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1.
In this paper we describe the results of a research campaign dedicated to the studies of aerosol optical properties in different regions of both the open Baltic Sea and its coastal areas. During the campaign we carried out simultaneous measurements of aerosol optical depth at 4 stations with the use of the hand-held Microtops II sun photometers. The studies were complemented with aerosol data provided by the MODIS. In order to obtain the full picture of aerosol situation over the study area, we added to our analyses the air mass back-trajectories at various altitudes as well as wind fields. Such complex information facilitated proper conclusions regarding aerosol optical depth and Ångström exponent for the four locations and discussion of the changes of aerosol properties with distance and with changes of meteorological factors. We also show that the Microtops II sun photometers are reliable instruments for field campaigns. They are easy to operate and provide good quality results.  相似文献   

2.
Agriculture crop residue burning in tropics is an important source of atmospheric aerosols and monitoring their long-range transport is an important element in climate change studies. Synchronous measurements using micro-pulsed lidar, MICROTOPS-II sun photometer, multi-filter rotating shadow band radiometer (MFRSR) on aerosol optical depth and ground reaching solar irradiance were carried at an urban location in central region of India. Aerosol backscatter profiles obtained from micro-pulse lidar showed elevated aerosol layers up to ～3 km on certain days during October 2007. Satellite data observations on aerosol properties suggested transport of particles from agriculture crop residue burning in Indo-Gangetic Plains over large regions. Radiative forcing of aerosols estimated from SBDART model with input information on aerosol chemical properties, aerosol optical depth and single scattering albedo and broadband solar irradiance measurements using MFRSR showed good correlation (R=0.98).  相似文献   

3.
This paper presents the measurements of a vertical structure of aerosol optical properties performed during the MACRON (Maritime Aerosol, Clouds and Radiation Observation in Norway) campaign, which took place in July and August 2007 at ALOMAR observatory on Andøya island (69.279°N, 16.009°E, elevation 380 m a.s.l.). The mean value of the aerosol optical thickness (AOT) at 500 nm during campaign was 0.12. Significant increase of the AOT above longtime mean value was observed on 7 and 8 August 2007 when the AOT exceeded 0.4 at 500 nm. Analyses of back trajectories show the aerosol transported from over Africa and Central Europe. The aerosol extinction coefficient obtained from the synergy of ceilometer and sun photometer observations reached 0.05–0.08 km?1 (at 1064 nm) in the dust layer. The single scattering albedo at the ALOMAR observatory decreased during the dust episode to 0.93–0.94, which indicates some absorptive aerosols in the lower PBL.  相似文献   

4.
Aerosol particle size distribution and chemical properties are important in studies related to human health and climate. The present study describes an analysis of aerosol mass loading, Aerosol Optical Depth (AOD), black carbon aerosol mass concentration and carbon monoxide over tropical urban region of Hyderabad, India, during March 2006, coinciding with active forest fires season over India. Aerosol optical depth, particulate matter mass loading and carbon monoxide were observed to be high on days with air mass coming from north of the study area. Spatial occurrence of forest fires was analysed using MODIS daytime data and DMSP-OLS nighttime data sets. Aerosol optical depth measured using Microtops-II sunphotometer correlated well with MODIS derived AOD values. Results of the study suggested that synoptic meteorological conditions play an important role in the observed aerosol properties over the study area during the forest fire season.  相似文献   

5.
The Multiangle Imaging SpectroRadiometer (MISR) launched by NASA in late 1999 has a unique multiangle design, which points nine cameras at fixed angles along the satellite flight track and collects reflected solar radiation simultaneously. This design allows the retrieval of a rich dataset of particle abundance, shape and composition over both land and ocean. Some of its capabilities have not been seen by any currently operating satellite aerosol sensors. Since MISR is sensitive to fine particles, it provides a new data source to study the spatial and temporal characteristics of air quality over large geographical regions. We first briefly introduce the MISR instrument, the retrieval and structure of MISR aerosol data, and then review the applications of MISR aerosol data in various aspects of air quality research since its launch. These include the spatial distributions of particle pollution events such as dust storms, wild fires, and urban pollution. Because of the high quality of MISR aerosol data, they can be used as quantitative indicators of particle pollution levels. We review the current modeling studies of surface level particle concentrations. Next, we introduce research results using MISR’s advanced data such as the plume heights, and particle microphysical properties. In the discussion, we compare MISR research with current MODIS research to the best of our ability as MODIS data have been more extensively explored by the Chinese scientific community. Finally, we summarize the advantages and disadvantages of MISR data related to its applications to the air quality research. Given the highly quantitative measurements and comprehensive aerosol information MISR can provide, we believe that it will provide great values to advance our understanding of the particle air pollution in China. Supported by Harvard-EPA Center on Particle Health Effects (Grant Nos. R-827353 and R-832416), NASA’s Climate and Radiation Research and Analysis Program, the EOS-MISR Instrument Project and the National High Technology Research and Development Program of China (Grant No. 2006AA06A305).  相似文献   

