Over the past decades, a large number of studies have been carried out in the field of urban meteorology in China. This paper summarizes the main progress in urban meteorology research from four aspects: urban meteorological observation network and field campaign, multi-scale model of urban meteorology, interaction between urban meteorology and atmospheric environment, and the impacts of urbanization on weather and climate. Major advances are as follows. China’s major cities have established or are improving comprehensive urban meteorological observation networks characterized by multi-platform, multi-variable, multi-scale, multi-link, and multi-function. Beijing, Nanjing, Shanghai, and other cities carried out urban meteorological field campaigns, which were included in the WMO research demonstration project. Wind tunnel experiments and scale-model outdoor experiments were successfully conducted. Multi-scale urban meteorological and air quality prediction numerical model systems have been developed and put into operational use. The urban heat island effect; urban impacts on precipitation, regional climate, and air quality; urban planning; and interaction between urban meteorology and atmospheric environment are extensively investigated. Finally, efforts to improve observational technology, data assimilation, and urban system modeling, to explore the impacts of urbanization on environment and human health, and to provide integrated urban hydro-meteorological climate and environmental services are planned ahead.

The enhanced CO oxidation by Au deposition and particularly He- and in situ-pretreatments was elucidated in light of the structural specialties associated with the facets of Co3O4 substrates and the corresponding Au–Co3O4 interfaces.

The expansion of urban size and denser buildings may have an impact on urban meteorology and environment,weakening urban’s diffusion capacity,which may lead to urban haze in China.NJU-CAQPS(NanJing U-niversity City Air Quality Prediction System)is used in this research to simulate the impact of urban growth on urban haze in Suzhou area.The land-use data of 1 986,1 995 and 2006 are used in the simulations and 18 d in Mid January,April,July and October are chosen to simulate.Another 2 pairs of sensitivity experiments are performed to study the impact of the height and density of buildings on the urban haze.The urban expansionin the last 2 decades may result in an increase of the PM2.5 concentration by 3~4 μg·m-3 (25~32 μg·m-3 in local area)and a decrease of visibility by 0.3~0.4 km(2~3 km in local area).Consequently,the average haze hours increase by 0.3~0.5 h(5 h at most),and the haze area increases by 1 70 km2 .The changes of building may result in an increase of PM2.5 concentration by 6~12 μg·m-3 in some area and a decrease of visibility by 0.1 km(0.3~0.6 km in local area).The impact of urbanization onpollutants concentration is more significant in the local area of pollutants source,and the expansion of urban size plays a more important role than the changes of buildings.The urban “muddy island”and“haze line”elevate as the urban size expand.

CORRESPONDING AUTHOR: Dr. Xuhui Lee, School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, E-mail: xuhui.lee@yale.edu

A forest canopy model is developed and coupled into the Regional Boundary Layer Model (RBLM) to fully consider the vertical structure of tree morphology. Instead of a slab surface model formerly used to represent trees in RBLM, the new version allows refinement of the radiation budgets as well as sensible and latent heat fluxes and, hence, more precise simulation of the thermal impacts of tree plantings on urban meteorological behavior. By applying this new version of RBLM, sensitivity tests are conducted to explore the potential impacts of different greenery scenarios on the thermal environment in an eastern Chinese city, Suzhou, during hot summer days. Greenings, both tree planting and grass surfacing, are beneficial in cooling the ambient air temperature. In general, tree planting is more beneficial than grass surfacing with the same coverage. In terms of surface energy balance, with tree coverage increasing from 0% to 20%, and then to 40%, the average surface net radiation fluxes at noon (1200 LST) are 591, 512, and 421 W m(-2), respectively. Correspondingly, the Bowen ratio is reduced from 8.78 to 1.20 and then to 0.43 as result of the redistribution of solar energy absorbed at the ground. The cooling effect of trees is more significant at noontime and can remarkably lower the daily maximum air temperature in urban areas. The cooling effect of urban greenery increases with its coverage. Using the study results, a tree coverage of around 40% may be a feasible and optimized urban greenery scheme.

The Hilbert spectral analysis based on the Empirical Mode Decomposition(EMD) method for analyzing nonlinear and non-stationary data is introduced and applied to the analysis of the Atmospheric Boundary Layer(ABL) turbulent signals for the first time.The effectiveness of Hilbert the spectral analysis in the research on the ABL turbulence is explored.The energy distribution characteristics and the degree of statistic stationarity of the turbulent data above the urban and forest canopies are studied.The results show the Hilbert spectral analysis is powerful and effective in the study of ABL turbulence.The Hilbert marginal spectrum is effective to get the energy distribution characteristics of ABL turbulent signals,and the analysis of the statistic stationarity is also effective to quantitatively measure the stationarity of the ABL turbulent signals.This will help establish the appropriate data quality control methods and improve the calculation of diffusion parameters of air quality and dispersion models.The case analysis shows that the turbulent flow is well mixed above both canopies.Compared with the urban canopy,the turbulent energy above the forest canopy is more concentrated in the eddies on larger scales,and the high-frequency part of wind disturbance is dominated by stronger intermittency.At a given height,turbulence eddies above the forest canopy are more unstable and contain less energy than those above the urban canopy.

