Condition of Retrieving Vertical Column Density of Atmospheric Pollution Gases by Using Scattered Solar Radiation

We present a method to monitor the vertical column density (VCD) of atmospheric pollution gases by using the scattered solar radiation. The necessary condition of capturing the useful scattered solar radiation is achieved. The condition is only dependent on the solar elevation angle, while independent of the solar azimuth angle, which could greatly simply the capturing equipment and procedure. Under the condition, the VCD of tropospheric NO₂ in Chengdu, China is retrieved from the scattered solar radiation, which is close to that from the direct solar radiation.