Impact of Eclipse of 21 August 2017 on the Atmospheric Boundary Layer

The (total) solar eclipse of 21 August 2017 presents a challenging opportunity to comprehensively measure (and improve understanding of) the physical response to decreases in turbulence within the ABL produced by a rapid reduction in solar radiation. In this case, the eclipse-induced transition will occur close to local solar noon, and hence will be more rapid than at natural sunset. A mesoscale network of three UAH boundary layer profiling systems will be set up around Clarksville, TN, and Hopkinsville, KY, to document the details of the physical response of the ABL to the rapid decrease in solar radiation. The region offers a heterogeneous surface, including expansive agricultural and forested regions. Data from the following mobile systems will be examined and compared:

• Mobile Integrated Profiling System (MIPS) with a 915 MHz Doppler wind profiler, X-band Profiling Radar (XPR), Microwave Profiling Radiometer (MPR), lidar ceilometer, and Doppler mini-sodar;
• Rapidly Deployable Atmospheric Profiling System (RaDAPS) with a 915 MHz Doppler wind profiler, MPR, lidar ceilometer, Doppler mini-sodar;
• Mobile Doppler Lidar and Sounding system (MoDLS) with a Doppler Wind Lidar and MPR.

A tethered balloon will provide high temporal and vertical resolution in situ sampling of the surface layer temperature and humidity vertical profiles over the lowest 120 m AGL. Two of the profiling systems (MIPS and MoDLS) will include 20 Hz sonic anemometer measurements for documentation of velocity component (u, v, w) variance, buoyancy flux, and momentum flux. The Mobile Alabama X-band (MAX) dual polarization radar will be paired with the Ft. Campbell WSR-88D radar, located 29 km east of the MAX, to provide dual Doppler radar coverage of flow within the ABL over the profiler domain. All profiling systems and the MAX radar will have cameras to produce time-lapse images of cumulus cloud evolution around the time of the eclipse.

The measurements during this eclipse will also provide information on the response of insects to rapidly changing lighting conditions. During the natural afternoon-to-evening transition, daytime insect concentrations decrease rapidly, and stronger-flying nighttime flyers emerge rapidly following sunset. We hypothesize that a similar but more limited transition will occur: nighttime flyers will emerge, but the daytime flyers will not rapidly disappear due to the short time scale of the darkness. This insect transition will also be measured with the radar profilers and the MAX and WSR-88D dual polarization radars.