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D. M. Rodgers
,
K. W. Howard
, and
E. C. Johnston

Abstract

An important class of convective weather system, the mesoscale convective complex (MCC), presents many challenges and problems to both the research and operational communities. In addition, thew very large and long-lived thunderstorm systems have a significant social and economic impact resulting from associated severe weather phenomena and widespread beneficial rain. Enhanced infrared satellite images were surveyed to document MCCs which occurred over the United States during 1982. Thirty-seven convective mesosystems were identified that displayed satellite-observable characteristics which satisfied the MCC criteria described by Maddox. Details of the life cycles of the 37 cases are given and several specific cases are discussed. Current and proposed future research will focus on what are perceived to be key questions surrounding these important weather systems. This annual summary is offered as a starting point for scientists interested in pursuing studies of mesoscale convective weather systems.

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R. A. Maddox
,
D. M. Rodgers
, and
K. W. Howard

Abstract

Satellite images are used to document the life cycles of Mesoscale Convective Complexes (MCCs) which occurred over the United States during the warm season months of 1981. These systems were found to exhibit characteristics similar to aspects of MCCs discussed recently in the literature; however, the behavior of several of the convective systems poses questions that can only be answered through detailed studies. The systems did produce a variety of significant weather events ranging from severe thunderstorms to locally heavy rains and flooding. Information is also provided for a number of other significant mesoscale convective systems that, although they did not meet the stringent MCC definition criteria, caught the investigators' attention. This documentation should provide a useful starting point for scientists who might wish to pursue studies of mesoscale convective weather systems.

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Robin J. Hogan
,
Mark D. Fielding
,
Howard W. Barker
,
Najda Villefranque
, and
Sophia A. K. Schäfer

Abstract

Several mechanisms have previously been proposed to explain differences between the shortwave reflectance of realistic cloud scenes computed using the 1D independent column approximation (ICA) and 3D solutions of the radiative transfer equation. When the sun is low in the sky, interception of sunlight by cloud sides tends to increase reflectance relative to ICA estimates that neglect this effect. When the sun is high, 3D radiative transfer tends to make clouds less reflective, which we argue is explained by the mechanism of “entrapment” whereby horizontal transport of radiation beneath a cloud layer increases the chances, relative to the ICA, of light being absorbed by cloud or the surface. It is especially important for multilayered cloud scenes. We describe modifications to the previously described Speedy Algorithm for Radiative Transfer through Cloud Sides (SPARTACUS) to represent different entrapment assumptions, and test their impact on 65 contrasting scenes from a cloud-resolving model. When entrapment is represented explicitly via a calculation of the mean horizontal distance traveled by reflected light, SPARTACUS predicts a mean “3D radiative effect” (the difference in top-of-atmosphere irradiances between 3D and ICA calculations) of 8.1 W m−2 for overhead sun. This is within 2% of broadband Monte Carlo calculations on the same scenes. The importance of entrapment is highlighted by the finding that the extreme assumptions in SPARTACUS of “zero entrapment” and “maximum entrapment” lead to corresponding mean 3D radiative effects of 1.7 and 19.6 W m−2, respectively.

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R. A. Maddox
,
D. S. Zaras
,
P. L. MacKeen
,
J. J. Gourley
,
R. Rabin
, and
K. W. Howard

Abstract

The new Doppler radars of the National Weather Service (i.e., the WSR-88D radars) are operated continuously in a volume scanning mode (called Volume Coverage Pattern, VCP) with the elevation tilt angles fixed for several VCPs. Because of the fixed VCPs, the radar data can be used to determine the heights of precipitation echo features only to limits of accuracy that depend upon the elevation angles used in the VCP, the radar beamwidth, and the range of echoes. Data from adjacent WSR-88D radars, if used simultaneously, could reduce significantly the height uncertainties inherent in single radar measurements. This is illustrated for idealized situations and also for an event involving a long-lived, tornadic thunderstorm. The use of coordinated scan strategies and combined data analysis procedures for adjacent WSR-88D radars during significant thunderstorm events should be considered for operational applications.

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Phillip B. Chilson
,
Winifred F. Frick
,
Jeffrey F. Kelly
,
Kenneth W. Howard
,
Ronald P. Larkin
,
Robert H. Diehl
,
John K. Westbrook
,
T. Adam Kelly
, and
Thomas H. Kunz

