Solar Radiative Transfer Research Articles

The effect of thin high altitude clouds and aerosol layers on the solar radiation transfer to the Earth surface in twilight conditions

The effect of thin high altitude clouds and aerosol layers on the solar radiation transfer to the Earth surface in twilight conditions

An Exponential Model of Urban Geometry for Use in Radiative Transfer Applications

In radiative transfer schemes for urban areas it is common to approximate urban geometry by infinitely long streets of constant width, or other very idealized forms. For solar and thermal-infrared radiative transfer applications, we argue that horizontal urban geometry is described uniquely by the probability distribution of wall-to-wall separation distances. The analysis of building layout from contrasting neighbourhoods in London and Los Angeles reveals this function to be well fitted by an exponential distribution. Compared to the infinite-street model, this exponential model of urban geometry is found to lead to a significantly more accurate description of the rates of exchange of radiation between the sky, the walls and the streets of an urban canopy.

Heat transfer and fluid flow analysis of porous medium solar thermochemical reactor with quartz glass cover

In this paper, heat transfer and fluid flow of porous media solar thermochemical receiver with quartz glass cover were investigated. The Surface-to-surface radiation model and Rosseland approximation for radiation heat transfer were adopted for the transport of diffused solar irradiance and radiative transfer in the fluid phase and porous medium. An experimental test was conducted on a laboratory-scale solar thermochemical reactor. The effects of structural parameters in term of diffused irradiance intensity, the mass flow rate, heat transfer coefficient, quartz glass and inner cavity wall surface emissivity, the porosity and extinction coefficient that could affect heat transfer and fluid flow performance of the proposed solar cavity receiver were sufficiently investigated. It was found that the substantial drops in temperature were mainly attributed to the thermal losses by radiative, convective and conductive heat transfer. The numerical results are compared with the experimental data for the model validation. The thermal loss at the solar flux inlet of the receiver was obviously inevitable due to the stronger effect of heat transfer coefficient that altered the over increasing temperature and heat flux at the surface of diffuse irradiance. However, the use of optimum pore size and higher porosity material could significantly enhance the thermal performance of porous media solar thermochemical reactor.

Evaluation of a high‐resolution numerical weather prediction model's simulated clouds using observations from CloudSat, GOES‐13 and in situ aircraft

This study aimed to assess tropical cloud properties predicted by Environment and Climate Change Canada's Global Environmental Multiscale (GEM) model when run with the Milbrandt–Yau double‐moment cloud microphysical scheme and one‐way nesting that culminated at a (∼300 km)2 inner domain with 0.25 km horizontal grid spacing. The assessment utilized satellite and in situ data collected during the High Ice Water Content (HIWC) and High Altitude Ice Crystals (HAIC) projects for a mesoscale convective system on 16 May 2015 over French Guiana. Data from CloudSat's cloud‐profiling radar and GOES‐13's imager were compared to data either simulated directly by GEM or produced by operating on GEM's cloud data with both the CFMIP (Cloud Feedback Model Intercomparison Project) Observation Simulator Package (COSP) instrument simulator and a three‐dimensional Monte Carlo solar radiative transfer model. In situ observations were made from research aircraft – Canada's National Research Council Convair‐580 and the French SAFIRE Falcon‐20 – whose flight paths were aligned with CloudSat's ground‐track. Spatial and temporal shifts of clouds simulated by GEM compared well to GOES‐13 imagery. There are, however, differences between simulated and observed amounts of high and low cloud. While GEM did well at predicting ranges of ice‐water content (IWC) near 11 km altitude (Falcon‐20), it produces too much graupel and snow near 7 km (Convair‐580). This produced large differences between CloudSat's and COSP‐generated radar reflectivities and two‐way attenuations. On the other hand, CloudSat's inferred values of IWC agree well with in situ samples at both altitudes. Generally, GEM's visible reflectances exceeded GOES‐13's on account of having produced too much low‐level liquid cloud. It is expected that GEM's disproportioning of cloud hydrometeors will improve once it includes a better representation of secondary ice production.

