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  • Author or Editor: J.C. Wilson x
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J. T. Schaefer
,
F. P. Ostby
,
C. A. Doswell III
,
L. R. Lemon
,
R. P. McNulty
,
S. J. Weiss
, and
L. F. Wilson
Full access
D. H. Bromwich
,
A. B. Wilson
,
L. Bai
,
Z. Liu
,
M. Barlage
,
C.-F. Shih
,
S. Maldonado
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K. M. Hines
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S.-H. Wang
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J. Woollen
,
B. Kuo
,
H.-C. Lin
,
T.-K. Wee
,
M. C. Serreze
, and
J. E. Walsh

Abstract

The Arctic is a vital component of the global climate, and its rapid environmental evolution is an important element of climate change around the world. To detect and diagnose the changes occurring to the coupled Arctic climate system, a state-of-the-art synthesis for assessment and monitoring is imperative. This paper presents the Arctic System Reanalysis, version 2 (ASRv2), a multiagency, university-led retrospective analysis (reanalysis) of the greater Arctic region using blends of the polar-optimized version of the Weather Research and Forecasting (Polar WRF) Model and WRF three-dimensional variational data assimilated observations for a comprehensive integration of the regional climate of the Arctic for 2000–12. New features in ASRv2 compared to version 1 (ASRv1) include 1) higher-resolution depiction in space (15-km horizontal resolution), 2) updated model physics including subgrid-scale cloud fraction interaction with radiation, and 3) a dual outer-loop routine for more accurate data assimilation. ASRv2 surface and pressure-level products are available at 3-hourly and monthly mean time scales at the National Center for Atmospheric Research (NCAR). Analysis of ASRv2 reveals superior reproduction of near-surface and tropospheric variables. Broadscale analysis of forecast precipitation and site-specific comparisons of downward radiative fluxes demonstrate significant improvement over ASRv1. The high-resolution topography and land surface, including weekly updated vegetation and realistic sea ice fraction, sea ice thickness, and snow-cover depth on sea ice, resolve finescale processes such as topographically forced winds. Thus, ASRv2 permits a reconstruction of the rapid change in the Arctic since the beginning of the twenty-first century–complementing global reanalyses. ASRv2 products will be useful for environmental models, verification of regional processes, or siting of future observation networks.

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S. Kalluri
,
C. Barnet
,
M. Divakarla
,
R. Esmaili
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N. Nalli
,
K. Pryor
,
T. Reale
,
N. Smith
,
C. Tan
,
T. Wang
,
J. Warner
,
M. Wilson
,
L. Zhou
, and
T. Zhu

Abstract

Infrared and microwave sounder measurements from polar-orbiting satellites are used to retrieve profiles of temperature, water vapor, and trace gases utilizing a suite of algorithms called the National Oceanic and Atmospheric Administration (NOAA) Unique Combined Atmospheric Processing System (NUCAPS). Meteorologists operationally use the retrievals similar to radiosonde measurements to assess atmospheric stability and aid them in issuing forecasts and severe weather warnings. Measurements of trace gases by NUCAPS enable detection, tracking, and monitoring of greenhouse gases and emissions from fires that impact air quality. During the polar winters, when ultraviolet measurements of ozone are not possible, absorption features in the infrared spectrum of the sounders enable the assessment of ozone concentration in the stratosphere. These retrievals are used as inputs to monitor the ozone hole over Antarctica. This article illustrates the utility of NUCAPS atmospheric profile retrievals in assessing meteorological events using several examples of severe thunderstorms, tropical cyclones, fires, and ozone maps.

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René Garreaud
,
M Ralph
,
A Wilson
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A M Ramos
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J Eiras-Barca
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H C Steen-Larsen
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J Rutz
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C Albano
,
N Tilinina
,
M Warner
,
M Viale
,
R Rondanelli
,
J McPhee
,
R Valenzuela
, and
I Gorodetskaya
Full access
B. W. Golding
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S. P. Ballard
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K. Mylne
,
N. Roberts
,
A. Saulter
,
C. Wilson
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P. Agnew
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L. S. Davis
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J. Trice
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C. Jones
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D. Simonin
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Z. Li
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C. Pierce
,
A. Bennett
,
M. Weeks
, and
S. Moseley

