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  • Author or Editor: David H. Bromwich x
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David H. Bromwich

Prominent warm signatures of strong, negatively buoyant, katabatic airstreams are present at thermal infrared wavelengths as a result of intense vertical mixing and drift-snow transport within stable boundary layers. These tracers are used to illustrate several aspects of the behavior of katabatic winds in the Ross Sea sector of the Antarctic. The satellite features are compared with surface-based observations whenever possible. Converging surface-wind signatures upslope from Terra Nova Bay are shown to closely follow the observed time-averaged streamlines of drainage airflow. The satellite-observed core of the katabatic airstream descends to sea level via a direct route, but complex three-dimensional trajectories are manifested in marginal regions. Katabatic winds propagating horizontally for hundreds of kilometers over the southwestern Ross Sea do not exhibit the expected influence of the Coriolis force. Katabatic signatures are shown to be climatological features over the Ross Ice Shelf which closely follow surface wind measurements. An approximate proportionality appears to exist between average signature size over the shelf and the magnitude of katabatic mass transport from the plateau.

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Andrew J. Monaghan
and
David H. Bromwich

Antarctica is a challenging region for conducting meteorological research because of its geographic isolation, climate extremes, vastness, and lack of permanent human inhabitants. About 15 observing stations have been in continuous operation since the onset of the modern scientific era in Antarctica during the International Geophysical Year in 1957/58. Identifying and attributing natural- and human-caused climate change signals from the comparatively short Antarctic dataset is confounded by large year-to-year fluctuations of temperature, atmospheric pressure, and snowfall. Yet there is increasing urgency to understand Antarctica's role in the global climate system for a number of reasons, most importantly the potential consequences of ice-mass loss on global sea level rise. Here, we describe recently-created records that allow Antarctic near-surface temperature and snowfall changes to be assessed in all of Antarctica's 24 glacial drainage systems during the past five decades. The new near-surface temperature and snowfall records roughly double the length of previous such datasets, which have complete spatial coverage over the continent. They indicate complex patterns of regional and seasonal climate variability. Of particular note is the occurrence of widespread positive temperature trends during summer since the 1990s, the season when melt occurs. In forthcoming years, careful monitoring of the summer trends will be required to determine whether they are associated with a natural cycle or the start of an anthropogenic warming trend. Key questions are raised during the International Polar Year.

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Jordan G. Powers
,
Kevin W. Manning
,
David H. Bromwich
,
John J. Cassano
, and
Arthur M. Cayette

The Antarctic Mesoscale Prediction System (AMPS) is a real-time numerical weather prediction (NWP) system covering Antarctica that has served a remarkable range of groups and activities for a decade. It employs the Weather Research and Forecasting model (WRF) on varying-resolution grids to generate numerical guidance in a variety of tailored products. While its priority mission has been to support the forecasters of the U.S. Antarctic Program, AMPS has evolved to assist a host of scientific and logistical needs for an international user base. The AMPS effort has advanced polar NWP and Antarctic science and looks to continue this into another decade. To inform those with Antarctic scientific and logistical interests and needs, the history, applications, and capabilities of AMPS are discussed.

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Jordan G. Powers
,
Andrew J. Monaghan
,
Arthur M. Cayette
,
David H. Bromwich
,
Ying-Hwa Kuo
, and
Kevin W. Manning

In support of the United States Antarctic Program (USAP), the National Center for Atmospheric Research and the Byrd Polar Research Center of The Ohio State University have created the Antarctic Mesoscale Prediction System (AMPS): an experimental, real-time mesoscale modeling system covering Antarctica. AMPS has been designed to serve flight forecasters at McMurdo Station, to support science and operations around the continent, and to be a vehicle for the development of physical parameterizations suitable for polar regions. Since 2000, AMPS has been producing high-resolution forecasts (grids to 3.3 km) with the “Polar MM5,” a version of the fifth-generation Pennsylvania State University-NCAR Mesoscale Model tuned for the polar atmosphere. Beyond its basic mission of serving the USAP flight forecasters at McMurdo, AMPS has assisted both in emergency operations to save lives and in programs to explore the extreme polar environment. The former have included a medical evacuation from the South Pole and a marine rescue from the continental margin. The latter have included scientific field campaigns and the daily activities of international Antarctic forecasters and researchers. The AMPS program has been a success in terms of advancing polar mesoscale NWP, serving critical logistical operations of the USAP, and, most visibly, assisting in emergency rescue missions to save lives. The history and performance of AMPS are described and the successes of this unique real-time mesoscale modeling system in crisis support are detailed.

