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A Study of Aerosol and Clouds Microphysical Properties Based on Aircraft Measurements

Author: LvYuHuan
Tutor: JinLianJi
School: Nanjing University of Information Engineering
Course: Atmospheric Physics and Atmospheric Environment
Keywords: aircraft observation aerosol cloud microphysical property
CLC: P426
Type: Master's thesis
Year: 2013
Downloads: 25
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Abstract


Aerosol and cloud, which play important role in atmospheric water cycle and global radiation balance, have significant impacts on weather, climate and environment. The interaction between aerosol and cloud is complicated and has the largest uncertainties in climate modeling. The aerosol size spectra, chemical composition and mixed state will have an impact on the cloud microphysical characteristics. Aircraft observational data from41flights during2009-2011in Tongliao, Inner Mongolia are statistically analyzed in this thesis. We focus on the analysis of cloud microphysics parameters, the spatial characteristics of aerosols and cloud condensation nuclei (CCN), as well as the interaction relationship between aerosols and CCN.The results show that a set of vertical profiles of aerosol number concentration and size distribution with diameter ranging from0.1to0.3μm is observed over Tongliao area, Inner Mongolia, China. The number concentration at this size scale reveals a relatively low aerosol number density in this region with average surface number concentration of about1800cm-3. Aerosol average effective diameter (De) from near the ground surface to high altitude slightly declines, especially in a boundary layer, but basically maintains near0.4μm. Meanwhile, measurements of the supersaturation spectra of CCN during the aircraft soundings over Tongliao under different synoptic conditions are presented. The measurements from the aircraft together with backward trajectories of aerosol simulated by HYSPLIT model and MODIS data show that under polluted condition, the polluted air mass from south of Tongliao was associated with high concentration of aerosol particles (1000-2500cm-3) at middle and low portion of troposphere with efficient radius of0.15μm. Concentration of CCN (NCCN) was linearly related to concentration of aerosol particles (NAP) according to NCCN~0.74and0.87NAP in polluted air at0.4and0.6%supersaturation rate, which indicates that the continuous influence of anthropogenic pollutants from such heavily polluted mega cities as Beijing and Tianjing slightly decreases the percentage of Aerosol particles to CCN in the relatively polluted atmosphere.Average cloud droplet number concentration (Nc (cm-3)) in different cloud are Sc(454.55±397.39)>Cu(142.3±163.12)>As(134.73±205.49)>Ns(125.11±147.23)> Ac(101.28±118.76) in order of size. Nc in precipitable clouds (Ns,As and Sc) generally span a large range, and the cumulative probability is reduced relatively gentle. Average LWC in precipitable clouds (Sc,Ns and As) are larger than those in non-precipitable clouds(Ac and Cu),besides, L WC in As and Ns are generally between0.01-0.3g m-3. The characteristics of average Dm for different clouds are similar to De, the cloud types with larger Nc have smaller droplet sizes. Average De are ranked for Ns>As>Ac>Cu>Sc. Precipitable clouds compared with non-precipitable clouds have more big droplets,which is conducive to the formation of precipitation. Moreover, the statistical results show that the relative dispersion of various types of cloud droplet spectrum spreads widely when Nc is small. With increasing of Nc, the relative dispersion constringes to0.3-0.6, eventually all kinds of cloud relative dispersion slowly converges to about0.4at the high Nc.Na(aerosol number concentration) all decreases from outside cloud to in-cloud, while Nc(cloud droplet number concentration) and LWC (liquid water content) increases. All the characteristics in polluted air changes more significantly than in the relatively clean atmosphere. Nc and LWC in the lateral boundary is less than in-cloud because of the impact of entrainment, turbulence and evaporation. Cloud droplet mean square deviation in-cloud is larger than in the cloud transition zone, which indicates that fluctuation in cumulus is rather wide. Cloud wet scavenging effect of aerosols mainly concentrates on the particles which is less than0.4μm,moreover, which under polluted air is stronger than under clean air. PSDs(particle size distribution) reveal different shapes of size distributions under the clean condition and the polluted condition. In polluted air, cloud droplet spectrum horizontal distribution is relatively uniform, the entrainment effect of the lateral boundary will have little impact on the cloud droplet spectrum, and the spectra of cloud droplets formed under this condition is very narrow. Cloud droplets spectra change a lot under clean condition. Besides, within cloud can form more big drops and than that in the lateral boundary. The spectrum shapes are relatively broad. Moreover, the entrainment effect of the lateral boundary has significant influence on the cloud droplet spectrum..

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CLC: > Astronomy,Earth Sciences > Atmospheric science (meteorology ) > Meteorological elements,atmospheric phenomenon > Water vapor,condensation,and precipitation
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