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F. Köpp
,
R. L. Schwiesow
, and
Ch Werner

Abstract

We have demonstrated practical measurement of profiles of horizontal wind magnitude and direction to altitudes of 750 m by making radial velocity measurements with a Doppler lidar using conical scanning. Comparison with surface anemometers and with profiles measured by balloon sondes allows one to evaluate the consistency between lidar measurements and more conventional sensors. Overall we find a correlation coefficient of 0.83 and an rms difference of 1.3 m s−1 for magnitude and a correlation coefficient of 0.91 and an rms difference of 12° for direction when the lidar and sonde profiles are compared. The differences are not a result of lidar errors because comparisons of 20 s averages between the lidar and a sonic anemometer show a correlation coefficient of 0.98, an rms difference of 0.19 m s−1, and a long-term average difference of 0.05 m s−1 for a single component. Profile differences are attributable to horizontal inhomogeneity in the wind field and uncertainty inherent in balloon sondes. Impaired visibility reduces the effective range of the lidar, and the vertical extent of the lidar sample region increases with height.s

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G. S. Kent
,
F. Köpp
, and
Ch Werner

Abstract

Remote sensing of the lower atmosphere by lidar yields profiles of the backscattering cross section along the optical path. These may be simply converted to give a qualitative picture of the distribution of atmospheric aerosol, but quantitative values can only be obtained if further information is available on aerosol properties such as refractive index and size distribution. In the experiments described below, use was made of a solar radiometer to give information on the second of these. This is then used to calculate an improved value for the ratio of backscattering to aerosol mass (β/m) for the interpretation of the lidar data. Comparison is made of the results of radiometer measurements, taken at a rural area outside Munich, with airborne lidar measurements of the tropospheric aerosol made in the same locality. Aerosol density profiles obtained in another flight made near Augsburg on 22 July 1977 show the presence of a heavy aerosol concentration over the city and the effects of the north wind are clearly visible.

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M. R. Hjelmfelt
,
R. D. Roberts
,
H. D. Orville
,
J. P. Chen
, and
F. J. Kopp

Abstract

An analysis is performed on a microburst line-producing cloud that occurred near Denver, Colorado on 13 July 1982. The cloud line developed in an environment conducive to the production of low-reflectivity microbursts. Doppler radar analysis revealed strong convergence above cloud base into the region of downdraft 3.5 to 4.5 km above ground. Aircraft measurements detected light rain with graupel aloft in microburst downdrafts. A two-dimensional cloud model simulation captured many of the observed features of the cloud line structure and wind fields. In particular, both the development of multiple microbursts and the convergence aloft were well simulated. The formation of graupel/hail was important to the precipitation process in the model. The loading of rain and graupel and the cooling effect of rain evaporation and graupel melting were all important in microburst production—the graupel in the formative stages of the downdraft, and the rain in the further intensification of the downdraft and enhancement of the microburst outflow.

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John D. Tuttle
,
V. N. Bringi
,
H. D. Orville
, and
F. J. Kopp

Abstract

Radar observations and model results are used to investigate the microphysical evolution of an isolated, intense storm observed on 20 July during the Microburst and Severe Thunderstorm (MIST) experiment. The storm grew to a height of 14 km and upon collapsing, produced heavy rain, pea-sized hail, and a microburst at the surface. The storm was observed by three Doppler radars and one of the radars was equipped to collect differential reflectivity (Z DR) and dual-frequency measurements. The radar observations indicate that the initial precipitation development was by collision-coalescence. Later, as the storm intensified, accretional growth became dominant leading to rapid precipitation development. Radar-derived rainfall rates peaked around 150 to 190 mm h−1. The microburst developed as the precipitation core descended to the surface and was likely initiated by a combination of mass loading and cooling due to melting.

Each morning during the experiment, a two-dimensional, time-dependent cloud model, initialized with the morning sounding, was run. This provided the unique opportunity to predict the day's convection before it actually began. The model results from the 20 July sounding are compared to the radar observations. Good agreement is shown in some aspects of the storm development, although the numerical simulation predicted a more vigorous storm than actually developed.

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Keith D. Hutchison
,
Robert L. Mahoney
,
Eric F. Vermote
,
Thomas J. Kopp
,
John M. Jackson
,
Alain Sei
, and
Barbara D. Iisager

Abstract

A geometry-based approach is presented to identify cloud shadows using an automated cloud classification algorithm developed for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. These new procedures exploit both the cloud confidence and cloud phase intermediate products generated by the Visible/Infrared Imager/Radiometer Suite (VIIRS) cloud mask (VCM) algorithm. The procedures have been tested and found to accurately detect cloud shadows in global datasets collected by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensor and are applied over both land and ocean background conditions. These new procedures represent a marked departure from those used in the heritage MODIS cloud mask algorithm, which utilizes spectral signatures in an attempt to identify cloud shadows. However, they more closely follow those developed to identify cloud shadows in the MODIS Surface Reflectance (MOD09) data product. Significant differences were necessary in the implementation of the MOD09 procedures to meet NPOESS latency requirements in the VCM algorithm. In this paper, the geometry-based approach used to predict cloud shadows is presented, differences are highlighted between the heritage MOD09 algorithm and new VIIRS cloud shadow algorithm, and results are shown for both these algorithms plus cloud shadows generated by the spectral-based approach. The comparisons show that the geometry-based procedures produce cloud shadows far superior to those predicted with the spectral procedures. In addition, the new VCM procedures predict cloud shadows that agree well with those found in the MOD09 product while significantly reducing the execution time as required to meet the operational time constraints of the NPOESS system.

