Measurements of tropospheric NO2 with an airborne multi-axis DOAS instrument

[摘要] The AMAXDOAS instrument is an airborne multi-axis DOAS instrumentcovering the spectral range from 300 to 600 nm. During oneflight of the SCIAVALUE campaign on 19 March 2003, the AMAXDOASonboard the DLR Falcon detected tropospheric NO₂ overEurope under both cloudy and cloud free conditions. By combiningthe measurements in nadir and zenith direction, and analysing thespectra in the UV and the visible spectral region, information wasderived on where the bulk of the observed NO₂ was located.Vertical columns of up to 5.7x10¹⁶ molec cm^-2 were observed close to Frankfurt, with adistribution peaking in the boundary layer and in good agreementwith surface measurements. On several occasions, strongtropospheric NO₂ signals were also detected when flyingabove clouds. The ratio of zenith and nadir measurements indicatesthat the NO₂ observed was located within the cloud, andassuming the same profile as for the cloud free situation theNO₂ vertical column was estimated to be 5.0x10¹⁶ molec cm^-2. The results are relevant for theretrieval of tropospheric NO₂ columns from space-borneinstruments in cloudy situations.

[学科分类] 大气科学