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EXPRESSO
ACD, in cooperation with scientists from several other American and European institutions (including the Aerology Laboratory of CNRS, Toulouse, France), successfully completed the EXPRESSO field campaign in the Congo and the Central African Republic. Ground based and airborne instrumentation provided unique information on the chemical composition of the lower atmosphere in this tropical region. High ozone production rates were recorded during the biomass burning season. The meteorological situation showed to be more complex than believed earlier, with strong mixing between the Harmattan and the monsoon layers. Field data are being analyzed.
MOZART Model
ACD completed the first version of a global three-dimensional chemical transport model (called MOZART). This model provides the global distribution and budget of approximately 50 chemical compounds involved in the chemistry of tropospheric ozone. A regional model, using a similar chemical scheme, is being developed and the first version will soon be completed.
GPS Dropsonde Development
In 1997 ATD's Surface and Sounding Systems Facility (SSSF) completed the development and testing of an advanced, lightweight, high-resolution dropsonde using Global Positioning System (GPS) wind-finding technology and state-of-the-art sensors. The new GPS Dropsonde was used operationally for the first time in two major research roles: in the Fronts and Storm Track Experiment (FASTEX) conducted over the North Atlantic in winter 1997, and in hurricane field studies carried out by NOAA. The development of the new system was funded jointly by ATD, NOAA, and the German Aerospace Research Establishment (DLR).
The task of developing the GPS Dropsonde was especially challenging. The specifications required, among other things, that the new sonde be capable of being launched from high-altitude, fast, jet aircraft, and that the system be able to acquire data from four sondes in the air at the same time. The requirements demanded high accuracy, precision, and resolution in the measurements under extreme environmental conditions of shock, vibration, and cold. The sonde had to be small, extremely light, and, most importantly, cheap, since it is expendable and is used in large quantities.
In its first field application, the FASTEX program (see below), the new GPS Dropsonde demonstrated that it offers the atmospheric science community unprecedented accuracy and resolution in vertical profiles of wind and PTH (pressure, temperature, and humidity). Measurements are obtained at intervals of 0.5 s, which corresponds to an average vertical resolution of 7 m (even better at lower altitudes close to the surface). This high resolution compares with the 60-s (LORAN) and up to 240-s (Omega) resolutions of the older LD2 sonde. Furthermore, the new system allows highly detailed measurements all the way down through the boundary layer to the surface.
The use of the new GPS Dropsonde in NOAA's hurricane research and reconnaissance operations has dramatically improved observing capabilities. The old NOAA Omega dropwindsonde (ODW) system had serious limitations (low vertical resolution, no winds in the boundary layer, and poor performance in bad weather) which restricted the use of the system to providing information only on the large-scale synoptic environment of the storm. The new GPS Dropsonde not only solves these problems, but for the first time allows measurements in the highly turbulent eyewall environments of hurricanes. Drops during August-September 1997 into the eyewall regions of Hurricanes Guillermo and Erika resulted in detailed wind and PTH profiles all the way to the surface. Maximum wind speeds of almost 150 knots were measured. These new capabilities are having a major impact on NOAA's hurricane research and reconnaissance programs, and are expected to lead to more accurate hurricane advisories and warnings.
Fronts and Atlantic Storm Track Experiment (FASTEX)
This international program was by far ATD's most challenging field deployment during the year. FASTEX was focused on studying the mesoscale structure of winter cyclones developing over the North Atlantic ocean and the relationship between cyclone intensification and upstream precursors embedded in the large-scale flow. ATD's role in the program was extensive: it supported both the airborne and surface portions of FASTEX observing operations, as well as computing network and communications activities at the main control center in Shannon, Ireland. The newly developed NCAR GPS Dropsonde was used for the first time on two NOAA aircraft (the G-IV and a WP-3D) as well as on an NCAR-leased Lear 36 aircraft. A total of 750 sondes were dropped during the experiment, with a data-capture rate of over 90% being achieved by the end of the program. The high-resolution, highly mobile vertical soundings from the airborne GPS Dropsondes allowed PIs to study target areas where small analysis errors were expected to most significantly affect predictions, or where cyclones were in early development stages.
ATD also operated an Integrated Sounding System (ISS) on board each of two research ships. The two ISS systems provided wind, temperature, and humidity profiles and surface meteorological measurements to document atmospheric boundary-layer structure and to help characterize surface fluxes on both sides of fronts at the surface.
The NCAR/NSF Electra aircraft, equipped with the ELDORA Doppler radar and a variety of microphysical and other sensors, was used by a group of NCAR, university, and French PIs to map mesoscale structures of mature or deepening cyclone systems. The rapid-scanning abilities of ELDORA helped document the turbulent ascent and descent of air in shallow rain showers associated with cold and warm frontal systems.