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C. M. Roithmayr
,
C. Lukashin
,
P. W. Speth
,
D. F. Young
,
B. A. Wielicki
,
K. J. Thome
, and
G. Kopp

Abstract

Highly accurate measurements of Earth’s thermal infrared and reflected solar radiation are required for detecting and predicting long-term climate change. Consideration is given to the concept of using the International Space Station to test instruments and techniques that would eventually be used on a dedicated mission, such as the Climate Absolute Radiance and Refractivity Observatory (CLARREO). In particular, a quantitative investigation is performed to determine whether it is possible to use measurements obtained with a highly accurate (0.3%, with 95% confidence) reflected solar radiation spectrometer to calibrate similar, less accurate instruments in other low Earth orbits. Estimates of numbers of samples useful for intercalibration are made with the aid of yearlong simulations of orbital motion. Results of this study support the conclusion that the International Space Station orbit is ideally suited for the purpose of intercalibration between spaceborne sensors.

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C. M. Roithmayr
,
C. Lukashin
,
P. W. Speth
,
D. F. Young
,
B. A. Wielicki
,
K. J. Thome
, and
G. Kopp
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Michael I. Mishchenko
,
Brian Cairns
,
Greg Kopp
,
Carl F. Schueler
,
Bryan A. Fafaul
,
James E. Hansen
,
Ronald J. Hooker
,
Tom Itchkawich
,
Hal B. Maring
, and
Larry D. Travis

The NASA Glory mission is intended to facilitate and improve upon long-term monitoring of two key forcings influencing global climate. One of the mission's principal objectives is to determine the global distribution of detailed aerosol and cloud properties with unprecedented accuracy, thereby facilitating the quantification of the aerosol direct and indirect radiative forcings. The other is to continue the 28-yr record of satellite-based measurements of total solar irradiance from which the effect of solar variability on the Earth's climate is quantified. These objectives will be met by flying two state-of-the-art science instruments on an Earth-orbiting platform. Based on a proven technique demonstrated with an aircraft-based prototype, the Aerosol Polarimetry Sensor (APS) will collect accurate multiangle photopolarimetric measurements of the Earth along the satellite ground track within a wide spectral range extending from the visible to the shortwave infrared. The Total Irradiance Monitor (TIM) is an improved version of an instrument currently flying on the Solar Radiation and Climate Experiment (SORCE) and will provide accurate and precise measurements of spectrally integrated sunlight illuminating the Earth. Because Glory is expected to fly as part of the A-Train constellation of Earth-orbiting spacecraft, the APS data will also be used to improve retrievals of aerosol climate forcing parameters and global aerosol assessments with other A-Train instruments. In this paper, we detail the scientific rationale and objectives of the Glory mission, explain how these scientific objectives dictate the specific measurement strategy, describe how the measurement strategy will be implemented by the APS and TIM, and briefly outline the overall structure of the mission. It is expected that the Glory results will be used extensively by members of the climate, solar, atmospheric, oceanic, and environmental research communities as well as in education and outreach activities.

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Bruce A. Wielicki
,
D. F. Young
,
M. G. Mlynczak
,
K. J. Thome
,
S. Leroy
,
J. Corliss
,
J. G. Anderson
,
C. O. Ao
,
R. Bantges
,
F. Best
,
K. Bowman
,
H. Brindley
,
J. J. Butler
,
W. Collins
,
J. A. Dykema
,
D. R. Doelling
,
D. R. Feldman
,
N. Fox
,
X. Huang
,
R. Holz
,
Y. Huang
,
Z. Jin
,
D. Jennings
,
D. G. Johnson
,
K. Jucks
,
S. Kato
,
D. B. Kirk-Davidoff
,
R. Knuteson
,
G. Kopp
,
D. P. Kratz
,
X. Liu
,
C. Lukashin
,
A. J. Mannucci
,
N. Phojanamongkolkij
,
P. Pilewskie
,
V. Ramaswamy
,
H. Revercomb
,
J. Rice
,
Y. Roberts
,
C. M. Roithmayr
,
F. Rose
,
S. Sandford
,
E. L. Shirley
,
Sr. W. L. Smith
,
B. Soden
,
P. W. Speth
,
W. Sun
,
P. C. Taylor
,
D. Tobin
, and
X. Xiong

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5–50 μm), the spectrum of solar radiation reflected by the Earth and its atmosphere (320–2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a “NIST [National Institute of Standards and Technology] in orbit.” CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

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