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Guangyu Zhao
and
Larry Di Girolamo

Abstract

The Multiangle Imaging Spectroradiometer (MISR), on board the Earth Observing System (EOS) satellite Terra, is the first high-resolution imager to make global, near-simultaneous multispectral and multiangle radiometric measurements of the earth. A standard product of MISR is the radiometric camera-by-camera cloud mask (RCCM), which provides a cloud mask for each of the nine MISR cameras. Validation of the RCCM is ongoing, and in this paper an automatic and efficient technique is described that is being used to flag scenes for which the quality of the RCCM may be suspect, thus allowing rapid convergence toward validation. The technique, herein called the F θ technique, makes use of the physical relationship that cloudiness increases with viewing obliquity. Where this behavior is not met for a given scene, the F θ technique flags the scene as potentially problematic. The technique is applied to ∼4 months of MISR data to demonstrate its utility and to identify common problems that exist in version F01_0010 of the RCCM. In the course of research into the F θ technique, the existence of greater radiative and spatial contrast between clear and cloudy pixels in oblique views that measure radiation in the forward-scatter direction, as compared with oblique views that measure radiation in the backscatter direction, have been observed. As a result, thinner clouds can be detected in views that measure radiation in the forward-scatter direction as compared with oblique views that measure radiation in the backscatter direction for a given air mass. It is hypothesized that a similar effect must exist with other cloud detection techniques using radiative and spatial measures constructed from solar channels. It is shown that this effect manifests itself as a unique angular signature in the MISR RCCM that may be exploited to flag scenes as potentially being dominated by thin cirrus or a thick haze.

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Robert M. Rauber
,
Guangyu Zhao
,
Larry Di Girolamo
, and
Marilé Colón-Robles

Abstract

This paper examines the effect of trade wind cumulus clouds on aerosol properties in the near-cloud environment using data from the Rain in Cumulus over the Ocean (RICO) campaign. Aerosol size distributions, particle concentrations, and optical properties are examined as a function of altitude and distance from cloud, at ambient relative humidity (RH) and adjusted to a constant RH to isolate effects of humidification from other processes.

The cloud humidity halo extended about 1500–2000 m from the cloud edge, with no clear altitude dependence on horizontal extent over an altitude range of 600–1700 m. The combined effects of vertical transport of aerosol by clouds and cloud processing contributed to the modification of aerosol size distributions within the clouds' humidity halos, particularly close to the cloud boundaries. Backscatter at 532 nm, calculated from the aerosol properties, exhibited no distinguishable trend with altitude within 400 m of cloud edges, increased toward lower altitudes beyond 400 m, and decreased away from cloud boundaries at all altitudes. The mean aerosol diameter was found to rapidly decline from 0.8 to 0.4 μm from near the cloud boundary to the boundary of the humidity halo. Aerosol optical depth at 532 nm within the layer between 600 and 1700 m increased near exponentially from 0.02 to 0.2 toward the cloud boundaries within the humidity halo. These trends agreed qualitatively with past space-based lidar measurements of trade wind cloud margins, although quantitative differences were noted that likely arose from different sampling strategies and other factors.

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Guang-Yu Shi
,
Tadahiro Hayasaka
,
Atsumu Ohmura
,
Zhi-Hua Chen
,
Biao Wang
,
Jian-Qi Zhao
,
Hui-Zheng Che
, and
Li Xu

Abstract

Solar radiation is one of the most important factors affecting climate and the environment. Routine measurements of irradiance are valuable for climate change research because of long time series and areal coverage. In this study, a set of quality assessment (QA) algorithms is used to test the quality of daily solar global, direct, and diffuse radiation measurements taken at 122 observatories in China during 1957–2000. The QA algorithms include a physical threshold test (QA1), a global radiation sunshine duration test (QA2), and a standard deviation test applied to time series of annually averaged solar global radiation (QA3). The results show that the percentages of global, direct, and diffuse solar radiation data that fail to pass QA1 are 3.07%, 0.01%, and 2.52%, respectively; the percentages of global solar radiation data that fail to pass the QA2 and QA3 are 0.77% and 0.49%, respectively. The method implemented by the Global Energy Balance Archive is also applied to check the data quality of solar radiation in China. Of the 84 stations with a time series longer that 20 yr, suspect data at 35 of the sites were found. Based on data that passed the QA tests, trends in ground solar radiation and the effect of the data quality assessment on the trends are analyzed. There is a decrease in ground solar global and direct radiation in China over the years under study. Although the quality assessment process has significant effects on the data from individual stations and/or time periods, it does not affect the long-term trends in the data.