Also flown on the Electra during FASTEX was the Weather Avoidance Radar Data System (WARDS), newly developed by ATD. The WARDS surveillance display allowed investigators to see convective bands ahead of the aircraft, and thus helped them to design and refine flight patterns for optimal ELDORA data collection.
Completion of a 300-year simulation with the initial version of the Climate System Model (CSM), in which there are no significant drifts in the surface temperatures.
Analysis of Nimbus-7 earth radiation budget data has shown that there is a global signature for enhanced shortwave cloud absorption. This signature appears in the ratio of the visible to near infrared cloud albedo. Analysis of the Atmospheric Radiation Measurement (ARM) program data confirms the existence of enhanced shortwave cloud absorption.
| Katz and the late Allan Murphy (University of Oregon) (editors) had their book published in FY97 on the Economic Value of Weather and Climate Forecasts (Cambridge University Press). This book is the first unified treatment of the economic value of weather and climate forecasts. It is a unique resource and provides a comprehensive synthesis of the literature on this subject. The individual chapters present detailed analyses of weather prediction (from a few hours to seasons ahead), forecast verification, and various approaches to assessment of forecast value. A wide range of value assessment methods, from descriptive to prescriptive, are also treated. The project was multidisciplinary in nature, including authors from meteorology, statistics, psychology, and economics. |  |
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Glantz organized and convened the ASP Summer Colloquium: A Systems Approach on ENSO: Oceanic, Atmospheric, Societal, Environmental, and Policy Perspectives 20 July - 1 August 1997 in Boulder. The colloquium merged disciplinary expertise with multidisciplinary interests to provide a broad understanding of ENSO as a system. The colloquium gathered together approximately 30 graduate students and a team of ENSO experts from around the world for this two-week event. It addressed the history, theory, modeling, observational aspects, ecological and societal impacts, and forecasting related to ENSO events. |
Using state-of-the-art observations delivered by the HAO/NSO Advanced Stokes Polarimeter, Bruce Lites, Andrew Skumanich, and Valentin Martinez Pillet (Instituto de Astrofisica de Canarias) recently completed an unprecedented observational study of small-scale emerging magnetic flux. These data provide the most complete and accurate observational description to date of newly emerging vector magnetic fields. Their analysis shows that coherent magnetic field systems erupt through the visible solar surface at equipartition field strengths, oriented parallel to the solar surface. As individual elements of magnetic flux migrate away from the emergence zone, they reorient themselves to lie perpendicular to the solar surface. In so doing their field strength increases into the kiloGauss range, which is more typical of mature small-scale magnetic flux features.
Paul Charbonneau and Steve Tomczyk, together with Jesper Schou (Stanford University) and Michael Thompson (Queen Mary and Westfield College), have analyzed data obtained during the first two years of LOWL observations in order to infer the rotational properties of the deep solar core. By applying the technique of Genetic Forward Modeling (previously developed at HAO by Charbonneau, Tomczyk, and collaborators) to the LOWL p-mode frequency splitting measurements, they have derived the best available picture of how the innermost portion of the Sun's radiative interior rotates. Their results indicate that the rotation of the solar core can be characterized as uniform (with 20% accuracy) down to a depth of 0.2 solar radii. They can also rule out departures from solid body rotation by a factor of two or more at depths between 0.1 and 0.2 solar radii.
Analysis of measurements by Lynn Russell (ASP) and Donald Lenschow from a Lagrangian experiment carried out by the NCAR C-130 aircraft during the Aerosol Characterization Experiment (ACE-1) southwest of Tasmania, Australia, shows that exchange of air can occur in both directions across the top of the boundary layer even in clear air (see figure). Figure Legend: Schematic of the two-layered structure observed during ACE-1 with the NCAR C-130 aircraft. Transport (entrainment fluxes) occurred in both directions between the boundary layer and the overlying "buffer layer," even in absence of clouds. They demonstrated this primarily by using aerosol and dimethyl sulfide as tracers of vertical transport. The air above the boundary layer was intermittently turbulent due to wind shear, but was still distinctly different from the boundary layer. This process has important implications in understanding the evolution of trace constituents in the marine boundary layer.
Scientists within the Mesoscale Prediction Group of the MMM Division are developing a variational data assimilation system based on MM5. During the last year, development of the tangent linear and adjoint of a "dry" version of MM5 was completed; these models were released to the users community. Although still incomplete, this primary version of the MM5 variational data assimilation system already offers the possibility of performing minimization in a twin experiment configuration and carrying out useful sensitivity experiments (see figure). A tutorial was offered at the time of the release and was attended by more than 30 interested users from NCAR and the university community.
