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Lewis J. Allison and Guenter Warnecke
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Lewis J. Allison, Thomas J. Schmugge, and Gavin Byrne

The chronological development and diminution of six floods in eastern Australia during January, February, and March 1974 were mapped for the first time by the Nimbus Electrically Scanning Microwave Radiometer (ESMR). Day and nighttime ESMR (19.35 GHz) coverage was analyzed for the low gradient, flooded Darling River system in New South Wales. Apparent movement of surface water as indicated by low brightness temperatures (<250 K, day and <240 K, night) was easily followed around the curved runoff basin along the northern shoreline of the flooded Darling River during this 3-month period. This pattern was in good agreement with flood crest data at selected river height gage stations, even under cloudy conditions.

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Joseph Steranka, Lewis J. Allison, and Vincent V. Salomonson

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The Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) monitors radiation in the 6.5–7.2 μm water vapor absorption region with a 23-km spatial resolution at the sub-satelite point. Radiation monitored in this spectral region results primarily from emission in the 250–500 mb region of the upper troposphere. The THIR 6.7μm observations are readily available in photofacsimile imagery form which shows very distinctive patterns associated with spatial variations in atmospheric water vapor.

These radiometric observations have been combined in several instances with moisture values measured in the upper troposphere by the standard radiosonde network. In each instance, the result is a much more consistent analysis showing increased spatial detail that agrees with the radiometric observations and does not compromise the conventional data. The improved moisture analyses show relatively dry and moist tongues that are very difficult or impossible to infer from the conventional data alone. The patterns in the moisture fields can be tracked over 12- and 24-hr periods. In addition, by keeping in mind the advective properties of the moisture field, success has been achieved in improving streamline analyses at the 400-mb level over data-sparse regions on a global scale.

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Lewis J. Allison, George W. Nicholas, and James S. Kennedy

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The High Resolution Infrared Radiometer (HRIR) carried by the Nimbus I meteorological Satellite provided detailed nighttime cloud information in the vertical as well as in the horizontal dimension. When the instantaneous field of view of the HRIR is completely filled by either a cloud or the earth's surface through clear skies, the temperature of the radiating surface can be inferred. Cloud top heights can, therefore, be deduced by relating the equivalent blackbody temperature from the satellite to the temperature-height profile of the atmosphere, providing the temperature decreases monotonically with height. Equivalent blackbody temperatures average 5K colder than air shelter temperatures based on 40 stations reporting clear skies. Cloud patterns over water are well defined from daytime HRIR data, but over land some clouds tend to be indistinguishable from land when the sum of the thermal emission and the reflected solar radiation from the cloud equals that from the land. The capability of both the photofacsimile displays and the computer maps to depict synoptic information demonstrates that HRIR data from future meteorological satellites should provide a new operational tool.

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Lewis J. Allison, G. Thomas Cherrix, and Harold Ausfresser
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Lewis J. Allison, Joseph Steranka, G. Thomas Cherrix, and Ernest Hilsenrath

Mid-tropospheric circulation features under essentially clear sky conditions have been noted in the data of the 6.7 μm channel of the Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) while at the same time these features were undetected by the 11.5 μm channel of the same instrument. The characteristic response of the 6.7 μm channel to atmospheric water vapor emission is primarily from the 250-mb (10.5 km) to 500-mb (5.5 km) levels with a peak contribution at 350 mb (8 km). Dry and moist patterns seen in the 6.7 μm data on 21 February 1971 have been integrated into a 400-mb moisture analysis over the United States. This analysis provided more detailed and timely information than was conventionally available about the advection of dry air aloft prior to development of the Mississippi Tornado of February 1971. The derivation of middle to upper atmosphere flow patterns from the Nimbus 4 THIR, 6.7 μm data under cloud-free conditions has a direct application on a global scale for the GARP and World Weather Watch Programs.

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Guenter Warnecke, Lewis J. Allison, Larry M. McMillin, and Karl-Heinz Szekielda

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Nimbus II High Resolution Infrared Radiometer (HRIR) data, sensitive in the 3.4–4.2 μ window, were analyzed over several oceanic regions. Current boundaries such as the north wall of the Gulf Stream have been located consistently within 10 km of the positions indicated by airplane radiation data. With present techniques, primarily designed for meteorological purposes, the Gulf Stream boundary has been seen, at least in significant parts, in about 50 out of 175 days. Similar results have also been obtained in analyses of the Agulhas Current boundary, and the boundary between the Brazil and Falkland Currents. The satellite radiation observations suggest that the Brazil-Falkland Current boundary which is associated with a surface temperature gradient is as sharp and strong as the Gulf Stream North Wall. The Agulhas Current exhibits a similar temperature gradient along its western boundary, separating it from the Benguela Current surface waters.

Comparisons of equivalent blackbody temperatures over the Gulf Stream from Nimbus II with low flying radiometer-equipped aircraft showed that the satellite data were on the average 0.5C warmer.

Seasonal sea surface temperature variations of 9C over the Persian Gulf and Somali region and the upwelling along the Somali Coast during the southwest monsoon were clearly detected in the nighttime HRIR data.

Daytime observations within the 3.4–4.2 μ window have also shown qualitatively the location of major current boundaries.

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Lewis J. Allison, Edward B. Rodgers, Thomas T. Wilheit, and Robert W. Fett

A selected group of 1973 North Pacific Ocean tropical cyclones was studied by using data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR), the Temperature-Humidity Infrared Radiometer (THIR), NOAA-2 and USAF DMSP imageries. From the unique combination of infrared, visible, and microwave data, it was possible during various stages of storm development to differentiate between dense cirrus outflow and rain areas, to identify centers of circulation and areas of low-level moisture, and by the use of a theoretical model to estimate semi-quantitatively areas of light, moderate, and heavy rainfall rates.

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Jacob Bjerknes, Lewis J. Allison, Earl R. Kreins, Frederic A. Godshall, and Guenter Warnecke

The generally held assumption, that the bulk of tropical rain over the oceans is generated where the sea is warmer than the air, is being largely verified in this article with the new tool of satellite cloudiness mapping. The discussion focuses on the satellite-observed variable position of the boundary between the west Pacific equatorial rain clouds over warm ocean water and the east Pacific aridity along the equator over cool upwelling water. The often quite abrupt changes between these two regimes in the mid-Pacific are known from an eighteen-year sequence of ocean and atmosphere data at Canton Island. This article describes the same phenomena delineated by satellite television data recorded during 1962–67, and adds features of the geographic cloudiness distribution not obtainable from the widely spaced fixed points of observation.

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Guenter Warnecke, Edith I. Reed, Walter B. Fowler, Earl R. Kreins, Lewis J. Allison, and Jaques E. Blamont

Abstract

The presence or absence of clouds, their characteristics, and variations of surface albedo have been correlated with observations made at several different wavelengths in the visible spectrum. These were made at high and low nighttime light levels by an airglow photometer aboard the OGO-4 satellite during August 1967 through January 1968. The wavelength regions studied were approximately 50 Å bands centered at 3914, 5577, 5893, 6225 and 6300 Å, in the energy range of 10−7 to 10−3 erg cm−2 sec−1−1 ster−1 with a field of view of ˜10 degrees. It was found that at the longer wavelengths (6225 and 6300 Å) the observations were strongly influenced by the variations of surface albedo. At the shorter wavelengths, the surface albedo variations were partly masked by the light returned through Rayleigh and Mie scattering. Preliminary analysis is made of surface and clouds by study of reflective radiance under moonlight and other nocturnal illuminations. Possibilities of further analysis are examined including methods of deducing cloud height information.

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