A Case Study of the Impacts of Dust Aerosols on Surface Atmospheric Variables and Energy Budgets in a Semi-Arid Region of China

The authors present a case study investigating the impacts of dust aerosols on surface atmospheric variables and energy budgets in a semi-arid region of China. Enhanced observational meteorological data, radiative fluxes, near-surface heat fluxes, and concentrations of dust aerosols were collected from Tongyu station, one of the reference sites of the International Coordinated Energy and Water Cycle Observations Project (CEOP), during a typical dust storm event in June 2006. A comprehensive analysis of these data show that in this semi-arid area, higher wind velocities and a continuously reduced air pressure were identified during the dust storm period. Dust storm events are usually associated with low relative humidity weather conditions, which result in low latent heat flux values. Dust aerosols suspended in the air decrease the net radiation, mainly by reducing the direct solar radiation reaching the land surface. This reduction in net radiation results in a decrease in soil temperatures at a depth of 2 cm. The combination of increased air temperature and decreased soil temperature strengthens the energy exchange of the atmosphere-earth system, increasing the surface sensible heat flux. After the dust storm event, the atmosphere was dominated by higher pressures and was relatively wet and cold. Net radiation and latent heat flux show an evident increase, while the surface sensible heat flux shows a clear decrease.

Long range trans-Pacific transport and deposition of Asian dust aerosols

在他们的横渡太平洋期间，运输可能引起重要海洋的浮游植物生物资源的亚洲灰尘喷雾器的免职增加。然而，横渡太平洋灰尘运输，免职，和空间分发的知识由于在亚洲次洲，北方太平洋，和北美洲的连续、同时的观察的缺乏仍然是差的。灰尘在 2001 年 4 月 6 日期间袭击的严格的亚洲人提供了一个机会获得横渡太平洋灰尘运输和免职的更好的理解，用从卫星的观察的一个全面集合，基于地面的轻察觉并且变化，飞机，和表面观察网络。观察和模型模拟构画出灰尘运输，免职，垂直侧面，和空间分发的一般模式。下列点被遵守：(1 ) 表面灰尘集中沿着运输小径从 80 ° E 与增加的灰尘运输距离指数地减少了到 120 ° W；(2 ) 灰尘集中山峰的高度与在北方太平洋区域增加运输距离增加了；并且(3 ) 灰尘免职的空间分发主要取决于横渡太平洋运输线路。

The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

由于大气尘埃喷雾器在对放射的效果的量的评价有大不确定性。光性质贡献大部分到那些不确定性。作者执行几个敏感实验在在这篇论文的地区性的放射的强迫上估计光特征的影响。实验在折射索引，单个散布反照率，不对称现象因素和光学深度包含。代表世界 MeteorologyOrganization (世界气象组织) 推荐的东方亚洲灰尘和灰尘的折射索引的更新的数据集对比地被分析并且使用。为有详细喷雾器 parameterization 的太阳、热的红外辐射; 红外线辐射的放射的转移代码被采用。自从另外的光参数强烈取决于它，最强壮的强调在折射索引上，并且作者发现在折射索引上的放射的强迫的强壮的敏感。研究显示出更强壮的散布、更弱的吸收并且在太阳的波长的东方亚洲尘粒的前面的散布，它导致更高否定的强迫，更低的积极强迫和在比 WMO 灰尘模型的空气(TOA ) 的顶强迫的更大的网。源于这二个灰尘模型的 TOAforcings 在某些区域有相反的符号，这也被发现，它在放射的强迫的量的评价暗示光性质的精确大小的重要性。

Direct Climatic Effect of Dust Aerosol in the NCAR Community Atmosphere Model Version 3 (CAM3)

Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 W m-2 in the solar spectrum and +0.09 W m-2 in the thermal spectrum on a global average. The magnitude of surface RF is larger than the TOA forcing, with global mean shortwave forcing of-1.76 W m-2 and longwave forcing of +0.31 W m-2 . As a result, dust aerosol causes the absorption of 1.1 W m-2 in the atmosphere. The RF of dust aerosol is predicted to lead to a surface cooling of 0.5 K over the Sahara Desert and Arabian Peninsula. In the meantime, the upper troposphere is predicted to become warmer because of the absorption by dust. These changes in temperature lead to a more stable atmosphere, which results in increases in surface humidity. The upward sensible and latent heat fluxes at the surface are reduced, largely balancing the surface energy loss caused by the backscattering and absorption of dust aerosol. Precipitation is predicted to decrease moderately on a global scale.

