Adaptive Observations in Fastex IOP-18: Data Impact and Synoptic Interpretation.

• Main Authors: Langland, Rolf H., Gelaro, Ronald, Rohaly, Gregory D., Shapiro, Melvyn A.
• Other Authors: OFFICE OF NAVAL RESEARCH ARLINGTON VA
• Format: Text
• Language: English
• Published: 1997
• Subjects: Theoretical Mathematics; Meteorology; *NUMERICAL ANALYSIS; *FORECASTING; *WEATHER FORECASTING; *MATHEMATICAL PREDICTION; *METEOROLOGY; *PATTERNS; POSITION(LOCATION); TEMPERATURE; AIRCRAFT; OBSERVATION; ERRORS; ADAPTIVE SYSTEMS; NORTH ATLANTIC OCEAN; CYCLONES; TEMPERATE REGIONS; DROPSONDES; METEOROLOGISTS; FASTEX(FRONTS AND ATLANTIC STORM TRACK EXPERIMENT); PE61153N; North Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA350156; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA350156

An issue of major importance in numerical weather prediction is the requirement to provide models with accurate initial conditions. The Fronts and Atlantic Storm Track Experiment (FASTEX) provides an opportunity to examine the impact of special observational data in 1-3 day forecasts of north Atlantic cyclones. An overview of FASTEX objectives and observational resources is contained in July et al (1997). The FASTEX field phase (January - February 1997) provided the first test of so-called "adaptive" observation techniques, in which objective guidance from numerical models was used to "target observational resources (e.g., dropsonde aircraft) to specific areas. In this study we describe the impact of targeted aircraft dropsonde, and GOES-8 wind data on a 24 hr forecast of the cyclone in FASTEX IOP-18. It is well established that numerical forecasts are much more sensitive to initial condition changes in certain locations than in others. In "sensitive" locations, changes to initial conditions (including changes which night result from new observational data) can have critical effects on the development of a forecast feature, such as a cyclone, or on measures of forecast error. Adjoint methods can be used to determine sensitivity patterns related to error growth in mid-latitude forecast situations, (for example, see Rabier et al. 1996). Both dry and moist adjoint sensitivity studies suggest that mid-latitude synoptic-scale cyclones (on the 1-3 day range) have maximum sensitivity to temperature and wind in the mid-lower troposphere (roughly 400-800 mb), in relatively localized areas of the upstream baroclinic storm track (also see Langland et al. 1995). The problem of adaptive observations does not center on identity%and correcting the largest analysis errors, but rather on correcting analysis error in critical locations, where any initial error can amplify with very large growth rates.