Control of the Dust Vertical Distribution over Western Africa by Convection and Scavenging

Saharan dust represents more than 50%of the total desert dust emitted around the globe and its radiative effect significantly affects the atmospheric circulation at a continental scale.Previous studies on dust vertical distribution and the Saharan Air Layer(SAL)showed some shortcomings that could be attributed to imperfect representation of the effects of deep convection and scavenging.The authors investigate here the role of deep convective transport and scavenging on the vertical distribution of mineral dust over Western Africa.Using multi-year(2006-2010)simulations performed with the variable-resolution(zoomed)version of the LMDZ climate model.Simulations are compared with aerosol amounts recorded by the Aerosol Robotic Network(AERONET)and with vertical profiles of the Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)measurements.LMDZ allows a thorough examination of the respective roles of deep convective transport,convective and stratiform scavenging,boundary layer transport,and advection processes on the vertical mineral dust distribution over Western Africa.The comparison of simulated dust Aerosol Optical Depth(AOD)and distribution with measurements suggest that scavenging in deep convection and subsequent re-evaporation of dusty rainfall in the lower troposphere are critical processes for explaining the vertical distribution of desert dust.These processes play a key role in maintaining a well-defined dust layer with a sharp transition at the top of the SAL and in establishing the seasonal cycle of dust distribution.This vertical distribution is further reshaped offshore in the Inter-Tropical Convergence Zone(ITCZ)over the Atlantic Ocean by marine boundary layer turbulent and convective transport and wet deposition at the surface.

Vertical distribution of plant nematodes in an aquic brown soil under different land uses

The vertical distribution of the dominant genera of plant nematodes at the depth of 0–150 cm of an aquic brown soil were studied for four land use patterns, i.e., paddy field, maize field, fallow field and woodland in the Shenyang Experimental Station of Ecology, Chi- nese Academy of Sciences in November of 2003. The results showed that the numbers of some dominant genera under different land uses decreased with the increase of soil depth. Helicotylenchus was most dominant genus under each land use type. Genera of Filenchus, Psilen- chus and Tylenchus in paddy field occurred at the depth of 0–20 cm; while Paratylenchus in fallow field and woodland, as well as Praty- lenchus in maize field presented in the deeper soil layers (0–80 cm). Significant correlations between the numbers of dominant genera of plant nematodes and soil chemical properties were found in this study. The number of Helicotylenchus under different land uses was posi- tively correlated with C/N ratio, total C, total N, total P, alkai-N, and Olsen-P. The numbers of Filenchus and Paratylenchus in paddy field, Pratylenchus in maize field and Paratylenchus in fallow field were negatively correlated with soil pH, and positively correlated with total C, total N and alkai-N. This study results showed that it is essential to sample at a certain depth according to the vertical distribution informa- tion of different genera of plant nematodes in adequately assessing the population size of plant nematodes.

Vertical Distribution and Seasonal Dynamics of Fine Root Parameters for Apple Trees of Different Ages on the Loess Plateau of China

The vertical distribution pattern and seasonal dynamics of fine root parameters for the apple trees of different ages （3, 10, 15, and 20 years old） on the Loess Plateau of China were studied. Soil coring method was used to determine the vertical distribution and seasonal dynamics of fine roots at different root radial distances （1.0, 1.5, and 2.0 m from the main tree trunk）. The fine root biomass density （FRD）, fine root length density （RLD）, and specific root length （SRL）, as well as soil water content and soil temperature were also measured. The FRD and RLD for the 10, 15, and 20 years old trees reached peak values in the 20-30 cm soil layer. For the 3 years old tree, the highest FRD and RLD were observed in the 10-20 cm soil layer. The FRD and RLD decreased with increased soil depth from the 10-20 or 20-30 cm soil layer for all age apple trees. The SRL declined with the increase of tree age. The FRD at the 1.0 m radial distance from the main tree trunk was higher than that at other radial distances in the 3 and 10 years old orchard. However, in the 15 and 20 years old orchards, especially the 20 years old orchard, the FRD at the 2.0 m radial distance was nearly equal to or higher than that at the 1.0 and 1.5 m radial distances. For all the root radiuses or the tree ages, the FRD, RLD, and SRL were the highest in spring and the lowest in autumn. The age of an apple tree does not affect the vertical distribution pattern but the biomass of fine roots and the SRL. Radial distance affects the root horizontal distribution of 3 and 10 years old trees but the 15 and 20 years old trees. Additionally, effects of soil temperature and soil moisture on fine root distribution or seasonal dynamics are not significant.

