ANALYSIS OF FINESCALE WEATHER PHENOMENA [Bulletin of the American Meteorological Society]
(Bulletin of the American Meteorological Society Via Acquire Media NewsEdge) T he accurate numerical analysis of finescale weather phenomena is of critical importance for 1) assessing the state of the atmosphere, 2) nowcasting severe and other types of weather for the upcoming hours using statistical methods, and 3) predicting severe and other weather using numerical weather prediction (NWP) models for time scales of and beyond several hours. To address these challenges, in the early 1990s the Forecast System Laboratory [FSL; the predecessor of today's Global Systems Division (GSD)] developed a sophisticated numerical data assimilation and forecast system called Local Analysis and Prediction System (LAPS; Albers et al. 1996).
Unique at the time, and to some extent even today, is LAPS's detailed 3D cloud and moisture variable analysis specifically designed for capturing convective processes for warn-on-forecast (WOF) applications. Since its introduction, LAPS has been periodically updated by the addition of new types of observations, scientifically comprehensive algorithms, and efficient computational approaches. Today, more than 150 groups across five continents use LAPS (see Fig. 1), some of them comprising a network such as the Weather Forecast Offices (WFOs) in all six regions of the National Weather Service (NWS). Yet, until recently, the users and developers of LAPS had no opportunity to meet to exchange ideas and develop stronger collaboration.
The First LAPS User Workshop was organized in 2010 by the Forecast Applications Branch (FAB) of the Global Systems Division of the National Oceanic and Atmospheric Administration/Office of Oceanic and Atmospheric Research (NOAA/OAR), the primary developers of LAPS. The main goal was to bring the users and developers of LAPS together with the aim of 1) assessing the current state of LAPS, 2) identifying gaps in the system to guide future developments, and 3) fostering collaboration among the users and developers. Representatives from a wide range of user groups attended the meeting, including scientists from NWS, NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) and OAR, the National Center for Atmospheric Research (NCAR), and the Cooperative Institute for Research in the Atmosphere (CIRA) from the academic community, private companies, and weather services from Finland, Spain, and China. Thirty presentations and two sets of working group discussions helped achieve the objectives of the meeting.
THE ROLE OF LAPS IN NWP. Unique features. The workshop offered an excellent opportunity to review LAPS's role in today's NWP activities. Participants noted a number of unique features that LAPS offers to its users:
* quality (i.e., consistency of LAPS analyses with observations);
* fine resolution (1 km or finer) facilitating the detailed description of severe weather phenomena;
* very rapid update (15 min or less) for continual monitoring of weather;
* diabatic initialization of NWP models (i.e., "hot start") initializing convective processes to minimize spinup problems associated with moist processes;
* high level of portability, allowing LAPS to be installed on a multitude of platforms; and
* ease of use facilitated by a number of user-friendly features.
Application areas. Two main application areas were noted. On one hand, LAPS is used for enhancing situational awareness. This is achieved by a detailed assessment of the state of the atmosphere, which is critical for nowcasting and forecast verification. The other main application of LAPS is the initialization of very short-range (0-6 h) forecasts for warn on forecasting, which is a rapidly emerging branch of NWP. Specific application areas for both situational awareness and WOF discussed at the workshop include convective, aviation, severe, fire, tropical, hydrometeorological, winter, and international weather forecasting.
User base. Because of its unique characteristics, LAPS has a wide range of users. The NWS is LAPS's primary user. LAPS is available operationally at the 122 WFOs of the NWS as part of the Advanced Weather Interactive Processing System (AWIPS), offering an indispensable tool in creating finescale analyses with local control of the quality of the observational data. Other U.S. agencies benefitting from the use of LAPS include the Department of Homeland Security (DHS), the Federal Aviation Administration (FAA), various agencies of the Department of Defense, and the National Aeronautics and Space Administration (NASA). Users in the private sector include companies specializing in renewable energy and international weather forecast services. Internationally, LAPS is used by numerous national weather agencies and research institutes on five continents.
USER REQUIREMENTS. Users at the workshop emphasized the need to maintain and further improve the unique features of LAPS. A number of presentations identified shortcomings such as the need for improved quality controlling of observational data, the lack of full balance and the presence of noise in analysis fields, and the associated spinup behavior in short-range forecasts. Solutions to some of the problems were also suggested by some of the LAPS developers. Participants asked that the various issues be prioritized according to their impact on analysis/forecast quality.
