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P.B. Russell
,
M.P. McCormick
,
T.J. Swissler
,
W.P. Chu
,
J.M. Livingston
,
W.H. Fuller
,
J.M. Rosen
,
D.J. Hofmann
,
L.R. McMaster
,
D.C. Woods
, and
T.J. Pepin

Abstract

We show results from the first set of measurements conducted to validate extinction data from the satellite sensor SAM II. Dustsonde-measured number density profiles and lidar-measured backscattering profiles for two days are converted to extinction profiles using the optical modeling techniques described in the companion Paper I (Russell et al., 1981). At heights ∼2 km and more above the tropopause, the dustsonde data are used to restrict the range of model size distributions, thus reducing uncertainties in the conversion process. At all heights, measurement uncertainties for each sensor are evaluated, and these are combined with conversion uncertainties to yield the total uncertainty in derived data profiles.

The SAM II measured, dustsonde-inferred, and lidar-inferred extinction profiles for both days are shown to agree within their respective uncertainties at all heights above the tropopause. Near the tropopause, this agreement depends on the use of model size distributions with more relatively large particles (radius ≳0.6 μm) than are present in distributions used to model the main stratospheric aerosol peak. The presence of these relatively large particles is supported by measurements made elsewhere and is suggested by in situ size distribution measurements reported here. These relatively large particles near the tropopause are likely to have an important bearing on the radiative impact of the total stratospheric aerosol.

The agreement in this experiment supports the validity of the SAM II extinction data and the SAM II uncertainty estimates derived from an independent error analysis. Recommendations are given for reducing the uncertainties of future correlative experiments.

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P. B. Russell
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J. Redemann
,
B. Schmid
,
R. W. Bergstrom
,
J. M. Livingston
,
D. M. McIntosh
,
S. A. Ramirez
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S. Hartley
,
P. V. Hobbs
,
P. K. Quinn
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C. M. Carrico
,
M. J. Rood
,
E. Öström
,
K. J. Noone
,
W. von Hoyningen-Huene
, and
L. Remer

Abstract

Aerosol single scattering albedo ω (the ratio of scattering to extinction) is important in determining aerosol climatic effects, in explaining relationships between calculated and measured radiative fluxes, and in retrieving aerosol optical depths from satellite radiances. Recently, two experiments in the North Atlantic region, the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2), determined aerosol ω by a variety of techniques. The techniques included fitting of calculated to measured radiative fluxes; retrievals of ω from skylight radiances; best fits of complex refractive index to profiles of backscatter, extinction, and size distribution; and in situ measurements of scattering and absorption at the surface and aloft. Both TARFOX and ACE-2 found a fairly wide range of values for ω at midvisible wavelengths (∼550 nm), with 0.85 ≤ ω midvis ≤ 0.99 for the marine aerosol impacted by continental pollution. Frequency distributions of ω could usually be approximated by lognormals in ω maxω, with some occurrence of bimodality, suggesting the influence of different aerosol sources or processing. In both TARFOX and ACE-2, closure tests between measured and calculated radiative fluxes yielded best-fit values of ω midvis of 0.90 ± 0.04 for the polluted boundary layer. Although these results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., thermal offsets, unknown gas absorption). The other techniques gave larger values for ω midvis for the polluted boundary layer, with a typical result of ω midvis = 0.95 ± 0.04. Current uncertainties in ω are large in terms of climate effects. More tests are needed of the consistency among different methods and of humidification effects on ω.

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Joseph J. Barsugli
,
David R. Easterling
,
Derek S. Arndt
,
David A. Coates
,
Thomas L. Delworth
,
Martin P. Hoerling
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Nathaniel Johnson
,
Sarah B. Kapnick
,
Arun Kumar
,
Kenneth E. Kunkel
,
Carl J. Schreck
,
Russell S. Vose
, and
Tao Zhang
Open access
Jielun Sun
,
Steven P. Oncley
,
Sean P. Burns
,
Britton B. Stephens
,
Donald H. Lenschow
,
Teresa Campos
,
Russell K. Monson
,
David S. Schimel
,
William J. Sacks
,
Stephan F. J. De Wekker
,
Chun-Ta Lai
,
Brian Lamb
,
Dennis Ojima
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Patrick Z. Ellsworth
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Leonel S. L. Sternberg
,
Sharon Zhong
,
Craig Clements
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David J. P. Moore
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Dean E. Anderson
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Andrew S. Watt
,
Jia Hu
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Mark Tschudi
,
Steven Aulenbach
,
Eugene Allwine
, and
Teresa Coons