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Márcio Rocha Francelino
,
Carlos Schaefer
,
Maria de Los Milagros Skansi
,
Steve Colwell
,
David H. Bromwich
,
Phil Jones
,
John C. King
,
Matthew A. Lazzara
,
James Renwick
,
Susan Solomon
,
Manola Brunet
, and
Randall S. Cerveny

ABSTRACT

Two reports of Antarctic region potential new record high temperature observations (18.3°C, 6 February 2020 at Esperanza station and 20.8°C, 9 February 2020 at a Brazilian automated permafrost monitoring station on Seymour Island) were evaluated by a World Meteorological Organization (WMO) panel of atmospheric scientists. The latter figure was reported as 20.75°C in the media. The panel considered the synoptic situation and instrumental setups. It determined that a large high pressure system over the area created föhn conditions and resulted in local warming for both situations. Examination of the data and metadata of the Esperanza station observation revealed no major concerns. However, analysis of data and metadata of the Seymour Island permafrost monitoring station indicated that an improvised radiation shield led to a demonstrable thermal bias error for the temperature sensor. Consequently, the WMO has accepted the 18.3°C value for 1200 LST 6 February 2020 (1500 UTC 6 February 2020) at the Argentine Esperanza station as the new “Antarctic region (continental, including mainland and surrounding islands) highest temperature recorded observation” but rejected the 20.8°C observation at the Brazilian automated Seymour Island permafrost monitoring station as biased. The committee strongly emphasizes the permafrost monitoring station was not badly designed for its purpose, but the project investigators were forced to improvise a nonoptimal radiation shield after losing the original covering. Second, with regard to media dissemination of this type of information, the committee urges increased caution in early announcements as many media outlets often tend to sensationalize and mischaracterize potential records.

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Helge F. Goessling
,
Thomas Jung
,
Stefanie Klebe
,
Jenny Baeseman
,
Peter Bauer
,
Peter Chen
,
Matthieu Chevallier
,
Randall Dole
,
Neil Gordon
,
Paolo Ruti
,
Alice Bradley
,
David H. Bromwich
,
Barbara Casati
,
Dmitry Chechin
,
Jonathan J. Day
,
François Massonnet
,
Brian Mills
,
Ian Renfrew
,
Gregory Smith
, and
Renee Tatusko
Full access
Dan Lubin
,
Damao Zhang
,
Israel Silber
,
Ryan C. Scott
,
Petros Kalogeras
,
Alessandro Battaglia
,
David H. Bromwich
,
Maria Cadeddu
,
Edwin Eloranta
,
Ann Fridlind
,
Amanda Frossard
,
Keith M. Hines
,
Stefan Kneifel
,
W. Richard Leaitch
,
Wuyin Lin
,
Julien Nicolas
,
Heath Powers
,
Patricia K. Quinn
,
Penny Rowe
,
Lynn M. Russell
,
Sangeeta Sharma
,
Johannes Verlinde
, and
Andrew M. Vogelmann

Abstract

The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) performed comprehensive meteorological and aerosol measurements and ground-based atmospheric remote sensing at two Antarctic stations using the most advanced instrumentation available. A suite of cloud research radars, lidars, spectral and broadband radiometers, aerosol chemical and microphysical sampling equipment, and meteorological instrumentation was deployed at McMurdo Station on Ross Island from December 2015 through December 2016. A smaller suite of radiometers and meteorological equipment, including radiosondes optimized for surface energy budget measurement, was deployed on the West Antarctic Ice Sheet between 4 December 2015 and 17 January 2016. AWARE provided Antarctic atmospheric data comparable to several well-instrumented high Arctic sites that have operated for many years and that reveal numerous contrasts with the Arctic in aerosol and cloud microphysical properties. These include persistent differences in liquid cloud occurrence, cloud height, and cloud thickness. Antarctic aerosol properties are also quite different from the Arctic in both seasonal cycle and composition, due to the continent’s isolation from lower latitudes by Southern Ocean storm tracks. Antarctic aerosol number and mass concentrations are not only non-negligible but perhaps play a more important role than previously recognized because of the higher sensitivities of clouds at the very low concentrations caused by the large-scale dynamical isolation. Antarctic aerosol chemical composition, particularly organic components, has implications for local cloud microphysics. The AWARE dataset, fully available online in the ARM Program data archive, offers numerous case studies for unique and rigorous evaluation of mixed-phase cloud parameterization in climate models.