The provision of weather forecasts for the London Olympic and Paralympic Games in 2012 offered the opportunity for the Met Office to accelerate the transition to operations of several advanced numerical modeling capabilities and to demonstrate their performance to external scientists. It was also an event that captured public interest, providing an opportunity to educate and build trust in the weather forecasting enterprise in the United Kingdom and beyond. The baseline NWP guidance for the duration of the Olympic Games came from three main configurations of the Met Office Unified Model: global 25-km deterministic, North Atlantic/Europe 18-km ensemble, and U.K. 1.5-km deterministic. The advanced capabilities demonstrated during the Olympic Games consisted of a rapid-update hourly cycle of a 1.5-km grid length configuration for the southern United Kingdom using four-dimensional variational data assimilation (4D-Var) and enhanced observations; a 2.2-km grid length U.K. ensemble; a 333-m grid length configuration of the Unified Model and 250-m configuration of the Simulating Waves Nearshore (SWAN) ocean wave model for Weymouth Bay; and a 12-km grid length configuration of Air Quality in the Unified Model with prognostic aerosols and chemistry. Despite their different levels of maturity, each of the new capabilities provided useful additional guidance to Met Office weather advisors, contributing to an outstanding service to the Olympic Games organizers and the public. The website provided layered access to information about the science and to selected real-time products, substantially raising the profile of Met Office weather forecasting research among the United Kingdom and overseas public.

Full access
M. Wendisch
,
H. Coe
,
D. Baumgardner
,
J.-L. Brenguier
,
V. Dreiling
,
M. Fiebig
,
P. Formenti
,
M. Hermann
,
M. Krämer
,
Z. Levin
,
R. Maser
,
E. Mathieu
,
P. Nacass
,
K. Noone
,
S. Osborne
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J. Schneider
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L. Schütz
,
A. Schwarzenböck
,
F. Stratmann
, and
J. C. Wilson

Aircraft inlets connect airborne instruments for particle microphysical and chemical measurements with the ambient atmosphere. These inlets may bias the measurements due to their potential to enhance or remove certain particle size fractions in the sample. The aircraft body itself may disturb the ambient air streamlines and, hence, the particle sampling. Also, anisokinetic sampling and transmission losses within the sampling lines may cause the sampled aerosol to differ from the ambient aerosol. In addition, inlets may change the particle composition and size through the evaporation of water and other volatile materials due to compressibility effects or heat transfer. These problems have been discussed at an international workshop that was held at the Leibniz-Institute for Tropospheric Research (IfT) in Leipzig, Germany, on 12–13 April 2002. The discussions, conclusions, and recommendations from this workshop are summarized here.

Full access
M. Wendisch
,
H. Coe
,
D. Baumgardner
,
J.-L. Brenguier
,
V. Dreiling
,
M. Fiebig
,
P. Formenti
,
M. Hermann
,
M. Krämer
,
Z. Levin
,
R. Maser
,
E. Mathieu
,
P. Nacass
,
K. Noone
,
S. Osborne
,
J. Schneider
,
L. Schütz
,
A. Schwarzenböck
,
F. Stratmann
, and
J. C. Wilson

Aircraft inlets connect airborne instruments for particle microphysical and chemical measurements with the ambient atmosphere. These inlets may bias the measurements due to their potential to enhance or remove certain particle size fractions in the sample. The aircraft body itself may disturb the ambient air streamlines and, hence, the particle sampling. Also, anisokinetic sampling and transmission losses within the sampling lines may cause the sampled aerosol to differ from the ambient aerosol. In addition, inlets may change the particle composition and size through the evaporation of water and other volatile materials due to compressibility effects or heat transfer. These problems have been discussed at an international workshop that was held at the Leibniz-Institute for Tropospheric Research (IfT) in Leipzig, Germany, on 12–13 April 2002. The discussions, conclusions, and recommendations from this workshop are summarized here.

Full access
Steven M. Martinaitis
,
Katie A. Wilson
,
Nusrat Yussouf
,
Jonathan J. Gourley
,
Humberto Vergara
,
Tiffany C. Meyer
,
Pamela L. Heinselman
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Alan Gerard
,
Kodi L. Berry
,
Andres Vergara
, and
Justin Monroe

