Walter F. Dabberdt

The Integrated Sounding System: Description and Preliminary Observations from TOGA COARE

Abstract An Integrated Sounding System (ISS) that combines state-of- the-art remote and in situ sensors into a single transportable facility has been developed jointly by the National Center for Atmospheric Research (NCAR) and the Aeronomy laboratory of the National Oceanic and Atmospheric Administration (NOAA/AL). The instrumentation for each ISS includes a 915-MHz wind profiler, a Radio Acoustic Sounding System (RASS), an Omega-based NAVAID sounding system, and an enhanced surface meteorological station. The general philosophy behind the ISS is that the integration of various measurement systems overcomes each systems respective limitations while taking advantage of its positive attributes. The individual observing systems within the ISS provide high-level data products to a central workstation that manages and integrates these measurements. The ISS software package performs a wide range of functions: real-time data acquisition, database support, and graphical displays; data archival and communications...

Meteorological Research Needs for Improved Air Quality Forecasting Report of the 11th Prospectus Development Team of the U.S. Weather Research Program

Abstract The U.S. Weather Research Program convenes expert working groups on a one-time basis to identify critical research needs in various problem areas. The most recent expert working group was charged to “identify and delineate critical meteorological research issues related to the prediction of air quality.” In this context, “prediction” is denoted as “forecasting” and includes the depiction and communication of the present chemical state of the atmosphere, extrapolation or nowcasting, and numerical prediction and chemical evolution on time scales up to several days. Emphasis is on the meteorological aspects of air quality. The problem of air quality forecasting is different in many ways from the problem of weather forecasting. The latter typically is focused on prediction of severe, adverse weather conditions, while the meteorology of adverse air quality conditions frequently is associated with benign weather. Boundary layer structure and wind direction are perhaps the two most poorly determined met...

Research Opportunities from Emerging Atmospheric Observing and Modeling Capabilities

Abstract The Second Prospectus Development Team (PDT-2) of the U.S. Weather Research Program was charged with identifying research opportunities that are best matched to emerging operational and experimental measurement and modeling methods. The overarching recommendation of PDT-2 is that inputs for weather forecast models can best be obtained through the use of composite observing systems together with adaptive (or targeted) observing strategies employing both in situ and remote sensing. Optimal observing systems and strategies are best determined through a three-part process: observing system simulation experiments, pilot field measurement programs, and model-assisted data sensitivity experiments. Furthermore, the mesoscale research community needs easy and timely access to the new operational and research datasets in a form that can readily be reformatted into existing software packages for analysis and display. The value of these data is diminished to the extent that they remain inaccessible. The comp...

Forecast Issues in the Urban Zone: Report of the 10th Prospectus Development Team of the U.S. Weather Research Program

The 10th Prospectus Development Team (PDT-10) of the U.S. Weather Research Program was charged with iden- tifying research needs and opportunities related to the short-term prediction of weather and air quality in urban forecast zones. Weather has special and significant impacts on large numbers of the U.S. population who live in major urban areas. It is recognized that urban users have different weather information needs than do their rural counterparts. Further, large urban areas can impact local weather and hydrologic processes in various ways. The recommendations of the team emphasize that human life and well-being in urban areas can be protected and enjoyed to a significantly greater degree. In particular, PDT-10 supports the need for 1) improved access to real-time weather information, 2) improved tailoring of weather data to the specific needs of individual user groups, and 3) more user-specific forecasts of weather and air quality. Specific recommendations fall within nine thematic areas: 1) development of a user-oriented weather database; 2) focused research on the impacts of visibility and icing on transportation; 3) improved understanding and forecasting of winter storms; 4) improved understanding and forecasting of convective storms; 5) improved forecasting of intense/ severe lightning; 6) further research into the impacts of large urban areas on the location and intensity of urban convec- tion; 7) focused research on the application of mesoscale forecasting in support of emergency response and air quality; 8) quantification and reduction of uncertainty in hydrological, meteorological, and air quality modeling; and 9) the need for improved observing systems. An overarching recommendation of PDT-10 is that research into understanding and predicting weather impacts in urban areas should receive increased emphasis by the atmospheric science community at large, and that urban weather should be a focal point of the U.S. Weather Research Program.

MULTIFUNCTIONAL MESOSCALE OBSERVING NETWORKS

Abstract More than 120 scientists, engineers, administrators, and users met on 8–10 December 2003 in a workshop format to discuss the needs for enhanced three-dimensional mesoscale observing networks. Improved networks are seen as being critical to advancing numerical and empirical modeling for a variety of mesoscale applications, including severe weather warnings and forecasts, hydrology, air-quality forecasting, chemical emergency response, transportation safety, energy management, and others. The participants shared a clear and common vision for the observing requirements: existing two-dimensional mesoscale measurement networks do not provide observations of the type, frequency, and density that are required to optimize mesoscale prediction and nowcasts. To be viable, mesoscale observing networks must serve multiple applications, and the public, private, and academic sectors must all actively participate in their design and implementation, as well as in the creation and delivery of value-added products...