Aeroecology is an emerging scientific discipline that integrates atmospheric science, Earth science, geography, ecology, computer science, computational biology, and engineering to further the understanding of biological patterns and processes. The unifying concept underlying this new transdisciplinary field of study is a focus on the planetary boundary layer and lower free atmosphere (i.e., the aerosphere), and the diversity of airborne organisms that inhabit and depend on the aerosphere for their existence. Here, we focus on the role of radars and radar networks in aeroecological studies. Radar systems scanning the atmosphere are primarily used to monitor weather conditions and track the location and movements of aircraft. However, radar echoes regularly contain signals from other sources, such as airborne birds, bats, and arthropods. We briefly discuss how radar observations can be and have been used to study a variety of airborne organisms and examine some of the many potential benefits likely to arise from radar aeroecology for meteorological and biological research over a wide range of spatial and temporal scales. Radar systems are becoming increasingly sophisticated with the advent of innovative signal processing and dual-polarimetric capabilities. These capabilities should be better harnessed to promote both meteorological and aeroecological research and to explore the interface between these two broad disciplines. We strongly encourage close collaboration among meteorologists, radar scientists, biologists, and others toward developing radar products that will contribute to a better understanding of airborne fauna.

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Zachary B. Wienhoff
,
Howard B. Bluestein
,
Louis J. Wicker
,
Jeffrey C. Snyder
,
Alan Shapiro
,
Corey K. Potvin
,
Jana B. Houser
, and
Dylan W. Reif

Abstract

In many instances, synchronization of Doppler radar data among multiple platforms for multiple-Doppler analysis is challenging. This study describes the production of dual-Doppler wind analyses from several case studies using data from a rapid-scanning, X-band, polarimetric, Doppler radar—the RaXPol radar—and data from nearby WSR-88Ds. Of particular interest is mitigating difficulties related to the drastic differences in scanning rates of the two radars. To account for differences in temporal resolution, a variational reflectivity tracking scheme [a spatially variable advection correction technique (SVAC)] has been employed to interpolate (in a Lagrangian sense) the coarser temporal resolution data (WSR-88D) to the times of the RaXPol volume scans. The RaXPol data and temporally interpolated WSR-88D data are then used to create quasi–rapid scan dual-Doppler analyses. This study focuses on the application of the SVAC technique to WSR-88D data to create dual-Doppler analyses of three tornadic supercells: the 19 May 2013 Edmond–Carney and Norman–Shawnee, Oklahoma, storms and the 24 May 2016 Dodge City, Kansas, storm. Results of the dual-Doppler analyses are briefly examined, including observations of the Z DR columns as a proxy for updrafts. Potential improvements to this technique are also discussed.

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S. Chen
,
P. E. Kirstetter
,
Y. Hong
,
J. J. Gourley
,
Y. D. Tian
,
Y. C. Qi
,
Q. Cao
,
J. Zhang
,
K. Howard
,
J. J. Hu
, and
X. W. Xue

Abstract

In this paper, the authors estimate the uncertainty of the rainfall products from NASA and Japan Aerospace Exploration Agency's (JAXA) Tropical Rainfall Measurement Mission (TRMM) Precipitation Radar (PR) so that they may be used in a quantitative manner for applications like hydrologic modeling or merging with other rainfall products. The spatial error structure of TRMM PR surface rain rates and types was systematically studied by comparing them with NOAA/National Severe Storms Laboratory's (NSSL) next generation, high-resolution (1 km/5 min) National Mosaic and Multi-Sensor Quantitative Precipitation Estimation (QPE; NMQ/Q2) over the TRMM-covered continental United States (CONUS). Data pairs are first matched at the PR footprint scale (5 km/instantaneous) and then grouped into 0.25° grid cells to yield spatially distributed error maps and statistics using data from December 2009 through November 2010. Careful quality control steps (including bias correction with rain gauges and quality filtering) are applied to the ground radar measurements prior to considering them as reference data. The results show that PR captures well the spatial pattern of total rainfall amounts with a high correlation coefficient (CC; 0.91) with Q2, but this decreases to 0.56 for instantaneous rain rates. In terms of precipitation types, Q2 and PR convective echoes are spatially correlated with a CC of 0.63. Despite this correlation, PR's total annual precipitation from convection is 48.82% less than that by Q2, which points to potential issues in the PR algorithm's attenuation correction, nonuniform beam filling, and/or reflectivity-to-rainfall relation. Finally, the spatial analysis identifies regime-dependent errors, in particular in the mountainous west. It is likely that the surface reference technique is triggered over complex terrain, resulting in high-amplitude biases.

