Global chemical weather forecasts for field campaign planning: predictions and observations of large-scale features during MINOS, CONTRACE, and INDOEX

[摘要] The first global tropospheric forecasts ofO₃ and its precursors have been used in the daily flight planning of field measurementcampaigns.The 3-D chemistry-transport model MATCH-MPIC is driven by meteorological data from a weather center (NCEP) to produce daily3-day forecasts of the global distributions of O₃ and relatedgases, as well as regional CO tracers.This paper describes the forecast system and its use in three field campaigns, MINOS, CONTRACEand INDOEX.An overview is given of the forecasts by MATCH-MPIC and by three other chemical weather forecast models(EURAD, ECHAM, and FLEXPART), focusing on O₃ and CO.Total CO and regional CO tracerswere found to be the most valuable gases for flight planning, due to their relatively well-defined anthropogenic source regions andlifetimes of one to a few months.CO was in good agreement with the observations on nearly all the flights (generally r > 0.7, and the relative RMS differences for the deviations from the means was lessthan 20%).In every case in which the chemical weather forecasts were primarily responsible for the flight plans, the targeted featureswere observed.Three forecasted phenomena are discussed in detail: outflow from Asia observed in the Mediterranean upper troposphereduring MINOS, outflow from North America observed in the middle troposphere over northern Europe during CONTRACE, and the location ofthe "chemical ITCZ'' over the Indian Ocean during INDOEX.In particular it is shown that although intercontinental pollution plumessuch as those observed during MINOS and CONTRACE occur repeatedly during the months around the campaigns, their frequency issufficiently low (~10--30% of the time) that global chemical weather forecasts are important for enabling them to be observedduring limited-duration field campaigns.The MATCH-MPIC chemical weather forecasts, including an interface for making customizedfigures from the output, are available for community use via http://www.mpch-mainz.mpg.de/~lawrence/forecasts.html.

[学科分类] 大气科学