Aircraft Observation On Cloud Microphysics And Aerosol In The Beijing And Surrounding Regions In Autumn, 2003

The six-flights aerosol data and four-flights observational data of cloud microphysics sampled with an airborne PMS (Particle Measuring System) in different atmospheric conditions during August -September in 2003 over Beijing and its surrounding areas were detailed analyzed.The aerosol data sampled with an airborne PMS for six flights under different atmospheric conditions during August to September of 2003 over Beijing and its surrounding areas were analyzed. The results show that duo to different atmospheric conditions, the distribution of aerosol particle concentration over Beijing and its surrounding areas is rather different. The maximum of mean number concentration of aerosol particles was 3.46×10~2cm~-3, the maximum number concentration of particles was 5.26×10~3 cm~-3, and the maximum one was an order larger than the minimum one. The maximum of mean diameter of particles was 1.392 μm, the maximum diameter of particles was 2.75 μm. The minimum of mean concentration of particles was 25.7 cm~-3. In the fog condition, aerosol particle number concentration decreased with increasing height near the surface. Aerosol particle diameter was complex. The number concentration and diameter of aerosol particles increased in the cloud and rain condition. In addition, a distinct accumulation zone of aerosol particles could be found under the weak inversion layers. There were vertically distinct different distributions of aerosol particles. Aerosol particles were unimodal distributions below the 0℃ layer. The aerosol particle spectrum were bimodal above the 0℃ layer. Cloud droplets were multimodal, and the peak diameters were 3.5 μm 12.5 μm 23.5 μm, respectively.The cloud microphysical data sampled with probes of Particles Measuring System (PMS) in four aircraft flights during August and September in 2003 in the Beijing and surrounding regions were analyzed;in particular, the more detailed analyses have been done for stratocumulus clouds on August 15 and stratiformclouds on September 4. The results show that the maximum number concentration of small particles sampled with FSSP-100 probe changed from 120 cm"3 for Sc clouds to 183 cm'3 for deep As clouds. The mean diameter was around 7.22~ 16.056 (im. The data of 2D-GA2 probe show that the maximum number concentration of large particles changed from 2.25><10"3 cm'3 to 3.29X10"1 cm"3. The maximum liquid water content explored with King-LWC probe was 0.423-0.691 g/m3 in Sc clouds. Both vertical and horizontal distribution in stratiform clouds show obviously inhomogeneous features, more than 120 cm"1 high number concentration of ice crystals exists at upper levels (above -10°C level) with also larger sizes, the maximum size reaches 20 urn. The liquid water contend decrease slightly with height and also keeps around 0.1-0.2 g/m3. The layers between -5.9—8°C were composed of a large number of column ice crystals and small number of riming particles, and those between -8- -12°C were almost rimed particles, and those above -20°C were primarily dentritic ice particles. The number concentration of large-size ice particles was around 0.01-1 L^.The layer-averaged size distributions of cloud particles were quite different in Sc and St clouds. The large particles follow unimodal distribution in Sc, and the width of spectrum reach to about 1500 urn. The low number concentration corresponds to the low layer of cloud. But layer-averaged size distributions in As cloud is quite different, for particles less than 400 urn in diameter, the size distribution averaged in the layers of 0~ -8°C and -8- -12°C are almost same while for particles larger than 400 um in diameter, the size distribution averaged in the layer of-8- -12°C has an obvious bimodal type, and that in the layer of 0- -8°C has multi-modal type. The width of spectrum is around 1300-1400 um .