2) flood plain and flood inundation mapping; (3) snow cover mapping; (4) glacier observations; (5) data collection systems; (6) surface waters; (7) wetlands mapping; (8) water quality; (9) soil mapping; (10) phreatophyte and riparian vegetation mapping; and (11) evapotranspiration.
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Water resources survey, management, and control by means of ERTS-1 data - Conference