Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)

Intense anthropogenic emissions over the Indian sub-continent lead to the formation of layers of particulate pollution that can be transported to the high altitude regions of the Himalaya-Hindu Kush (HKH). Aerosol particles contain a substantial fraction of strongly absorbing material, including black carbon (BC), organic compounds (OC), and dust all of which can contribute to atmospheric warming, in addition to greenhouse gases. Using a 3-year record of continuous measurements of aerosol optical properties, we present a time series of key climate relevant aerosol properties including the aerosol absorption and scattering coefficients as well as the single-scattering albedo (w0). Results of this investigation show substantial seasonal variability of these properties, with long range transport during the pre- and post-monsoon seasons and efficient precipitation scavenging of aerosol particles during the monsoon season. The monthly averaged scattering coefficients range from 0.1 Mm-1 (monsoon) to 20 Mm-1 while the average absorption coefficients range from 0.5 Mm-1 to 3.5 Mm-1. Both have their maximum values during the premonsoon period (April) and reach a minimum during Monsoon (July–August). This leads to dry w0 values from 0.86 (pre-monsoon) to 0.79 (monsoon) seasons. Significant diurnal variability due to valley wind circulation is also reported. Using aerosol optical depth (AOD) measurements,we calculated the resulting direct local radiative forcing due to aerosols for selected air mass cases. We found that the presence of absorbing particulate material can locally induce an additional top of the atmosphere (TOA) forcing of 10 to 20 W m-2 for the first atmospheric layer (500 m above surface). The TOA positive forcing depends on the presence of snow at the surface, and takes place preferentially during episodes of regional pollution occurring on a very regular basis in the Himalayan valleys. Warming of the first atmospheric layer is paralleled by a substantial decrease of the amount of radiation reaching the surface. The surface forcing is estimated to range from -4 to -20 W m-2 for small-scale regional pollution events and large-scale pollution events, respectively. The calculated surface forcing is also very dependent on surface albedo, with maximum values occurring over a snow-covered surface. Overall, this work presents the first estimates of aerosol direct radiative forcing over the high Himalaya based on in-situ aerosol measurements, and results suggest a TOA forcing significantly greater than the IPCC reported values for green house gases.

Citation proposal
S. Marcq (CNRS Laboratory of Meteorology Physics - Laboratory of Glaciology) - Paolo Laj (CNRS Laboratory of Meteorology Physics - Laboratory of Glaciology) - J. C. Roger (Blaise Pascal University ,CNRS) - Paolo Villani (Blaise Pascal University ,CNRS) - Karine Sellegri (Blaise Pascal University,CNRS) - Paolo Bonasoni (Institute of Atmospheric Sciences and Climate (ISAC) - CNR) - Angela Marinoni (Institute of Atmospheric Sciences and Climate (ISAC) - CNR) - Paolo Cristofanelli (Institute of Atmospheric Sciences and Climate (ISAC) - CNR) - Giampietro Verza (Ev-K2-CNR) - Michael H. Bergin (Georgia Institute of Technology, Civil and Environmental Engineering) (2010) . Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.). Copernicus GmbH (Copernicus Publications) https://geoportal.mountaingenius.org/geonetwork/srv/api/records/1ff2a446-cbfa-4498-9240-9ad162a4e006

INSPIRE
SDS

INSPIRE

Identification

File identifier: 1ff2a446-cbfa-4498-9240-9ad162a4e006 XML

Online resource

Protocol: WWW:LINK-1.0-http--link

Protocol: WWW:DOWNLOAD-1.0-http--download

Protocol: WWW:LINK-1.0-http--related

Resource identifier

Metadata language: eng

Encoding

Projection

Classification of data and services

Topic category

Climatology, meteorology, atmosphere
Environment

Classification of data and services

Coupled resource

Classification of data and services

Coupled resource

Keywords

Other keywords

Keywords ( Theme )

Atmospheric Brown Clouds

Keywords ( Place )

Himalayas , Nepal Climate Observatory-Pyramid , Nepal

Keywords ( Theme )

Aerosol optical properties , radiative forcing , aerosol optical depth

Geographic coverage

Temporal reference

Temporal extent

Date ( Publication ): 2010-07-02T00:00:00

Quality and validity

Lineage

The book contains the scientific papers by EvK2Cnr researchers in a special issue of Atmospheric Chemistry and Physics, entitled "Atmospheric brown clouds in the Himalayas "

ACP (Atmospheric Chemistry and Physics) - Special Issue Atmospheric brown cloud in the Himalayas. Editor(s): G. McFiggans and J. J. Schauer

"Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.)". S. Marcq, P. Laj, J. C. Roger, P. Villani, K. Sellegri, P. Bonasoni, A. Marinoni, P. Cristofanelli, G. P. Verza, and M. Bergin. Atmos. Chem. Phys., 10, 5859-5872, 2010.