Forecast, observation and modelling of a deep stratospheric intrusion event over Europe

[摘要] A wide range of measurements was carried out in central and southeastern Europewithin the framework of the EU project STACCATO (Influence of Stratosphere-TroposphereExchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity) with the principle goal to create a comprehensive data set onstratospheric air intrusions into the troposphere along a rather frequently observedpathway over central Europe from the North Sea to the Mediterranean Sea. Themeasurements were based on predictions by suitable quasi-operational trajectorycalculations using ECMWF forecast data. A predicted deep Stratosphere to Troposphere Transport(STT) event, encountered during the STACCATO period on 20-21 June 2001, was followed by the measurements network almost from itsinception. Observations provide evidence that the intrusion affected large parts ofcentral and southeastern Europe. Especially, the ozone lidar observations on20-21 June 2001 at Garmisch-Partenkirchen, Germany captured the evolution of two markedtongues of high ozone with the first one descending to nearly 2 km, thus providing anexcellent data set for model intercomparisons and validation. In addition, for the firsttime to our knowledge concurrent surface measurements of the cosmogenic radionuclides¹⁰Be and ⁷Be and their ratio ¹⁰Be/⁷Be are presented together as stratospheric tracers in a casestudy of a stratospheric intrusion. The ozone tracer columns calculated with theFLEXPART model were found to be in good agreement with water vapour satelliteimages, capturing the evolution of the observed dry streamers of stratospheric origin.Furthermore, the time-height cross section of ozone tracer simulated with FLEXPART over Garmisch-Partenkirchen captures many details of the evolution ofthe two observed high-ozone filaments measured with the IFU lidar, thus demonstrating the considerable progress in model simulations. Finally, the modelledozone (operationally available since October 1999) from the ECMWF (EuropeanCentre for Medium-Range Weather Forecasts) atmospheric model is shown to be invery good agreement with the observations during this case study, which provides thefirst successful validation of a chemical tracer that is derived operationally from aweather forecast model. This suggests that coupling chemistry and weather forecastmodels may significantly improve both weather and chemical forecasts in the future.

[学科分类] 大气科学