To study the impact of urbanization on the urban heat island( UHI) in Suzhou under the circumstance of Taihu lake-land breeze,sunny weather with gentle wind on August 12,2006 was taken as background synoptic condition,and a series of numerical experiment was conducted with the use of a regional boundary layer model developed by Nanjing University. Results indicated that the wind field over Suzhou area was dominated by the combined influence of large scale system,lake-land and UHI circulation. Additionally,the intensity of lake-land circulation was stronger than that of UHI circulation. The influence of UHI can extend to about 400 m altitude in Suzhou area. Furthermore,under the influence of such wind field configuration,the temperature distribution in this area showed a significant feature of downwind effect,whose range was approximately 10 km. This kind of downwind effect,weakened with the height increased,was obvious at the level below 400 m. With the urbanization process in Suzhou for recent 20 years( 1986- 2006),the flux of sensitive heat increased to 200 W / m2; the flux of latent heat to 200 W / m2; the turbulent kinetic energy to 0. 045 m2/ s2; the daily average UHI intensity to 0. 4 ℃.The UHI circulation strengthened,and the mixing layer depth during daytime rose to 400 m,but the inversion layer depth changed a little. Moreover,the increase of surface sensitive heat flux,turbulent kinetic energy,UHI intensity and the decrease of latent heat flux resulted from the urbanization were slightly offset by the Taihu Lake effects.

Characteristics of haze in Suzhou were analyzed using data of the hourly visibility,relative humidity,concentration of pollutants(including PM10,PM2.5,BC(black carbon))and scattering coefficient from June 2009 to May 2010.The result showed that the total haze days accounted for 46.6 percent of the whole year days;rainy and blue days accounted for 33.2 percent and 21.9 percent respectively.Among all haze days,slight haze weather accounted for 70.6 percent of the total haze days,occurred the most frequently,while moderate and serious haze weather occurred rarely.Haze exhibited a significant diurnal variations,which occurred less often in the daytime than in the nighttime,the largest frequency of haze appeared at 5-8 a.m,and the least appeared at 14-16 p.m.Compared with non-haze days,the concentration of pollutants was higher in haze days.With the level of haze increased,the concentration of black carbon increased obviously;except serious haze days,the concentration of PM10,PM2.5 also increased,as well as the scattering coefficient.

Nanjing University City Air Quality Prediction System(NJU-CAQPS)is used to simulate haze weather in Mid January,April,July and October.The ratios of PM10,PM2.5,visibility,etc.between the simulated values and the observed values are 0.9,1.1,and 0.9 respectively.The suburb area in northern Suzhou suffers from high value of PM10 and PM2.5 beyond the threshold,the concentration of sulfate and nitrate has hot spot on west side of city.During the 456 simulation hours,there are 99 hours that haze occurred,which covers 21.7% of total time.Sulfate in downtown area contributes the most to extinction coefficients,with ratio of 39.1%,nitrate,organics and black carbon respectively contributes 15.6%,18.3% and 10.0%,which are significant higher than those in suburb area.

The multi-scale numerical modeling system is an effective tool to evaluate the atmospheric physical environment amid urban planning quantitatively. With the adoption of the model, the variations of urban temperature, humidity, wind speed, atmospheric diffusion conditions, and their impact on urban atmospheric environment under the dispersed and converged green spaces with different proportion are simulated respectively. Taking green space planning of Chengdu as the example, the modeling is carried out to analyze the difference between the urban atmospheric environments in Chengdu before and after the planning.

In an attempt to understand the land-atmosphere feed back invoked by urban and rural heterogeneous surface,the parameterized model of surface energy balance is used with both MODIS and AWS( Automatic Weather Station) meteorological data to calculate surface fluxes in this paper.Surface energy fluxes are analyzed in order to explain the detailed energy differences between urban and rural areas.The results show that the model is feasible and effective.The solution is approximately in agreement with the literature data.This,thereby,provides a useful method for researches on urban climate and environment.

