Abstract
Peak analyzed jet stream wind speeds are compared with independent aircraft observations over Canada and the continental United States. The results permit a study of the accuracy of analyzed jet streak strength for the data-sparse 85% of the earth's surface versus the data-dense 15%. The observations come from the Global Aircraft Data Set (GADS) experiment, which since 1996 has collected flight data recorder information from every flight of 56 British Airways 747-400 aircraft. The study is timely because automated aircraft observations are reaching their near-asymptotic limits (there are not many uncovered commercial aircraft routes left), and we are about to enter a new, third-generation, satellite-sounding-instrument era. Future reanalyses will mix time periods from both eras. This study gives an estimate of the analysis accuracy of data assimilation using second-generation satellite systems.
The results show that major current generation assimilation models have peak wind speed errors of −5% to −9% over data-sparse Canada compared with −2% to −5% over the data-dense continental United States. When these additional aircraft observations are assimilated as a part of the normal observational input data stream, a small but statistically significant improvement is shown for 1-month forecast experiments over two consecutive winters.
Corresponding author address: Joel Tenenbaum, Division of Natural Sciences, State University of New York, Purchase, NY 10577. Email: joel@zephyr.ns.purchase.edu