Vertical distribution characteristics of dust aerosol mass concentration in the Taklimakan Desert hinterland

The different height mass concentrations of dust aerosol data from the atmosphere environment observation station(Tazhong Station)was continuously observed by instruments of Grimm 1.108,Thermo RP 1400a and TSP from January of2009 to February of 2010 in the Taklimakan Desert hinterland.Results show that:(1)The mass concentration value of 80m PM10was higher,but PM2.5and PM1.0concentrations at 80 m was obviously lower than 4 m PM10,and the value of 80 m PM1.0mass concentration was the lowest.(2)The PM mass concentrations gradually decreased from night to sunrise,with the lowest concentration at 08:00,with the mass concentration gradually increased,up to the highest concentration around18:00,and then decreased again.It was exactly the same with the changes of wind speed.(3)The high monthly average mass concentration of TSP mainly appeared from March to September,and the highest concentration was in April and May,subsequently gradually decreased.Also,March–September was a period with high value area of PM monthly average mass concentration,with the highest monthly average mass concentration of 846.0μg/m3for 4 m PM10appeared in May.The concentration of PM10was much higher than those of PM2.5and PM1.0at 80 m.There is a small difference between the concentration of PM2.5and PM1.0.Dust weather was the main factor which influenced the concentration content of the different diameter dust aerosol,and the more dust weather days,the higher content of coarse particle,conversely,fine particle was more.(4)The mass concentration of different diameter aerosols had the following sequence during dust weather:clear day<blowing dust<floating and blowing dust<sandstorm.In different dust weather,the value of PM10/TSP in fine weather was higher than that in floating weather,and much higher than those in blowing dust and sandstorm weather.(5)During the dust weather process,dust aerosol concentration gradually decreased with particle size decreasing.The dust aerosol mass concentration at different heights and diameter would have a peak value area every 3–4days according to the strengthening process of dust weather.

Simulation on the spatio-temporal distribution and emission flux of dust aerosol over East Asia in 2000-2009

A regional climate model (RegCM3), coupled with an online dust module, is used to simulate the spatio-temporal distribution and emission flux of dust aerosol (smaller than 20 μm in diameter) over East Asia in the period from 2000 to 2009. The model performance is firstly evaluated against available observations. Simulation results show that the model can capture the characteristics of spatio-temporal distribution of dust aerosol very well over East Asia. There always exist two extremes of dust aerosol optical depth (AOD) and column burden (CB), one is in the Taklimakan Desert of Xinjiang Uygur Autonomous Region, China, and the other is in the Badain Jaran Desert of Inner Mongolian Autonomous Region, China. The maximum value of CB appears in spring, secondary maximum in winter and minimum in autumn. To the east of 110°E, dust is transported eastward from a maximum center at a height of 700 hPa over the East Asian continent. Dust emission sources are mainly located in the Taklimakan Desert, Badain Jaran Desert, North Qinghai-Tibetan Plateau and Southwest Mongolia. There is also an obvious seasonal variation of dust emission flux (EF). Annual mean dust EF is 1,015.34 mg/(m 2 ·d), of which 62.4% and 2.3% are re-deposited onto the East Asian continent through a dry and wet deposition process, respectively, and the remaining 35.3% is injected into the atmosphere or subject to long-range transport.