Experimental assessment of the thermal behavior of a living wall system in semi-arid environments of central Mexico

The City of Queretaro is located in a semi-arid region that receives an elevated annual solar radiation (2200 kWh/m2 in AVG) with high UV factor indices (6+ in AVG) and a low rainfall accumulated throughout the year (550 mm in AVG), which represents a serious problem that affects the environment, buildings and finally people. The aim of this work is to illustrate the behavior of living walls and their beneficial effects under such semi-arid environments in central Mexico.The present study monitored two experimental huts, built with the most common materials used for Housing in Mexico. In one of them a living wall was placed at the south façade, while the other served as a control bare wall. Temperature and humidity sensors were located inside the huts and between the wall layers. Data about inside and outside conditions of the buildings were collected to evaluate: (a) temperature reduction inside huts; (b) rainfall and water demand of the living wall; (c) temperature and solar radiation transfer on buildings. Results demonstrate that living walls on such climate conditions, help to improve time and percentage of loss/heat gain of the enclosure, increase permeable green surfaces and favor social interaction.

Comparative studies of different radiation schemes within vegetation in land model

The lower boundary condition in the atmosphere is provided by a land surface process model. One of the directions of research of the land surface model is to perfect land surface model in existence. Since the accurate estimation of the albedo is required in climate modeling and there are some shortages in either the accuracy or the application area for radiative transfer scheme within a canopy, it is necessary to develop an accurate and simple four-stream radiation transfer model within a canopy based on the second vegetation radiative transfer model. The four-stream model can simulate the process of short-wave solar radiative transfer within a canopy. The four-stream model utilizes the four-stream approximation method in the atmosphere to provide analytical solutions to the basic equation of radiative transfer within a canopy. The four-stream solar radiative transfer model within a canopy in the land surface process model is based on the two-stream short-wave radiative transfer model. The two-stream model developed by Dickinson is computational efficiency and can gain accurate analytical solution. Sellers ever calculate the canopy hemisphere albedo in visible band and near infrared band by use of the two-stream model and can gain analytical solution. Many land surface models still use the two-stream model. But the two-stream model is not very accurate, thus it is necessary to develop more accurate four-stream radiative model. The radiative transfer theory within a canopy is based on the radiative transfer theory in the atmosphere. Each parameter in the basic canopy equation canopy accounts for the special geometry and optical character of the leaf or canopy. The upward or downward radiative fluxes are related to the diffuse phase function, G -function, leaf reflectivity and leaf transmission, leaf area index, and the solar angle of incident beam direction. The four-stream model and the two-stream model can simulate the reflectance, transmittance and absorption of the canopy. The newly developed the four-stream model can reduce the calculate difference of land surface radiative in theory. To compare and determine differences between the results predicted by the two models, several experiments were carried out to examine the effects on the canopy albedo by varying the leaf area index, leave angle distribution and the optical properties of the leaf and ground surface under the canopy. To better assess the simulation performance of the new four-steam model in the application for a land surface model, we needed to determine the parameters for the four-steam scheme and the second-stream scheme to utilize in an off-line test. These parameters also included calculating the reflectance, absorbance and transmission at different sun angles and different leaf area indexes for the 16 kinds of vegetation canopy. The offline test results showed that the sun angle had a significant impact on the solar radiative transfer process within vegetation and on the simulations of two schemes for reflectance and transmittance and absorption varies with different vegetation types. The offline test results show that the sun angle has significantly impact on the solar radiative transfer process within vegetation, and the simulations of two schemes for reflectance and transmittance and absorption varies with different vegetation types. To evaluate the simulations of the four-stream model for solar radiative flux reflected by the land surface in the land surface model, the four-stream model and the two-stream models were coupled into a land surface process model. These tests indicated that the simulation of the land surface process model coupled to the four-stream scheme outperformed two-stream scheme radiative transfer models regarding the global surface albedo, leaf area index and net primary productivity.

Effect of Orientation of Ice Crystals in Cirrus on Direct and Scattered Solar Radiation Fluxes

The problem of solar radiation transfer by cirrus containing horizontally oriented ice crystals urgent today is considered. The results of a complex radiation experiment are described in which solar radiation fluxes at the Earth’s surface are measured and high-level clouds are vertically sensed by a polarization lidar. The lidar allows the full backscattering phase matrix (BSPM) to be determined. The degree of orientation of ice crystals in cirrus is estimated from the form of the BSPM elements and their interrelations. It is shown experimentally for the first time that the degree of orientation of crystalline particles in cirrus has a significant effect on the direct and scattered solar radiation fluxes arriving at the Earth’s surface.

