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Don Cline
,
Simon Yueh
,
Bruce Chapman
,
Boba Stankov
,
Al Gasiewski
,
Dallas Masters
,
Kelly Elder
,
Richard Kelly
,
Thomas H. Painter
,
Steve Miller
,
Steve Katzberg
, and
Larry Mahrt

Abstract

This paper describes the airborne data collected during the 2002 and 2003 Cold Land Processes Experiment (CLPX). These data include gamma radiation observations, multi- and hyperspectral optical imaging, optical altimetry, and passive and active microwave observations of the test areas. The gamma observations were collected with the NOAA/National Weather Service Gamma Radiation Detection System (GAMMA). The CLPX multispectral optical data consist of very high-resolution color-infrared orthoimagery of the intensive study areas (ISAs) by TerrainVision. The airborne hyperspectral optical data consist of observations from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Optical altimetry measurements were collected using airborne light detection and ranging (lidar) by TerrainVision. The active microwave data include radar observations from the NASA Airborne Synthetic Aperture Radar (AIRSAR), the Jet Propulsion Laboratory’s Polarimetric Ku-band Scatterometer (POLSCAT), and airborne GPS bistatic radar data collected with the NASA GPS radar delay mapping receiver (DMR). The passive microwave data consist of observations collected with the NOAA Polarimetric Scanning Radiometer (PSR). All of the airborne datasets described here and more information describing data collection and processing are available online.

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Steve Keighton
,
Douglas K. Miller
,
David Hotz
,
Patrick D. Moore
,
L. Baker Perry
,
Laurence G. Lee
, and
Daniel T. Martin

Abstract

In late October 2012, Hurricane Sandy tracked along the eastern U.S. coastline and made landfall over New Jersey after turning sharply northwest and becoming posttropical while interacting with a complex upper-level low pressure system that had brought cold air into the Appalachian region. The cold air, intensified by the extreme low pressure tracking just north of the region, combined with deep moisture and topographically enhanced ascent to produce an unusual and high-impact early season northwest flow snow (NWFS) that has no analog in recent history. This paper investigates the importance of the synoptic-scale pattern, forcing mechanisms, moisture characteristics (content, depth, and likely sources), and low-level winds, as well as the evolution of some of these features compared to more typical NWFS events in the southern Appalachian Mountains. Several other aspects of the Sandy snowfall event are investigated, including low-level stability and mountain wave formation as manifested in vertical profiles and radar observations. The importance to operational forecasters of recognizing and understanding these factors and differences from more common NWFS events is also discussed.

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Michael F. Donovan
,
Earle R. Williams
,
Cathy Kessinger
,
Gary Blackburn
,
Paul H. Herzegh
,
Richard L. Bankert
,
Steve Miller
, and
Frederick R. Mosher

Abstract

Three algorithms based on geostationary visible and infrared (IR) observations are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The performance of these algorithms in detecting potentially hazardous cells is determined through verification with Tropical Rainfall Measuring Mission (TRMM) satellite observations of lightning and radar reflectivity, which provide internal information about the convective cells. The probability of detection of hazardous cells using the satellite algorithms can exceed 90% when lightning is used as a criterion for hazard, but the false-alarm ratio with all three algorithms is consistently large (∼40%), thereby exaggerating the presence of hazardous conditions. This shortcoming results in part from the algorithms’ dependence upon visible and IR observations, and can be traced to the widespread prevalence of deep cumulonimbi with weak updrafts but without lightning over tropical oceans, whose origin is attributed to significant entrainment during ascent.

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Thomas E. Lee
,
Steven D. Miller
,
F. Joseph Turk
,
Carl Schueler
,
Richard Julian
,
Steve Deyo
,
Patrick Dills
, and
Sherwood Wang

The National Polar-orbiting Operational Environmental Satellite System (NPOESS) will feature the Visible-Infrared Imager-Radiometer Suite (VIIRS), a 22-channel imager that will contribute to nearly half of the NPOESS environmental data records. Included on VIIRS will be the Day/Night band (DNB), a visible channel designed to image the Earth and its atmosphere in all conditions ranging from bright solar illumination, to nocturnal lunar illumination, and negligible external illumination. Drawing heritage from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) instruments orbiting since the late 1960s, the DNB will be used to detect clouds at night, understand patterns of urban development based on the emissions of cities, monitor fires, and image scenes of snow and ice at the surface of the Earth. Thanks to significant engineering improvements, the DNB will produce superior capabilities to the OLS for a number of new applications.