Effects of climate changes on dust aerosol over East Asia from RegCM3

In order to understand impacts of global warming on dust aerosol over East Asia, a regional climate model(RegCM3) coupled with a dust model is employed to simulate the present(1991-2000, following the observed concentration of the greenhouse gases) and future(2091-2100,following the A1B scenario) dust aerosol. Three experiments are performed over East Asia at a horizontal resolution of 50 km, driven by the outputs from a global model of the Model for Interdisciplinary Research on Climate(MIROC3.2_hires), two without(Exp.1 for the present and Exp.2 for the future) and one with(Exp.3 for the future) the radiative effects of dust aerosols. Effects of climate changes on dust aerosols and the feedback of radiative effects in the future are investigated by comparing differences of Exp.2 and Exp.1, Exp.3 and Exp.2, respectively. Results show that global warming will lead to the increases of dust emissions and column burden by 2% and 14% over East Asia, characterized by the increase in December-January-February-March(DJFM) and the decrease in Aprile May(AM). Similar variations are also seen in the projected frequencies of high dust emission events, showing an advanced active season of dust in the future. The net top-of-atmosphere(TOA)radiative forcing is positive over the desert source regions and negative over downwind regions, while the surface radiative forcing is negative over the domain, which will lead to a reduction of dust emissions and column burden.

Impact of Dust Aerosol on Glacial–Interglacial Climate

The temperature anomaly and dust concentrations recorded from central Antarctic ice core records display a strong negative correlation. The dust concentration recorded from an ice core in central Antarctica is 50–70 times higher during glacial periods than interglacial periods. This study investigated the impact of dust aerosol on glacial–interglacial climate, using a zonal energy balance model and dust concentration data from an Antarctica ice core. Two important efects of dust, the direct radiative efect and dust-albedo feedback, were considered. On the one hand, the direct radiative efect of dust significantly cooled the climate during the glacial period, with cooling during the last glacial maximum being as much as 2.05℃ in Antarctica. On the other hand, dust deposition onto the ice decreased the surface albedo over Antarctica, leading to increased absorption of solar radiation, inducing a positive feedback that warmed the region by as much as about 0.9℃ during the glacial period. However, cooling by the direct dust efect was found to be the controlling efect for the glacial climate and may be the major influence on the strong negative correlation between temperature and dust concentration during glacial periods.

Assessment of Dust Aerosol Optical Depth and Shortwave Radiative Forcing over the Northwest Pacific Ocean in Spring Based on Satellite Observations

Dust aerosol optical depth (AOD) and its ac-companying shortwave radiative forcing (RF) are usually simulated by numerical models.Here,by using 9 months of Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol product data in combination with Clouds and the Earth's Radiant Energy System Single Scanner Footprint (CERES/SSF) data,dust AOD and its shortwave RF were estimated over the cloud-free north-west (NW) Pacific Ocean in the springs of 2004,2005,and 2006.The results showed that in this region,the mean dust AOD and its shortwave RF were 0.10 and 5.51 W m 2,respectively.In order to validate the dust AOD de-rived by MODIS,results from the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model were also used here.The correlation coefficient between the monthly averaged dust AOD derived by MODIS measurements and the model simulation results was approximately 0.53.Since the estimates of the dust AOD and its shortwave RF obtained in this study are based mainly on satellite data,they offer a good reference for numerical models.

Influence of dust aerosols on eastern Pacific tropical cyclone intensity

热带地区大气的热力学状态对台风的发展起着重要作用.本项研究结果表明,东太平洋台风强度与沙尘AOD之间存在一定的负相关.同时,MERRA-2再分析数据和CMIP6的GCM模拟的分析结果,都表明了低层大气中云对沙尘AOD的负响应.沙尘颗粒物的准直接辐射效应可以解释上述响应:沙尘颗粒物吸收太阳辐射,并用此热量促进云层蒸发.理论上,这种气溶胶驱动的汽化作用会影响台风周围空气的焓.根据台风的潜在强度理论,与沙尘相关的台风强度变化,实则是沙尘的准直接辐射效应引起的台风周围空气焓值变化的结果.