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Dan Lubin
,
Damao Zhang
,
Israel Silber
,
Ryan C. Scott
,
Petros Kalogeras
,
Alessandro Battaglia
,
David H. Bromwich
,
Maria Cadeddu
,
Edwin Eloranta
,
Ann Fridlind
,
Amanda Frossard
,
Keith M. Hines
,
Stefan Kneifel
,
W. Richard Leaitch
,
Wuyin Lin
,
Julien Nicolas
,
Heath Powers
,
Patricia K. Quinn
,
Penny Rowe
,
Lynn M. Russell
,
Sangeeta Sharma
,
Johannes Verlinde
, and
Andrew M. Vogelmann
Full access
Thomas Jung
,
Neil D. Gordon
,
Peter Bauer
,
David H. Bromwich
,
Matthieu Chevallier
,
Jonathan J. Day
,
Jackie Dawson
,
Francisco Doblas-Reyes
,
Christopher Fairall
,
Helge F. Goessling
,
Marika Holland
,
Jun Inoue
,
Trond Iversen
,
Stefanie Klebe
,
Peter Lemke
,
Martin Losch
,
Alexander Makshtas
,
Brian Mills
,
Pertti Nurmi
,
Donald Perovich
,
Philip Reid
,
Ian A. Renfrew
,
Gregory Smith
,
Gunilla Svensson
,
Mikhail Tolstykh
, and
Qinghua Yang

Abstract

The polar regions have been attracting more and more attention in recent years, fueled by the perceptible impacts of anthropogenic climate change. Polar climate change provides new opportunities, such as shorter shipping routes between Europe and East Asia, but also new risks such as the potential for industrial accidents or emergencies in ice-covered seas. Here, it is argued that environmental prediction systems for the polar regions are less developed than elsewhere. There are many reasons for this situation, including the polar regions being (historically) lower priority, with fewer in situ observations, and with numerous local physical processes that are less well represented by models. By contrasting the relative importance of different physical processes in polar and lower latitudes, the need for a dedicated polar prediction effort is illustrated. Research priorities are identified that will help to advance environmental polar prediction capabilities. Examples include an improvement of the polar observing system; the use of coupled atmosphere–sea ice–ocean models, even for short-term prediction; and insight into polar–lower-latitude linkages and their role for forecasting. Given the enormity of some of the challenges ahead, in a harsh and remote environment such as the polar regions, it is argued that rapid progress will only be possible with a coordinated international effort. More specifically, it is proposed to hold a Year of Polar Prediction (YOPP) from mid-2017 to mid-2019 in which the international research and operational forecasting communites will work together with stakeholders in a period of intensive observing, modeling, prediction, verification, user engagement, and educational activities.

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William L. Smith Jr.
,
Christy Hansen
,
Anthony Bucholtz
,
Bruce E. Anderson
,
Matthew Beckley
,
Joseph G. Corbett
,
Richard I. Cullather
,
Keith M. Hines
,
Michelle Hofton
,
Seiji Kato
,
Dan Lubin
,
Richard H. Moore
,
Michal Segal Rosenhaimer
,
Jens Redemann
,
Sebastian Schmidt
,
Ryan Scott
,
Shi Song
,
John D. Barrick
,
J. Bryan Blair
,
David H. Bromwich
,
Colleen Brooks
,
Gao Chen
,
Helen Cornejo
,
Chelsea A. Corr
,
Seung-Hee Ham
,
A. Scott Kittelman
,
Scott Knappmiller
,
Samuel LeBlanc
,
Norman G. Loeb
,
Colin Miller
,
Louis Nguyen
,
Rabindra Palikonda
,
David Rabine
,
Elizabeth A. Reid
,
Jacqueline A. Richter-Menge
,
Peter Pilewskie
,
Yohei Shinozuka
,
Douglas Spangenberg
,
Paul Stackhouse
,
Patrick Taylor
,
K. Lee Thornhill
,
David van Gilst
, and
Edward Winstead

Abstract

The National Aeronautics and Space Administration (NASA)’s Arctic Radiation-IceBridge Sea and Ice Experiment (ARISE) acquired unique aircraft data on atmospheric radiation and sea ice properties during the critical late summer to autumn sea ice minimum and commencement of refreezing. The C-130 aircraft flew 15 missions over the Beaufort Sea between 4 and 24 September 2014. ARISE deployed a shortwave and longwave broadband radiometer (BBR) system from the Naval Research Laboratory; a Solar Spectral Flux Radiometer (SSFR) from the University of Colorado Boulder; the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) from the NASA Ames Research Center; cloud microprobes from the NASA Langley Research Center; and the Land, Vegetation and Ice Sensor (LVIS) laser altimeter system from the NASA Goddard Space Flight Center. These instruments sampled the radiant energy exchange between clouds and a variety of sea ice scenarios, including prior to and after refreezing began. The most critical and unique aspect of ARISE mission planning was to coordinate the flight tracks with NASA Cloud and the Earth’s Radiant Energy System (CERES) satellite sensor observations in such a way that satellite sensor angular dependence models and derived top-of-atmosphere fluxes could be validated against the aircraft data over large gridbox domains of order 100–200 km. This was accomplished over open ocean, over the marginal ice zone (MIZ), and over a region of heavy sea ice concentration, in cloudy and clear skies. ARISE data will be valuable to the community for providing better interpretation of satellite energy budget measurements in the Arctic and for process studies involving ice–cloud–atmosphere energy exchange during the sea ice transition period.

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