At the time of the workshop, LAPS was being ported for use by WFOs onto the new AWIPS2 platform. Keeping LAPS highly portable remains a top priority for the LAPS user community. Computational efficiency and ease of use are not far behind: LAPS must remain easily configurable, with intuitive and user-friendly interfaces.
DATA NEEDS. Participants agreed that the portability of LAPS could be significantly enhanced by using emerging communication and computational technologies (e.g., wireless and web-enabled data access). LAPS, for example, can fully utilize the web-enabled technology being developed for the Next Generation Air Transportation System (NEXTGEN) by the FAA and its partners. This system will allow users to download observational and other data needed for LAPS pertinent to their area of interest, significantly reducing the latency of LAPS products. The distribution of output data will also gain from advances in information technology. LAPS analyses and forecasts are expected to become an integral part of NEXTGEN's 4D data cube.
Presentations and discussion covered existing and expected needs for three types of data. First, how "static" data such as high-resolution terrain and land surface information are being accessed by LAPS is being modernized via utilities called "topograbber" and the Weather Research and Forecasting model (WRF) Domain Wizard. Second, a number of new types of observations will be added, including dual polarization, terminal Doppler wind, airborne, shipborne, and spaceborne radars, lidar, and additional types of satellite observations. Third, participants suggested that the use of short-range forecasts originating from a preceding LAPS analysis (i.e., cycled data assimilation) or very high-resolution European Centre for Medium-Range Weather Forecasts (ECMWF) global forecasts as background fields should be explored to improve the quality of the analysis fields.
SOFTWARE REQUIREMENTS. One of the main recommendations from the workshop called for the development of a comprehensive graphical user interface (GUI) for accessing the various current and future features of LAPS. The GUI should handle configuring, running, and monitoring LAPS, including access to and quality control of data, and the initialization and creation of WRF forecasts. Several elements of such a GUI already exist. The additions will greatly benefit potential applications in the field by incident meteorologists and other users requiring quick and easy setup.
Other software-related developments reviewed or requested at the workshop include the parallelization of LAPS codes for vastly increased computational efficiency, the continued use of coding standards, the exploration of new opportunities such as what geographic information systems (GIS) may offer for LAPS, proper documentation of all software, and a more formal protocol for contributions from the vast array of national and international users. LAPS is already being developed as a community effort with the help of visiting scientists as well as user feedback and software contributions. Ensuring that improvements made by one group benefit all other users is a growing priority. For example, formal agreements with major user groups such as national weather services in South Korea, Finland, Spain, China, and Taiwan may benefit the entire LAPS user community.
SCIENTIFIC OPPORTUNITIES. The presentations and discussions associated with research opportunities constituted one of the most animated parts of the meeting. Many components in the traditional analysis package of LAPS were developed in the late 1980s and early 1990s, before variational data assimilation became well established. Though it has variational elements, the traditional data assimilation component of LAPS follows a Barnes scheme.
Work is underway to frame the carefully designed traditional analysis in LAPS in a 3D/4D variational data assimilation (3DVAR/4DVAR) context. The new version of the analysis component of LAPS under development is called the Space-Time Multiscale Analysis System (STMAS; Xie et al. 2011). The new system will have a number of advanced features including a multigrid approach, better use of observational data by considering the exact time each observation is taken, cross-variable background error covariances, and physical balance relationships used in the variational context.
When a fine-resolution LAPS analysis is first performed over a particular area where only a coarser-resolution background field is available, a newly developed dynamical downscaling algorithm can be applied. For successful initialization of NWP predictions for cycled data assimilation or warn on forecasting, the consistency between the analysis fields and numerical models can be critical. For example, the consistency between the analysis and the vertical coordinate, microphysics, and land surface scheme in a model initialized with a LAPS analysis must also be carefully considered.
Work is also underway to objectively estimate error variances in observational data from various observing systems. Improvements to quality controlling, as well as estimating representativeness errors in, the observational data are also areas of active development. The estimation of error variances and covariances in background forecasts may be even more important for the improved performance of data assimilation systems. When fully developed, the new variational data assimilation component in LAPS, the STMAS, will be a hybrid scheme, where a finescale ensemble forecast system would provide case-dependent information on forecast error covariances. These and other new features in LAPS/STMAS should lead to analysis fields that are in better dynamical balance and contain less noise, potentially benefitting the LAPS analysis and WOF user community.