A significant fraction of Earth consists of mountainous terrain. However, the question of how to monitor the surface–atmosphere carbon exchange over complex terrain has not been fully explored. This article reports on studies by a team of investigators from U.S. universities and research institutes who carried out a multiscale and multidisciplinary field and modeling investigation of the CO2 exchange between ecosystems and the atmosphere and of CO2 transport over complex mountainous terrain in the Rocky Mountain region of Colorado. The goals of the field campaign, which included ground and airborne in situ and remote-sensing measurements, were to characterize unique features of the local CO2 exchange and to find effective methods to measure regional ecosystem–atmosphere CO2 exchange over complex terrain. The modeling effort included atmospheric and ecological numerical modeling and data assimilation to investigate regional CO2 transport and biological processes involved in ecosystem–atmosphere carbon exchange. In this report, we document our approaches, demonstrate some preliminary results, and discuss principal patterns and conclusions concerning ecosystem–atmosphere carbon exchange over complex terrain and its relation to past studies that have considered these processes over much simpler terrain.

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J. E. Harries
,
J. E. Russell
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J. A. Hanafin
,
H. Brindley
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J. Futyan
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J. Rufus
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S. Kellock
,
G. Matthews
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R. Wrigley
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A. Last
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J. Mueller
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R. Mossavati
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J. Ashmall
,
E. Sawyer
,
D. Parker
,
M. Caldwell
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P M. Allan
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A. Smith
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M. J. Bates
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B. Coan
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B. C. Stewart
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D. R. Lepine
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L. A. Cornwall
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D. R. Corney
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M. J. Ricketts
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D. Drummond
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D. Smart
,
R. Cutler
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S. Dewitte
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N. Clerbaux
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L. Gonzalez
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A. Ipe
,
C. Bertrand
,
A. Joukoff
,
D. Crommelynck
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N. Nelms
,
D. T. Llewellyn-Jones
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G. Butcher
,
G. L. Smith
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Z. P Szewczyk
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P E. Mlynczak
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A. Slingo
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R. P. Allan
, and
M. A. Ringer

This paper reports on a new satellite sensor, the Geostationary Earth Radiation Budget (GERB) experiment. GERB is designed to make the first measurements of the Earth's radiation budget from geostationary orbit. Measurements at high absolute accuracy of the reflected sunlight from the Earth, and the thermal radiation emitted by the Earth are made every 15 min, with a spatial resolution at the subsatellite point of 44.6 km (north–south) by 39.3 km (east–west). With knowledge of the incoming solar constant, this gives the primary forcing and response components of the top-of-atmosphere radiation. The first GERB instrument is an instrument of opportunity on Meteosat-8, a new spin-stabilized spacecraft platform also carrying the Spinning Enhanced Visible and Infrared (SEVIRI) sensor, which is currently positioned over the equator at 3.5°W. This overview of the project includes a description of the instrument design and its preflight and in-flight calibration. An evaluation of the instrument performance after its first year in orbit, including comparisons with data from the Clouds and the Earth's Radiant Energy System (CERES) satellite sensors and with output from numerical models, are also presented. After a brief summary of the data processing system and data products, some of the scientific studies that are being undertaken using these early data are described. This marks the beginning of a decade or more of observations from GERB, as subsequent models will fly on each of the four Meteosat Second Generation satellites.

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Charles O. Stanier
,
R. Bradley Pierce
,
Maryam Abdi-Oskouei
,
Zachariah E. Adelman
,
Jay Al-Saadi
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Hariprasad D. Alwe
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Timothy H. Bertram
,
Gregory R. Carmichael
,
Megan B. Christiansen
,
Patricia A. Cleary
,
Alan C. Czarnetzki
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Angela F. Dickens
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Marta A. Fuoco
,
Dagen D. Hughes
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Joseph P. Hupy
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Scott J. Janz
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Laura M. Judd
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Donna Kenski
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Matthew G. Kowalewski
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Russell W. Long
,
Dylan B. Millet
,
Gordon Novak
,
Behrooz Roozitalab
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Stephanie L. Shaw
,
Elizabeth A. Stone
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James Szykman
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Lukas Valin
,
Michael Vermeuel
,
Timothy J. Wagner
,
Andrew R. Whitehill
, and
David J. Williams