Experimental Study on Suspended Sediment Concentration and Its Vertical Distribution under Spilling Breaking Wave Actions in Silty Coast

In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump, formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves. Assuming that the sediment diffusion coefficient, which is related with energy dissipation, is proportional to water depth, formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves, and the prediction shows a good agreement with the measurement.

Temporal and vertical distribution of microphytobenthos biomass in mangrove sediments of Zhujiang (Pearl River) Estuary

Being a primary producer, Microphytobenthos （MPB） play an important role in the benthic ecosystem of mangrove swamps. The temporal and vertical distribution of MPB biomass, expressed as chlorophyll a （Chl a）, was investigated in mangrove swamps on the Qi＇ao island and the Futian Mangrove Nature Reserve, Guangdong Province, South China. Both locations are situated in the Zhujiang （Pearl River） Estuary. For each location, bi-monthly sampling was carried out at four sites during low tide period. Except one site on the Qi＇ao Island, which was in Phragrnites australis marsh, all sites were in mangrove swamps. The Chl a concentration in surface （0-1 cm） sediment ranged from 0.2/2g/cm3 to 8.3 #g/cm3 in the Qi＇ao Island and from 2.1/zg/cm3 to 15.6/2g/cm3 in the Futian Mangrove Reserve. The peak Chl a concentration occurred in winter or early spring, while the lowest Chl a concentration, with a value of about one quarter of the peak, was observed in summer or early autumn. The vertical distribution of Chl a concentration exhibited an exponential decline with depth, which indicated a muddy sediment with high organic matter, and the slope of the curve was positively related to Chl a concentration in the surface sediment. The MPB biomass of the Qi＇ao Island was significantly lower than that of the Futian Mangrove Reserve. Our results suggest that the overlaying water quality might influence the MPB biomass in surface sediments.

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 （Ta- zhong Station） was continuously observed by instruments of Grimm 1.108, Thermo RP 1400a and TSP from January of 2009 to February of 2010 in the Taklimakan Desert hinterland. Results show that： （1） The mass concentration value of 80 m PMl0 was higher, but PM2.5 and PM1.0 concentrations at 80 m was obviously lower than 4 m PMl0, and the value of 80 m PM1.0 mass 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 around 18：00, 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 846.0 p.g/m3 for 4 m PM^0 appeared in May. The concentration of PM10 was much higher than those of PM2.5 and PM1.0 at 80 m. There is a small difference between the concentration of PM2.5 and PM~ 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 PM^o/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 3-4 days according to the strengthening process of dust weather.

Vertical Distribution of Momentum Exchange Coefficient and Sediment Concentration in Estuarine and Coastal Waters

Vertical structures of momentum exchange coefficient and sediment concentration are the keys in the research on es- tuarine and coastal suspended sediment transport. Based on the parabolic mixing length distribution pattern, the distribu- tion pattern of vertical momentum exchange coefficient which is suitable for estuarine and coastal waters is constructed. A compari^n with steady flow and measured momentum exchange coefficient during one tidal cycle in the Menai Strait of England shows that the result of this pattern is closer to the measured values than those of commonly used Rouse＇ s and van Rijn＇s patterns, and the pattern is also suitable for estuarine and coastal waters. Successively, based on the precon- dition that momentum exchange coefficient is equivalent to sediment turbulent diffusion coefficient, and combining with the Diffusion Theory, we obtain the exponential vertical distribution pattern of sediment concentration, which is also suitable for estuafine and coastal waters, Thereby, using measured vertical stratified sediment concentration data of the South and the North Passages of the Yangtze Estuary and Zhoushan archipelago waters for fitting calculation, and comparing the results with those from Rouse＇s （1938） and Zhang et al. ＇s （1989） formulas, the results show that the exponential vertical distribution pattern of sediment concentration obtained in the present study not only overcomes the defect of Rouse＇s formula that the surface sediment concentration will be 0, but also has a holistic higher precision along the vertical lines than those of Rouse＇s and Zhang et al. ＇s formulas.

