Aircraft Observational Study On Aerosol And Cloud Microphysical Properties In Northern China

Cloud and aerosols can make profound effects on the weather and climate. However, there is still great uncertain in the interaction between the aerosol and clouds due to the poor understanding in the spatial distribution, chemical compositions of aerosol and characteristics of cloud condensation nuclear (CCN). In this study, the cloud observational data from 11 flights in Shanxi Province as well as the conventional weather station data is employ to investigate the aerosol distribution, nuclear processes and cloud microphysics structures in North China during the summer.The results show that the inversion layer make significant impacts on the vertical distribution of aerosol particles. The aerosol number concentration will be higher when the inversion structure is present and the aerosol particles will accumulate at the top of inversion layer.Under this situation, the effect diameter of aerosols seems uniformity in the boundary layer and increases along with altitude above boundary layer. Lower aerosol number concentration in the boundary layer is observed and the aerosol effect diameter shows a declining or constant trend along with the altitude at the of absence inversion structure. The aerosol number concentrations of both of the two conditions decrease with the altitude while the concentration under the inversion condition is twice than that of the other condition. CCN and aerosol show the similar vertical profiles, which is declining with the altitude, and the CCN concentration under the inversion condition is 1.5 times than that of the normal condition. Affecting by the airmass from Northwest or Mongolia, there is greater aerosol diameter under the clear sky and smaller diameter under the cloudy sky in the upper troposphere at North China. When the aerosols at the low levels are mainly due to the local emission, it shows the characteristics of smaller diameter. However, it shows a greater diameter when the main source of aerosols is the long-distance transport from Northeast China or Mongolia.The shape of aerosol spectrum varies along with time at the low levels while it changes little at the upper troposphere. There are differences in the shape of aerosol spectrums of different levels; unimodal and doublet structures can be happened at the low levels while the upper troposphere always shows a unimodal shape. The percentage of particles with greater diameter increases at the upper troposphere while the spectrum keeps its shape.The number concentration of aerosol shows a good correlation with the number concentration of CCN and this correlation relationship is better when the mean effect diameter is greater than 0.4μm. There is a linear relationship between the ratio of CCN and the diameter of aerosols. Therefore, there is a smaller/greater ratio of CCN due to the small/great diameter of aerosol at the low/upper troposphere. A linear regression of y=1.3x-616.3is found between the aerosol below cloud base and CCNand the conversion rate from aerosol to cloud drops is about 47%. A linear regression of y=1.6x-473.8is detected between the CCN below cloud base and cloud dropsand the conversion rate from CCN to cloud drops is about 69%.Stratiform cloud shows inhomogeneity in horizontal and vertical direction. The clouds ahead the cold front is deeper with lower cloud base,stronger vertical velocity and interlayer. The number concentration and mean diameter of cloud drop and the liquid water content are greater than the cloud behind cold front; thespectrum of cloud drop shows unimodal and doublet structures. The cloud after cold front show the characteristics of higher cloud base and thinner cloud layer and thespectrum of its cloud drop shows doublet and multi-peaks structures.The fitting results of Γ distribution is close to the real distribution.