Vertical profiles of NO2, SOA precursor gases, and aerosol extinction measured from ground: the Ganges Valley Aerosol Experiment (GVAX) and first data from CARES

Description

The Ganges Valley Aerosol Experiment (GVAX) presents a unique opportunity to study aerosol sources and distributions in a region that stands out on global scales in terms of high aerosol optical depth and trace gas vertical columns. The GV is also one of the least-sampled areas of the world. The University of Colorado will combine in situ and innovative remote sensing instruments based on Multi-Axis DOAS (MAX-DOAS) and Light-Emitting Diode Cavity Enhanced DOAS (LED-CE-DOAS) to measure near-surface and vertical profile observations of SOA precursor trace gases and aerosol optical properties. This presentation will give an overview about the instruments that have been developed in the Atmospheric Trace Molecule Spectroscopy Laboratory (ATMOSpeclab) recently, and how this novel information facilitates 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. MAX-DOAS has the unique capability to measure multispectral aerosol extinction vertical profiles, aerosol, and ozone precursor gases with a single instrument, simultaneously, and over the same extended spatial scale, thus averaging over local concentration gradients and measuring directly regionally aggregated distributions. LED-CE-DOAS measures most of these parameters in situ. The GVAX measurement strategy will be discussed. Further, from 11 to 29 June 2010, a CU ground MAX-DOAS instrument was installed at the T1 site, also known as the Cool site, during the CARES (Carbonaceous Aerosols and Radiative Effects Study) campaign in California. Results will be presented for NO2, CHOCHO, and aerosol extinction. These data are especially useful for validation purposes since the spatial scales are similar to the footprint of satellite pixels and model grid boxes. Our initial plan is to deploy an updated version of the MAX-DOAS instrument in the Ganges Valley, India, during GVAX. Details of the mission, with emphasis on the information content towards aerosol properties achievable with the extended observation geometry, will be discussed using radiative transfer simulations.