Monte Carlo Simulation of the Solar Radiation Transfer in a Cloudy Atmosphere with the Use of Graphic Processor and NVIDIA CUDA Technology

Problems of improving the efficiency of the Monte Carlo numerical simulation of solar radiation propagation in the Earth’s atmosphere by transition from sequential to parallel computations are discussed. A new parallel algorithm oriented to a computational system with the NVIDIA CUDA enabled graphics processor is presented. The efficiency of parallelization is analyzed by an example of calculating the upward and downward fluxes of solar radiation both in a vertically homogeneous and in an inhomogeneous model of the atmosphere. The results of testing the new algorithm under various atmospheric conditions including continuous single-layered and multilayered cloudiness are presented, with allowance for selective molecular absorption and without regard to it. The results of testing the code using video cards with different computational capabilities are analyzed. It is shown that the changeover of computing from conventional PCs to the architecture of graphics processors gives more than a hundredfold increase in performance and fully reveals the capabilities of the technology used.

Cooling energy saving associated with exterior greenery systems for three US Department of Energy (DOE) standard reference buildings

Exterior greenery systems such as green walls and green roof can provide energy saving and environmental benefits. Several previous studies examined thermal impacts of green roof/walls on a test envelope or simplified buildings in local climates. However, few studies examined the effects of exterior greenery systems considering building types, air conditioning operating conditions, and wall orientations in varied climates. The objective of this study is to investigate cooling energy savings associated with exterior greenery systems for the US Department of Energy (DOE) standard reference buildings, depending on building type, wall orientation, and local climate. Hourly energy consumption was examined for three types of reference buildings: (1) medium office, (2) hospital, and (3) primary school. For the three reference buildings, hourly solar radiation and latent heat transfer rates were calculated for four representative local climates (i.e., hot-dry, hot-humid, cold-humid, and warm-dry). Results show that latent heat transfer due to plant transpiration can dominate heat transfer through the exterior greenery systems. Among the four climates studied herein, heat removal due to evaporation by green walls and roof over the summer months (June to August) is the largest (up to 680 kWh/m2) in Phoenix, while it is in similar range (300–350 kWh/m2) for green walls and roof in other cities. Building type also has notable impacts on the energy performance of the exterior greenery system. Primary school achieves the most significant cooling energy saving in all climates because of high envelope heat gains compared to medium office and hospital. For the primary school in Phoenix, annual cooling energy saving can be maximized up to 27,000 kWh/y with green walls and up to 69,000 kWh/y with a green roof. Latent heat transfer due to evaporation is similar (< 6%) between south and west green walls, implying that utilizing a west green wall could be a good alternative or complement to using a south green wall for cooling energy saving.

Atmospheric Correction of Multispectral Satellite Images Based on the Solar Radiation Transfer Approximation Model

A model of the solar radiation transfer in the Earth’s atmosphere is developed for explicit calculations of the transfer characteristics of the atmosphere (brightness coefficients, transmission, and spherical albedo) in the visible and near-IR atmospheric windows depending on the surface air pressure (or terrain elevation), aerosol optical parameters, and angles indicating the position of the Sun and the satellite system with respect to the Earth’s surface. The model is based on spectrally dependent approximations obtained using the atmospheric radiative transfer code DISORT. The effect of altitudinal stratification of the atmospheric optical parameters on the accuracy of underlying surface spectral albedo retrieval from the brightness coefficients at the top of the atmosphere is investigated. An algorithm is developed for radiometric correction of multispectral satellite images based on the model suggested. Approbation of the algorithm is performed using MERIS (Medium Resolution Imaging Spectrometer) data. It is shown that accounting for optical properties of the atmosphere and adjacency effects in processing satellite images substantially improves the visibility of the underlying surface and renders their spectral reflectance parameters.

A Fast Algorithm for Retrieving Maps of Atmospheric Pollution by Fine Particulate Matter from Multispectral Satellite Images

A new algorithm for retrieving the total content of atmospheric fine particulate matter (FPM) (particles with a size of less than 1.0 and 2.5 μm) from multispectral satellite images in visible and IR regions of the electromagnetic spectrum is described. The algorithm is based on the regression relations between the top of atmosphere (TOA) reflectance, microphysical parameters of aerosol, and geometrical parameters of the satellite scene. The regression equations are built based on the calculated TOA brightness in the spectral channels of the satellite instrument for the ensemble of randomly generated parameters of the atmospheric radiative transfer model and geometrical parameters of the satellite scenes. Subsequently, this allows real-time mapping of the atmospheric FPM pollution directly from the satellite images without solving ill-posed inverse problems based on the solar radiation transfer in the atmosphere and aerosol light scattering. The algorithm suggested is implemented and tested for the MERIS (Medium Resolution Imaging Spectrometer) satellite instrument. Comparison of the MERIS-retrieved total content of the atmospheric FPM with AERONET (Aerosol Robotic Network) data shows a standard deviation of ~0.5 μg/cm2. The applicability of the algorithm developed to real-time monitoring of the regional and transboundary transport of the atmospheric FPM pollutants during wildfires is demonstrated.