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Steve Keighton
,
Laurence Lee
,
Blair Holloway
,
David Hotz
,
Steven Zubrick
,
Jeffrey Hovis
,
Gary Votaw
,
L. Baker Perry
,
Gary Lackmann
,
Sandra E. Yuter
,
Charles Konrad
,
Douglas Miller
, and
Brian Etherton

Upslope-enhanced snowfall events during periods of northwesterly flow in the southern Appalachians have been recognized as a significant winter forecasting problem for some time. However, only in recent years has this problem received noteworthy attention by both the academic and operational communities. The complex meteorology of these events includes significant topographic influences, as well as a linkage between the upstream Great Lakes and resultant southern Appalachian snowfall. A unique collaborative team has recently formed, working toward the goals of improving the physical understanding of the mechanisms at work in these events and developing more accurate forecasts and more detailed climatologies. The literature shows only limited attention to this problem through the 1990s. However, with modernization of the National Weather Service (NWS) in the mid-1990s came opportunities to bring more attention to new or poorly understood forecast problems. These opportunities included the establishment of new forecast offices, often collocated with universities, the deployment of the Weather Surveillance Radar-1988 Doppler (WSR-88D) network, expansion of the surface observational network in both space and time, improved access to sophisticated numerical models, and growth of the spotter and cooperative observer networks.

A collaborative team, consisting of faculty from five universities and meteorologists from six NWS forecast offices, has established an ongoing, structured dialogue to help advance the understanding and improve the forecasting of these events. The team utilizes a variety of communication strategies to discuss emerging research findings, review recent events, and share data and ideas. The ultimate goal is to continue fostering working relationships among research and operational meteorologists, climatologists, and students, all with a common motivation of continually improving forecasts and understanding of this important phenomenon. This group may serve as a model for other collaborative efforts between the research and operational communities interested in a common forecast problem.

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John R. Gyakum
,
Marco Carrera
,
Da-Lin Zhang
,
Steve Miller
,
James Caveen
,
Robert Benoit
,
Thomas Black
,
Andrea Buzzi
,
Cliément Chouinard
,
M. Fantini
,
C. Folloni
,
Jack J. Katzfey
,
Ying-Hwa Kuo
,
François Lalaurette
,
Simon Low-Nam
,
Jocelyn Mailhot
,
P. Malguzzi
,
John L. McGregor
,
Masaomi Nakamura
,
Greg Tripoli
, and
Clive Wilson

Abstract

The authors evaluate the performance of current regional models in an intercomparison project for a case of explosive secondary marine cyclogenesis occurring during the Canadian Atlantic Storms Project and the Genesis of Atlantic Lows Experiment of 1986. Several systematic errors are found that have been identified in the refereed literature in prior years. There is a high (low) sea level pressure bias and a cold (warm) tropospheric temperature error in the oceanic (continental) regions. Though individual model participants produce central pressures of the secondary cyclone close to the observed during the final stages of its life cycle, systematically weak systems are simulated during the critical early stages of the cyclogenesis. Additionally, the simulations produce an excessively weak (strong) continental anticyclone (cyclone); implications of these errors are discussed in terms of the secondary cyclogenesis. Little relationship between strong performance in predicting the mass field and skill in predicting a measurable amount of precipitation is found. The bias scores in the precipitation study indicate a tendency for all models to overforecast precipitation. Results for the measurable threshold (0.2 mm) indicate the largest gain in precipitation scores results from increasing the horizontal resolution from 100 to 50 km, with a negligible benefit occurring as a consequence of increasing the resolution from 50 to 25 km. The importance of a horizontal resolution increase from 100 to 50 km is also generally shown for the errors in the mass field. However, little improvement in the prediction of the cyclogenesis is found by increasing the horizontal resolution from 50 to 25 km.

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