CLAMPS Boundary Layer Evolution Observations during VORTEX-SE-2016

The Collaborative Lower Atmospheric Mobile Profiling System (CLAMPS) is a 16-foot trailer that houses three remote sensors that provide high temporal resolution (better than 5 minute) observations of the boundary layer.  The three instruments are a Doppler lidar, an Atmospheric Emitted Radiance Interferometer (AERI), and a microwave radiometer.  The facility also includes a surface met station, and an on-board data system for processing and displaying the data in real-time.  The facility can be powered using either shore power (220 V / 50 Amp service) or the on-board diesel generator.  This allows CLAMPS to support both long-term field experiments and highly mobile field campaigns.

The CLAMPS Doppler lidar transmits pulses of 1.5 µm wavelength energy into the atmosphere, recording data at 30-m vertical and 1-s temporal resolution.  The energy is scattered by aerosol particles (which are small enough to be tracers of atmospheric motion) and measures the Doppler shift of the backscattered energy. It has a scanner that can point the lidar beam in any direction, but it is operated in two scanning modes.  The first mode is a plane-parallel-indicator (PPI) scan at 70 degrees elevation every two minutes, while the second mode is 1-s vertical measurements between the PPI scans.  The PPI scans are processed with the velocity azimuth display (VAD) method to derive horizontal wind speed and direction profiles. 

The AERI measures downwelling radiance in the 3-19 µm spectral region at high spectral resolution.  The AERI is calibrated with two well-characterized blackbodies that are able to maintain calibration better than 1% of the ambient radiance.  From these spectra, profiles of temperature and humidity in the boundary layer are retrieved using a 1-dimensional variational method. 

The microwave radiometer measures downwelling radiance in 14 channels between 22 and 60 GHz.  These observations are also sensitive to the profile of temperature and humidity, but are used primarily to retrieve precipitable water vapor and liquid water path above the instrument.

CLAMPS was deployed at the Belle Mina site (20 miles SSW of Huntsville, Alabama) to support the VORTEX-SE-2016 from 2 March until 6 June.  During that period of time, the AERI and MWR operated over 99% of the time.  Unfortunately, the CLAMPS Doppler lidar suffered an internal failure on 9 March; however, the NOAA Air Resources Laboratory had collocated their Doppler lidar next to CLAMPS and thus the impact of the lidar failure was negligible.  The CLAMPS data are being used to study the evolution of the boundary layer thermodynamic and kinematic structure over the entire 3 month time period, but especially during the 4 intensive operating periods (IOPs) during this field experiment.  Data from these IOPs will be shown, and comparisons between the CLAMPS observations and the real-time output from the RAP model will be shown.