| Aerosol climatic effects, espectively the effects of aerosol on cloud geometric, mircophysic characteristics and interaction between the aerosol and cloud, are one of the most uncertain factors in climimate research. During the EAST-AIRC campaign, an atmospheric&environment observatory at the Yangtze Delta region of China was installed by Nanjing University of Information Science&Technology, where, hands of advanced instruments were jointly used to measure the surface radiation, aerosol and cloud properties to understand the radiative characteristics of aerosol and cloud, and further to estimate their interaction. This paper mainly focuses on the non-precipation cloud fraction, cloud base distribution, cirrus properties and cloud optical and mircophysic characteristics over this region. Meanwhile, long-term aerosol optical properties, vertical distribution, as well as the aerosol direct radiative effects were investigated, and the influences of aerosol on radiative energy distribution in atmosphere were firstly estimated. To understand the dust aerosol properties and their potential effects on cloud properties over East China, the aerosol optical properties, vertical evolution, transport behavor and radiative effects during the two dust events in2009were also analyzed. This study plays an important role on understanding the aerosol climate effects and the interaction between aerosol and cloud. The main conclusions are as follows:1. The new afterpulse correction method is estabilished based on complete attenuated signals, which can increase the times of afterpulse correction and improve the micropulse lidar retrieval accuracy under the lack of correction experiments condition.2. One year's (June2008-May2005) worth of observations showed that clouds occupy the sky41%of the time and annual mean cloud fractions experienced a significant diurnal cycle with amplitudes of～24.6%. The cloud fractions and cloud base height varied seasonally, with more cloud in winter and higher cloud base in spring and summer. High annual mean cloud base were found for total, daytime and nighttime clouds with3.05±2.73,2.46±2.08and3.51±3.07km, respectively. The occurrence of cirrus is approximate36.2%of total observational nights with peak in summer. The all detected annual mean cirrus properties are following:cloud base height:8.89±1.65km, cloud top height:10.73±1.86km, cloud thickness:1.83±0.91km, lidar ratio:25±17sr, extinction coefficient:0.21±0.31km-1, optical depth:0.34±0.33. Approximately12%of the cases are sub-visible cirrus, about43%are thin cirrus and45%are dense cirrus. More frequent, thicker cirrus occurred during summer.3. Cloud optical depth retrievals based on zenith radiance measurements by High-resolution analytical spectral devices success to capture the temporal tendency of overhead cloud and have more advantages of capturing the cloud temporal tendency than the retrievals based on hemispherical flux. Even for overcast cases, MODIS cloud retrievals are suffered the substantial cloud inhomogeneity. Our results indicated that the MODIS cloud products still suffer from variation limitations in this region and more works on the comparsion methods between surface and satellite, assessment and improvement of cloud properties retrieved from MODIS are needed. One year mean of cloud liquid water path, cloud optical depth and cloud droplet effective radius in this region is115.8±90.8g/m2,28.5±19.2and6.9±4.2μm, respectively.4. Multiyear (2006-2009) means of aerosol optical depth (AOD) at500nm, Angstrom exponent (a) at440-675nm, single scattering albedo(SSA) and asymmetric factor(ASY) at675nm are0.74±0.45,1.20±0.27,0.912±0.035and0.655±0.036with moderate inter-annual variations. AOD, SSA and ASY shows a maximum in summer and minimum in winter, and a is large in autumn and small in spring. The majority of aerosol particles were located below2km, and the maximum extinction coefficients were found near the surface and gradually decreased with height. Strong near-surface extinction coefficients were associated with relatively strong easterly and southeasterly wind, suggesting that the regional transport of locally generated aerosol particles from densely populated areas surrounding the site may contribute to loading at the surface at Taihu. In spring, autumn and winter, the majority of air masses ending at0.5and2.5km were tracked to northern/northwestern China, as well as remote regions of Mongolia and Siberia, and in summer, air masses originate over the seas to the east of site. Dust aerosols not only enhanced particle extinction coefficients at high altitudes, but also at low altitudes in spring.5. Heavy aerosol loading results in significant warming of the lower troposphere and cooling at the surface. Annual mean direct radiative forcing at the surface, top of atmosphere and within the atmosphere were34.8±9.1,-8.2±4.8and26.7±9.4W/m2. Meanwhile, aerosol can change the fraction of direct and diffuse components of surface global irradiance, with decrease annual mean direct radiance of-109.2±49.4and increase diffuse radiance of66.8±33.3W/m2. From the surface to2km, the mean heating rate is0.74K/day.The vertical profiles of heating induced by aerosols are the key to understand their impact on atmospheric dynamics, especially feedbacks between pollution and boundary layer development.6. Two dust events in spring in2009showed that the transport behavior of dust originatednorthwest China to southest is more complication than that we understanded. The existence of multiple and elevated dust layers consisting of mixtures of dust aerosols and anthropogenic pollution aerosols were found. Since dust aerosols have strong scattering, more shortwave radiation are reflected into space, so they have more significant forcing effects in the top of atmosphere. The high levels of dust aerosols significantly heat the upper atmosphere, which significantly affect convection and stability in the lower troposphere.
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