Study on Air Film Formation Mechanism and Cooling in Large-Span Air-Conditioning Plant Rooms without Natural Wind

Large-span air-conditioning plant rooms have a large roof area and suffer from serious solar radiation in summer. The outside roof surface temperature is very high, so cooling load of roof occupies a large proportion in the envelope structure cooling load of large-span air-conditioning plant rooms. Based on the Coanda airfoil air induction unit, the author combined with exhaust air in large-span air-conditioning plant rooms to design the roof air film cooling system of large-span air-conditioning plant rooms. The adherence air film formed on the outside surface takes away heat on the outside surface of the roof, so as to reduce outside roof surface temperature of the roof, decrease heat transfer temperature difference between inside and outside roof surfaces of, and reduce roof cooling cold. Furthermore, the mathematical model and numerical simulation method of considering fluid-structure interaction for heat transfer and influences of solar radiation on air film formation of outside surface and cooling were constructed. Moreover, the numerical simulation method was conducted the validation of effectiveness. Also, the author discussed the air film formation mechanism and air film cooling ability of outside surface in large-span air-conditioning plant rooms without natural wind, developed a new air film cooling technology for the roof of large-span air-conditioning plant rooms, and supplemented the existing roof cooling technology.

Hydrothermal processes of thermokarst ponds in the Tibetan Plateau and its thermal impact on the underlying permafrost

以青藏高原查拉坪地区一处热融湖塘（40 m×50 m，最大深度为1 m）为研究对象，由实测数据对比分析了热融湖塘与天然地表相同深度的温度变化特征.结果表明：与天然地表相比，热融湖塘融化时间长，冻结时间短，且存在接近4℃的水温变化；受太阳辐射及热对流的影响，垂向水温梯度仅在水表从4℃降温及冻结阶段较大，其余时段接近0；湖底年均温度比相同深度的天然地表高约6.4℃，湖底下部存在约14 m深随时间发展的融区，土体吸热增大，放热减小；热融湖塘2.5~3.0 m土体的年内热交换为19592.0 kJ/m²，约是天然地表的230倍，其中吸热量及放热量分别为后者的1.4倍及8.7%.湖塘下部的融化夹层是深层冻土的主要热源，湖塘对下部土体放热的抑制作用是湖塘对土体产生热影响的主要原因.;A thermokarst pond (40 m×50 m, the maximum depth is 1 m) in the Chalaping of Tibetan Pleatu was regarded as a research object. Based on the measured data, the temperature variations and characteristics of thermokarst pond and natural ground at the same depth were analyzed. The results indicated that, compared with the natural ground, the thermokarst pond had a longer thawed time, a shorter frozen time, and a special time with water temperature being about 4℃. Due to the solar short radiation and convective heat transfer, the water temperature gradient in vertical was large during the surface temperature being decreasing from 4℃ and in the frozen stage, and other stages the water temperature gradient in vertical was almost zero. The annual average temperature at the bottom of pond was higher about 6.4℃ than that at the same depth of the natural ground. Besides, there was a talik being about 14 m depth under the bottom of pond being developing with time, and the heat absorbed and released of soil under the pond were increased and decreased, respectively. The heat absorbed from the depth of 2.5 to 3.0 m under the thermokarst pond was about 19592.0 kJ/m² being about 230 times of that under the natural ground,the heat absorbed was 1.4 times of the natural ground, but the heat released was only 8.7% of the natural ground. So, the talik was the main heat resource to the deeper permafrost, and the thermal impact of thermokarst pond on the permafrost underlying was due to the decrease of heat released from the soil.

