The well-being of hundreds of millions of residents in northeastern India depends on the fertile land around the Ganges River, which is fed by monsoon rains and runoff from the nearby Himalayan Mountains. Any disturbance to the monsoon rains could threaten the population. In the same region, increased industrial activities due to economic growth are releasing small aerosol particles, such as soot and dust, that absorb and scatter sunlight and thus can change cloud formation processes and the heat distribution in the atmosphere. Such changes could greatly increase or decrease the monsoon rains, with consequences for the residents of the Ganges Valley.
In the Ganges Valley Aerosol Experiment (GVAX) — a long-term collaborative effort between DOE and the Indian Institute of Science — EVS atmospheric scientists led the deployment of a portable climate research laboratory in the Ganges Valley from June 2011 to March 2012, before, during, and after the monsoon. The site chosen for the deployment was Nainital, India, the relatively pristine mountaintop location of a permanent observatory operated by the Aryabhatta Research Institute of Observational Sciences.
Professor S.K. Satheesh of the Indian Institute of Science in Bangalore, India, helped to organize GVAX, in close cooperation with EVS researchers. “Because the Gangetic Basin experiences a mixture of various aerosol types throughout the seasons,” Professor Satheesh said, “it is an ideal location to study how aerosols impact clouds and energy transfer in the atmosphere.”
Upon approval of a detailed science plan, the DOE Office of Science agreed to dedicate its Atmospheric Radiation Measurement (ARM) Mobile Facility, AMF1, for the duration of the work at Nainital. The instruments aboard the AMF1 made continuous measurements of clouds, precipitation, radiative energy, and aerosols – their composition, size, and changes over time. Combined with data from existing ground stations operated by other agencies elsewhere on the subcontinent, the AMF1 measurements showed how aerosols absorb or reflect sunlight. The results can be used to determine how clouds are affected by high concentrations of pollutants.
The GVAX goal was to gain a better understanding of the impact of aerosols on the regional climate, particularly the monsoons. Moreover, as EVS scientist Rao Kotamarthi explained, “India isn't the only place with these kinds of conditions. The global implications of changes in precipitation patterns are a concern for many regions around the world that rely heavily on seasonal rainfall.”
The GVAX data will be used to improve global climate models. Most of these models assume either uniform distribution of aerosols in the lower part of the atmosphere or that all the aerosols are above the atmospheric boundary layer, with a smooth decrease in concentration. In contrast, the GVAX data show distinct atmospheric heating profiles due to aerosols that can be used to build greater detail into climate models and improve their ability to predict future change.