Apprenticeship 2017-2018: Douglas Keller

The radiation balance at the Earth’s surface is significantly affected by the continuous presence of the atmospheric boundary layer (ABL). This layer responds to the convoluted action of surface aerodynamic and radiative properties, atmospheric radiation levels and the dynamic of the atmospheric flow. The ABL plays the fundamental role of an atmospheric interface of variable thickness regulating radiative and turbulent flux exchanges between the surface and the free-troposphere. The most important structural parameter defining the ABL in space and time is the height of the temperature inversion layer. The ABL has a different behavior and thermodynamic structure when summer cases are compared to winter cases, especially in polar atmospheres. At these latitudes, the ABL acquires a complex layered structure with the addition of multiple elevated inversion layers (EI) depending upon synoptic meteorological forcing [Mayfield and Fochesatto, 2013]. Experimental determination of the ABL structure is done twice daily through thermodynamic soundings (RAOBS) around the world (http://weather.uwyo.edu/upperair/sounding.html). Regionally, this information is obtained at the NWS station at the Fairbanks International Airport (station code PAFA 70261). However, because the ABL is bounded by surface and atmospheric flow; it experiences intraday variability due to surface heating/cooling as well as variations in the meteorological conditions (e.g., the presence of wind; increasing/decreasing clouds and precipitation). This variability can be determined by continuous Lidar profiling, such as that found through NASA’s Micro Pulse Lidar Network (MPLNET, https://mplnet.gsfc.nasa.gov/sites), if appropriate methods are available to retrieve such information and deduce the ABL structure. Therefore, this research puts forward three overall science questions to address: 
 
1. Is the current MPLNET algorithm [Lewis et al, 2013] for ABL detection valid for high latitude boundary layers? And, is the same methodology valid for summer and winter conditions? Currently, MPLNET does not have an operational ABL height detection product that has been extensively tested for polar latitudes.   2. How variable is the ABL throughout the day and how well is it represented by the radiosonde thermodynamic profiling? 3. Can the NASA MPLNET instrument determine the evolution of elevated temperature inversions?