The WTWS System was accepted by the Hong Kong Government on 17 July 1997, after 44 months of research and development. The $16 million project included basic and applied research on wind flow over Hong Kong's rugged terrain, a scientific field study, warning system concept and feasibility studies, system design, construction, implementation and training. The program was managed by B. Donaldson, Weather Information and Technologies, Inc. (WITI), R. Wagoner and W. Mahoney, both of NCAR/RAP. See Hong Kong Operational Windshear Warning System (OWWS) Completion, Section VI.
WSDDM is a real-time weather system designed to improve decision making at airports during winter storms. Snowfall and weather information are used by ground personnel conducting aircraft deicing operations, airline station control managers and dispatchers coordinating flights, airport managers coordinating runway plowing activities, and air traffic managers involved with gate hold programs. WSDDM provides decision makers with the information needed to anticipate both the onset and termination of snow at the aiport and surrounding regions, its intensity, and water content.
The WSDDM System was demonstrated to a variety of users at LaGuardia Airport in New York, and O'Hare Airport in Chicago. New York users included Delta Airlines, USAIR Airlines, and New York TRACON. In Chicago, United and American Airlines had displays. The system required the use of 25 workstations and displays at 8 user sites. Communications were designed and implemented by T. Hofmeister, F. Hage and R. Tescher and required the use of 56 kB dedicated phone lines and local networks all linked and working together. All the users were able to access workstations independently with no degradation of performance during high weather demand periods.
An important aspect of the system is the ability to rapidly loop the radar data in order to visually examine snowband motions and growth or decay trends. The response of the system to user commands was excellent, with new loops or reflectivity images appearing typically within a second or two of selection.
This network is one of the most complicated ever set up at RAP. The WSDDM System is managed by R. Rasmussen. See Operational Evaluation of the Weather Support to Deicing Decision Makers in Chicago and New York, Section XIV for more information.
This project is a cooperative effort between NCAR's Data Support Section (DSS) and the National Centers for Environmental Prediction (NCEP) of NOAA. NCEP is responsible for the numerical analyses of the data, while the DSS is responsible for the majority of input data collection and preparation and output data archiving and distribution. This project is a good example of interagency cooperation to achieve a mutually beneficial scientific goal.
In general, the project goal is to reanalyze the previous 50 years of atmospheric data. Over 40 years are now completed. The project is described in the Bulletin of the American Meteorological Society (BAMS), March 1996. A near final draft of the BAMS article is available online, and less detailed information concerning the project and model description, and project status is also online.
The complete output archive is approximately 54 GB of data per year and contains many subset data products. Various resolutions are also available beginning with 4x daily temporally, approximately 2.0 degrees horizontally, and 28 levels vertically. In many ways this scientific data collection is unmatched by any other at this time.
All reanalysis data products are available from the NCAR MSS for users with NCAR computing accounts at no cost, and they can be provided to other users at the minimal cost of copying the data to magnetic media. Software to access the data and information on how to order the reanalysis data are available online. The wide distribution of reanalysis data is enhanced by a set of annual CD-ROMs. The CD-ROMs contain the most popular reanalysis data products and necessary software to read and display the data. Below is an example of two-meter-height air temperature (degrees Kelvin) data from 0Z, 15 December, 1996, taken from the CD-ROM and illustrated (with reduced resolution here) using the GrADS display software.
The NCEP/NCAR reanalysis dataset is proving to be popular. During 1997, average monthly statistics show that the archive on the NCAR MSS has about 10 unique users, accessing over 1000 files containing about 300 GB of data. Data usage delivered by CD-ROMs and magnetic media are not included in these statistics. Overall, 1150 CD-ROMs have been distributed to fulfill 450 requests, and about 150 orders have been served with magnetic tape media.
Other organizations within NOAA are also distributing the reanalysis data and providing some interesting real-time access and displays using the web. One such site is provided through the NOAA-CIRES Climate Diagnostics Center. Here a web-based atlas allows anyone to access and visualize many different data products.
Many scientific evaluations of the NCEP/NCAR reanalysis archive have been completed, and many more will take place in coming years. An example of the level of scientific interest was demonstrated at the October 1997 International Workshop on Reanalysis in Silver Spring, MD, sponsored by the International Global Energy and Water Cycle Experiment (GEWEX) Project office. Here the NCEP/NCAR reanalysis was a central topic of many presentations. The workshop agenda emphasizes how reanalyses can be applied to a wide range of scientific investigations.
More information related to the NCEP/NCAR Global Atmospheric Reanalysis Project appears in the FY97 SCD Research Data report.
