Search Results

You are looking at 21 - 26 of 26 items for

  • Author or Editor: J. A. Weinman x
  • Refine by Access: All Content x
Clear All Modify Search
J. L. Schols
,
J. A. Weinman
,
G. D. Alexander
,
R. E. Stewart
,
L. J. Angus
, and
A. C. L. Lee

Abstract

Microwave brightness temperatures emanating from a North Atlantic cyclone were measured by the Special Sensor Microwave/Imager (SSM/I) on the Defense Meteorological Satellite Program satellite. As other investigators have found before, low 85.5-GHz brightness temperatures (215 ± 20 K) were observed from cumulonimbus clouds along the squall line; however, 85.5-GHz microwave brightness temperatures observed from the nimbostratus clouds north of the low center were significantly higher (255 ± 20 K). In situ measurements from aircraft during the Canadian Atlantic Storm Program II showed that heavy snowfall consisting of large tenuous aggregates existed in the nimbostratus clouds at the time of the SSM/I overpass.

Distributions of snow, rain, liquid cloud water, and cloud ice mass were computed from a modified version of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model. That model employed a mixed-phase ice microphysics (MPIM) scheme that only considered one type of frozen hydrometeor. The frozen hydrometeor size distributions, density, and mass flux were modified to match the in situ observations where they were available and to account for the SSM/I observations using radiative transfer theory. Those revised hydrometeor representations were constrained to preserve the vertical hydrometeor mass flux distributions obtained from the MPIM scheme throughout the analysis.

Frozen dense accreted particles were required near the squall line to account for the microwave scattering effect. Snow aggregates, with density that decreased with increasing size, were needed to reproduce the high brightness temperatures observed from the nimbostratus clouds.

Full access
W. J. Williams
,
J. N. Brooks
,
D. G. Murcray
,
F. H. Murcray
,
P. M. Fried
, and
J. A. Weinman

Abstract

Infrared emission spectra were measured in the stratosphere at various altitudes and from various zenith angles by means of a balloon-borne Czerny-Turner spectrometer. The equation of radiative transfer was applied to the radiances measured at 11.2μ to yield a concentration profile of HNO3 vapor. The resulting HNO3 concentration profile was characterized by a negligible concentration below 14 km, a maximum concentration of ∼(1.5±0.5)×1010 molecules cm−3 at ∼(19±5) km, and a diminishing concentration above these altitudes.

Full access
R. W. Spencer
,
W. S. Olson
,
Wu Rongzhang
,
D. W. Martin
,
J. A. Weinman
, and
D. A. Santek

Abstract

In an examination of microwave data from the Nimbus 7 satellite, brightness temperatures were found that were much lower than those expected for the radiation emanating from rain-producing clouds. Every case of very cold brightness temperature coincided with heavy thunderstorm rainfall. The cold temperatures can be attributed to scattering by a layer of ice hydrometeors in the upper parts of the storms. Thus it appears that brightness temperatures observed by satellite microwave radiometers can at times distinguish heavy rain over land.

Full access
J. J. Deluisi
,
P. M. Furukawa
,
D. A. Gillette
,
B. G. Schuster
,
R. J. Charlson
,
W. M. Porch
,
R. W. Fegley
,
B. M. Herman
,
R. A. Rabinoff
,
J. T. Twitty
, and
J. A. Weinman

Abstract

An exploratory field experiment was undertaken to determine the practicality of a method specifically designed to obtain the optical properties of aerosols as they relate to the earth's radiation balance. The method requires a basic set of data consisting of the vertical distribution of aerosol concentrations, size distribution, optical depth, and net radiation fluxes. From these data radiation absorptions are determined, and effective aerosol refractive indices consistent with the actual absorption are deduced through the application of precision radiative transfer calculations. The results of 11 experiment episodes involving a combined aircraft and surface-based measurement system are described. The episodes took place in an arid desert region located near Blythe, California, and in a semiarid agricultural region located near Big Spring, Texas. Part I deals with the physical-numerical depiction of such aerosol properties as optical depth, size distribution, and vertical profiles of concentration. Part II will deal with the analysis of measurements of the radiation field leading to the deduction of the effective aerosol refractive index compatible with the absorption of solar radiation.

Full access
J. J. DeLuisi
,
P. M. Furukawa
,
D. A. Gillette
,
B. G. Schuster
,
R. J. Charlson
,
W. M. Porch
,
R. W. Fegley
,
B. M. Herman
,
R. A. Rabinoff
,
J. T. Twitty
, and
J. A. Weinman

Abstract

The experimental results in Part I are used in the theoretical interpretation of the radiation flux measurements which were taken with an aircraft. The absorption term of the complex refractive index of aerosols is estimated to be approximately 0.01 for a real part of 1.5 for the wavelength bandwidth 0.32–0.68 μm. A regional variation in the refractive index is noted.

Atmospheric heating and cooling rates due to aerosol and molecular absorption in the solar and terrestrial wavelengths are determined from the radiation flux measurements. The magnitudes of these rates are compared and their relative importance is discussed.

Full access

atmospheric sciences and problems of society

A series of statements on the relevance of the scientific and technological areas of AMS STAC Committees to national and international problems

Earl G. Droessler
,
John S. Perry
,
Lance F. Bosart
,
Robert F. Dale
,
Walter A. Lyons
,
Robert E. Dickinson
,
Floyd C. Elder
,
Harold W. Baynton
,
J. A. Weinman
,
V. E. Derr
, and
William R. Bandeen
Full access