The Potential Vertical Distribution of Bigeye Tuna (Thunnus obesus) and Its Influence on the Spatial Distribution of CPUEs in the Tropical Atlantic Ocean

Understanding the potential vertical distribution of bigeye tuna(Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical distribution of this fish while foraging and determine the influences of the distribution on longline efficiency in the tropical Atlantic Ocean, the catch per unit effort(CPUE) data were compiled from the International Commission for the Conservation of Atlantic Tunas and the Argo buoy data were downloaded from the Argo data center. The raw Argo buoy data were processed by data mining methods. The CPUE was standardized by support vector machine before analysis. We assumed the depths with the upper and lower limits of the optimum water temperatures of 15℃ and 9℃ as the preferred swimming depth, while the lower limit of the temperature(12℃) associated with the highest hooking rate as the preferred foraging depth(D12) of bigeye tuna during the daytime in the Atlantic Ocean. The preferred swimming depth and foraging depth range in the daytime were assessed by plotting the isobath based on Argo buoy data. The preferred swimming depth and vertical structure of the water column were identified to investigate the spatial effects on the CPUE by using a generalized additive model(GAM). The empirical cumulative distribution function was used to assess the relationship between the spatial distribution of CPUE and the depth of 12℃ isolines and thermocline. The results indicate that 1) the preferred swimming depth of bigeye tuna in the tropical Atlantic is from 100 m to 400 m and displays spatial variation;2) the preferred foraging depth of bigeye tuna is between 190 and 300 m and below the thermocline;3) the number of CPUEs peaks at a relative depth of 30 –50 m(difference between the 12℃ isolines and the lower boundary of the thermocline);and 4) most CPUEs are within the lower depth boundary of the thermocline levels(LDBT) which is from 160 m to 230 m. GAM analysis indicates that the general relationship between the nominal CPUE and LDBT is characterized by a dome shape and peaks at approximately 190 m. The oceanographic features influence the habitat of tropical pelagic fish and fisheries. Argo buoy data can be an important tool to describe the habitat of oceanic fish. Our results provide new insights into how oceanographic features influence the habitat of tropical pelagic fish and fisheries and how fisheries exploit these fish using a new tool(Argo profile data).

Vertical Distribution of Stratospheric Ozone over China

Based on the Stratospheric Aerosol and Gas Experiment (SAGE) II and the Halogen Occultation Ex-periment (HALOE) ozone profiles and the Total Ozone Mapping Spectrometer (TOMS) total ozone data sets,the characteristics and variations of the vertical distribution of stratospheric ozone covering the latitude bands of 50oN±5oN,40oN±5oN,30oN±5oN,and 20oN±5oN and the longitude range of 75-135oE are investigated.The results indicate that the ozone distribution pattern over China not only has general behaviors,but also has particular char-acteristics.In view of the situation that ozone distribu-tions have substantial deviation from zonal symmetry in northern China,the differences of the vertical ozone dis-tribution between the east and the west part of northern China are studied.The results indicate that during winter,spring,and autumn,in the latitude bands of 50oN±5oN,40oN±5oN,ozone concentrations in the eastern part (105 -135oE) are obviously higher than those of the west (75-105oE) at the altitudes of ozone density maximum and below;during summer,in the latitude band of 50oN±5oN,the east-west ozone profile difference is small,but in the latitude band of 40oN±5oN,the east-west total ozone difference becomes as large as 14.0 DU,and the east-west ozone profile difference mainly exists in the lowermost stratosphere and troposphere.

