Observations of Smoke Aerosol Impacts on Land-Atmosphere Interactions During GRAINEX

Smoke aerosols reduce downwelling solar radiation at the surface and impacts boundary layer development, surface temperature, humidity and photochemical production of trace gases such as ozone. In turn, surface characteristics and soil moisture conditions modulate the effects of the reduction in downwelling solar radiation at the surface. High spatial and temporal resolution datasets for investigating such boundary layer impacts of smoke aerosols are rare. In the summer of 2018, multiple incidents of smoke plume transport occurred over counties surrounding Lincoln, NE, the site of the Great Plains Irrigation Experiment (GRAINEX) field campaign. During GRAINEX, a high-density observational network was established to study the impact of irrigation on boundary layer evolution, cloud and precipitation formation. The observational network included a dozen eddy covariance surface energy budget flux stations and two integrated sounding systems (ISS) operated by the NCAR Earth Observing Laboratory (NCAR EOL). Two-hourly radiosonde profiles are available from five different locations with the study domain. In addition, seventy-five Environmental Monitoring Economical Sensor Hubs (EMESH) stations were deployed from late May through July of 2018.

Prolonged periods of cloud free conditions occur during smoke events observed during June 1 and June 14-15 of 2018. Eastward moving smoke plumes were observed by the surface flux stations at different times and intercomparison between sites allows for observational estimates of impacts of smoke on surface radiation budget. Variability in land cover and soil moisture conditions across the study domain provide the basis for analyzing how land-atmosphere interaction are impacted by smoke radiative forcing. In situ, surface observations of ozone are also available which allow for analysis of smoke radiative forcing on surface ozone concentrations. The presentation will discuss the above described aspects of smoke radiative forcing impacts on land-atmosphere interactions which are being studied using both GRAINEX observational data and single column modeling.