Wei‐Mei JIANG's research while affiliated with Nanjing University and other places

For investigating the impact of large citiespsila expansion on air pollution, some numerical experiments are employed by adopting the typical meteorological condition in this paper. The simulation results show that the urban development has great effect on the transportation and diffusion of pollution. The existent of Beijing downtown area leads to the decrease of the total allowable emission about 18.02 t-d-1. Identically, the contribution ratio of the surrounding towns expanding to PM10 concentration of downtown area reaches about 0.192 t-d-1.

For investigating the urbanization development effect on the local and surrounding atmospheric environment, some numerical experiments are employed by adopting the typical meteorological condition in this paper. The simulation region was chosen for the urban district and three important satellite town of Beijing, which are the main developing direction of Beijing planning in recent twenty years. The simulation results show that, firstly, the urban development has great effect on the local environment. On a clear, calm summer meteorological condition, as urban area fraction in simulation region increasing of 19%, the mean air temperature on urban region increase 1.91°C; and as the vegetation fraction reducing 20% the mean specific humidity decrease 3.3 g·kg–1. Furthermore, the different urban layout and scale lead to the different influence on meteorological environment. At the same time, the variety of local urban scale and layout influence the atmospheric environment of surrounding region greatly, and the urban area is larger, the influence is more marked. Such as, 1) reasoning for the existent of Beijing downtown area, the temperature increment of surrounding towns reach the maximum of 1.2°C at 14:00, the mixture layer depth rise about 150 m, and the turbulence kinetic energy increase about 0.15 m2·s–2; 2) The urban construction and development change the meteorological environment. At the same time, the air pollution transporting and dispersing have been altered. The existent of Beijing downtown area leads to the decrease of the total allowable emission about 18.02 t·d–1. Identically, the contribution ratio of the surrounding towns expanding to PM10 concentration of downtown area reaches about 0.192 t·d–1.

In order to understand how urban development changes the local urban boundary layer structure, the high-resolution satellite observation data have been used to get detailed information of land-use types, surface albedo, vegetation index and so on for regional boundary layer simulation. It is proved that this is an effective method and these data will help to get more reasonable simulation which are close to the realities. The numerical results illustrate that with the urban developing, the surface albedo decreases, the vegetation cover decreases and the surface wetness decreases, so surface sensible heat flux increases with a maximum of 140 W/m2, and less vegetation will lead to decrease of latent heat consumption and increase the Bowen ratio in urban areas. The kinetic heat flux will increase and the turbulence exchange will be stronger, at 14:00 the mixing layer is even lifted by a 500 m. The decreases of both kinetic moisture flux and vapor concentration cause that more energy will heat the earth surface and atmosphere, the diurnal change of earth surface temperature and atmospheric temperature will increase.

To study the problem about how to incorporate the anthropogenic heat flux into the model, we simulate some cases using the Regional Boundary Layer Model developed by Nanjing University (NJU-RBLM) in different cities and different seasons. The simulated results show that the best scheme of including anthropogenic heat flux into the PBL model is to account for the urban canopy heating terms both in the surface energy budget and in the atmospheric heat conservation equation with certain proportions. Results of sensitivity tests about changing the value of the anthropogenic heat flux show that anthropogenic heat flux plays an important role in the urban heat environment. The contribution of anthropogenic heat to UHI is 29.6% with Nanjing anthropogenic heat data in 2002. When heat emission doubles, it reaches 42.9%. The anthropogenic heat emission has impacts on PBL inversion structure during the morning and the intensity of UHI cyclone, and it could results in a 0.5~1.0°C surface temperature increase at night.

To research the direct radiative effect of dust aerosols over East Asia region, a dust emission scheme, a transport model and a radiative scheme of dust aerosol have been added into Regional Climate Model Version 3(RegCM3). Based on the simulation between March 2001 to February 2002, it is found that Northwest China and Mongolia are the main dust sources of East Asia, where the emission rates exceed 1μg/(m2·s) with the maximum value of 90μg/(m2·s). The maximum column burden of dust aerosol is about 5g/m2, which emerges over Taklimakan desert and Qinling Mountains; The direct radiative forcing at TOA is positive over land and negative over sea, and its regional average values in Spring, Summer, Autumn, Winter are 1.08, 0.88, 0.37, 0.40W/m2 respectively. The solar radiative forcing is also positive over land and negative over sea, but the infrared radiative forcing is positive in all modeling region; The radiative forcing values at surface for four seasons are –5.64, –2.25, –1.37, –1.87W/m2 respectively. Radiative forcing can be affected deeply by the change of single scattering albedo of dust aerosol.