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Robert F. Cahalan
,
Lazaros Oreopoulos
,
Alexander Marshak
,
K. Franklin Evans
,
Anthony B. Davis
,
Robert Pincus
,
Ken H. Yetzer
,
Bernhard Mayer
,
Roger Davies
,
Thomas P. Ackerman
,
Howard W. Barker
,
Eugene E. Clothiaux
,
Robert G. Ellingson
,
Michael J. Garay
,
Evgueni Kassianov
,
Stefan Kinne
,
Andreas Macke
,
William O'hirok
,
Philip T. Partain
,
Sergei M. Prigarin
,
Alexei N. Rublev
,
Graeme L. Stephens
,
Frederic Szczap
,
Ezra E. Takara
,
Tamas Várnai
,
Guoyong Wen
, and
Tatiana B. Zhuravleva

The interaction of clouds with solar and terrestrial radiation is one of the most important topics of climate research. In recent years it has been recognized that only a full three-dimensional (3D) treatment of this interaction can provide answers to many climate and remote sensing problems, leading to the worldwide development of numerous 3D radiative transfer (RT) codes. The international Intercomparison of 3D Radiation Codes (I3RC), described in this paper, sprung from the natural need to compare the performance of these 3D RT codes used in a variety of current scientific work in the atmospheric sciences. I3RC supports intercomparison and development of both exact and approximate 3D methods in its effort to 1) understand and document the errors/limits of 3D algorithms and their sources; 2) provide “baseline” cases for future code development for 3D radiation; 3) promote sharing and production of 3D radiative tools; 4) derive guidelines for 3D radiative tool selection; and 5) improve atmospheric science education in 3D RT. Results from the two completed phases of I3RC have been presented in two workshops and are expected to guide improvements in both remote sensing and radiative energy budget calculations in cloudy atmospheres.

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J. K. Andersen
,
Liss M. Andreassen
,
Emily H. Baker
,
Thomas J. Ballinger
,
Logan T. Berner
,
Germar H. Bernhard
,
Uma S. Bhatt
,
Jarle W. Bjerke
,
Jason E. Box
,
L. Britt
,
R. Brown
,
David Burgess
,
John Cappelen
,
Hanne H. Christiansen
,
B. Decharme
,
C. Derksen
,
D. S. Drozdov
,
Howard E. Epstein
,
L. M. Farquharson
,
Sinead L. Farrell
,
Robert S. Fausto
,
Xavier Fettweis
,
Vitali E. Fioletov
,
Bruce C. Forbes
,
Gerald V. Frost
,
Sebastian Gerland
,
Scott J. Goetz
,
Jens-Uwe Grooß
,
Edward Hanna
,
Inger Hanssen-Bauer
,
Stefan Hendricks
,
Iolanda Ialongo
,
K. Isaksen
,
Bjørn Johnsen
,
L. Kaleschke
,
A. L. Kholodov
,
Seong-Joong Kim
,
Jack Kohler
,
Zachary Labe
,
Carol Ladd
,
Kaisa Lakkala
,
Mark J. Lara
,
Bryant Loomis
,
Bartłomiej Luks
,
K. Luojus
,
Matthew J. Macander
,
G. V. Malkova
,
Kenneth D. Mankoff
,
Gloria L. Manney
,
J. M. Marsh
,
Walt Meier
,
Twila A. Moon
,
Thomas Mote
,
L. Mudryk
,
F. J. Mueter
,
Rolf Müller
,
K. E. Nyland
,
Shad O’Neel
,
James E. Overland
,
Don Perovich
,
Gareth K. Phoenix
,
Martha K. Raynolds
,
C. H. Reijmer
,
Robert Ricker
,
Vladimir E. Romanovsky
,
E. A. G. Schuur
,
Martin Sharp
,
Nikolai I. Shiklomanov
,
C. J. P. P. Smeets
,
Sharon L. Smith
,
Dimitri A. Streletskiy
,
Marco Tedesco
,
Richard L. Thoman
,
J. T. Thorson
,
X. Tian-Kunze
,
Mary-Louise Timmermans
,
Hans Tømmervik
,
Mark Tschudi
,
Dirk van As
,
R. S. W. van de Wal
,
Donald A. Walker
,
John E. Walsh
,
Muyin Wang
,
Melinda Webster
,
Øyvind Winton
,
Gabriel J. Wolken
,
K. Wood
,
Bert Wouters
, and
S. Zador
Free access
Howard J. Diamond
,
Carl J. Schreck III
,
Emily J. Becker
,
Gerald D. Bell
,
Eric S. Blake
,
Stephanie Bond
,
Francis G. Bringas
,
Suzana J. Camargo
,
Lin Chen
,
Caio A. S. Coelho
,
Ricardo Domingues
,
Stanley B. Goldenberg
,
Gustavo Goni
,
Nicolas Fauchereau
,
Michael S. Halpert
,
Qiong He
,
Philip J. Klotzbach
,
John A. Knaff
,
Michelle L'Heureux
,
Chris W. Landsea
,
I.-I. Lin
,
Andrew M. Lorrey
,
Jing-Jia Luo
,
Kyle MacRitchie
,
Andrew D. Magee
,
Ben Noll
,
Richard J. Pasch
,
Alexandre B. Pezza
,
Matthew Rosencrans
,
Michael K. Tippet
,
Blair C. Trewin
,
Ryan E. Truchelut
,
Bin Wang
,
Hui Wang
,
Kimberly M. Wood
,
John-Mark Woolley
, and
Steven H. Young
Free access