Jianning Sun

Nanjing University | NJU · Department of Atmospheric Physics

Low clouds play a key role in the Earth-atmosphere energy balance and influence agricultural production and solar-power generation. Smoke aloft has been found to enhance marine stratocumulus through aerosol-cloud interactions, but its role in regions with strong human activities and complex monsoon circulation remains unclear. Here we show that bio...

The effects of the urban morphological characteristics on the spatial variation of near-surface PM2.5 air quality were examined. Unlike previous studies, we performed the analyses in real urban environments using continuous observations covering the whole scale of urban densities typically found in cities. We included data from 31 measurement stati...

Based on observation data from urban observation stations in Nanjing and Suzhou at two heights in the roughness sublayer above the canopy and observation data at three heights in the SORPES station at the Xianlin Campus of Nanjing University in a suburban area, the representativeness of land-atmosphere turbulent flux exchange and the energy balance...

Gaseous sulfuric acid (H2SO4) is a crucial precursor for secondary aerosol formation, particularly for new particle formation (NPF) that plays an essential role in the global number budget of aerosol particles and cloud condensation nuclei. Due to technology challenges, global-wide and long-term measurements of gaseous H2SO4 are currently very chal...

The impacts of urban hydrological processes, such as anthropogenic latent heat (ALH), multilayer green roof systems (GRO), evaporation from impervious surfaces (EIMP), urban irrigation (IRR), and the urban “oasis effect” (OASIS) on regional hydrometeorology in Nanjing, are assessed by the Weather Research and Forecasting Single‐Layer Urban Canopy M...

Haze pollution caused by PM2.5 is the largest air quality concern in China in recent years. Long-term measurements of PM2.5 and the precursors and chemical speciation are crucially important for evaluating the efficiency of emission control, understanding formation and transport of PM2.5 associated with the change of meteorology, and accessing the...

Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze events. The impact of aerosols on fog formation, yet to be revealed, can be critical in unders...

The vertical turbulent velocity variance $\overline{w^2}$ normalized by the convective velocity squared $w_*^2$ as a function of the boundary layer depth-normalized height $z/z_i$ (i.e., $\overline{w^2}/w_*^2 = f(z/z_i)$) in the convective boundary layer (CBL) over homogeneous surface exhibits a near universal profile, as demonstrated by field obse...

Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze event. The impact of aerosols on fog formation, yet to be revealed, can be critical in underst...

Atmosphere boundary layer (ABL or BL) acts as a pivotal part in the climate by regulating the vertical exchange of moisture, aerosol, trace gases and energy between the earth surface and free troposphere (FT). However, compared with research on the exchange between earth surface and ABL, there are fewer researches on the exchange between ABL and FT...

In this study, large-eddy simulations (LES) are conducted to investigate the interaction between the urban heat island (UHI) circulation and the sea breeze (SB) circulation. An idealized city, which has higher surface heat flux and lager roughness length than the rural surface, is located adjacent to or at a distance from the coastline. The heat fl...

Eddy-correlation measurements have been carried out at six different heights above the urban canopy in three cities of China, i.e., Nanjing, Changzhou and Suzhou. Observations at these heights are used to evaluate the dependence of normalized standard deviations of velocity components σi/u*l (i = u, v, w) and temperature σTv/Tv*l on local atmospher...

The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions t...

The scale properties of anisotropic and isotropic turbulence in the urban surface layer are investigated. A dimensionless anisotropic tensor is introduced and the turbulent tensor anisotropic coefficient, defined as C, where \(C = 3d_{3}\,+\,1 (d_{3}\) is the minimum eigenvalue of the tensor) is used to characterize the turbulence anisotropy or iso...

Radiative aerosols are known to influence the surface energy budget and hence the evolution of the planetary boundary layer. In this study, we develop a method to estimate the aerosol-induced reduction in the planetary boundary layer height (PBLH) based on two years of ground-based measurements at a site, the Station for Observing Regional Processe...