A graphical method, named space time-index plots for detecting dynamical nonstationarity in general time series is addressed. In the method, the graph is V-shaped due to nonstationarity. The method is used to detect dynamical nonstationarity in atmospheric boundary layer turbulence in this paper. The high resolution temperature, humidity and three components of wind speed under various land surface obtained from HUBEX (Study of Energy and Water Cycle Over Huaihe River Basin) and PFRD (Park Falls Ranger District of the Chequamegon National Forest, about 15km east of Park Falls, Wisconsin, U.S.A.) are analyzed. The results show space time-index plots method can effectively detect whether dynamical nonstationarity exists in atmospheric boundary layer turbulence signal. There is almost few dynamical stationarity in atmospheric boundary layer turbulence signal neither under rice field from HUBEX nor under forest from PFRD. Dynamical nonstationarity is maybe one common property of atmospheric boundary layer turbulence signal. The intermittency and coherent structures in atmospheric boundary layer turbulence lead to some differences in nonstationarity graph shape between atmospheric boundary layer turbulence and general time series. The results show the turbulence signal over forest from PFRD is dominated by more distinct coherent structures and intermittency than that over rice from HUBEX.

The vegetation types have great effect on urban meteorological environment. Beijing is taken as an example, we aim to investigate the feasibility to study this effect using a regional boundary layer model. We simulate how the greenbelts and their types affect the meteorological environment in Beijing in winter and summer with the city design data and the afforesting plans which are in discussion. The interactions of the surface-atmosphere processes are analyzed to investigate the effects on the meteorological environment of the changes of surface flux. It shows that the regional boundary layer model can simulate the effect of greenbelt on urban meteorological environment well. The simulated results show that the increase of forests and lawn can reduce the surface wind speed about 0.5m/s. In winter, the increase of forests or lawn in the north of Beijing leads to a temperature increase in daytime and decrease in night of 0.5 ~ 1°C, the effect of greenbelt in southeast of Beijing is little; in summer the increase of forests and lawn in the north of Beijing leads to a temperature decrease less than 2°C and can weaken the high temperature in Beijing in daytime .

Using orthonormal wavelet transform, We made analysis of experimental data of convective boundary layer turbulence in water tank, including multi-scale decomposition and high frequency noise removing. Spectrum analyses show that turbulence in mixed layer is very different from that in entrainment zone. This difference may be caused by various characteristics of large scale element in turbulence. While the small scale turbulence in both mixed layer and entrainment zone are similar, which are homogeneous and their spectra are satisfied with Kolmogorov's scaling law with –5/3 exponent.

In this paper, we set up a heterogeneous chemical model which includes dust emission and connected it to an advanced meso-scale meteorological—atmospheric chemical model system. A lot of cases were simulated by this model system to study the heterogeneous chemical process of dust aerosol and its climate effect. The results show that the heterogeneous reaction will reduce the concentration of SO2 and O3 but increase sulfate concentration. In some areas, it can decrease the NO2 concentration, but it can also increase it in other areas. The change of annual average sulfate is 2.6mg/m2. The maximum values of radiative forcing caused by heterogeneous reaction are −0.24,−1.0,−2.0,−0.6W/m2 respectively in January, April, July, and October. The annual average radiative forcing is −0.033W/m2. The maximum temperature variation in January, April, July, October are −0.16,−0.35,−0.5,−0.48K respectively and the annual temperature variation in whole domain is –0.021K. The heterogeneous process also has evident effect on precipitation.

The ozone variation led by biomass burning in Spring 2000 over South East Asia and South of China region was simulated with a combined regional climate model and atomospheric chemical model. It was found that ozone was added by the pollutant of biomass burning both over source area and down wind area. The ozone of lower troposphere was affected by the pollutant over source area, so did the ozone in middle troposphere over down wind area. An ozone increase of 9.0-12.0 x 10(-2) g/m2 over South of China was found. The range of ozone increase between 1000-900 hPa over source area was more than 36 x 10(-9) m3/m3.