title: Increase in upper tropospheric and lower stratospheric aerosol levels and its potential connection with Asian pollution.
abstract: Satellite observations have shown that the Asian Summer Monsoon strongly influences the upper troposphere and lower stratosphere (UTLS) aerosol morphology through its role in the formation of the Asian Tropopause Aerosol Layer (ATAL). Stratospheric Aerosol and Gas Experiment II solar occultation and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations show that summertime UTLS Aerosol Optical Depth (AOD) between 13 and 18 km over Asia has increased by three times since the late 1990s. Here we present the first in situ balloon measurements of aerosol backscatter in the UTLS from Western China, which confirm high aerosol levels observed by CALIPSO since 2006. Aircraft in situ measurements suggest that aerosols at lower altitudes of the ATAL are largely composed of carbonaceous and sulfate materials (carbon/sulfur elemental ratio ranging from 2 to 10). Back trajectory analysis from Cloud-Aerosol Lidar with Orthogonal Polarization observations indicates that deep convection over the Indian subcontinent supplies the ATAL through the transport of pollution into the UTLS. Time series of deep convection occurrence, carbon monoxide, aerosol, temperature, and relative humidity suggest that secondary aerosol formation and growth in a cold, moist convective environment could play an important role in the formation of ATAL. Finally, radiative calculations show that the ATAL layer has exerted a short-term regional forcing at the top of the atmosphere of -0.1 W/m2in the past 18 years.
  
  
  CONCLUSIONS
  Increase of summertime upper tropospheric aerosol levels over Asia since the 1990s Upper tropospheric enhancement also observed by in situ backscatter measurements Significant regional radiative forcing of -0.1 W/m2.
authors.affiliation: Science Systems and Applications, Inc Hampton, Virginia, USA ; NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: J-P
authors.initials: JP
authors.lastname: Vernier
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: T D
authors.initials: TD
authors.lastname: Fairlie
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: M
authors.initials: M
authors.lastname: Natarajan
authors.affiliation: Swiss Federal Institute of Technology Zurich, Switzerland.
authors.forename: F G
authors.initials: FG
authors.lastname: Wienhold
authors.affiliation: LAGEO, Institute of Atmospheric Physics, Chinese Academy of Sciences Beijing, China.
authors.forename: J
authors.initials: J
authors.lastname: Bian
authors.affiliation: Department of Physics, Lund University Lund, Sweden.
authors.forename: B G
authors.initials: BG
authors.lastname: Martinsson
authors.affiliation: LOA, CNRS-Université Lille1 Villeneuve d'Ascq, France.
authors.forename: S
authors.initials: S
authors.lastname: Crumeyrolle
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: L W
authors.initials: LW
authors.lastname: Thomason
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Bedka
keywords: aerosol; pollution; trend