Enrichment and transfer of polycyclic aromatic hydrocarbons (PAHs) through dust aerosol generation from soil to the air

Polycyclic aromatic hydrocarbons(PAHs)are major organic pollutants in soil.It is known that they are released to the atmosphere by wind via dust aerosol generation.However,it remains unclear how these pollutants are transferred through the air/soil interface.In this study,dust aerosols were generated in the laboratory using soils(sandy loam and loam)with various physicochemical properties.The PAH concentrations of these soils and their generated dust aerosol were measured,showing that the enrichment factors(EFs)of PAHs were affected by soil texture,PAH contamination level,molecular weight of PAH species and aerosol sizes.The PAHs with higher EFs(6.24–123.35 in dust PM_(2.5);7.02–47.65 in dust PM_(10))usually had high molecular weights with more than four aromatic rings.In addition,the positive correlation between EFs of PAHs and the total OCaerosol content of dust aerosol in different particle sizes was also statistically significant(r=0.440,P<0.05).This work provides insights into the relationship between atmospheric PAHs and the contaminated soils and the transfer process of PAHs through the soil-air interface.

Vertical Profile Comparison of Aerosol and Cloud Optical Properties in Dominated Dust and Smoke Regions over Africa Based on Space-Based Lidar

This study evaluates the vertical profiles of aerosol and cloud optical properties in 40 dominated dust and smoke regions in Western-Northern Africa (WNA) and Central-Southern Africa (CSA), respectively, from the surface to 10km and from 2008 to 2011 based on LIVAS (LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies). Aerosol extinction (AE), aerosol backscatter (AB), and aerosol depolarization (AD) generally increase from the surface to 1.2 km and decrease from 1.2 km to the upper layers in both WNA and CSA. AE and AB in CSA (maximum of 0.13 km-1, 0.14 km-1, 0.0021 km-1‧sr-1, 0.0033 km-1‧sr-1) are higher than in WNA (maximum of 0.07 km-1, 0.08 km-1, 0.0017 km-1‧sr-1, 0.0015 km-1‧sr-1) at 532 and 1064 nm respectively. AD in WNA (maximum of 0.25) is significantly higher than in CSA (maximum of 0.05). There is a smooth change with the height of cloud extinction and backscatter in WNA and CSA, while there is a remarkable increase of cloud depolarization with height, whereby it is high in CSA and low in WNA due to high and low fraction of cirrus respectively. Altocumulus has the highest extinction in NA (0.0139 km-1), CA (0.058 km-1), WA (0.013 km-1), while low overcast transparent (0.76 km-1) below 1 km in SA. The major findings of this study may contribute to the improvement of our understanding of aerosol-cloud interaction studies in dominated dust and smoke aerosol regions.

Mongolia Contributed More than 42%of the Dust Concentrations in Northern China in March and April 2023

Dust storms are one of the most frequent meteorological disasters in China,endangering agricultural production,transportation,air quality,and the safety of people’s lives and property.Against the backdrop of climate change,Mongolia’s contribution to China’s dust cannot be ignored in recent years.In this study,we used the Weather Research and Forecasting model coupled with Chemistry(WRF-Chem),along with dynamic dust sources and the HYSPLIT model,to analyze the contributions of different dust sources to dust concentrations in northern China in March and April 2023.The results show that the frequency of dust storms in 2023 was the highest observed in the past decade.Mongolia and the Taklimakan Desert were identified as two main dust sources contributing to northern China.Specifically,Mongolia contributed more than 42%of dust,while the Taklimakan Desert accounted for 26%.A cold high-pressure center,a cold front,and a Mongolian cyclone resulted in the transport of dust aerosols from Mongolia and the Taklimakan Desert to northern China,where they affected most parts of the region.Moreover,two machine learning methods[the XGBoost algorithm and the Synthetic Minority Oversampling Technique(SMOTE)]were used to forecast the dust storms in March 2023,based on ground observations and WRF-Chem simulations over East Asia.XGBoost-SMOTE performed well in predicting hourly PM10 concentrations in China in March 2023,with a mean absolute error of 33.8μg m−3 and RMSE of 54.2μg m−3.

