During intense spring and early summer storms, substantial volumes of dust from east Asian desert regions are lofted over the continent and transported by prevailing winds across the Pacific Ocean. The phenomenon has wide reaching effects including long range nutrient and sediment transport as well as radiative forcing. Mauna Loa Observatory (MLO) is an atmospheric baseline station in Hawaii at an altitude of 3397-m.a.s.l.. MLO’s CCD Camera Lidar (CLidar) has fine near-ground altitude resolution, which makes it a useful system for Asian dust detection, especially at high altitude sites such as MLO. A 20-Watt, 532-nm Nd:YAG laser was vertically transmitted into the atmosphere above MLO. The side-scatter from atmospheric constituents, such as clouds, aerosols, and air molecules was detected by a wide-angle CCD camera situated 139-m from the laser. The obtained signal was range-normalized using a molecular scattering model and corrected for transmission with a column-averaged aerosol phase function derived from MLO-based AERONET photometer measurements. In several of the resulting aerosol extinction profiles, notable aerosol layers were observed near altitude ranges in which Asian dust is typically transported by prevailing winds. Corresponding relative humidity measurements made by nearby radiosondes were examined to differentiate aerosol scattering from cloud scattering. To further examine layers exhibiting both aerosol extinction peaks and relative humidity levels below that of tenuous ice clouds, back trajectories were conducted using NOAA’s Hybrid Single Particle Lagrangian Integrated Trajectory model. Several layers from 2008 and 2009 were traced back to East Asian deserts.
A wide-angle CCD camera based bistatic lidar (CLidar) is used to monitor aerosol profiles in the atmosphere of The Bahamas. A 2-Watt CW laser beam ranging from ground to zenith is captured in a single image by a camera fitted with a fisheye lens which is placed at a different location from the laser. Scattering altitude is determined simply from the geometry of the CLidar in contrast to monostatic lidar which requires expensive electronics to measure the time of flight of the returned signal. Each image contains both molecular and aerosol single angle scattering. A cloud free image is used to normalize the signal intensity to a model of molecular scattering at a region free of aerosol layer. Then molecular portion is subtracted to retrieve aerosol side scattering. An aerosol phase function was assumed to convert side scatter to aerosol extinction. Corrections due to transmission effects are then iteratively calculated until convergence is reached. Aerosol extinction drops off sharply above 1 km indicating the planetary boundary level which agrees well with the relative humidity measurements obtained from the radiosonde data of Nassau airport observation. Additionally, aerosols originated from the smoke of a charcoal grill operating near experimental site were efficiently detected near ground levels. Aerosol extinction at 20 m above sea level is 0.085 km<sup>-1</sup> during grilling compared to 0.03 km<sup>-1</sup> during no grilling. Excellent altitude resolution of the CLidar at the ground levels allows its use for in-situ environmental characterization without the overlap effects faced when using traditional lidar.
A bistatic CCD camera lidar (CLidar) was used at the National Oceanic and Atmospheric Administration’s Mauna Loa
Observatory (MLO) to map aerosol light scattering. Laser light from a 532 nm, Nd:YAG laser was vertically transmitted
into the atmosphere and the scatter off clouds, aerosols and air molecules was detected using a CCD camera with wide
angle optics and a laser line filter. The intensity of each CCD camera pixel imaging the beam was normalized to a
molecular scattering model in an aerosol free region for subtraction of molecular scattering. Aerosol extinction was
derived using a column average aerosol phase function derived from AERONET sun photometer measurements at MLO.
The CLidar design allows measurements of aerosol scattering all the way to the ground without an overlap correction.
MLO, at 3397 m.a.s.l., typically receives free tropospheric air. During spring months, prevailing winds can occasionally
transport dust from Asian sources with high dust activity over MLO. Aerosol scattering measurements were taken by the
CLidar during spring months at MLO and revealed extinction peaks at mid-range altitudes. Back trajectories of air
parcels from MLO at the altitudes of these peaks were conducted using NOAA’s Hybrid Single Particle Lagrangian
Integrated Trajectory (HYSPLIT) model and it was found that they passed over regions of Eastern Asia known as
sources of high dust activity. Relative humidity data from radiosondes and the NOAA stratospheric lidar’s water vapor
channel were examined to differentiate aerosol scattering from tenuous cloud scattering. This paper presents aerosol
extinction data with observations of Asian dust as measured by the CLidar during spring months at MLO.