Bistatic lidar measurements in the boundary layer using a CCD camera

A CCD based bistatic lidar (CLidar) system has been developed and constructed to measure scattering in the atmospheric boundary layer. The system used is based on a CCD camera, wide-angle optics and laser. Measuring near the ground with the standard monostatic lidar method is difficult due to the huge change in signal strength with altitude and the incomplete overlap between the laser and the telescope. High spatial (altitude) resolution is also desired near the ground for comparison with in-situ aerosol instruments. Imaging a vertical laser beam from the side with a CCD camera and wide-angle field of view optics overcomes both of these problems. While the molecular signal changes many orders of magnitude in the standard method, it only changes about one order with the CLidar method. In addition, the CLidar resolution near the ground is less than a meter. For perpendicular polarization, the molecular signal is nearly constant all the way to the ground. Other advantages of the CLidar method include low cost and simplicity. The signal is integrated on the CCD rather than with specialized electronics. With the bistatic CLidar method the scattering angle changes with altitude. The variation of scattering intensity with the scattering angle will be influenced by the aerosol size distribution and thus could help provide information on aerosol parameters of interest in the boundary layer.