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Impact of Aircraft Wind Data On Ecmwf Analyses and Forecasts During the Fgge Period, 8‐19 November 1979
Author(s) -
Baede A. P. M.,
Kållberg P.,
Uppala S.
Publication year - 1987
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711347709
Subject(s) - data assimilation , environmental science , meteorology , satellite , climatology , geography , geology , aerospace engineering , engineering
This paper describes the results of an observing system experiment, set up to assess the impact of aircraft wind data on ECMWF analyses and forecasts. Two parallel data assimilation runs for an 11‐day period during the Global Weather Experiment (FGGE) in November 1979 show that the ECMWF system is able to extract valuable and sometimes essential information from such single‐level data. the impact was particularly significant in the tropics, though limited elsewhere. Especially for the aviation community it is interesting to note that a positive impact of aircraft data was found on both wind analyses and 6‐hour forecasts along flight tracks. On average an improvement of about 1 m s −1 is found for both wind components but locally and in individual cases this may be considerably larger. In order to assess the possible redundancy of aircraft and satellite data outside the tropics, the with‐ and without‐aircraft data assimilations were repeated with satellite winds and satellite temperatures excluded from the data base. This experiment confirmed our suspicion but suggested that the redundancy may be less serious in operational non‐FGGE conditions and may also be a consequence of the particular synoptic situation during the period. From an intercomparison with a similar experiment carried out at the Meteorological Office it is inferred that a multi‐variate scheme with a proper vertical coupling is advantageous in extracting and directing information to the rotational modes of the model. A quality control on the data showed that the reliability of the automatically transmitted aircraft data (ASDAR and AIDS) is high. Therefore the results of this experiment may be unfavourably biased by the more abundant but less reliable conventional aircraft (AIREP) data. This leads us to conclude that a future system of aircraft data, based entirely on ASDAR, will be a valuable contribution to the global observing system.