Eddy-covariance observations above the densely built-up Centre of Nanjing were made from December 2011 to August 2012. Separate eddy-covariance systems installed at two levels on a 36-m tower located on a rooftop were operated simultaneously, and observations grouped into two sectors (A, B) according to the prevalent wind directions. For sector A,...

The aerosol optical and physical properties as well as its direct radiative forcing (DRF) in urban area of Nanjing (urNJ) are investigated, based on the measurements of Cimel sun-photometer combined with a radiation transfer model. We find that the annual mean 550 nm aerosol optical depth (AOD) of the total aerosols is about 0.65, dominated by scat...

Anthropogenic land use has a significant impact on climate change. Located in the typical East Asian monsoon region, the land–atmosphere interaction in the lower reaches of the Yangtze River is even more complicated due to intensive human activities and different types of land use in this region. To better understand these effects on microclimate c...

Vegetation has always been an integral part of the urban scene, affecting ambient air quality through both direct and indirect ways: by enhancing the dry deposition process of air pollutants and by contributing to the formation of ozone due to the emission of biogenic volatile organic compounds (BVOC). In this study, hourly measurements of gaseous...

Large-eddy simulations are conducted to investigate the impacts of the scale of chessboard-like heterogeneous surface heating and the background wind on secondary circulations (SCs) in the convective boundary layer (CBL). When the wind blows along the diagonal of the chessboard pattern, the cases with different heterogeneity length scales (λ = 1.2,...

Anthropogenic land use has significant impact on climate change. Located in the typical East Asian monsoon region, the land-atmosphere interaction in the lower reaches of Yangtze River is even more complicated due to intensive human activities and different types of land use in this region. To better understand these effects on microclimate change,...

Field observations of the atmospheric boundary layer were made over urban and suburban terrain in the Yangtze River Delta, China. A multiresolution decomposition was applied over three different types of terrain: flat homogeneous terrain, suburban terrain and urban terrain, with results indicating that, (1) the average scale contribution of u, v, w...

The entrainment flux ratio A e and the inversion layer (IL) thickness are two key parameters in a mixed layer model. A e is defined as the ratio of the entrainment heat flux at the mixed layer top to the surface heat flux. The IL is the layer between the mixed layer and the free atmosphere. In this study, a parameterization of A e is derived from t...

Following the parameterization of sheared entrainment obtained in the companion paper, Liu et al. (2016), the present study aims to further investigate the characteristics of entrainment, and develop a simple model for predicting the growth rate of a well-developed and sheared CBL. The relative stratification, defined as the ratio of the stratifica...

This work presents an overall introduction to the Station for Observing Regional Processes of the Earth System–SORPES in Nanjing, East China, and gives an overview about main scientific findings in studies of air pollution-weather/climate interactions obtained since 2011. The main results summarized in this paper include overall characteristics of...

Biomass burning is a main source for primary carbonaceous particles in the atmosphere and acts as a crucial factor that alters Earth's energy budget and balance. It is also an important factor influencing air quality, regional climate and sustainability in the domain of Pan-Eurasian Experiment (PEEX). During the exceptionally intense agricultural f...

The mid- to lower reaches of the Yangtze River valley are located within the typical East Asian monsoon zone. Rapid urbanization, industrialization, and development of agriculture have led to fast and complicated land use and land cover change in this region. To investigate land–atmosphere interaction in this region where human activities and monso...

To evaluate the influence of urban non-uniformity on precipitation, the area of a city was divided into three categories (commercial, high-density residential, and low-density residential) according to the building density data from Landsat satellites. Numerical simulations of three corresponding scenarios (urban non-uniformity, urban uniformity, a...

Atmospheric aerosol greatly influences human health and the natural environment, as well as the weather and climate system. Therefore, atmospheric aerosol has attracted significant attention from society. Despite consistent research efforts, there are still uncertainties in understanding its effects due to poor knowledge about aerosol vertical tran...

