Highly resolved observations of trace gases in the lowermost stratosphere and upper troposphere from the Spurt project: an overview

[摘要] During SPURT (Spurenstofftransport in der Tropopausenregion, trace gastransport in the tropopause region) we performed measurements of a widerange of trace gases with different lifetimes and sink/sourcecharacteristics in the northern hemispheric upper troposphere (UT) andlowermost stratosphere (LMS). A large number of in-situ instruments weredeployed on board a Learjet 35A, flying at altitudes up to 13.7 km, at timesreaching to nearly 380 K potential temperature. Eight measurement campaigns(consisting of a total of 36 flights), distributed over all seasons andtypically covering latitudes between 35° N and 75° N in the Europeanlongitude sector (10° W–20° E), were performed. Here we present anoverview of the project, describing the instrumentation, the encounteredmeteorological situations during the campaigns and the data set availablefrom SPURT. Measurements were obtained for N₂O, CH₄, CO, CO₂,CFC12, H₂, SF₆, NO, NO_y, O₃ and H₂O. We illustratethe strength of this new data set by showing mean distributions of themixing ratios of selected trace gases, using a potential temperature-equivalent latitude coordinate system. The observations reveal that the LMSis most stratospheric in character during spring, with the highest mixingratios of O₃ and NO_y and the lowest mixing ratios of N₂O andSF₆. The lowest mixing ratios of NO_y and O₃ are observedduring autumn, together with the highest mixing ratios of N₂O andSF₆ indicating a strong tropospheric influence. For H₂O, however,the maximum concentrations in the LMS are found during summer, suggestingunique (temperature- and convection-controlled) conditions for this moleculeduring transport across the tropopause. The SPURT data set is presently themost accurate and complete data set for many trace species in the LMS, andits main value is the simultaneous measurement of a suite of trace gaseshaving different lifetimes and physical-chemical histories. It is thus verywell suited for studies of atmospheric transport, for model validation, andfor investigations of seasonal changes in the UT/LMS, as demonstrated inaccompanying and elsewhere published studies.

[学科分类] 大气科学