Abstract

The Lake Michigan Ozone Study 2017 (LMOS 2017) was a collaborative multiagency field study targeting ozone chemistry, meteorology, and air quality observations in the southern Lake Michigan area. The primary objective of LMOS 2017 was to provide measurements to improve air quality modeling of the complex meteorological and chemical environment in the region. LMOS 2017 science questions included spatiotemporal assessment of nitrogen oxides (NO x = NO + NO2) and volatile organic compounds (VOC) emission sources and their influence on ozone episodes; the role of lake breezes; contribution of new remote sensing tools such as GeoTASO, Pandora, and TEMPO to air quality management; and evaluation of photochemical grid models. The observing strategy included GeoTASO on board the NASA UC-12 aircraft capturing NO2 and formaldehyde columns, an in situ profiling aircraft, two ground-based coastal enhanced monitoring locations, continuous NO2 columns from coastal Pandora instruments, and an instrumented research vessel. Local photochemical ozone production was observed on 2 June, 9–12 June, and 14–16 June, providing insights on the processes relevant to state and federal air quality management. The LMOS 2017 aircraft mapped significant spatial and temporal variation of NO2 emissions as well as polluted layers with rapid ozone formation occurring in a shallow layer near the Lake Michigan surface. Meteorological characteristics of the lake breeze were observed in detail and measurements of ozone, NOx, nitric acid, hydrogen peroxide, VOC, oxygenated VOC (OVOC), and fine particulate matter (PM2.5) composition were conducted. This article summarizes the study design, directs readers to the campaign data repository, and presents a summary of findings.

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C. P. Weaver
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X.-Z. Liang
,
J. Zhu
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P. J. Adams
,
P. Amar
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J. Avise
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M. Caughey
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J. Chen
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R. C. Cohen
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E. Cooter
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J. P. Dawson
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R. Gilliam
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A. Gilliland
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A. H. Goldstein
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A. Grambsch
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D. Grano
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A. Guenther
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W. I. Gustafson
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R. A. Harley
,
S. He
,
B. Hemming
,
C. Hogrefe
,
H.-C. Huang
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S. W. Hunt
,
D.J. Jacob
,
P. L. Kinney
,
K. Kunkel
,
J.-F. Lamarque
,
B. Lamb
,
N. K. Larkin
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L. R. Leung
,
K.-J. Liao
,
J.-T. Lin
,
B. H. Lynn
,
K. Manomaiphiboon
,
C. Mass
,
D. McKenzie
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L. J. Mickley
,
S. M. O'neill
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C. Nolte
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S. N. Pandis
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P. N. Racherla
,
C. Rosenzweig
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A. G. Russell
,
E. Salathé
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A. L. Steiner
,
E. Tagaris
,
Z. Tao
,
S. Tonse
,
C. Wiedinmyer
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A. Williams
,
D. A. Winner
,
J.-H. Woo
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S. WU
, and
D. J. Wuebbles

This paper provides a synthesis of results that have emerged from recent modeling studies of the potential sensitivity of U.S. regional ozone (O3) concentrations to global climate change (ca. 2050). This research has been carried out under the auspices of an ongoing U.S. Environmental Protection Agency (EPA) assessment effort to increase scientific understanding of the multiple complex interactions among climate, emissions, atmospheric chemistry, and air quality. The ultimate goal is to enhance the ability of air quality managers to consider global change in their decisions through improved characterization of the potential effects of global change on air quality, including O3 The results discussed here are interim, representing the first phase of the EPA assessment. The aim in this first phase was to consider the effects of climate change alone on air quality, without accompanying changes in anthropogenic emissions of precursor pollutants. Across all of the modeling experiments carried out by the different groups, simulated global climate change causes increases of a few to several parts per billion (ppb) in summertime mean maximum daily 8-h average O3 concentrations over substantial regions of the country. The different modeling experiments in general do not, however, simulate the same regional patterns of change. These differences seem to result largely from variations in the simulated patterns of changes in key meteorological drivers, such as temperature and surface insolation. How isoprene nitrate chemistry is represented in the different modeling systems is an additional critical factor in the simulated O3 response to climate change.

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Thomas C. Peterson
,
Richard R. Heim Jr.
,
Robert Hirsch
,
Dale P. Kaiser
,
Harold Brooks
,
Noah S. Diffenbaugh
,
Randall M. Dole
,
Jason P. Giovannettone
,
Kristen Guirguis
,
Thomas R. Karl
,
Richard W. Katz
,
Kenneth Kunkel
,
Dennis Lettenmaier
,
Gregory J. McCabe
,
Christopher J. Paciorek
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Karen R. Ryberg
,
Siegfried Schubert
,
Viviane B. S. Silva
,
Brooke C. Stewart
,
Aldo V. Vecchia
,
Gabriele Villarini
,
Russell S. Vose
,
John Walsh
,
Michael Wehner
,
David Wolock
,
Klaus Wolter
,
Connie A. Woodhouse
, and
Donald Wuebbles

Weather and climate extremes have been varying and changing on many different time scales. In recent decades, heat waves have generally become more frequent across the United States, while cold waves have been decreasing. While this is in keeping with expectations in a warming climate, it turns out that decadal variations in the number of U.S. heat and cold waves do not correlate well with the observed U.S. warming during the last century. Annual peak flow data reveal that river flooding trends on the century scale do not show uniform changes across the country. While flood magnitudes in the Southwest have been decreasing, flood magnitudes in the Northeast and north-central United States have been increasing. Confounding the analysis of trends in river flooding is multiyear and even multidecadal variability likely caused by both large-scale atmospheric circulation changes and basin-scale “memory” in the form of soil moisture. Droughts also have long-term trends as well as multiyear and decadal variability. Instrumental data indicate that the Dust Bowl of the 1930s and the drought in the 1950s were the most significant twentieth-century droughts in the United States, while tree ring data indicate that the megadroughts over the twelfth century exceeded anything in the twentieth century in both spatial extent and duration. The state of knowledge of the factors that cause heat waves, cold waves, floods, and drought to change is fairly good with heat waves being the best understood.