Abstract

There are ongoing efforts to move beyond the current paradigm of using deterministic products driven by observation-only data to make binary warning decisions. Recent works have focused on severe thunderstorm hazards, such as hail, lightning, and tornadoes. This study discusses one of the first steps toward having probabilistic information combined with convective-scale short-term precipitation forecasts available for the prediction and warning of flash flooding. Participants in the Hydrometeorology Testbed–MRMS Hydrology (HMT-Hydro) experiment evaluated several probabilistic-based hydrologic model output from the probabilistic Flooded Locations and Simulated Hydrographs (PRO-FLASH) system during experimental real-time warning operations. Evaluation of flash flood warning performance combined with product surveys highlighted how forecasters perceived biases within the probabilistic information and how the different probabilistic approaches influenced warnings that were verified versus those that were unverified. The incorporation of the Warn-on-Forecast System (WoFS) ensemble precipitation forecasts into the PRO-FLASH product generation provided an opportunity to evaluate the first coupling of subhourly convective-scale ensemble precipitation forecasts with probabilistic hydrologic modeling at the flash flood warning time scale through archived case simulations. The addition of WoFS precipitation forecasts resulted in an increase in warning lead time, including four events with ≥29 min of additional lead time but with increased probabilities of false alarms. Additional feedback from participants provided insights into the application of WoFS forecasts into warning decisions, including how flash flood expectations and confidence evolved for verified flash flood events and how forecast probabilistic products can positively influence the communications of the potential for flash flooding.

Open access
T. Keenan
,
P. Joe
,
J. Wilson
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C. Collier
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B. Golding
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D. Burgess
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P. May
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C. Pierce
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J. Bally
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A. Crook
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A. Seed
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D. Sills
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L. Berry
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R. Potts
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I. Bell
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N. Fox
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E. Ebert
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M. Eilts
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K. O'Loughlin
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R. Webb
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R. Carbone
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K. Browning
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R. Roberts
, and
C. Mueller

The first World Weather Research Programme (WWRP) Forecast Demonstration Project (FDP), with a focus on nowcasting, was conducted in Sydney, Australia, from 4 September to 21 November 2000 during a period associated with the Sydney 2000 Olympic Games. Through international collaboration, nine nowcasting systems from the United States, United Kingdom, Canada, and Australia were deployed at the Sydney Office of the Bureau of Meteorology (BOM) to demonstrate the capability of modern forecast systems and to quantify the associated benefits in the delivery of a real-time nowcast service. On-going verification and impact studies supported by international committees assisted by the WWRP formed an integral part of this project. A description is given of the project, including component systems, the weather, and initial outcomes. Initial results show that the nowcasting systems tested were transferable and able to provide valuable information enhancing BOM nowcasts. The project provided for unprecedented interchange of concepts and ideas between forecasters, researchers, and end users in an operational framework where they all faced common issues relevant to real time nowcast decision making. A training workshop sponsored by the World Meteorological Organization (WMO) was also held in conjunction with the project so that other member nations could benefit from the FDP.

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Cloudnet

Continuous Evaluation of Cloud Profiles in Seven Operational Models Using Ground-Based Observations

A. J. Illingworth
,
R. J. Hogan
,
E.J. O'Connor
,
D. Bouniol
,
M. E. Brooks
,
J. Delanoé
,
D. P. Donovan
,
J. D. Eastment
,
N. Gaussiat
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J. W. F. Goddard
,
M. Haeffelin
,
H. Klein Baltink
,
O. A. Krasnov
,
J. Pelon
,
J.-M. Piriou
,
A. Protat
,
H. W. J. Russchenberg
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A. Seifert
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A. M. Tompkins
,
G.-J. van Zadelhoff
,
F. Vinit
,
U. Willén
,
D. R. Wilson
, and
C. L. Wrench

The Cloudnet project aims to provide a systematic evaluation of clouds in forecast and climate models by comparing the model output with continuous ground-based observations of the vertical profiles of cloud properties. In the models, the properties of clouds are simplified and expressed in terms of the fraction of the model grid box, which is filled with cloud, together with the liquid and ice water content of the clouds. These models must get the clouds right if they are to correctly represent both their radiative properties and their key role in the production of precipitation, but there are few observations of the vertical profiles of the cloud properties that show whether or not they are successful. Cloud profiles derived from cloud radars, ceilometers, and dual-frequency microwave radiometers operated at three sites in France, Netherlands, and the United Kingdom for several years have been compared with the clouds in seven European models. The advantage of this continuous appraisal is that the feedback on how new versions of models are performing is provided in quasi-real time, as opposed to the much longer time scale needed for in-depth analysis of complex field studies. Here, two occasions are identified when the introduction of new versions of the ECMWF and Météo-France models leads to an immediate improvement in the representation of the clouds and also provides statistics on the performance of the seven models. The Cloudnet analysis scheme is currently being expanded to include sites outside Europe and further operational forecasting and climate models.

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