Biomass burning is a main source for primary carbonaceous particles in the atmosphere and acts as a crucial factor that alters Earth's energy budget and balance. It is also an important factor influencing air quality, regional climate and sustainability in the domain of Pan-Eurasian Experiment (PEEX). During the exceptionally intense agricultural fi...

Aerosol-Planetary Boundary Layer (PBL) interactions have been found to enhance air pollution in megacities in China. We show that black carbon (BC) aerosols play the key role in modifying the PBL meteorology and hence enhancing the haze pollution. With model simulations and data analysis from various field observations in December 2013, we demonstr...

The mid- to lower reaches of Yangzi River Valley is located within the typical East Asia monsoon zone. Rapid urbanization, industrialization, and development of agriculture have led to fast and complicated land use and land cover changes in this region. To investigate land-atmosphere interaction in this region where human activities and monsoon cli...

Severe air pollution episodes have been frequent in China during the recent years. While high emissions are the primary reason for increasing pollutant concentrations, the ultimate cause for the most severe pollution episodes has remained unclear. Here we show that a high concentration of particulate matter (PM) will enhance the stability of an urb...

Following the parameterization of sheared entrainment obtained in the companion paper, Liu et al. (2016), the present study aims to further investigate the characteristics of entrainment, and develop a simple model for predicting the growth rate of a well-developed and sheared CBL. The relative stratification, defined as the ratio of the stratifica...

In this paper som periods of air pollution, observed in China during the recent years are analyzed. It i showed that high concentration of particulate matter (PM) minimizes the boundary layer height and leads to increasing pollutant concentrations. Critical number for concentration is 200 gm⁻³-after it feedback between boundary layer height and con...

Investigating sulfate formation processes is important not only for air pollution control but also for understanding the climate system. Although the mechanisms of secondary sulfate production have been widely studied, in situ observational evidence implicating an important role of NO2 in SO2 oxidation in the real atmosphere has been rare. In this...

Aerosol particles play important roles in regional air quality and global climate change. In this study, we analyzed 2 years (2011–2013) of measurements of submicron particles (6–800 nm) at a suburban site in the western Yangtze River Delta (YRD) of eastern China. The number concentrations (NCs) of particles in the nucleation, Aitken and accumulati...

Aerosol particles play important roles in regional air quality and global climate change. In this study, we analyzed 2 years (2011–2013) of measurements of submicron particles (6–800 nm) at a suburban site in the western Yangtze River Delta (YRD) of eastern China. The number concentrations (NCs) of particles in the nucleation, Aitken and accumulati...

Field measurements of the momentum flux and wind velocity gradient were carried out at three urban sites in the cities of Nanjing, Changzhou and Suzhou, China. The observational data in the urban roughness sublayer are analyzed to derive the momentum flux-gradient relations in terms of framework of the local similarity theory with a least square fi...

Nitrous acid (HONO) plays a key role in atmospheric chemistry by influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration with th...

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 pre...

The statistics of momentum exchange in the urban roughness sublayer are investigated. The analysis focuses on the characteristics of the dimensionless friction velocity, , which is defined as the square root of the drag coefficient. The turbulence observations were made at a height of 47 m above the ground on the 325-m meteorological tower, which i...

The atmospheric refractive index consists of both real and imaginary parts. The intensity of refractive index fluctuations is generally expressed as the refractive index structure parameter, with the real part reflecting the strength of atmospheric turbulence and the imaginary part reflecting absorption in the light path. A large aperture scintillo...

The convective atmospheric boundary layer was modeled in the water tank. In the entrainment zone (EZ), which is at the top of the convective boundary layer (CBL), the turbulence is anisotropic. An anisotropy coefficient was introduced in the presented anisotropic turbulence model. A laser beam was set to horizontally go through the EZ modeled in th...