6.
Advances in studying interactions between aerosols and monsoon in China   总被引：1，自引：0，他引：1  
Scientific issues relevant to interactions between aerosols and the Asian monsoon climate were discussed and evaluated at the 33rd “Forum of Science and Technology Frontiers” sponsored by the Department of Earth Sciences at the Chinese Academy of Sciences. Major results are summarized in this paper. The East Asian monsoon directly affects aerosol transport and provides a favorable background circulation for the occurrence and development of persistent fog-haze weather. Spatial features of aerosol transport and distribution are also influenced by the East Asian monsoon on seasonal, inter-annual, and decadal scales. High moisture levels in monsoon regions also affect aerosol optical and radiative properties. Observation analyses indicate that cloud physical properties and precipitation are significantly affected by aerosols in China with aerosols likely suppressing local light and moderate rainfall, and intensifying heavy rainfall in southeast coastal regions. However, the detailed mechanisms behind this pattern still need further exploration. The decadal variation in the East Asian monsoon strongly affects aerosol concentrations and their spatial patterns. The weakening monsoon circulation in recent decades has likely helped to increase regional aerosol concentrations. The substantial increase in Chinese air pollutants has likely decreased the temperature difference between land and sea, which favors intensification of the weakening monsoon circulation. Constructive suggestions regarding future studies on aerosols and monsoons were proposed in this forum and key uncertain issues were also discussed.  相似文献   

7.
Aerosol optical properties have been studied for spring seasons when increased values of PM10 are registered. Measurements of aerosol optical properties were taken by collocated lidar and sun-photometers at Belsk, Poland, and Minsk, Belarus. A significant increase of registered aerosol optical thickness (AOT) was found during episodes with elevated PM10 concentrations. An increase of AOT at 1020 nm amounted to 50% in the case of Minsk and 18% in the case of Belsk, while an increase of AOT at 400 nm was 66% and 33%, respectively. We noted an increase of Ångström exponent by 6% at both stations and no significant increase of single scattering albedo. The LIDAR measurements together with NAAPS model results and backtrajectory analysis suggest that both the biomass burning products and the Saharan dust are responsible for increased PM10 concentrations and large AOT values during spring time. The smoke aerosol is transported over Central Europe mainly in the boundary layer, increasing both PM10 concentration and AOT. The dust aerosol transported in the free troposphere slightly affects the AOT values only. Statistically significant correlation between PM10 concentration and AOT was found during reporting period.  相似文献   

8.
Summary Eight vertical profiles compiled from simultaneous measurements of Aitken nuclei and ozone concentrations over Germany in different weather conditions are discussed. The position and shape of the profiles is shown to depend on the prevailing weather conditions and the type of air masses. High aerosol concentrations in smoke plumes correlate in some cases with lower ozone concentrations, indicating that ozone in such cases is destroyed in the presence of high concentrations of pollutants such as aerosols and gases. A layered structure in the profiles was found only in association with temperature inversions and where the air above 2 km was subsiding, and was not found in convective parts of the troposphere.  相似文献   

9.
An algorithm based on simulated satellite signal calculated by the 6S radiative transfer model has been developed in order to retrieve the aerosol optical thickness of dust over the Atlantic ocean. The algorithm is applied to the visible channel of Geostationary Operational Environmental Satellite (GOES 8) images. The inversion uses a look-up table giving the satellite signal intensity as a function of surface albedo, viewing geometry, solar illumination and the optical properties of the aerosols. The study consists of assessing the feasibility of monitoring and mapping the transport of suspended particles across the Atlantic from the Sahara to the Caribbean. The study area is between 10 and 25 N and 30 and 65 W. The optical thickness of aerosols has been calculated over a period of 11 days between 10th and 20th of June 1997 for the 14:15 UT GOES image acquisition. The calculated aerosol optical thickness ranges from 0.0 to 0.81 with an important event of dust presence occurring between 13th and 16th of June. The retrieved aerosol optical thickness is in good agreement with the values obtained between 14h UT and 15h UT from ground based sun photometer measurements on the island of Guadeloupe, and a coefficient correlation (R2) of 0.88 has been found between the data sets.  相似文献   

10.
Summary The vertical profile of the aerosol attenuation coefficient can be calculated from the measurements of the spectral flux density of direct solar radiation and spectral radiance in a clear sky in a certain sun aureola by using the theory applied in this article. The process of solar radiation scattering is solved up to third order.  相似文献   