A Comparison Analysis of Chemical Composition of Aerosols in the Dust and Non-Dust Periods in Beijing

Dust events occurred frequently in Beijing in recent years. In this work, 120 aerosol samples were collected in two typical dust events (21-22 March and 15 May) and a non-dust period in Beijing from March to May 2001. Samples were analyzed for major elemental components by the Proton Induced Xray Emission (PIXE) method. Results show that the enrichment factors of crustal elements such as Mg,Al, and Ti had little differences between the dust period and the non-dust period in Beijing, while the enrichment factors of other elements that have a relation to anthropogenic emissions were very low during the dust period. The results derived by using multivariate factor analysis from the observation data show that the sources such as soil dust, industry, and fuel combustion were among the major contributors to the particles in Beijing.

Modeling Study of the Global Distribution of Radiative Forcing by Dust Aerosol

To quantitatively understand the dust aerosol effects on climate change,we calculated the global distribution of direct radiative forcing due to dust aerosol under clear and cloudy skies in both winter and summer,by using an improved radiative transfer model and the global distribution of dust mass concentration given by GADS (Global Aerosol Data Set).The results show that the global means of the solar forcing due to dust aerosol at the tropopause for winter and summer are –0.48 and –0.50 W m-2 ,respectively;the corresponding values for the longwave forcing due to dust are 0.11 and 0.09 W m-2 ,respectively.At the surface,the global means of the solar forcing due to dust are –1.36 W m-2 for winter and –1.56 W m-2 for summer,whereas the corresponding values for the longwave forcing are 0.27 and 0.23 W m-2 ,respectively.This work points out that the absolute values of the solar forcing due to dust aerosol at both the tropopause and surface increase linearly with the cosine of solar zenith angle and surface albedo.The solar zenith angle influences both the strength and distribution of the solar forcing greatly.Clouds exert great effects on the direct radiative forcing of dust,depending on many factors including cloud cover,cloud height,cloud water path,surface albedo,solar zenith angle,etc.The effects of low clouds and middle clouds are larger than those of high clouds.The existence of clouds reduces the longwave radiative forcing at the tropopause,where the influences of low clouds are the most obvious.Therefore,the impacts of clouds should not be ignored when estimating the direct radiative forcing due to dust aerosol.

Size distribution and element composition of dust aerosol in Chinese Otindag Sandland

Part physical and chemical characteristics of dust aerosol were determined for samples collected from Otindag Sandland of China in spring, 2001. Number con- centration, mass concentration, chemical element concentra- tion and size distribution of aerosol particles with 0.5 μ m < Dp < 100.0 μ m were examined. The average number and mass concentrations of aerosols were 274.8 cm-3 and 0.54 mg/m3 for the field period respectively, and 31.4 cm-3 and 0.07 mg/m3 for the non-dusty days. PM10 played a dominant role in the aerosol mass concentrations. The particles with Dp < 8.0 μ m accounted for about 93.7% of total aerosol number loading in dusty days. The particle size distributions of aero- sols were characterized by bi-modal logarithm normal func- tion in heavy and moderate dusty days, and mono-modal in windblown and non-dusty days. Crustal elements such as Al, Fe, etc. in aerosols almost originated from soils. Pollutant elements of S, Pb, etc. associated with aerosols were affected by remote anthropogenic pollutant sources in upwind regions. Mo, V and Co in aerosols were possibly from other dust sources other than local soils. The aerosols over Otindag Sandland consisted of particles from local soils, upwind pol- lutant sources and other dust sources.

COMPARISON OF SIMULATING MINERAL DUST AEROSOLS IN EAST ASIA BY TWO EMISSION SCHEMES

Two common surface-dust emission schemes using critical wind speed and friction velocity were com-pared with the regional climate model RegCM3 in East Asia. In the comparison, transport of mineral dust and its distri-bution were simulated from March to April, 2001. Simulation results were also compared with TOMS aerosol index, showing that obvious differences exist in dust emission quantity and its column burden simulated by the dust emission schemes of friction velocity and wind speed criteria. The results obtained by the wind speed criterion are higher than that by friction velocity, bringing forth the problem whether or not the dust emission scheme matches the model. The obvious difference in the two schemes also explains the uncertainty of simulating mineral dust aerosol by modeling.