A three-dimensional model of solar radiation transfer in a non-uniform plant canopy

A three-dimensional (3D) model of solar radiation transfer in a non-uniform plant canopy was developed. It is based on radiative transfer equations and a so-called turbid medium assumption. The model takes into account the multiple scattering contributions of plant elements in radiation fluxes. These enable more accurate descriptions of plant canopy reflectance and transmission in different spectral bands. The model was applied to assess the effects of plant canopy heterogeneity on solar radiation transmission and to quantify the difference in a radiation transfer between photosynthetically active radiation PAR (=0.39-0.72 μm) and near infrared solar radiation NIR (Δλ = 0.72-3.00 μm). Comparisons of the radiative transfer fluxes simulated by the 3D model within a plant canopy consisted of sparsely planted fruit trees (plant area index, PAI - 0.96 m2 m-2) with radiation fluxes simulated by a one-dimensional (1D) approach, assumed horizontal homogeneity of plant and leaf area distributions, showed that, for sunny weather conditions with a high solar elevation angle, an application of a simplified 1D approach can result in an underestimation of transmitted solar radiation by about 22% for PAR, and by about 26% for NIR.

TiO2/antimony-doped tin oxide: Highly water-dispersed nano composites with excellent IR insulation and super-hydrophilic property

In this work, a novel aqueous self-dispersed TiO2 is synthesized and then used to produce the highly water-dispersed ATO/TiO2 composite particles, which has strong IR insulation property. Thus, it can be used to block the solar radiative heat transfer in a building. The primary particle size of ATO/TiO2 composites detected by TEM ranges from 5 to 12nm, but that of the initial ATO nano particles is more than 2µm. A small amount of TiO2 (16.7% wt) increases the Zeta potential in water from 6.7 to 37.01mV, which represents the stability is largely enhanced. The IR transmittance in IR band is decreased from 91% (original glass) to 4.3% (ATO 83.33% wt). The thermal performances of glass with such coatings are simulated based on Hong Kong climate situation. For the best sample, the electricity used in air-conditioning and lighting is 27% less than uncoated glass. Furthermore, the TiO2 makes the water contact angle of the coating ranging from 3 to 5.6°. Therefore, the coating film can be prevented from fouling due to super-hydrophilicity and have a longer life time.

Multi-objective optimization of the solar absorptivity distribution inside a cavity solar receiver for solar power towers

The solar flux distribution on the receiver of a solar power tower is usually not uniform, which can cause a number of problems for the energy efficiency and system safety, particularly, the local hot spot and the thereby caused thermal stress and thermal deformation. Therefore, homogenization of the solar flux distribution is critical and important. The objective of the present study is to homogenize the solar flux distribution while keeping the optical loss (reflection loss) as low as possible through optimization of the distribution of the solar absorptive coating. An integrated approach coupling the Monte-Carlo ray tracing method and the Gebhart method is applied to simulate the process of the solar radiation transfer in the solar power system. The multi-objective optimization of the distribution of solar absorptivity is performed by using the non-dominated sorting genetic algorithm. The following conclusions are drawn from the study. (1) The improvement of the uniformity of the distribution of solar flux can lead to more reflection loss due to the fact that more solar energy is distributed on the position with greater view factor to the aperture; (2) The Pareto optimal front obtained from the multi-objective optimization provides the trade-off between the non-uniformity of the solar flux distribution and the reflection loss. (3) The optimal solar absorptivity distribution provided by the Pareto optimal front can significantly flatten the solar flux distribution at a minimum cost of optical loss. (4) The optimal distribution of the solar absorptivity is approximately opposite to the distribution of solar flux projected onto the active surfaces from the heliostat fields.

Scaling properties of observed and simulated satellite visible radiances

AbstractStructure functions Sq, which are related to power spectra and used to study turbulence, were computed for GOES‐13 visible radiances measured on 16 May 2015 over French Guiana and adjacent Atlantic Ocean. The nested Global Environmental Multiscale (GEM) numerical weather prediction (NWP) model was run for the same time and area. Cloud data generated by GEM over (300 km)2 domains, with one‐way nesting ending at horizontal grid‐spacing of 0.25 km, were operated on by a 3‐D solar radiative transfer model with resulting radiances degraded to GOES‐13 resolution (~1 km) and Sq computed for them, too. For GOES‐13 radiances, scaling exponents ζ(2) associated with S2, for separation distances between 5 km and 25 km, were typically &gt;0.6 for deep convective and marine boundary layer clouds and &lt;0.4 for shallow cumuli over land. ζ(2) for GEM agreed well with GOES‐13 for deep convective clouds. This suggests that the self‐organizing properties of deep convection in GEM exhibit realistic geometric features, a potentially important point given the link between cloud structure and precipitation, with the latter being much more difficult to measure and assess than visible radiances. Regarding radiances for GEM's marine boundary layer clouds, their Sq differed markedly from GOES‐13's; better resembling fair‐weather cumulus. Likewise, GEM's shallow cumuli over land appear to have bypassed the “scattered” fair‐weather stage and went straight into more organized convection. Thus, it appears that comparing time series of Sq for geostationary satellite data and corresponding modeled radiances has the potential to benefit assessment of cloud system‐resolving models.