11.
This paper investigates the annual cycle in aerosol optical thickness (AOT) and Angstrom exponent in Darwin, Australia, a coastal site in the Tropical Warm Pool where the major aerosol sources are biomass burning and sea salt. We have used radiometer measurements from the Tropical Western Pacific Atmospheric Radiation Measurement facility for the period March 2002–June 2003. Strong seasonal cycles in AOT and Angstrom exponent were observed, peaking during the burning season (May–November). Investigation of the spectral dependence of optical thickness showed that the Angstrom formula can be satisfactorily fitted to the AOT data during the burning season but not on summer and autumn afternoons due to the presence of sea salt aerosols.  相似文献   

12.
Altitude profile of aerosol Single Scattering Albedo (SSA), derived from simultaneous in-situ airborne measurements of the coefficients of aerosol absorption and scattering off the west coast of India over the Arabian Sea (AS), during January 2009 is presented. While both the absorption and scattering coefficients decreased with altitude, their vertical structure differed significantly. Consequently, the derived SSA, with a surface value of 0.94, decreased with altitude, illustrating increasing relative dominance of aerosol absorption at higher altitudes. Altitude profile of SSA, when examined in conjunction with that of hemispheric backscatter fraction, revealed that the continental influence on the aerosol properties was higher at higher altitude, rather than the effect of marine environment. During an east–west transect across the peninsular India at an altitude of ～2500 m (free troposphere), it was found that the aerosol scattering coefficients remained nearly the same over both east and west coasts.  相似文献   

13.
Continuous measurements of solar spectral radiation using the Multi-filter Rotating Shadow Band Radiometer (MFRSR) are performed at the Actinometric Station of the National Observatory of Athens (ASNOA). The present study utilizes three clear-sky days of continuous observations, from local sunrise to local sunset, in order to investigate the daily variation of the radiation components (diffuse, global and direct-beam) as well as their ratios (diffuse-to-global, DGR, and diffuse-to-direct-beam, DDR) under different atmospheric conditions. Both ratios have received great scientific interest, especially for investigating solar irradiance modifications under various atmospheric conditions, aerosol load and optical properties. Apart from this, the present study shows that the DDR can constitute a measure of atmospheric turbidity when it is determined at longer wavelengths, while the DGR cannot. The effect of the solar zenith angle (SZA) on both ratios is significant at the shorter wavelengths with varying sensitivities depending on the aerosol field and sun elevation. The present study confirms the results obtained by previous solar irradiance measurements in Athens and also those computed via radiative transfer codes and sheds light on the scientific knowledge of the use of spectral DDR as an atmospheric turbidity index.  相似文献   

14.
Atmospheric aerosols are a crucial link in the physical processes, involved in the formation and growth of precipitating clouds. Extensive aerosol measurements in surface air and in the lower troposphere were made at inland and coastal stations of different regions in India. At inland stations, the hygroscopic fraction of the total aerosol content is found to be a useful characteristic for distinguishing between the monsoon and summer airflow, as well as an indicator for a good or a badly developed monsoon. At coastal stations, however, this feature is not observed.Measurements as a function of height brought out that the aerosol varied widely in air over different seasons. During monsoon, the hygroscopic fraction was found highest at the cloud base level and was closely linked to the development of rain. Details of these investigations are presented.  相似文献   

15.
Error analysis of multi-wavelength sun photometry   总被引：6，自引：0，他引：6  
The error terms involved in precision multi-wavelength sun photometry, as used to study atmospheric aerosols, are analyzed. The error terms treated include instrumental errors, calibration errors, and errors imposed by the atmosphere. It is shown that in order to derive accurate aerosol parameters, one must exercise great care in the photometer calibration. A procedure for accurate calibration is described, based on an intercalibration between extrapolations of the extraterrestrial solar spectral irradiance and irradiance of a standard lamp. Methods are described to assess, and reduce, uncertainties brought about by diffuse radiation in the photometer's field of view, temporal variations in aerosol optical depth, and gaseous absorption features at the operating wavelength. It is shown that if care is taken sun photometry can be used to derive monochromatic aerosol optical depth to an accuracy of several thousandths.  相似文献   

16.
Two prognostic experiments taking into account real atmospheric forcing for 2006 and 2011 were carried out based on the eddy-resolving numerical model with a horizontal resolution of 1.6 km for the Black Sea. The main dynamic features such as the Rim Current, the Sevastopol, and Batumi anticyclones are reproduced in both experiments. The model results are confirmed via observation data. We accomplished the analysis of simulated circulation and energetics. The results demonstrate that both the vertical viscosity and vertical diffusion along with the energy inflow from the wind have been the main contributors to the annual and seasonal budgets of kinetic and potential energies of the Black Sea circulation. It is shown that two regimes of the Black Sea general circulation are implemented depending on a magnitude of wind contribution to the kinetic energy in winter. Intensive mesoscale eddy formation was observed along the Anatolian, Caucasian, and Crimean coasts. The analysis of the Black Sea circulation and eddy energetics allowed us to conclude that the generation and development of the mesoscale coastal eddies is associated with the barotropic instability in case of intensive coastal currents and is associated with both the barotropic and baroclinic instability in case of weak coastal currents.  相似文献   

