Aerosol sources and processing at the Ganges Valley Aerosol Experiment (GVAX) Pantnagar supersite

Description

The Ganges Valley (GV) region has some of the highest observed aerosol optical depths in the world. The aerosol layer extends over a vast area, and increasing aerosol loading may have significant impacts on regional and global climate. Evaluating the role of aerosols in climate change requires understanding the sources, sinks, and atmospheric processing of aerosol particles. These are not well-characterized in the GV, one of the least-sampled areas of the world. The DOE Ganges Valley Aerosol Experiment (GVAX) campaign will address aerosol-climate connections through a year-long campaign of radiative measurements at the Nainatal Observatory (at 2000 m) in the foothills of the Himalayas. A two-month intensive, planned for early 2012, will focus on aerosol chemical composition and aging as particulate matter is transported across the Ganges Valley plain and into the foothills. Intensive measurement sites include Pantnagar (25 km south of Nainatal) and Lucknow (360 km south of Pantnagar), as well as flights of the DOE G-1 instrumented aircraft from Lucknow. In addition, an instrumented van operated and funded by the Indian Institute of Science/Indian Space Research Organization (IISc/ISRO) and supported by DOE will operate between these measurement sites. At the Pantnagar supersite, we will deploy instruments to make critical measurements for understanding aerosol life cycle processes and the fundamental microphysics of aerosol-cloud interaction, including continuous, high-time-resolution measurements of aerosol chemistry and microphysics, gas-phase tracers and secondary organic aerosol (SOA) precursors, hygroscopic properties of the aerosol particles, and in situ and column aerosol optical properties. Specific goals include optical and CCN closure studies, particulate emissions source characterization, and understanding the atmospheric processing of aerosol particles in the GV. We will combine in situ, remote sensing column, and vertical profile observations of SOA precursor trace gases and aerosol optical properties to link the ground-based data set with that from DOE’s G-1 aircraft, assess boundary layer dynamics, and bridge to the spatial scales predicted by atmospheric models. The Pantnagar supersite and instrumented van are critical for coupling surface observations to the remote sensing and radiation measurements at Nainital site for a regional overview of aerosol chemical and physical properties.