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Bjorn Stevens
,
Donald H. Lenschow
,
Gabor Vali
,
Hermann Gerber
,
A. Bandy
,
B. Blomquist
,
J. -L. Brenguier
,
C. S. Bretherton
,
F. Burnet
,
T. Campos
,
S. Chai
,
I. Faloona
,
D. Friesen
,
S. Haimov
,
K. Laursen
,
D. K. Lilly
,
S. M. Loehrer
,
Szymon P. Malinowski
,
B. Morley
,
M. D. Petters
,
D. C. Rogers
,
L. Russell
,
V. Savic-Jovcic
,
J. R. Snider
,
D. Straub
,
Marcin J. Szumowski
,
H. Takagi
,
D. C. Thornton
,
M. Tschudi
,
C. Twohy
,
M. Wetzel
, and
M. C. van Zanten

The second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study is described. The field program consisted of nine flights in marine stratocumulus west-southwest of San Diego, California. The objective of the program was to better understand the physics a n d dynamics of marine stratocumulus. Toward this end special flight strategies, including predominantly nocturnal flights, were employed to optimize estimates of entrainment velocities at cloud-top, large-scale divergence within the boundary layer, drizzle processes in the cloud, cloud microstructure, and aerosol–cloud interactions. Cloud conditions during DYCOMS-II were excellent with almost every flight having uniformly overcast clouds topping a well-mixed boundary layer. Although the emphasis of the manuscript is on the goals and methodologies of DYCOMS-II, some preliminary findings are also presented—the most significant being that the cloud layers appear to entrain less and drizzle more than previous theoretical work led investigators to expect.

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Masashi Nagata
,
Lance Leslie
,
Yoshio Kurihara
,
Russell L. Elsberry
,
Masanori Yamasaki
,
Hirotaka Kamahori
,
Robert Abbey Jr.
,
Kotaro Bessho
,
Javier Calvo
,
Johnny C. L. Chan
,
Peter Clark
,
Michel Desgagne
,
Song-You Hong
,
Detlev Majewski
,
Piero Malguzzi
,
John McGregor
,
Hiroshi Mino
,
Akihiko Murata
,
Jason Nachamkin
,
Michel Roch
, and
Clive Wilson

The Third Comparison of Mesoscale Prediction and Research Experiment (COMPARE) workshop was held in Tokyo, Japan, on 13–15 December 1999, cosponsored by the Japan Meteorological Agency (JMA), Japan Science and Technology Agency, and the World Meteorological Organization. The third case of COMPARE focuses on an event of explosive tropical cyclone [Typhoon Flo (9019)] development that occurred during the cooperative three field experiments, the Tropical Cyclone Motion experiment 1990, Special Experiment Concerning Recurvature and Unusual Motion, and TYPHOON-90, conducted in the western North Pacific in August and September 1990. Fourteen models from nine countries have participated in at least a part of a set of experiments using a combination of four initial conditions provided and three horizontal resolutions. The resultant forecasts were collected, processed, and verified with analyses and observational data at JMA. Archived datasets have been prepared to be distributed to participating members for use in further evaluation studies.

In the workshop, preliminary conclusions from the evaluation study were presented and discussed in the light of initiatives of the experiment and from the viewpoints of tropical cyclone experts. Initial conditions, depending on both large-scale analyses and vortex bogusing, have a large impact on tropical cyclone intensity predictions. Some models succeeded in predicting the explosive deepening of the target typhoon at least qualitatively in terms of the time evolution of central pressure. Horizontal grid spacing has a very large impact on tropical cyclone intensity prediction, while the impact of vertical resolution is less clear, with some models being very sensitive and others less so. The structure of and processes in the eyewall clouds with subsidence inside as well as boundary layer and moist physical processes are considered important in the explosive development of tropical cyclones. Follow-up research activities in this case were proposed to examine possible working hypotheses related to the explosive development.

New strategies for selection of future COMPARE cases were worked out, including seven suitability requirements to be met by candidate cases. The VORTEX95 case was withdrawn as a candidate, and two other possible cases were presented and discussed.

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