17.
The aim of the atmospheric nitrogen inputs into the coastal ecosystem (ANICE) project is to improve transport–chemistry models that estimate nitrogen deposition to the sea. To achieve this, experimental and modelling work is being conducted which aims to improve understanding of the processes involved in the chemical transformation, transport and deposition of atmospheric nitrogen compounds. Of particular emphasis within ANICE is the influence of coastal zone processes. Both short episodes with high deposition and chronic nitrogen inputs are considered in the project. The improved transport–chemistry models will be used to assess the atmospheric inputs of nitrogen compounds into the European regional seas (the North Sea is studied as a prototype) and evaluate the impact of various emission reduction strategies on the atmospheric nitrogen loads. Assessment of the impact of atmospheric nitrogen on coastal ecosystems will be based on comparisons of phytoplankton nitrogen requirements, other external nitrogen inputs to the ANICE area of interest and the direct nitrogen fluxes provided by ANICE. Selected results from both the experimental and modelling components are presented here. The experimental results show the large spatial and temporal variability in the concentrations of gaseous nitrogen compounds, and their influences on fluxes. Model calculations show the strong variation of both concentrations and gradients of nitric acid at fetches of up to 25 km. Aerosol concentrations also show high temporal variability and experimental evidence for the reaction between nitric acid and sea salt aerosol is provided by size-segregated aerosol composition measured at both sides of the North Sea. In several occasions throughout the experimental period, air mass back trajectory analysis showed connected flow between the two sampling sites (the Weybourne Atmospheric Observatory on the North Norfolk coast of the UK and Meetpost Noordwijk, a research tower at 9 km off the Dutch coast). Results from the METRAS/SEMA mesoscale chemistry transport model system for one of these cases are presented. Measurements of aerosol and rain chemical composition, using equipment mounted on a commercial ferry, show variations in composition across the North Sea. These measurements have been compared to results obtained with the transport–chemistry model ACDEP which calculates the atmospheric inputs into the whole North Sea area. Finally, the results will be made available for the assessment of the impact of atmospheric nitrogen on coastal ecosystems.  相似文献   

18.
This study is aimed to understand the hydraulic mechanism of coastal aquifer systems that include highly permeable layers (HPLs). These hydrologic conditions can be found in many volcanic islands that are composed of a series of lava flows discharged into sea or other standing body of water. In the first part, we developed a numerical model based on the geologic and hydrologic data obtained from the eastern Jeju Island, Korea, of which the aquifer contains clinker and hyaloclastite layers. The simulation results reproduced spatial location of fresh‐saline water interface, especially the abrupt decline of interface at the inland part and the thickness variation of transition zone along the cross‐section observed at the eastern Jeju coastal aquifer. We were able to find out that these phenomena are strongly related to the presence of the HPL. In the second part, quantitative analyses were conducted with the use of hypothetical models in order to understand the dynamic characteristics of coastal system that includes HPLs. A series of sensitivity studies were conducted to assess the effect of the horizontal length and vertical depth of HPL on the spatial location of the interface toe and the configuration of transition zone. Various case studies have shown that the seawater intruded into the inland more as the horizontal length of HPL was increased and its vertical depth was decreased. In other simulations including two HPLs, the vertical distance between these two HPLs primarily controlled the flow regime, flux variations, and the configuration of the transition zone. Finally, we performed simulations to evaluate the effect of a rising sea‐level. This study provides more understanding of how the presence of HPL controls the seawater intrusion processes, and the spatial configurations of fresh‐saline water interface at coastal aquifers. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

19.
In this paper, optical measurements of aerosol properties made during a ship cruise from Poland to Antarctic Station in September and October 2006, and during the cruise back to Gdynia in April and May 2007 are described. A large gradient of pollution between the clear South Atlantic and the dusty North Atlantic was observed. The maximum of aerosol optical thickness at a wavelength of 500 nm reached 0.4 at 20°N in September 2006 and 0.3 at 40°N in May 2007, respectively. Strong Saharan dust transport is suggested as an explanation for the small values of Ångström exponent observed (values of 0.2 and 0.4 on these respective dates). On the Southern Hemisphere the aerosol optical thickness at 500 nm ranged from 0.05 to 0.2. Significant increases of the aerosol optical thickness were associated with strong wind and sea salt production. Good agreement was found when the in situ measurements of aerosol optical thickness were compared to satellite retrievals and modelling results.  相似文献   

20.
The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.  相似文献   

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