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F. M. Ralph
,
P. J. Neiman
,
D. W. van de Kamp
, and
D. C. Law

A brief description is given of NOAA's 404-MHz Wind Profiler Demonstration Network (WPDN), including the radar configuration, sampling strategy, site locations and characteristics, and a discussion of the Doppler power spectrum and its first three spectral moments: signal power (S), radial velocity (Vr ), and velocity variance (σ 2). Evidence is presented showing that 6-min time resolution spectral moment data from the vertically pointing beam of a WPDN wind profiler can be used to identify when precipitation is present above the profiler. Signatures of snow, light and moderate stratiform rain, heavy convective rain, freezing rain, and snow within jet stream cirrus are illustrated and summarized. Although radar reflectivity factor (Z) cannot be determined from WPDN wind profilers, the precipitation rates and fall speeds shown to be observable in the cases documented here are roughly consistent with earlier studies suggesting that precipitation with Z > 0–15 dBZ should typically be observable at 404 MHz, and that precipitation or clouds with Z < 0 dBZ should not be readily distinguishable from clear-air echoes. General signatures common to most precipitation, and characteristics in the data that allow different types of precipitation to be distinguished from one another, are revealed from three case studies. The most useful indicators of stratiform rain are downward Vr > 3–5 m s−1 and σ 2 > 1.0 m2 s−2. Snow is indicated by 2m s−1 > Vr > 0.5–0.9 ms−1 and σ 2< 1.0m2 s−2. Evidence of a melting level in S, Vr , and σ 2 is a very good indicator of stratiform precipitation, and when absent helps identify precipitation as convective when S and σ 2 are large. Because the spectral moment data are regularly archived, this information can be examined in real time and compared with simultaneously measured wind profiles. Such information should be useful in both research and operational meteorology. The ability to infer relationships between precipitation and kinematic features evident in the observed winds is also illustrated.

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K. P. Moran
,
D. B. Wuertz
,
R. G. Strauch
,
N. L. Abshire
, and
D. C. Law

Abstract

A network of 31 radar wind profilers is being installed in the central United States by the National Oceanic and Atmospheric Administration (NOAA). The radars are expected to measure the vertical profile of horizontal and vertical wind starting at 500 m above the surface (AGL) and extending to about 16 km AGL. These 404.37-MHz radars can also be adapted to measure virtual temperature profiles in the lower troposphere by the radio acoustic sounding system (RASS) technique. RASS experiments were conducted using the prototype radar of the NOAA network, and results showed that virtual temperature profiles can be measured starting at 500 m AGL (the lowest height observed with this radar) and extending to 3.5–5.2 km AGL.

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B. L. Weber
,
D. B. Wuertz
,
D. C. Law
,
A. S. Frisch
, and
J. M. Brown

Abstract

Vertical velocities were observed during the month of June 1990 with two side-by-side wind profilers at Platteville, Colorado. Many of the observations reveal strong wave motion, probably mountain lee waves, that sometimes caused vertical velocity changes of several meters per second in less than an hour. It is demonstrated that, under these conditions, hourly averages cannot always be used to accurately account for the effects of vertical motion on the profiler measurements. It is also shown that it is impossible to accurately remove the effects of vertical motion from the horizontal wind component estimates when the horizontal scale of vertical-motion variability is comparable to the horizontal separation distance between antenna beams. The Radio Acoustic Sounding System (RASS) temperature measurements, however, are not affected by the small spatial scales because those measurements are made on the same vertical antenna beam as the vertical velocity measurements. Nevertheless, it is important that these temperature measurements be made simultaneously with vertical velocity measurements so that valid vertical velocity corrections can be made.

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D. C. Law
,
S. A. McLaughlin
,
M. J. Post
,
B. L. Weber
,
D. C. Welsh
,
D. E. Wolfe
, and
D. A. Merritt

Abstract

The design, construction, and first results are presented of a 915-MHz Doppler wind profiler that may be mounted on a moving platform such as a mobile land vehicle, ocean buoy, or a ship. The long dwell times in multiple beam directions, required for the detection of weak atmospheric radar echoes, are obtained by a passive phased array antenna, controlled by a motion control and monitoring (MCM) computer that acquires platform motion measurements and compensates in real time for the platform rotations. The platform translational velocities are accounted for in the signal processing system (SPS) before the calculation of the wind velocity profiles. The phased array antenna, MCM, and SPS are described, and radar-derived wind profiles are compared with those from rawinsonde balloons released during the first test cruise of the system, as the NOAA R/V Ronald H. Brown performed ship maneuvers.

