An atmospheric transparency was measured using a LIDAR with a pulsed UV laser ( 355nm ) at the observation site of Telescope Array in Utah , USA .
The measurement at night for two years in 2007 \sim 2009 revealed that the extinction coefficient by aerosol at the ground level is 0.033 ^ { +0.016 } _ { -0.012 } km ^ { -1 } and the vertical aerosol optical depth at 5km above the ground is 0.035 ^ { +0.019 } _ { -0.013 } .
A model of the altitudinal aerosol distribution was built based on these measurements for the analysis of atmospheric attenuation of the fluorescence light generated by ultra high energy cosmic rays .