English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present a HCN climatology of the years 2002–2012, derived from FTIR limbemission spectra measured with the Michelson Interferometer for PassiveAtmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus onbiomass burning signatures in the upper troposphere and lower stratosphere.HCN is an almost unambiguous tracer of biomass burning with a troposphericlifetime of 5–6 months and a stratospheric lifetime of about 2 years. TheMIPAS climatology is in good agreement with the HCN distribution obtained bythe spaceborne ACE-FTS experiment and with airborne in situ measurementsperformed during the INTEX-B campaign. The HCN amounts observed by MIPAS inthe southern tropical and subtropical upper troposphere have an annual cyclepeaking in October–November, i.e. 1–2 months after the maximum of southernhemispheric fire emissions. The probable reason for the time shift is thedelayed onset of deep convection towards austral summer. Because of overlapof varying biomass burning emissions from South America and southern Africawith sporadically strong contributions from Indonesia, the size and strengthof the southern hemispheric plume have considerable interannual variations,with monthly mean maxima at, for example, 14 km between 400 and more than700 pptv. Within 1–2 months after appearance of the plume, a considerableportion of the enhanced HCN is transported southward to as far as Antarcticlatitudes. The fundamental period of HCN variability in the northern uppertroposphere is also an annual cycle with varying amplitude, which in thetropics peaks in May after and during the biomass burning seasons in northerntropical Africa and southern Asia, and in the subtropics peaks in July due totrapping of pollutants in the Asian monsoon anticyclone (AMA). However,caused by extensive biomass burning in Indonesia and by northward transportof part of the southern hemispheric plume, northern HCN maxima also occuraround October/November in several years, which leads to semi-annual cycles.There is also a temporal shift between enhanced HCN in northern low and mid-to high latitudes, indicating northward transport of pollutants. Due toadditional biomass burning at mid- and high latitudes, this meridionaltransport pattern is not as clear as in the Southern Hemisphere. Uppertropospheric HCN volume mixing ratios (VMRs) above the tropical oceansdecrease to below 200 pptv, presumably caused by ocean uptake,especially during boreal winter and spring. The tropical stratospheric taperecorder signal with an apparently biennial period, which was detected in MLSand ACE-FTS data from mid-2004 to mid-2007, is corroborated by MIPAS HCN data.The tape recorder signal in the whole MIPAS data set exhibits periodicitiesof 2 and 4 years, which are generated by interannual variations in biomassburning. The positive anomalies of the years 2003, 2007 and 2011 are causedby succession of strongly enhanced HCN from southern hemispheric andIndonesian biomass burning in boreal autumn and of elevated HCN from northerntropical Africa and the AMA in subsequent spring and summer. The anomaly of2005 seems to be due to springtime emissions from tropical Africa followed byrelease from the summertime AMA. The vertical transport time of the anomaliesis 1 month or less between 14 and 17 km in the upper troposphere and8–11 months between 17 and 25 km in the lower stratosphere

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