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Robert J. H. Dunn
,
F. Aldred
,
Nadine Gobron
,
John B. Miller
,
Kate M. Willett
,
M. Ades
,
Robert Adler
,
Richard, P. Allan
,
Rob Allan
,
J. Anderson
,
Anthony Argüez
,
C. Arosio
,
John A. Augustine
,
C. Azorin-Molina
,
J. Barichivich
,
H. E. Beck
,
Andreas Becker
,
Nicolas Bellouin
,
Angela Benedetti
,
David I. Berry
,
Stephen Blenkinsop
,
Olivier Bock
,
X. Bodin
,
Michael G. Bosilovich
,
Olivier Boucher
,
S. A. Buehler
,
B. Calmettes
,
Laura Carrea
,
Laura Castia
,
Hanne H. Christiansen
,
John R. Christy
,
E.-S. Chung
,
Melanie Coldewey-Egbers
,
Owen R. Cooper
,
Richard C. Cornes
,
Curt Covey
,
J.-F. Cretaux
,
M. Crotwell
,
Sean M. Davis
,
Richard A. M. de Jeu
,
Doug Degenstein
,
R. Delaloye
,
Larry Di Girolamo
,
Markus G. Donat
,
Wouter A. Dorigo
,
Imke Durre
,
Geoff S. Dutton
,
Gregory Duveiller
,
James W. Elkins
,
Vitali E. Fioletov
,
Johannes Flemming
,
Michael J. Foster
,
Stacey M. Frith
,
Lucien Froidevaux
,
J. Garforth
,
Matthew Gentry
,
S. K. Gupta
,
S. Hahn
,
Leopold Haimberger
,
Brad D. Hall
,
Ian Harris
,
D. L. Hemming
,
M. Hirschi
,
Shu-pen (Ben) Ho
,
F. Hrbacek
,
Daan Hubert
,
Dale F. Hurst
,
Antje Inness
,
K. Isaksen
,
Viju O. John
,
Philip D. Jones
,
Robert Junod
,
J. W. Kaiser
,
V. Kaufmann
,
A. Kellerer-Pirklbauer
,
Elizabeth C. Kent
,
R. Kidd
,
Hyungjun Kim
,
Z. Kipling
,
A. Koppa
,
B. M. Kraemer
,
D. P. Kratz
,
Xin Lan
,
Kathleen O. Lantz
,
D. Lavers
,
Norman G. Loeb
,
Diego Loyola
,
R. Madelon
,
Michael Mayer
,
M. F. McCabe
,
Tim R. McVicar
,
Carl A. Mears
,
Christopher J. Merchant
,
Diego G. Miralles
,
L. Moesinger
,
Stephen A. Montzka
,
Colin Morice
,
L. Mösinger
,
Jens Mühle
,
Julien P. Nicolas
,
Jeannette Noetzli
,
Ben Noll
,
J. O’Keefe
,
Tim J. Osborn
,
T. Park
,
A. J. Pasik
,
C. Pellet
,
Maury S. Pelto
,
S. E. Perkins-Kirkpatrick
,
G. Petron
,
Coda Phillips
,
S. Po-Chedley
,
L. Polvani
,
W. Preimesberger
,
D. G. Rains
,
W. J. Randel
,
Nick A. Rayner
,
Samuel Rémy
,
L. Ricciardulli
,
A. D. Richardson
,
David A. Robinson
,
Matthew Rodell
,
N. J. Rodríguez-Fernández
,
K.H. Rosenlof
,
C. Roth
,
A. Rozanov
,
T. Rutishäuser
,
Ahira Sánchez-Lugo
,
P. Sawaengphokhai
,
T. Scanlon
,
Verena Schenzinger
,
R. W. Schlegel
,
S. Sharma
,
Lei Shi
,
Adrian J. Simmons
,
Carolina Siso
,
Sharon L. Smith
,
B. J. Soden
,
Viktoria Sofieva
,
T. H. Sparks
,
Paul W. Stackhouse Jr.
,
Wolfgang Steinbrecht
,
Martin Stengel
,
Dimitri A. Streletskiy
,
Sunny Sun-Mack
,
P. Tans
,
S. J. Thackeray
,
E. Thibert
,
D. Tokuda
,
Kleareti Tourpali
,
Mari R. Tye
,
Ronald van der A
,
Robin van der Schalie
,
Gerard van der Schrier
,
M. van der Vliet
,
Guido R. van der Werf
,
A. Vance
,
Jean-Paul Vernier
,
Isaac J. Vimont
,
Holger Vömel
,
Russell S. Vose
,
Ray Wang
,
Markus Weber
,
David Wiese
,
Anne C. Wilber
,
Jeanette D. Wild
,
Takmeng Wong
,
R. Iestyn Woolway
,
Xinjia Zhou
,
Xungang Yin
,
Guangyu Zhao
,
Lin Zhao
,
Jerry R. Ziemke
,
Markus Ziese
, and
R. M. Zotta
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