As a short-lived climate forcing agent, black carbon (BC) aerosol plays an important role in climate change, atmospheric environment, and human health. In this study, continuous measurements of BC and trace gases were made at an urban site in Nanjing, Yangtze River Delta (YRD) of China in 2012. The annual mean BC concentration in Nanjing was found...

Based on the NOAA’s Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres Extended (PATMOS-x) monthly mean cloud amount data, variations of annual and seasonal mean cloud amount over the Yangtze River Delta (YRD), China were examined for the period 1982–2006 by using a linear regression analysis. Both total and high-level cloud am...

An offline single-layer urban canopy model (SLUCM) was driven by the surface energy balance observations in winter in Nanjing, China, to evaluate the capability of the model to simulate the urban surface energy balance. The results of the evaluation suggest that the simulated daytime net radiation is approximately 20% lower than the observed and di...

Water tank experiments and numerical simulations are employed to investigate the characteristics of light propagation in the convective boundary layer (CBL). The CBL, namely the mixed layer (ML), was simulated in the water tank. A laser beam was set to horizontally go through the water tank, and the image of two-dimensional (2D) light intensity flu...

A comprehensive measurement study of mercury wet deposition and size-fractionated particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume-weighted mean (VWM) concentration of merc...

Nitrous acid (HONO) plays a key role in atmospheric chemistry via influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement period of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration...

Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD) at the Station for Observing Regional Processes of the Earth System, Nanjing University (SORPES-NJU). Air ions in the diameter range 0.8–42 nm were measured using an air ion spectrometer, and a differential mobility particle sizer (DMPS) provided p...

A comprehensive measurement study of mercury wet deposition and size-fractionated particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume-weighted mean (VWM) concentration of merc...

The influence of air pollutants, especially aerosols, on regional and global climate has been widely investigated, but only a very limited number of studies report their impacts on everyday weather. In this work, we present for the first time direct (observational) evidence of a clear effect of how a mixed atmospheric pollution changes the weather...

Sea-breeze circulations in a stably stratified environment have been simulated in a water tank. The floor of the tank was divided into two halves representing land and sea; the land side was heated from the bottom of the tank, and the sea side was insulated by an underlying sponge slab. The temperature profiles over both land and sea sides, the lan...

Using the continuous measurements of carbon monoxide (CO) at Urban Atmospheric Environment Observation Station (32°03′20″N, 118°46′32″E) of Nanjing University from January to December 2011, the concentration characteristics of CO was investigated. Backward trajectory and cluster analysis were used to isolate air masses reaching Nanjing with differe...

Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD), at the SORPES station of Nanjing University. Air ions in the diameter range 0.8–42 nm were measured using an air ion spectrometer, and a DMPS provided particle number size distributions between 6 and 800 nm. Additionally, meteorological data, trac...

This work presents an overview of 1 yr measurements of ozone (O3) and fine particular matter (PM2.5) and related trace gases at a recently developed regional background site, the Station for Observing Regional Processes of the Earth System (SORPES), in the western part of the Yangtze River Delta (YRD) in eastern China. Ozone and PM2.5 showed strong...

The influence of air pollutants, particularly aerosols, on regional and global climate is widely investigated, but only a very limited number of studies reports their impacts on everyday weather. In this work, we present for the first time direct (observational) evidence of a clear effect how a mixed atmospheric pollution changes the weather with a...

This work presents an overview of 1-yr measurements of ozone (O3) and fine particular matter (PM2.5) and related trace gases at a recently developed regional background site, the Station for Observing Regional Processes of the Earth System (SORPES), in the western part of the Yangtze River Delta (YRD) in East China. O3 and PM2.5 showed distinguishe...

Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD), at the SORPES station of Nanjing University. Air ions between 0.8 and 42 nm were measured using an air ion spectrometer; a DMPS provided particle size distributions between 6 and 800 nm. Additionally, meteorological data, trace gas concentrations,...

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...

