Seasonal and interannual variations of HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

• Main Authors: Glatthor, N., Höpfner, M., Stiller, G. P., Clarmann, T. von, Funke, B., Lossow, S., Eckert, E., Grabowski, U., Kellmann, S., Linden, A., Walker, K. A., Wiegele, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geosciences Union 2015
• Subjects: annual variation; atmospheric chemistry; biomass burning; inorganic compound; MIPAS; seasonal variation; Southern Hemisphere; stratosphere; tracer; troposphere; Indonesia; South America; Southern Africa; ddc:550; Earth sciences; info:eu-repo/classification/ddc/550; Antarctic; Austral; Antarc*
• Online Access: https://publikationen.bibliothek.kit.edu/1000046050; https://publikationen.bibliothek.kit.edu/1000046050/3434452; https://doi.org/10.5445/IR/1000046050; http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:swb:90-460508

We present a HCN climatology of the years 2002-2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5-6 months and a stratospheric lifetime of about 2 years. The MIPAS climatology is in good agreement with the HCN distribution obtained by the spaceborne ACE-FTS experiment and with airborne in situ measurements performed during the INTEX-B campaign. The HCN amounts observed by MIPAS in the southern tropical and subtropical upper troposphere have an annual cycle peaking in October-November, i.e. 1-2 months after the maximum of southern hemispheric fire emissions. The probable reason for the time shift is the delayed onset of deep convection towards austral summer. Because of overlap of varying biomass burning emissions from South America and southern Africa with sporadically strong contributions from Indonesia, the size and strength of the southern hemispheric plume have considerable interannual variations, with monthly mean maxima at, for example, 14 km between 400 and more than 700 pptv. Within 1-2 months after appearance of the plume, a considerable portion of the enhanced HCN is transported southward to as far as Antarctic latitudes. The fundamental period of HCN variability in the northern upper troposphere is also an annual cycle with varying amplitude, which in the tropics peaks in May after and during the biomass burning seasons in northern tropical Africa and southern Asia, and in the subtropics peaks in July due to trapping of pollutants in the Asian monsoon anticyclone (AMA). However, caused by extensive biomass burning in Indonesia and by northward transport of part of the southern hemispheric plume, northern HCN maxima also occur around October/November in several years, which leads to semi-annual cycles. There is ...