In the summer of 2005 and the spring of 2006,flux measurements were twice taken in Nanjing Municipal Party School and Pukou area.Heat flux,latent heat flux,carbon dioxide flux as well as friction velocity were obtained applying the eddy-covariance(EC) technique.In order to eliminate the impact of complex terrain,a planar-fit(PF) method for tilt correction was adopted.A thorough analysis of the PF method indicated that PF coefficients are closely related to wind direction.Thus,wind directions must be taken into consideration when processing data.To be specific,winds from all directions were divided into several sectors and PF method was applied to each of them in order to generate a fitted plane for each sector.This method was named sector planar fit(SPF) as distinguished from the general planar fit(GPF) which doesn't consider wind sectors.The differences of corrected fluxes by the two methods(GPF/SPF) for the two seasons and two locations were mainly considered.It was clearly revealed that both urban and suburban flux results share a consistent trend in spring and summer;geographically,in urban areas,the corrected fluxes using SPF and GPF show obvious differences,differences are much smaller in suburban areas.Moreover,the vertical velocity w was corrected using the two methods and it was found that w also exhibits significant differences.Finally,according to the probability distribution of corrected vertical wind velocity by the two methods,it was concluded that the distribution of corrected vertical velocities by SPF is closer to normal than GPF.

The presence of coherent structures in turbulent shear flows is a great finding in turbulence research,which shows the orderly flows in turbulence which seems fully random.This article analyses the high-speed coherent structure in unstable PBL using the data measured at Pukou,Nanjing.These data include wind velocity measured by the sonic anemometer at the heights of 40 m and 2 m,and the vertical profiles of wind velocity measured with a Doppler wind-profile radar.The authors analyse the fluctuation velocity by employing wavelet transforming at the time scale of 400 s,and the high-speed coherent structure is recognized and located using the threshold value.By comparison with the corresponding wind profiles acquired by radar,these coherent structures satisfy our convention understanding which has long time scales(more than 5 min) and large vertical scales(about thickness of PBL).The nondimensional intervalbetween the coherent structures for the three days is about 6,which means that at the distance of six thickness of PBL,one coherent structure can be found.The wavelet coefficient of vertical fluctuation velocity is correlated with the corresponding wavelet coefficient of horizontal fluctuation velocity,which shows that the downward vertical velocity apparently exists in the high-speed coherent structure,this result is similar to the Gustiness theory in earlier research.Sweep motion and ejection motion are two dominant types of turbulence motion,which transport minus momentum flux.The high-speed coherent structure influences significantly the momentum flux by promoting the sweep motion and restraining the ejection motion.

Air pollution process in Nanjing on 7 January 2005 induced by typical weather condition was simulated with the modified Nanjing University City Air Quality Prediction System（NJU-CAQPS）.The contribution ratios of urban anthropogenic heat source,urban buildings and various anthropogenic heat sources to the concentration of several main pollutants and the impacts of the anthropogenic heat sources on visibility distribution were analyzed.The result shows that in main urban district,the daily average surface visibility reduced below 8 km,and the hourly surface visibility is less than 10 km for 18 h in one day;this condition should be considered as a heavy haze process.The industrial point source dominates mostly the daily average surface concentration of SO2,its peak value is above 110 μg·m-3;mobile source contributs the most to the daily average NO2 surface concentration,its peak value is above 70 μg·m-3;area and point sources have the significant contribution to the daily average surface concentration of PM2.5,the peak value is more than 100 μg·m-3 and 45 μg·m-3,respectively.Due to the anthropogenic heat source release, the lower layer temperature air increased and wind converged,the vertical speed over urban district increased,all these lead to the decreases of surface concentration of SO2,NO2,PM2.5 in urban district,the surface visibility increased correspondingly,and the area of regions over where visibility less than 10 km has decreased 20.2 km2.The horizontal wind speed over urban district decreased because of the building distribution,so that mass of pollutants concentrate over urban area and upper drift to the urban district,and in this district the concentration of various pollutants obviously increased.The concentration of fine particles（PM2.5） has increased 10 μg·m-3, comparing with the case without building effects. The comparison also showed that the ground visibility could decrease by a maximum of 2 km,the duration of visibility below 10 km increased by 2 hours,and the area of regions with haze increased by 134.2 km2 when the simulation concerned about the effects of buildings rather than not.

An anthropogenic emissions inventory for the Beibu Gulf for the year 2007 was developed based on emissions census data. Medium/long term reference scenarios (REF15/REF20) and long-term control scenarios (SCEi20) were also projected based on the industrial planning data. Using these emissions data,the present air quality and future changes under different scenarios in the Beibu Gulf were depicted by WRF-Chem. The simulated monthly mean SO2 and NO2 concentrations are close to the observations. The levels of pollutant concentrations are high in Guangdong and Guangxi provinces,but low in Hainan. The straddling transportation characteristics indicate that the pollutant concentrations are mainly affected by the local emissions,while the emissions from other regions are less important. On the other hand,the emissions from Guangdong province have a relatively large impact on SO2 and NO2 concentrations in Guangxi and Hainan provinces. The emission changes have significant impacts on future air quality. Under the REF15 scenarios,the levels of SO2 and NO2 increase in the Beibu Gulf due to the significant increment of emissions,except for SO2 in Maoming which decreases due to the reduced SO2 emissions. Since O3 undergoes more complex chemical reactions,the concentrations increase in several cities,but decrease in others. The significantly increased emissions under the REF20 scenarios lead to a large increase of SO2 and NO2 concentrations,however,the increment is relatively small for O3. The increment of gaseous pollutant concentrations is somewhat smaller for the SCEi20 scenarios than those of REF20.

