The Discussion And Application Of Lidar In Semi-arid Area

Lidar is an important tool of remote sensing in current, especially in detection for atmospheric aerosols and clouds.we focus on the observational data from two lidar in Lanzhou University(CAMLTM CE-370-2 and MPL) in july 2005 to to march 2009 data, through a lot of data processing, we ascertained on the Actual observation hight with different calculation method and selected parameters and discussed results in the differences. According to the calculation results, detailed demonstrates the change process of atmospheric aerosol in semiarid areas of sand, cloudy weather. Finally discussed the aerosol boundary layer.1, The discussion of Actual observation level:comparing the echo signal of CAMLTM CE-370-2 and MPL-4B, we found that:the Actual observation level of MPL-4B are higher than CAMLTM CE-370-2. the former's maximum observation level is 8km,and an average observation level is 6.6km, the latter were 22.8km and 12.4km.2, The selection of parameter:the parameter k's value is taken a more reasonable 0.78; the parameter S1's value is taken hierarchical:2km below:15, from 2 to 15km:20, from 15 to 20 km:40, from 20 to 25 km:50;3, The difference of calculation method:comparing the aerosol extinction coefficient which calculate in method "Fernald" and method "Klett",we fond that:for CAMLTM CE-370-2, In height respects, the aerosol extinction coefficient calculated in two kinds of methods are basically accord. but appeared deviation in the critical height, the results with method "Fernald" are larger, In the weather respects, when atmospheric is clean, and the weather is fine, aerosol extinction coefficient contour of two methods basically fitting. For MPL, we found that,, the results with method "Fernald" is less than that with method "Klett" in lower, but is larger than that with method "Klett" in higher4, The difference of instrument, aerosol extinction coefficient is basically the same magnitude and vertical distribution trends are very similar, also the aerosol concentration are consistent. In addition, although MPL-4B detection actual height is hither, but aerosol extinction coefficient will appear larger values of the situation in high-level5, Demonstrated completely variation process of aerosol extinction coefficient in floating weather and blowing sand weather (30 April 2008-2 may 2008). There are difference of aerosol extinction coefficient between floating weather and blowing sand weather:when it is floating weather:aerosol extinction coefficient will appear smaller values than that in blowing sand weather in low-level, and there exists a aerosols'denseness in the high-level (5-7 km), because of the dust transmission, these characteristics are fitting of the definition of two weathers.6, Demonstrated completely variation process of aerosol extinction coefficient in cloud weather(3 April 2007). There are aerosols'denseness in 5km range in 3 o'clock,and the maximum aerosol extinction coefficient is about 0.2 km-1, there are aerosols' denseness in 4km range and 8km range on 9 o'clock to 15 o'clock,and the maximum aerosol extinction coefficient is about 0.25-0.6 km-1, after 18 o'clock, all the layers of aerosols is distributed evenly and t aerosol extinction coefficient is about 0.05 km-1.7, Seleced the data in spring, summer, autumn and winter, we got aerosol extinction coefficient near the boundary layer in semiarid areas, analyzed the change of boundary layer:the atmospheric aerosol extinction coefficient in semiarid areas is smaller and smaller according to the winter,spring, summer and autumn sequence, and in winter aerosol extinction coefficient is very largh in bottom. aerosol extinction coefficient near the boundary layer in semiarid areas is larger on 12 o'clock to 15 o'clock in every season.