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R. J. Alvarez II
,
C. J. Senff
,
A. O. Langford
,
A. M. Weickmann
,
D. C. Law
,
J. L. Machol
,
D. A. Merritt
,
R. D. Marchbanks
,
S. P. Sandberg
,
W. A. Brewer
,
R. M. Hardesty
, and
R. M. Banta

Abstract

The National Oceanic and Atmospheric Administration/Earth System Research Laboratory/Chemical Sciences Division (NOAA/ESRL/CSD) has developed a versatile, airborne lidar system for measuring ozone and aerosols in the boundary layer and lower free troposphere. The Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) lidar was deployed aboard a NOAA Twin Otter aircraft during the Texas Air Quality Study (TexAQS 2006) and the California Research at the Nexus of Air Quality and Climate Change (CalNex 2010) field campaigns. TOPAZ is capable of measuring ozone concentrations in the lower troposphere with uncertainties of several parts per billion by volume at 90-m vertical and 600-m horizontal resolution from an aircraft flying at 60 m s−1. The system also provides uncalibrated aerosol backscatter profiles at 18-m vertical and 600-m horizontal resolution. TOPAZ incorporates state-of-the-art technologies, including a cerium-doped lithium calcium aluminum fluoride (Ce:LiCAF) laser, to make it compact and lightweight with low power consumption. The tunable, three-wavelength UV laser source makes it possible to optimize the wavelengths for differing atmospheric conditions, reduce the interference from other atmospheric constituents, and implement advanced analysis techniques. This paper describes the TOPAZ lidar, its components and performance during testing and field operation, and the data analysis procedure, including a discussion of error sources. The performance characteristics are illustrated through a comparison between TOPAZ and an ozonesonde launched during the TexAQS 2006 field campaign. A more comprehensive set of comparisons with in situ measurements during TexAQS 2006 and an assessment of the TOPAZ accuracy and precision are presented in a companion paper.

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B. L. Weber
,
D. B. Wuertz
,
R. G. Strauch
,
D. A. Merritt
,
K. P. Moran
,
D. C. Law
,
D. van de Kamp
,
R. B. Chadwick
,
M. H. Ackley
,
M. F. Barth
,
N. L. Abshire
,
P. A. Miller
, and
T. W. Schlatter

Abstract

The first wind profiler for a demonstration network of wind profilers recently passed the milestone of 300 h of continuous operation. The horizontal wind component measurements taken during that period are compared with the WPL Platteville wind profiler and the NWS Denver rawinsonde. The differences between the network and WPL wind profilers have standard deviations of 2.30 m s−1 and 2.16 m s−1 for the u- and v-components, respectively. However, the WPL wind profiler ignores vertical velocity, whereas the network radar measures it and removes its effects from the u- and v-component measurements. The differences between the network wind profiler and the NWS rawinsonde (separated spatially by about 50 km) have standard deviations of 3.65 m s−1 and 3.06 m s−1 for the u- and v-components, respectively. These results are similar to those found in earlier comparison studies. Finally, the new network wind profiler demonstrates excellent sensitivity, consistently reporting measurements at all heights msl from 2 to nearly 18 km with very few outages.

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D. L. Westphal
,
T. R. Holt
,
S. W. Chang
,
N. L. Baker
,
T. F. Hogan
,
L. R. Brody
,
R. A. Godfrey
,
J. S. Goerss
,
J. A. Cummings
,
D. J. Laws
, and
C. W. Hines

Abstract

The Marine Meteorology Division of the Naval Research Laboratory (NRL), assisted by the Fleet Numerical Meteorology and Oceanography Center, has performed global and mesoscale reanalyses to support the study of Gulf War illness. Realistic and quantitatively accurate atmospheric conditions are needed to drive dispersion models that can predict the transport and dispersion of chemical agents that may have affected U.S. and other coalition troops in the hours and days following the demolition of chemical weapons at Khamisiyah, Iraq, at approximately 1315 UTC 10 March 1991. The reanalysis was conducted with the navy’s global and mesoscale analysis and prediction systems: the Navy Operational Global Atmospheric Prediction System and the NRL Coupled Ocean–Atmosphere Mesoscale Prediction System. A comprehensive set of observations has been collected and used in the reanalysis, including unclassified and declassified surface reports, ship and buoy reports, observations from pibal and rawinsonde, and retrievals from civilian and military satellites. The atmospheric conditions for the entire globe have been reconstructed using the global system at the effective spatial resolution of 0.75°. The atmospheric conditions over southern Iraq, Kuwait, and northern Saudi Arabia have been reconstructed using the mesoscale system at the spatial resolutions of 45, 15, and 5 km. In addition to a baseline reanalysis, perturbation analyses were also performed to estimate the atmospheric sensitivity to observational error and analysis error. The results suggest that the reanalysis has bounded the variability and that the actual atmospheric conditions were unlikely to differ significantly from the reanalysis.