Using boundary layer data with regard to sea fog observed at the Science Experiment Base for Marine Meteorology at Bohe, Guangdong Province, the structure of the atmospheric boundary layer and the characteristics of the tops of the fog and the clouds were analyzed. In addition, the effects of advection, radiation, and turbulence during sea fog were also investigated. According to the stability definition of saturated, wet air, the gradient of the potential pseudo-equivalent temperature equal to zero was defined as the thermal turbulence interface. There is evidence to suggest that two layers of turbulence exist in sea fog. Thermal turbulence produced by long-wave radiation is prevalent above the thermal turbulence interface, whereas mechanical turbulence aroused by wind shear is predominant below the interface. The height of the thermal turbulence interface was observed between 180 m and 380 m. Three important factors are closely related to the development of the top of the sea fog: (1) the horizontal advection of the water vapor, (2) the long-wave radiation of the fog top, and (3) the movement of the vertical turbulence. Formation, development, and dissipation are the three possible phases of the evolution of the boundary-layer structure during the sea fog season. In addition, the thermal turbulence interface is the most significant turbulence interface during the formation and development periods; it is maintained after sea fog rises into the stratus layer.

Data of particulate mass concentration,including black carbon(BC),PM2.5 and PM10,were analyzed together with surface meteorological factors in Suzhou,China,from September 2009 to May 2010.We conducted correlation analysis between visibility and particulate mass concentration,as well as meteorological elements including relative humidity,wind speed,wind direction and air temperature.The results indicated that visibility was negatively correlated with mass concentration of BC,PM2.5 and PM10,with correlation coefficients of-0.465,-0.359 and-0.238,respectively.Under low relative humidity(≤60%) conditions,the correlation coefficients were-0.675,-0.411 and-0.364,respectively.The correlation coefficients between visibility and air temperature,wind velocity and relative humidity were 0.132,0.188 and-0.632,respectively.A linear regression model based on BC,PM10 and relative humidity was built,though the result was not good enough.Based on the linear model,we built a more complicated regression model,in which the multiple correlation coefficient was 0.865 and the coefficient of determination was 0.749.

文中将建筑物动力冠层方案引入到城市边界层精细模式中,该方案描叙了城市地Ⅸ建筑物对气流的拖曳作用以及建筑物形态对城市地区湍流活动动量输送的影响.采用建筑物拖曳法和建筑物动力冠层方案两种不同建筑物动力学处理方法对北京地区东南部进行模拟,通过城市地区水平风速的模拟结果与自动气象站实测资料对比发现模拟结果与实测相当吻合,建筑物动力冠层方案的引入能够更好地实施对城市地区的水平风速分布的数值模拟.分别采用建筑物拖曳法与建筑物动力冠层方案对一个实际小规模城市进行模拟试验,分析表明引入建筑物动力冠层方案可以模拟出小规模城市地区水平风速偏低的现象;还可以模拟出城市地区建筑物动力作用对湍流活动的影响;对湍流动能模拟结果表明比较符合实际分布情形.采用建筑物动力冠层方案对小规模城市地区建筑物高度变化对城市地区的流场及湍流活动的影响进行模拟分析,结果表明:城市地区建筑物高度增加,风速变小,但是高大建筑物底部风速略高于低矮建筑物底部;城市地区大气湍能增加,高大建筑物底部湍能较小,冠层高度内湍能随高度增加而增加;同时城市地Ⅸ的垂直扩散系数也随建筑物高度增加而增加;城市地区污染物排放高度处污染物浓度较低,下游乡村地区地面污染物浓度较低,但高空污染物浓度却较高.

The state-of-art Computational Fluid Dynamics (CFD) codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FLUENT on describing the wind field details over a complex terrain. The results of the numerical tests show that FLUENT can simulate the wind field over extremely complex terrain, which cannot be simulated by mesoscale models. The reason why FLUENT can cope with extremely complex terrain, which can not be coped with by mesoscale models, relies on some particular techniques adopted by FLUENT, such as computer-aided design (CAD) technique, unstructured grid technique and finite volume method. Compared with mesoscale models, FLUENT can describe terrain in much more accurate details and can provide wind simulation results with higher resolution and more accuracy.