Impact of reflecting land surface on radiation environment over Hornsund, Spitsbergen – a model study for cloudless skies

Abstract This paper addresses the influence of land topography and cover on 3D radiative effects under cloudless skies in the Hornsund area, Spitsbergen, Svalbard. The authors used Monte Carlo simulations of solar radiation transfer over a heterogeneous surface to study the impact of a non-uniform surface on: (1) the spatial distribution of irradiance transmittance at the fjord surface under cloudless skies; (2) the spectral shortwave aerosol radiative forcing at the fjord surface; (3) normalized nadir radiance at the Top Of the Atmosphere (TOA) over the fjord. The modelled transmittances and radiances over the fjord are compared to the transmittances and radiances over the open ocean under the same conditions. The dependence of the 3D radiative effects on aerosol optical thickness, aerosol type, surface albedo distribution, solar azimuth and zenith angle and spectral channel is discussed. The analysis was done for channels 3 (459-479 nm) and 2 (841-876 nm) of the MODIS radiometer. In the simulations a flat water surface was assumed. The study shows that snow-covered land surrounding the fjord strongly modifies the radiation environment over the fjord surface. The enhancement of the mean irradiance transmittance over the fjord with respect to the open ocean is up to 0.06 for channel 3. The enhancement exceeds 0.11 in the vicinity of sunlit cliffs. The influence of the snow-covered land on the TOA radiance over the fjord in channel 3 is comparable to the impact of an increase in aerosol optical thickness of over 100%, and in lateral fjords of up to several hundred percent. The increase in TOA radiance is wavelength dependent. These effects may affect retrievals of aerosol optical thickness.

Effects of solar array on the thermal performance of stratospheric airship

The harsh stratosphere environment has brought great risks when stratospheric airship is under the long endurance flight, such as supercool and superheat phenomena in the thermal performance. As the critical power source during flight, the existence of solar array deteriorates the thermal performance of stratospheric airship, but the research on the thermal effects of solar array is rare. In this paper, a simplified thermal model of stratospheric airship with solar array including direct solar radiation, infrared radiation, reflected radiation, scattered radiation and convection heat transfer was presented. On this basis, the user define function (UDF) program was developed to investigate the thermal effects of solar array on stratospheric airship using computational fluid dynamic (CFD) software. A ground experiment was carried out to verify the effectiveness of the theoretical model. Then the temperature distributions of stratospheric airship with solar array, as well as the velocity distributions were analyzed in detail. The simulation results showed that the solar array had a great influence on the thermal performance of stratospheric airship. The theoretical model developed in this paper suggests a pathway towards developing the thermal control technologies of stratospheric airship.

Concentration and Viability of Bacterial Aerosols Associated with Weather in Asian Continental Outflow: Current Understanding

Constituting a major fraction of bioaerosols, airborne bacteria take part in various atmospheric processes. Studies have suggested that airborne bacteria likely play an important role in cloud formation and consequently influence the solar radiation transfer and chemical conversions in the atmosphere, in addition to acting as links between geographically isolated microbial communities. However, how bacteria are dispersed in airflows remains poorly understood, because of the lack of reliable methods to describe the variations of airborne bacteria responding to changes in weather. We developed a simple method based on epifluorescence enumeration using LIVE/DEAD BacLight stain, by which we measured the concentrations of viable and non-viable bacterial cells in open air at a time resolution of 1 h or less. Although this method is labor-intensive, laboratory experiments and applications in field observations have demonstrated its reliability and effectiveness in studies on the correlation between airborne bacteria and Asian dust, the dependence of airborne bacteria on regional and synoptic weather, and the presence of bacteria in rainwater. In this short review, we briefly introduce the method, report the progress with its application to bacteria in Asian continental outflow, address the significance of meteorological factors in controlling the variation of airborne bacteria, and give perspectives on future studies in terms of the dynamics of bacterial aerosols in the atmosphere.