The synoptic conditions at and after the time of the detonation were typical of the transitional period after a Shamal and controlled by eastward-propagating small-amplitude troughs and ridges. On the mesoscale, the conditions over the Tigris–Euphrates Valley were further modulated by the diurnal variation in the local circulations between land, the Persian Gulf, and the Zagros Mountains. The boundary layer winds at Khamisiyah were from NNW at the time of the detonation and shifted to WNW in the nocturnal boundary layer. On the second day, a strong high passed north of Khamisiyah and the winds strengthened and turned to the ESE. During the third day, the region was dominated by the approach and passage of a low pressure system and the associated front with the SE winds veering to NW.

A transport model for passive scalars was used to illustrate the sensitivity to the reanalyzed fields of potential areas of contamination. Transport calculations based on various release scenario and reanalyzed meteorological conditions suggest that the mean path of the released chemical agents was southward from Khamisiyah initially, turning westward, and eventually northwestward during the 72-h period after the demolition. Precipitation amounts in the study area were negligible and unlikely to have an effect on the nerve agent.

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J.K. Fletcher
,
C.A. Diop
,
E. Adefisan
,
M. Ahiataku
,
S.O. Ansah
,
C.E. Birch
,
H.L. Burns
,
S.J. Clarke
,
J. Gacheru
,
T.D. James
,
C.K. Ngetich Tuikong
,
D. Koros
,
V.S. Indasi
,
B.L. Lamptey
,
K.A. Lawal
,
D.J. Parker
,
A.J. Roberts
,
T.H.M. Stein
,
E. Visman
,
J. Warner
,
B.J. Woodhams
,
L.H. Youds
,
V.O. Ajayi
,
E.N. Bosire
,
C. Cafaro
,
C.A.T. Camara
,
B. Chanzu
,
C. Dione
,
W. Gitau
,
D. Groves
,
J. Groves
,
P.G. Hill
,
I. Ishiyaku
,
C.M. Klein
,
J.H. Marsham
,
B.K. Mutai
,
P.N. Ndiaye
,
M. Osei
,
T.I. Popoola
,
J. Talib
,
C.M. Taylor
, and
D. Walker

Abstract

Testbeds have become integral to advancing the transfer of knowledge and capabilities from research to operational weather forecasting in many parts of the world. The first high-impact weather testbed in tropical Africa was recently carried out through the African SWIFT program, with participation from researchers and forecasters from Senegal, Ghana, Nigeria, Kenya, the United Kingdom, and international and pan-African organizations.

The testbed aims were to trial new forecasting and nowcasting products with operational forecasters, to inform future research, and to act as a template for future testbeds in the tropics. The African SWIFT testbed integrated users and researchers throughout the process to facilitate development of impact-based forecasting methods and new research ideas driven both by operations and user input.

The new products are primarily satellite-based nowcasting systems and ensemble forecasts at global and regional convection-permitting scales. Neither of these was used operationally in the participating African countries prior to the testbed. The testbed received constructive, positive feedback via intense user interaction including fishery, agriculture, aviation, and electricity sectors.

After the testbed, a final set of recommended standard operating procedures for satellite-based nowcasting in tropical Africa have been produced. The testbed brought the attention of funding agencies and organizational directors to the immediate benefit of improved forecasts. Delivering the testbed strengthened the partnership between each country’s participating university and weather forecasting agency and internationally, which is key to ensuring the longevity of the testbed outcomes.

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Dennis Baldocchi
,
Eva Falge
,
Lianhong Gu
,
Richard Olson
,
David Hollinger
,
Steve Running
,
Peter Anthoni
,
Ch. Bernhofer
,
Kenneth Davis
,
Robert Evans
,
Jose Fuentes
,
Allen Goldstein
,
Gabriel Katul
,
Beverly Law
,
Xuhui Lee
,
Yadvinder Malhi
,
Tilden Meyers
,
William Munger
,
Walt Oechel
,
K. T. Paw U
,
Kim Pilegaard
,
H. P. Schmid
,
Riccardo Valentini
,
Shashi Verma
,
Timo Vesala
,
Kell Wilson
, and
Steve Wofsy

FLUXNET is a global network of micrometeorological flux measurement sites that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. At present over 140 sites are operating on a long-term and continuous basis. Vegetation under study includes temperate conifer and broadleaved (deciduous and evergreen) forests, tropical and boreal forests, crops, grasslands, chaparral, wetlands, and tundra. Sites exist on five continents and their latitudinal distribution ranges from 70°N to 30°S.

