Raman-Mie Lidar (RML), a double wavelengths (532 and 1064 nm) Nd-YAG laser is employed as emitting source, which was developed by Lidar group at Anhui Institute of Optics and Fine Mechanics (AIOFM), Hefei Institutes of Physical Science(shown in figure 1).

Figure 1. The schematic diagram and photo of RML system set at the experimental base of CMA MOC in Beijing (Images by WANG Zhenzhu)

To realize back-scattering signals detection from atmosphere aerosol and cloud, it consists of four channels, say, 1064 nm Mie, 607 nm N2 Raman and two 532 nm Orthogonal Polarization channels.

The temporal and spatial resolutions for this system, which operates with a continuing mode (24/7) automatically, are 30s and 7.5m, respectively. The measured data are used to investigate the dust events, haze pollutions and cloud properties from combining of signal intensity, extinction coefficient, polarization ratio and color ratio profiles.

This year, at the beginning of May, the North of China suffered the strongest dust events, which was captured by RML.

Figure 2. The vertical distribution of dust monitored by the RML over Beijing on May 4-5th. (Images by WANG Zhenzhu)

RML set at the experimental base of China Meteorological Administration (CMA) Meteorological Observation Center (MOC), and has monitored this dust event in Beijing.

The dust weather covered Xinjiang, Gansu, Inner Mongolia, Beijing, Tianjin and other 10 provinces or cities, affecting an area of 1630000 km², which was close to 1/6 of the territory area of China. The range and intensity of this dust process reached the highest since the beginning of this year, while the value of PM10 remained over 1000 μg/m³ in Beijing.

According to RML, the heavy dust loadings were found from near the ground to about 3 km in Height on May 4^th, and has existed continuously until the next morning at 8 am on May 5^th. (as shown in the figure 2). Then the dust began to disperse due to strong winds, and completely disappeared at noon.

However, several days later the dust from the North attacked Beijing area again during May 11-12^th, when the value of PM10 was up to 200-500 μg/m³. The dust loadings were found below 1 km from 10 a.m. of May 11th to 16 p.m. of May 12^th, which were observed by the RML(as shown in the figure 3).

Figure 3. The vertical distribution of dust monitored by the RML over Beijing on May 11-12th. (Images by WANG Zhenzhu)

As described above, this "dust exploration test" is actually a training for the operational operation of lidar atmospheric detection, and the lidar system will be developed in the direction of automation, miniaturization, intelligence and unattended operation.

It is believed that the Raman lidar will be widely used in the near future under the efforts of researchers, which will become a technical weapon for the public meteorological service and the environmental protection department to strive for beautiful Chinese "normal blue".

 

Contact:

WANG Zhenzhu.
Anhui Institute of Optics and Fine Mechanics
Hefei, Anhui 230031, China
E-mail ：zzwang@aiofm.ac.cn
Tel ：86-551-65591007