Vertical profiles of lightning-produced NO2 enhancements in the upper troposphere observed by OSIRIS

[摘要] The purpose of this study is to perform a global search of the uppertroposphere (z≥10 km) for enhancements of nitrogen dioxide anddetermine their sources. This is the first application of satellite-basedlimb scattering to study upper tropospheric NO₂. We have searched twoyears (May 2003–May 2005) of OSIRIS (Optical Spectrograph and InfraredImager System) operational NO₂ concentrations (version 2.3/2.4) to findlarge enhancements in the observations by comparing with photochemical boxmodel calculations and by identifying local maxima in NO₂ volume mixingratio. We find that lightning is the main production mechanism responsiblefor the large enhancements in OSIRIS NO₂ observations as expected.Similar patterns in the abundances and spatial distribution of the NO₂enhancements are obtained by perturbing the lightning within the GEOS-Chem3-dimensional chemical transport model. In most cases, the presence oflightning is confirmed with coincident imagery from LIS (Lightning ImagingSensor) and the spatial extent of the NO₂ enhancement is mapped usingnadir observations of tropospheric NO₂ at high spatial resolution fromSCIAMACHY (Scanning Imaging Absorption Spectrometer for AtmosphericChartography) and OMI (Ozone Monitoring Instrument). The combination of thelightning and chemical sensors allows us to investigate globally the role oflightning to the abundance of NO₂ in the upper troposphere (UT).Lightning contributes 60% of the tropical upper tropospheric NO₂ inGEOS-Chem simulations. The spatial and temporal distribution of NO₂enhancements from lightning (May 2003–May 2005) is investigated. Theenhancements generally occur at 12 to 13 km more frequently than at 10 to 11 km. Thisis consistent with the notion that most of the NO₂ is formingand persisting near the cloud top altitude in the tropical uppertroposphere. The latitudinal distribution is mostly as expected. In general,the thunderstorms exhibiting weaker vertical development (e.g. 11≤z≤13 km) extend latitudinally as far poleward as 45° but thethunderstorms with stronger vertical development (z≥14 km) tend to belocated within 33° of the equator. There is also the expectedhemispheric asymmetry in the frequency of the NO₂ enhancements, as mostwere observed in the northern hemisphere for the period analyzed.

[学科分类] 大气科学