Aerosol Black Carbon In The Indo-Gangetic Plains And In The Foothills Of Himalayas, Measurements vs. Global Modeling
Abstract
Aerosol particles associated with atmospheric brown clouds are highly absorbing due to their large black carbon (BC) content and the occasional presence of large amounts of desert dust. This causes a reduction of solar radiation at the surface accompanied by a substantial atmospheric heating. Direct field observations show that the aerosol pollution from the Indo-Gangetic Plains is transported to the Himalayan foothills especially during the pre-monsoon season. Satellite studies indicate that this pollution is transported further to the higher Himalayas. This would affect the mass balance of the Himalayan glaciers, as they would be influenced by the atmospheric heating caused by the absorbing aerosols, as well as the surface darkening of bright surfaces caused by BC deposition. Global models may be used to estimate the atmospheric concentrations of BC and their subsequent surface deposition. Using different emission scenarios, predictions of possible future trends may also be conducted. However, detailed comparisons between modeled and measured aerosol data should be made to reveal how well the measured aerosol properties can be simulated with the existing emission inventories. In this study, we compare the results of a global atmospheric model (ECHAM5-HAM) against measurements of BC surface concentrations in India. The model is run at an atmospheric resolution of T42L19, implying a horizontal resolution of about 2.8 degrees and 19 vertical levels. Aerosol transport, removal and chemistry are simulated. The emission inventories used are the REAS and GAINS inventories, and three emission scenarios are considered. BC data from two different stations is used: The first station is located in the Indo-Gangetic Plains, in Gual Pahari, about 35 km south of New Delhi. The second station is on the foothills of the Himalayas, in Mukteshwar, about 350 km east of New Delhi at an elevation of about 2 km ASL. Data from Mukteshwar is available from September 2005; data from Gual Pahari spans from December 2007 to January 2010. The model, that has been successfully evaluated against MODIS AOD, reproduces the local features of the BC concentrations qualitatively on a seasonal level: higher concentrations in the pre-monsoon season and the fall with concentrations in Gual Pahari being higher than those in Mukteshwar. This is in contrast with BC concentration averages in India changing smoothly from low in the summer to high in the winter. Simulations indicate significant BC concentrations also at higher parts of the Himalayas, especially during the pre-monsoon season. This is related to the elevated boundary layer height, and implies that BC originating from the brown cloud in the Indo-Gangetic Plains may be transported to the Himalayan glaciers, thus affecting their mass balance.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A12A..01H
- Keywords:
-
- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional