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P. Krishna Rao

Abstract

Examples of NOAA-2 VHRR visible and infrared images presented in this paper show the importance and usefulness of these images, particularly in detecting cirrus clouds, when they are used together.

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P. Krishna Rao

Abstract

No abstract available.

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P. Krishna Rao
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S. Fritz and P. Krishna Rao

Abstract

On the basis of satellite and other types of information, it is shown, both on observational and theoretical grounds, that cirrus clouds have a higher transmission for radiation at 10 μ than for radiation at 6 μ. Thus, in the case studied, at 10 μ the cirrus clouds had a fractional transmission of about 50%, while at 6 μ the clouds were essentially opaque. This fact has an important bearing on attempts to use a “humidity diagram” to estimate relative humidity above clouds. The satellite data show that measurements at 6 or 10 μ can be used to locate regions of substantial cloudiness, which are therefore regions of high relative humidity in the troposphere. To use these satellite measurements to estimate the relative humidity above clouds would be misleading. However, the use of radiation measurements in both channels can perhaps be helpful for specifying the transmissivity of cirrus clouds, and in the absence of clouds, for locating regions of low relative humidity.

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JAY S. WINSTON and P. KRISHNA RAO

Abstract

Daily composite Northern Hemisphere charts of outgoing long-wave radiation were derived from TIROS II measurements for about 25 days in late November and December 1960. Although data coverage was incomplete and variable each day, both latitudinal and overall daily averages of long-wave radiation were obtained. Large-scale temporal variations in the long-wave radiation are observed and are found to be generally related to temporal variations in kinetic and available potential energy over the Northern Hemisphere. Examination of the radiation latitudinally for various stages of an energy cycle that occurred at this time shows that the outgoing radiation, particularly at lower latitudes, decreased as westerly flow increased at lower latitudes. An average latitudinal profile of the TIROS long-wave data for all days studied shows rather good agreement with previous estimates made by investigators of the atmospheric heat budget.

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S. Fritz, P. Krishna Rao, and M. Weinstein

Abstract

A method is described for comparing satellite measurements of reflected solar radiation with pryheliometric measurements at the ground and with measurements from airplanes. When data from accurate, well-calibrated satellite instruments become available, this method can be used to compute the solar energy absorbed directly in the atmosphere. In the meantime the method is applied to solar radiation measurements from TIROSIII, although these data are of doubtful accuracy.

TIROSIII measured the solar energy reflected by the planet Earth. Several of these measurements, taken over the United States near noon on 12 July 1963 are described. The corresponding “albedos” which varied from 0.65 over a bright overcast area to 0.05 over some cloudless areas, may be too low. The reflected energy is correlated with pyrheliometer measurements at the ground at 31 stations. The correlation coefficient was −0.9. The relationship between the satellite measurement and the ground pyrheliometer measurements is further compared with similar measurements made from airplanes in previous years. It is this comparison which suggests that the satellite measurements of albedo may he too low.

From the satellite measurements and the ground pyrheliometer measurements, the solar energy absorbed by the atmosphere itself can be computed after reasonable assumptions about the ground albedo are made. These absorptions sometimes exceed 35 per cent of the solar energy entering the top of the atmosphere; the values appear to be too large and are a consequence of the relatively low satellite values of measured reflectivity over cloudy areas.

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Harry G. Stumpf and P. Krishna Rao

Abstract

Pronounced eddies along the western edge of the Gulf Stream were again observed by the Very High Resolution Radiometer aboard the NOAA-2 satellite. A rare sequence of infrared images obtained over a period of seven days shows for the first time the complete evolution of meanders through the eddy stage.

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Richard J. DeRycke and P. Krishna Rao

Abstract

Pronounced eddies along the western edge of the Gulf Stream were observed by the Very High Resolution Radiometer aboard the NOAA-2 satellite. Similar eddies were seen on one previous occasion. In each case, there was an apparent relationship between the occurrence of the eddies and strong westerly winds. These eddies can also be attributed to the bottom topography of the region and the baroclinic instability along the Gulf Stream boundary.

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JAY S. WINSTON and P. KRISHNA RAO

Abstract

Daily composite charts of outgoing long-wave radiation between latitudes 55°N. and 55°S. were derived from TIROS II measurements for 26 days between late November 1960 and early January 1961. Samples of these charts reveal the wealth of information available about the radiation patterns over the earth and about the synoptic distributions of the major cloud fields. Mean maps of outgoing long-wave radiation for four periods of generally more abundant radiation data portray the broad-scale variations in the radiation pattern both geographically and in time. For the Northern Hemisphere these maps show how the long-wave radiation varied during some very large-scale changes in 700-mb. mean flow which were part of a remarkable energy, or index, cycle in this period. Most pronounced were the sharp decreases in outgoing radiation that accompanied the penetration of westerlies into the subtropics where anticyclones had prevailed previously. In the Southern Hemisphere some sizable temporal variations also occurred; these appeared to be representative of a change in circulation from a zonal to a more meridional type. Average latitudinal profiles of the outgoing radiation for these four mean periods and for the entire 26 days are also presented. The overall distribution shows maxima of outgoing radiation near 20°N. and 20°S. with lower values toward higher latitudes in both hemispheres and in equatorial regions. Comparisons of these measurements from TIROS II with previous estimates of outgoing long-wave radiation by investigators of the heat budget show relatively good agreement.

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P. Krishna Rao and Jay S. Winston

Abstract

Several samples of infrared radiation measurements in the 8–13 micron water-vapor “window” made by TIROS II are studied in relation to conventionally observed information on pressure systems, cloudiness and temperature These cases demonstrate further the synoptic capabilities, as well as some of the limitations, of these data for cloud detection; determination of cloud-top height; and observation of spatial gradients and temporal changes in the temperature of water-, land-, and snow-covered surfaces.

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