Aerosol Optical Properties Affected by a Strong Dust Storm over Central and Northern China

Aerosol observational data at 8 ground-based observation sites in the Chinese Sun Hazemeter Network(CSHNET)were analyzed to characterize the optical properties of aerosol particles during the strong dust storm of 16-21 April 2005.The observational aerosol optical depth(AOD)increased significantly during this dust storm at sites in Beijing city(86%),Beijing forest(84%),Xianghe(13%),Shapotou(27%),Shenyang(47%),Shanghai(23%),and Jiaozhou Bay(24%).The API(air pollution index)in Beijing and Tianjin also had a similar rise during the dust storm,while the Angstrm exponent(α)declined evidently at sites in Beijing city(21%),Beijing forest(39%),Xianghe(19%),Ordos(77%),Shapotou(50%),Shanghai(12%),and Jiaozhou Bay(21%),respectively.Furthermore,The observational AOD andαdemonstrated contrary trends during all storm stages(pre-dust storm,dust storm,and post-dust storm),with the AOD indicating an obvious"Valley-Peak-Valley"pattern of variation,whileαdemonstrated a"Peak-Valley-Peak"pattern. In addition,the dust module in a regional climate model(RegCM3)simulated the dust storm occurrence and track accurately and RegCM3 was able to basically simulate the trends in AOD.The simulation results for the North China stations were the best,and the simulation for dust-source stations was on the high side,while the simulation was on the low side for coastal sites.

Numerical analysis for contribution of the Tibetan Plateau to dust aerosols in the atmosphere over the East Asia

Although the Tibetan Plateau is widely thought as a potential dust source to the atmosphere over East Asia,little is known about the temporal changes of Tibetan dust activities and Tibetan dust source strength.In this study,we address these two issues by analyzing dust storm frequencies and aerosol index through remote sensing data and by means of numerical simulation.The findings indicate that monthly dust profiles over the Tibetan Plateau vary significantly with time.Near the surface,dust concentration increases from October,reaches its maximum in February March,and then decreases.In the middle to upper troposphere,dust concentration increases from January,reaches its maximum in May June,and decreases thereafter.Although Tibetan dust sources are important contributors to dust in the atmosphere over the Tibetan Plateau,their contribution to dust in the troposphere over eastern China is weaker.The contribution of Tibetan dust sources to dust in the atmosphere over the Tibetan Plateau decreases sharply with height,from 69% at the surface,40% in the lower troposphere,and 5% in the middle troposphere.Furthermore,the contribution shows seasonal changes,with dust sources at the surface at approximately 80% between November and May and 45% between June and September;in the middle and upper troposphere,dust sources are between 21% from February to March and less than 5% in the other months.Overall,dust aerosols originating from the Tibetan Plateau contribute to less than 10% of dust in East Asia.

Simulation of the Direct Radiative Effect of Mineral Dust and Sea Salt Aerosols in a Doubled Carbon Dioxide Climate

The authors examine the equilibrium climatic response to the direct radiative effect(DRE)of mineral dust and sea salt aerosols in a doubled-CO2climate with two-way coupling of aerosol-climate interactions.In response to the drier and windier conditions,dust emissions increase by 26%in the Sahara Desert and by 18%on the global scale relative to present day.Sea salt emissions increase in high latitudes(>60°)but decrease in middle latitudes(30°–60°)of both hemispheres due to the poleward shift of westerlies,leading to a 3%decrease in global emissions.The burdens of dust and sea salt increase by 31%and 7%respectively,because reductions in rainfall over the tropical oceans increase the lifetime of particles in the warmer climate.The higher aerosol loading in the doubled-CO2climate reinforces aerosol DRE by0.2 W m 2,leading to an additional cooling of 0.1°C at the surface compared with the climatic effects of aerosols in present day.The additional cooling from changes in natural aerosols compensates for up to 15%of the regional warming induced by doubled CO2.