Contrasting vertical distribution between prokaryotes and fungi in different water masses on the Ninety-East Ridge, Southern Indian Ocean

Although the microbial diversity of the Indian Ocean has been extensively investigated,little is known about the community composition of microbes in the Southern Indian Ocean.In the present study,we divided 60 water column samples on the Ninety-East Ridge(NER)into fi ve water masses according to the temperature-salinity curves.We presented,for the fi rst time,a full description of the microbial biodiversity on NER through high-throughput amplicon sequencing approach,including bacteria,archaea,and fungi.We found that bacteria exhibited higher richness and diversity than archaea and fungi across the water masses on NER.More importantly,each water mass on NER featured distinct prokaryotic microbial communities,as indicated by the results of non-metric multidimensional scaling.In contrast,fungi were eurybathic across the water masses.Redundancy analysis results demonstrated that environmental factors might play a pivotal role in the formation and stability of prokaryotic communities in each water mass,especially that of archaea.In addition,indicator species might be used as fi ngerprints to identify corresponding water masses on NER.These results provide new insights into the vertical distribution,structure,and diversity of microorganisms on NER from the perspective of water mass.

Vertical distributions of COS and CS_ in Beijing City

Vertical distributions of COS and CS 2 were measured at a meteorological tower in Beijing City. The mixing ratios of COS and CS 2 are in the range of 371—1681 pptv and 246—1222 pptv, respectively. The significant high mixing ratios of the two compounds at ground level and distinct vertical distributions indicated the existence of strong anthropogenic sources of COS and CS 2 in Beijing City. Domestic stoves and central heaters are important sources of COS during winter season. Cesspools may play significant role on COS over whole seasons. Chemical productions may be responsible for the observed high mixing ratios of CS 2 in Beijing City.

An Empirical Model for Estimating Stratospheric Ozone Vertical Distributions over China

Based on the Stratospheric Aerosol and Gas Experiment （SAGE） Ⅱ and the Halogen Occultation Experiment （HALOE） ozone profiles and the Total Ozone Mapping Spectrometer （TOMS） total ozone data sets, an empirical model for estimating the vertical distribution of stratospheric ozone over China is proposed. By using this model, the vertical distribution of stratospheric （16-50 km） ozone can be estimated according to latitude, month and total ozone. Comparisons are made between the modeled ozone profiles and the SAGEII/HALOE monthly mean ozone measurements, and the results show that the model calculated ozone concentrations conform well with the SAGEII/HALOE measured values, with the differences being less than 15% between 16 km and 18 km, less than 5% between 19 km and 40 km, and less than 10% between 41 km and 50 kin. Comparisons of the model results with balloon-borne ozonesonde measurements performed in Beijing also show good agreement, within 5%, at altitudes between 19 km and 30 km.

Study on Differences of Temperature and Humidity and Vertical Distribution of Human Comfort between City and Countryside of Heilongjiang Province in Summer

[ Objective] The research aimed to study differences of temperature and humidity and vertical distribution of human comfort between city and countryside of Heilongjiang in summer. [Method] By using temperature, humidity and wind velocity data at 10 and 70 m of two iron towers in urban and rural districts of Heilongjiang from June 1 to August 31,2010, the characteristics at temperature and humidity fields and change rule of human comfort index in urban and rural areas in summer were analyzed. [Result] Compared with rural areas, heat island effect of urban districts was obvious, and it was the strongest during 21：00 -23：00 and the weakest during 05：00 -06：00. Daily change rules of wind velocity at 10 m of two anemometer towers were basically consistent. Wind velocity was big at daytime and small at night. Daily change of wind velocity at 70 m of urban districts was consistent with that at 10 m, while wind velocity change at 70 m of rural areas was different from that at 10 m, which had obvious high-altitude wind characteristics. Daily change rules of humidity in two towers were basically consistent, and occurrence time of extremum at 70 m delayed for 1 h. At vertical height, humidity at 10 m was higher than that at 70 m at daytime, and was lower than that at 70 m at night. [ Conclusion] The city had obvious wet island effect during 00：00 -06：00 and dry island effect at nightfall. Comfort index of urban districts was higher than that in rural areas, and difference was the maximum during 19：00 -21：00. Comfort index at 10 m was higher than that at 70 m at daytime in the city and countryside, and was lower than that at 70 m at night. Occurrence frequencies of Grade Zero of comfort at 10 and 70 m of urban districts were both over 60%, while occurrence frequency of ≥ Grade Three of comfort was very small. At vertical height, human comfort had small difference at night. At daytime, as height rise, human comfort index significantly declined, and human feeling was more comfortable than that at low layer.