The boundary layer is very important to human activity as the transition zone between the surface and free atmosphere. Turbulence structure of the boundary layer especially the entrainment layer is an important aspect for the boundary layer research, which is very important to improve understanding of the boundary layer and the research of the boun...

Several studies have been selected to review water tank modeling of the atmospheric boundary layer (ABL) and demonstrate that water tank simulations have been a key factor in developing scientific knowledge and promoting further research of the ABL. The areas discussed include similarity analysis of modeling, basic dispersion processes, characteris...

Large-eddy simulations (LESs) are employed to investigate the turbulence characteristics in the shear-free convective boundary layer (CBL) driven by heterogeneous surface heating. The patterns of surface heating are arranged as a chessboard with two different surface heat fluxes in the neighbouring patches, and the heterogeneity scale Λ in four dif...

Based on the momentum flux–wind profile relationship of the Monin–Obukhov Similarity (MOS) theory, the observational data from the urban boundary layer field campaign in Nanjing are used to calculate the friction velocity (\( {u_*} \)) at the top of the urban canopy and the calculated results are evaluated. The urban surface roughness parameters (t...

The characteristics of horizontal temperature of the convective boundary layer (CBL) were analyzed using water tank simulation. Based on the geometric similarity, kinematic similarity and dynamic similarity, the initial and boundary conditions can be set for simulation. The dimension of the water tank is 1.5mXl.5mXO.6m. The degassed water was first...

In this paper, the equilibrium entrainment into a shear-free, linearly stratified atmosphere is discussed under the framework of bulk models, namely, the zero-order jump model (ZOM) and the first-order jump model (FOM). The parameterizations for the dimensionless entrainment rate versus the convective Richardson number in the two models are compare...

In this note, two different approaches are used to estimate the entrainment-flux to surface-flux ratio for a sheared convective boundary layer (CBL); both are derived under the framework of the first-order jump model (FOM). That suggested by Sun and Wang (SW approach) has the advantage that there is no empirical constant included, though the dynami...

The boundary layer is the transition zone between the surface and free atmosphere. Because of its high level it is difficult to detect the refined structure of the boundary's top layer extensively. Generation and evolution of the atmospheric convective layer were simulated in laboratory convective water tank with the dimension of 150 cm × 150 cm ×...

This study focuses on how to verify the aerodynamic roughness parameters in an urban area by using observational data collected in the roughness sub‐layer. Anemometrical observations were made in the downtown area of Nanjing, China, in summer and winter. Data were collected using both slow and fast response anemometers mounted on a 36 m tower. The...

Large eddy simulations have been performed within and over different types of urban building arrays. This paper adopted three dimensionless parameters, building frontal area density (λf), the variation degree of building height (ωh), and the staggered degree of building range (rs), to study the systematic influence of building spacing, height and l...

The parameterization of the dimensionless entrainment rate (w e /w *) versus the convective Richardson number (Ri δθ ) is discussed in the framework of a first-order jump model (FOM). A theoretical estimation for the proportionality coefficient in this parameterization, namely, the total entrainment flux ratio, is derived. This states that the tota...

Entrainment zone (EZ) at the top of convective boundary layer is a transition layer between the atmospheric convective boundary layer (ACBL) and free atmosphere, the turbulence structure of entrainment zone is one of the main properties. Because of the high level of entrainment zone, it is difficult to detect extensively, and little comprehension i...

The study of boundary layer inhomogeneous is of great importance in studying the characteristic of atmospheric turbulence and the applicability of the classic theory. In this paper, the development of atmosphere boundary layer is simulated in a laboratory simulation tank, and beam patterns of mixed layer are recorded. Using wavelet transform method...

Based on the measurement of the velocity field in the convective boundary layer (CBL) in a convection water tank with the particle image velocimetry (PIV) technique, this paper studies the characteristics of the CBL turbulent velocity in a modified convection tank. The experiment results show that the velocity distribution in the mixed layer clearl...