FLUXNET has several primary functions. First, it provides infrastructure for compiling, archiving, and distributing carbon, water, and energy flux measurement, and meteorological, plant, and soil data to the science community. (Data and site information are available online at the FLUXNET Web site, http://www-eosdis.ornl.gov/FLUXNET/.) Second, the project supports calibration and flux intercomparison activities. This activity ensures that data from the regional networks are intercomparable. And third, FLUXNET supports the synthesis, discussion, and communication of ideas and data by supporting project scientists, workshops, and visiting scientists. The overarching goal is to provide information for validating computations of net primary productivity, evaporation, and energy absorption that are being generated by sensors mounted on the NASA Terra satellite.

Data being compiled by FLUXNET are being used to quantify and compare magnitudes and dynamics of annual ecosystem carbon and water balances, to quantify the response of stand-scale carbon dioxide and water vapor flux densities to controlling biotic and abiotic factors, and to validate a hierarchy of soil–plant–atmosphere trace gas exchange models. Findings so far include 1) net CO2 exchange of temperate broadleaved forests increases by about 5.7 g C m−2 day−1 for each additional day that the growing season is extended; 2) the sensitivity of net ecosystem CO2 exchange to sunlight doubles if the sky is cloudy rather than clear; 3) the spectrum of CO2 flux density exhibits peaks at timescales of days, weeks, and years, and a spectral gap exists at the month timescale; 4) the optimal temperature of net CO2 exchange varies with mean summer temperature; and 5) stand age affects carbon dioxide and water vapor flux densities.

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Douglas J. Parker
,
Alan M. Blyth
,
Steven J. Woolnough
,
Andrew J. Dougill
,
Caroline L. Bain
,
Estelle de Coning
,
Mariane Diop-Kane
,
Andre Kamga Foamouhoue
,
Benjamin Lamptey
,
Ousmane Ndiaye
,
Paolo Ruti
,
Elijah A. Adefisan
,
Leonard K. Amekudzi
,
Philip Antwi-Agyei
,
Cathryn E. Birch
,
Carlo Cafaro
,
Hamish Carr
,
Benard Chanzu
,
Samantha J. Clarke
,
Helen Coskeran
,
Sylvester K. Danuor
,
Felipe M. de Andrade
,
Kone Diakaria
,
Cheikh Dione
,
Cheikh Abdoulahat Diop
,
Jennifer K. Fletcher
,
Amadou T. Gaye
,
James L. Groves
,
Masilin Gudoshava
,
Andrew J. Hartley
,
Linda C. Hirons
,
Ishiyaku Ibrahim
,
Tamora D. James
,
Kamoru A. Lawal
,
John H. Marsham
,
J. N. Mutemi
,
Emmanuel Chilekwu Okogbue
,
Eniola Olaniyan
,
J. B. Omotosho
,
Joseph Portuphy
,
Alexander J. Roberts
,
Juliane Schwendike
,
Zewdu T. Segele
,
Thorwald H. M. Stein
,
Andrea L. Taylor
,
Christopher M. Taylor
,
Tanya A. Warnaars
,
Stuart Webster
,
Beth J. Woodhams
, and
Lorraine Youds

Abstract

Africa is poised for a revolution in the quality and relevance of weather predictions, with potential for great benefits in terms of human and economic security. This revolution will be driven by recent international progress in nowcasting, numerical weather prediction, theoretical tropical dynamics, and forecast communication, but will depend on suitable scientific investment being made. The commercial sector has recognized this opportunity and new forecast products are being made available to African stakeholders. At this time, it is vital that robust scientific methods are used to develop and evaluate the new generation of forecasts. The Global Challenges Research Fund (GCRF) African Science for Weather Information and Forecasting Techniques (SWIFT) project represents an international effort to advance scientific solutions across the fields of nowcasting, synoptic and short-range severe weather prediction, subseasonal-to-seasonal (S2S) prediction, user engagement, and forecast evaluation. This paper describes the opportunities facing African meteorology and the ways in which SWIFT is meeting those opportunities and identifying priority next steps. Delivery and maintenance of weather forecasting systems exploiting these new solutions requires a trained body of scientists with skills in research and training, modeling and operational prediction, and communications and leadership. By supporting partnerships between academia and operational agencies in four African partner countries, the SWIFT project is helping to build capacity and capability in African forecasting science. A highlight of SWIFT is the coordination of three weather forecasting “Testbeds”—the first of their kind in Africa—which have been used to bring new evaluation tools, research insights, user perspectives, and communications pathways into a semioperational forecasting environment.

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