Analysis of the Relationship between Vertical Distribution of Four Automatic Stations and Local Precipitation in Taihang Mountain of Linzhou

[ Objective] The reseamh aimed to analyze the relationship between vertical distribution of four automatic stations and local precipitation in Taihang Mountain of Linzhou. [ Method] Using mesoscale detection and statistical data of the automatic stations in Henan, the geographical distribution of the precipitation affected by underlying surface in mountainous area of Linzhou was analyzed. [ Result] Surface mesoscale wind field convergence line formed by thermal action of inhomogeneous underlying surface and mountainous terrain and upward movement played the strengthening role to the low-level jet. They affected formation and development of strong convective weather. The geographic distribution of precipitation in mountainous area was highly affected by the terrain, and rainfall, precipitation days and intensity in mountainous area were significantly greater than that in the surrounding hills region. In particular, rainfall on the windward slope significantly increased, and rainfall increased as mountain height within a certain height. [ Conclusion] Hourly ground data analysis at automatic stations had very good forecast indication role in formation, development and dissipation of heavy rain in mountainous areas.

Vertical distribution of zooplankton in centre of South China Sea

Four comprehensive surveys with different depths and subjects were performed byState Oceanic Administration (SOA), China in the centre of the South China Sea(12°-19°30′N, 111°-118°E) from September 1983 to January 1985. According to the data,the vertical distribution pattern of the total biomass and species of zooplankton down to a4000 m depth was for the first time reported and analysed, and the vertical composition ofpopulation was studied.

SOC Vertical Distribution Pattern of Economic Plants in the Loess Gully Areas of China

Three economic plants from the loess gully areas in China to explore the changing vertical distribution characteristics of soil organic carbon.The results showed that:(1) with the increase of depth,the average SOC content of economic plants decreased from 13.98 to 1.39 g/kg on the 0-100 cm soil profile,in the form of a power function;(2) the constructed depth spatial distribution models for different plants could help accurately assess the spatial distribution pattern of soil organic carbon;(3) compared with traditional agricultural planting,the carbon sink function for walnut and grape at a soil depth of 100 cm increased by 92.8±8.98 t/hm^(2) and 45.7±7.7 t/hm^(2),respectively.The adjustment of agricultural planting structure increases the content of soil organic carbon,and economic plants are of great significance to enhance the carbon sink function of the agricultural ecosystem in the loess gully area.

Vertical Distribution and Transport of Aerosols during a Dust Event in Xinjiang,Northwest China

Dust aerosols profoundly influence the radiative balance of the earth–atmosphere system and hence the global and regional climates.In this study,using multi-source satellite and ground-level observations combined with meteorological data,we investigated the three-dimensional evolution and transport characteristics of aerosols during a dust event that occurred in Xinjiang,China from 19 to 21 March 2019.Analysis of the meteorological data reveals that the dust air mass initially appeared in the northwest of Xinjiang and was subsequently transported to the Hami and Turpan areas due to the prevailing northwesterly winds,after which the direction of the airflow shifted due to topography,and the dust air masses were transported into southern Xinjiang.The air quality in the affected areas decreased rapidly,accompanied by a significant increase in aerosol optical depth (AOD),with the maximum value exceeding 3.5 in some areas.In addition,the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations(CALIPSO) data reveal that the aerosol particles in the dust-affected areas were mainly dust aerosols,with small amounts of pollutant dust aerosols.A reduction in the attenuated backscatter coefficient (β532||) was found with increasing altitude,with the dust aerosol pollution mainly distributed in the lower troposphere.The size of dust particles in the lower troposphere was relatively small and irregular.The depolarization ratio (PDR) values at altitudes of 8–10 km were relatively lower than those recorded in the lower troposphere,whereas the color ratio (CR)values were higher,which may have been influenced by the sparse vegetation coverage and poor subsurface conditions in Xinjiang,and attributable to the fact that regular large particles of dust are more likely to be dispersed to altitudes between 8 and 10 km within a short period of time.As a consequence of the meteorological conditions and topography,the dusting process in Xinjiang persisted for a relatively long period.These findings will contribute to enhanced understanding of the vertical distribution of aerosols in Northwest China.