COMMUNITY OUTREACH. Given its highly portable and unique features, the workshop participants recommended that the Developmental Testbed Center (DTC) include LAPS among the NWP systems it supports. This should include the LAPS analysis system, as well as an option for the initialization of WRF forecasts. With some basic support, many tools developed by the DTC (e.g., verification) would become available for the NWS and external LAPS user community.
Another recommendation by the workshop was the formal testing of LAPS in the Hazardous Weather Testbed (HWT) and other experiments. It is important that LAPS analyses and forecasts are formally assessed and compared with other available numerical guidance for both situational awareness (nowcasting) and warn-on-forecast applications.
Workshop participants also emphasized the need for thorough training packages both on how to set up and run LAPS and how to use it in AWIPS2 and other application areas. A description of the available products with real-life examples and a discussion of good practices are critical for the efficient utilization of LAPS capabilities both within and outside the NWS.
As discussed above, LAPS has a list of features that make it unique among NWP data assimilation and forecast systems. It is important, however, that the development of LAPS and other NWP methods used in the community is well coordinated. To ensure that all NWP methods are developed in an efficient way and to their full potential, workshop participants identified three key elements. First, LAPS should build on and use, wherever available and practical, community-supported tools and file formats [e.g., GIS protocols, Binary Universal Form for the Representation of meteorological data (BUFR) file format, WRF-Geogrid]. Second, the improvements introduced by the broad national and international LAPS community should be included in the main LAPS repository for better efficiency. Third, efforts should be made to transfer methods successfully tested and used in LAPS into NWP systems maintained by the National Centers for Environmental Prediction (NCEP).
SUMMARY RECOMMENDATIONS. In summary, the workshop participants formulated two main recommendations:
* NOAA should continue the development and user support of the LAPS system to serve the needs of the weather enterprise for 1) finescale data assimilation (situational awareness and nowcasting applications) and 2) diabatic initialization of NWP forecasts (warn-on-forecast applications) and
* NOAA should maintain and further enhance the unique features of LAPS by improving its quality, convective initialization method ("hot start"), timeliness, geographical resolution, portability, and ease of use.
Workshop participants also requested that future LAPS workshops be organized on an annual or biannual basis.
ACKNOWLEDGMENTS. The organizers of the workshop enjoyed the full support of Dr. Steve Koch, director of GSD at the time of the meeting. Dan Birkenheuer's, Paul Schultz's, and Paula McCaslin's contributions to the organization of the workshop are gratefully acknowledged. Adrienne Rose and Joanne Krumel provided excellent administrative support. Kirk Holub helped with the preparation of Fig. 1. Expert comments on an earlier version of this report by Matt Foster (NWS) are also acknowledged.
First Local Analysis and Prediction System (LAPS) User Workshop
What: Approximately 40 experts in the analysis of finescale weather phenomena from the United States, Europe, and Asia met to assess the state of the LAPS system and discuss promising future developments.
When: 25-27 October 2010
Where: Boulder, Colorado
Albers, S., J. McGinley, D. Birkenheuer, and J. Smart, 1996: The Local Analysis and Prediction System (LAPS): Analyses of clouds, precipitation, and temperature. Wea. Forecasting, 11, 273-287.
Xie, Y., S. Koch, J. McGinley, S. Albers, P. E. Bieringer, M. Wolfson, and M. Chan, 2011: A space-time multiscale analysis system: A sequential variational analysis approach. Mon. Wea. Rev., 139, 1224-1240.
AFFILIATIONS: Toth and Xie-Global Systems Division, NOAA/OAR/ESRL, Boulder, Colorado; Albers-Cooperative Institute for Research in the Atmosphere, Colorado State University, Boulder, Colorado
CORRESPONDING AUTHOR: Zoltan Toth, NOAA/OAR/ESRL/GSD, 325 Broadway, Boulder, CO 80305
In final form 29 July 2011
©2012 American Meteorological Society
(c) 2012 American Meteorological Society
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