Ganges Valley Aerosol Experiment: proposed experiment details, expected data, and forecast modeling products

Description

The Ganges Valley region is one of the largest and most rapidly developing sections of the Indian subcontinent. Recent satellite-based measurements have indicated that the upper Ganges Valley has some of the highest persistently observed aerosol optical depth values. The aerosol layer covers a vast region, extending across the Indo-Gangetic Plain to the Bay of Bengal during the winter and early spring of each year. Our proposed field study will provide critical data to address these hypotheses and will contribute to developing better parameterizations for tropical clouds, convection, and aerosol-cloud interactions. The primary science questions for the mission are as follows: (1) What are the sources and sinks of the aerosols comprising the aerosol cloud over this region and what effects does it have on clear-sky radiation fields, as well as on cloud microphysical and macrophysical properties? What effect does the diurnal PBL cycle in the Ganges Valley have on the atmospheric distribution of aerosols? (2) What effect do increasing aerosols in the Ganges Valley have on the ISM? What effect do aerosols have on shortwave radiative forcing, mid-tropospheric heating, and convective activity over continental India? To achieve these science objectives, an implementation has been devised in collaboration with scientists in India. The primary anchor facility for the project is the ARM Mobile Facility. A deployment starting in approximately April 2011 and lasting to April 2012 at the ARIES observatory located in Nainital is anticipated for AMF ground operations. During this one-year deployment of the AMF there will be two intensive periods, one during the pre-monsoon and the second during the winter-early spring of 2012. These measurements and the subsequent data sets must be placed in a larger regional context in order to relate the data to a particular dynamic state of the atmosphere and begin developing hypotheses that explain observed phenomena. The regional context will be developed within the conditions generated by a 3D regional scale model. Baseline simulations of the 3D regional scale model will provide the necessary analytical support for the scientific studies done under GVAX. In support of the one-year deployment, we plan to produce daily model forecasts for the Nainital site and the two intensive periods. Expected model products, models used for the forecasts, and plans for making them available to interested users and project participants will be presented.