The NCAR Atmosphere-Surface Turbulent Exchange Research (ASTER) Facility

Abstract The Atmosphere-Surface Turbulent Exchange Research (ASTER) facility developed at the National Center for Atmospheric Research (NCAR) will support observational research on the structure of the atmospheric surface layer. ASTER will provide state-of-the-art measurements of surface fluxes of momentum, sensible heat, and water vapor, and support measurements of surface fluxes of trace chemical species. The facility will be available to the scientific community in the spring of 1990. The motivation for the development of ASTER and the elements that constitute this new national facility are briefly discussed.

Fractal Geometry of Isoconcentration Surfaces in a Smoke Plume

Abstract The fractal properties of isoconcentration surfaces in a smoke plume are studied in an atmospheric boundary layer wind tunnel. Instantaneous high-resolution two-dimensional images of the fine particle concentration at Schmidt number Sc → ∞ were obtained in three plume cross sections with a video imaging technique. The fractal dimension D of isoconcentration contours is estimated with box-counting and area-perimeter methods; the range of thresholds is 0.5 ≤ c*/c ≤ 1.5, where c is the mean particle concentration for a particular image and c* is the threshold. Using the box-counting method, the local values of D = −d(log Nϵ)/d(log ϵ) are found to be constant over variations in ϵ that are more than a decade, where Nϵ, is the number of boxes with size ϵ required to cover an isoconcentration curve. Using the area-perimeter method, the fractal dimension is estimated with the relation P ∼ AD/2, where P and A denote the perimeter and area of the individual closed isoconcentration curves. The noise influ...

First Test of a Shipboard Wind Profiler

Abstract The Aeronomy Laboratory of the National Oceanic and Atmospheric Administration and the Atmospheric Technology Division of the National Center for Atmospheric Research are jointly developing Integrated Sounding Systems (ISS) for use in support of TOGA (Tropical Ocean Global Atmosphere) and TOGA COARE (Coupled Ocean-Atmosphere Response Experiment). Some of the ISS units will have to be operated on research ships during TOGA COAREs intensive observing period in late 1992 and early 1993. The greatest technical challenge in adapting the ISS to shipboard use is to stabilize the UHF wind profiler that is an integral part of the ISS. In June 1991 a UHF wind-profiling Doppler radar was installed on a stabilized platform aboard the NOAA research vessel Malcolm Baldrige on an eight-day cruise in the Atlantic Ocean. The wind profiler was gyrostabilized and profiler winds were corrected for ship motion utilizing the Global Positioning System. During the eight days at sea, CLASS (Cross-Chain LORAN Atmospheric...

POLLUTION DISPERSION AT COMPLEX STREET CONFIGURATIONS: COVERED ROADWAYS

Dispersion of vehicular pollutants emitted from covered roadways is particularly important in describing and controlling local air quality conditions at many complex urban roadway geometries. We have conducted a joint measurement and numerical modelling study to describe, understand and simulate the kinematics of the atmospheric transport and dispersion processes, and to assess the representativeness of various numerical model simulations. The measurement program was conducted in an environmental boundary-layer wind tunnel and involved the controlled line-source release of a tracer gas (ethane, C2 H6) and subsequent in situ sampling of concentration fields. The covered section was open to one side; two aspect ratios (width to height) for the covered section were tested 3.6 and 7.2. With the open side of the covered section to leeward of the ambient flow, pedestrian-level concentrations were observed to be fairly uniform within the covered section and were an order of magnitude greater than those downwind. An abrupt transition zone exists at the trailing edge of the covered section. A Navier-Stokes model (Fluent) realistically simulated the major transport and dispersion characteristics. A simple Gaussian line source equation was also evaluated because its numerical analogues (e.g. CAL3QHC) are often used for regulatory applications involving similarly complex geometries. As expected, this approach does not yield representative results. However, using the Gaussian model with the measured concentrations, we are able to characterise the downwind profile of the vertical dispersion (sigma) function and quantify the enhanced dispersion in the transition zone.

SURF: Understanding and Predicting Urban Convection and Haze

AbstractUrbanization modifies atmospheric energy and moisture balances, forming distinct features, e.g., urban heat islands (UHIs) and enhanced or decreased precipitation. These produce significant challenges to science and society, including rapid and intense flooding, heat waves strengthened by UHIs, and air pollutant haze. The Study of Urban-Impacts on Rainfall and Fog/Haze (SURF) has brought together international expertise on observations and modeling, meteorology and atmospheric chemistry, and research and operational forecasting. The SURF overall science objective is a better understanding of urban, terrain, convection, and aerosol interactions for improved forecast accuracy. Specific objectives include: a) promoting cooperative international research to improve understanding of urban summer convective precipitation and winter particulate episodes via extensive field studies; b) improving high-resolution urban weather and air quality forecast-models; and c) enhancing urban weather forecasts for soc...