Characteristics of Aerosol Activation Efficiency and Aerosol and CCN Vertical Distributions in North China

By analyzing airborne observations over North China from 30 flights during spring and autumn of 2005-2007, characteristics of the vertical distributions of aerosol and cloud condensation nuclei （CCN） at 0.3% supersaturation in various locations of North China are investigated. The measurement samplings were conducted over different surfaces such as plains, plateau, and sea. The results show that the number concentration of accumulation mode aerosols was greater in autumn than in spring, but the reverse is true for CCN. This means that more aerosols with diameters smaller than 100 nm could be activated as CCN in spring, and this could induce higher aerosol activation efficiency. The aerosol activation efficiency over the plains near the Taihang Mountain was greater in spring than in autumn, and it was greater over sea than over land. The aerosol activation efficiency above the boundary layer over the Bashang Plateau was very low. Based on a fit of the negative exponential vertical distributions of aerosol and CCN, a spatial parameterization model of aerosol and CCN as well as aerosol activation efficiency over North China was proposed. The results show that aerosol activation efficiency was not clearly dependent on altitude because it was mainly affected by regional physical and chemical characteristics of aerosols and the ambient atmospheric conditions. The mean aerosol activation efficiency is 0.66, with values of 0.70 and 0.53 in spring and autumn, respectively.

Effects of plant protection UAV-based spraying on the vertical distribution of droplet deposition on Japonica rice plants in Northeast China

In order to study the regularity of the vertical distribution of droplet deposition on rice plants during pesticide spraying operated by a low-flying multi-rotor plant protection unmanned aviation vehicle(UAV),water-sensitive spray cards were placed on the leaves at the top,in the middle,and at the bottom of rice plants to acquire data on droplet deposition.In this study,a suspension containing tricylazole and hexaconazole was used in the spraying.The water-sensitive spray cards were analyzed by the droplet deposition processing software iDAS to obtain the vertical distribution of the droplets sprayed by the plant protection UAV.The results showed that (1)significant variation was found in the coverage of the droplets in different vertical positions of the rice plants.Within the effective spray width,the best coverage of the droplets was found in the area just below the rotors,whereas the coverage of areas farther away from the rotors was poor.For the different vertical positions of the rice plants,the overall droplet coverage was 58.38%at the top,33.55%in the middle,and 11.34%at the bottom of the plants;(2)for all vertical positions,the average size of the droplets ranged between 110μm and 140μm,which was suitable for the control of plant diseases and insect pests.The highest droplet density was found at the top of the plants,and the distribution of the droplet density was similar in the middle and at the bottom of the rice plants;(3)the diffusion ratio at the top of the rice plants(0.84)was better than that in the middle(0.57)and at the bottom(0.37).The overall relative span could meet the requirements for the actual application.Except for the position in the middle of the plants,the relative span for the other positions of the plants was over 0.67,which is the standard value.This study demonstrated the distribution regularity of droplet deposition along with the vertical direction of rice plants during UAV-based spraying,which is of guiding significance for the use of UAVs in plant protection,the improvement of chemical utilization efficiency,and the reduction of pesticide and fertilizer pollution.

Vertical distribution of aerosol optical properties based on aircraft measurements over the Loess Plateau in China

Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients（σsc）, absorption coefficients（σab）,Angstr？m exponent（α）, single scattering albedo（ω）, backscattering ratio（βsc）, aerosol mass scattering proficiency（Q sc） and aerosol surface scattering proficiency（Q sc′） were obtained. The mean statistical values of σsc were 77.45 Mm-1（at 450 nm）, 50.72 Mm-1（at 550 nm）, and32.02 Mm-1（at 700 nm）. The mean value of σab was 7.62 Mm-1（at 550 nm）. The mean values ofα, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters（ED） of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Q sc and Q sc′ showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Q sc, Q sc′, σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.