Merging regional and global aerosol optical depth records from. Use of satellitebased aerosol optical depth and spatial. The negative slope or first derivative of aot with wavelength in logarithmic scale is known as the angstrom parameter. This parameter see equation 1 can be calculated from two or more wavelengths using a least squares fit. Use was made of groundbased observation, chemistrytransport models, and satellite. Aerosol optical depth aod is the measure of aerosols e. Windblown dust, sea salts, volcanic ash, smoke from wildfires, and pollution from factories are all examples of aerosols. Comparison of aerosol optical thickness with in situ. Modis dark target products collection 6 and onward to. This example showed how to create a histogram of calipso feature optical depth values for dust aerosols over the saharan desert with some basic quality screening. These particles are important to scientists because they can affect climate, weather, and peoples health. Pdf satellite instruments provide a vantage point for studying aerosol loading consistently over different regions of the world. The aerosol particle size parameter is provided only over ocean.
Pnas plus microphysical effects determine macrophysical. Longterm aerosol optical depth trend over iran and identification of. The aerosol optical depth after the middle of august is. This study analyzes the spatiotemporal variations of seasonal moderate resolution imaging spectroradiometer modis deep blue db aod at 550 nm from the aqua satellite over saudi arabia for the period 2002. For example, the effect of changes in the current aerosol emissions on climate depends on the background aerosol load during the preindustrial era e. Aerosol optical depth retrieval by neural networks. Abstract merging multisensor aerosol optical depth aod products is an. Spatiotemporal variability of aerosols over east china. Merging aerosol optical depth data from multiple satellite.
Pdf merging regional and global aerosol optical depth records. These data allow the optical depth representing the aerosol amount of coarse and fine radius groundbased sun photometry were made in bern, switzerland during two and a half years primarily to provide quantitative corrections for atmospheric effects in remotely sensed data in the visible and nearinfrared spectral region. The data records are merged on a daily basis by applying a state of the art quality. Taking the moderate resolution imaging spectroradiometer modis remote sensor data as the data source, the aerosol optical depth of shanghai area on december 6, 20 is inversed from the use of second simulation of satellite. Aod trend estimation from multiple satellite missions for the last four decades. Comparison of modis 3km and 10km resolution aerosol optical depth retrievals over land with airborne sunphotometer measurements during arctas summer 2008, atmos. Importance of aerosol optical depth in the atmospheric. Aerosol optical depth is a measure of the extinction of the solar beam by dust and haze. Cooler colors in this image indicate lower values of the longwave radiative flux than normal, and hence more and higher clouds. Pdf seasonal aerosol optical depth aod variability.
Aerosol optical depth aer can be expressed as function of wavelength through angstrom s equation. Tiny solid and liquid particles suspended in the atmosphere are called aerosols. Thanks go to aeronet for providing aerosol optical depth data and fine mode. Though we only looked at feature optical depth values, the same approach can be taken for other data in the level 2 aerosol. Aerosol optical depth from 2000 to 2019 gis english. Inversion of aerosol optical depth based on modis remote. Aerosol optical depth as a measure of particulate exposure. Aerosol optical depth aerosol particle size volcanic ash mass loading. However, increasing the data coverage by merging the dt and db merged aod product has recently become the focus of research. The use of the term optical density for optical depth is discouraged. Collection 5 introduced the deep blue algorithm for retrieval of aerosol optical depth aod over bright arid surfaces hsu et al. A method to determine atmospheric aerosol optical depth. Jpss assistt overview and star enterprise algorithm development.
Merging modis and groundbased fine mode fraction of aerosols. The optical depth due to extinction by the aerosol component of the atmosphere. Aerosol optical depth and burden from large sea salt. Longterm groundbased measurements of aerosol optical depth. The key quantity they report is aerosol optical depth aod, a measure of the amount of light that aerosols scatter and absorb in the atmosphere and generally prevent from reaching the surface. In chemistry, a closely related quantity called absorbance or decadic absorbance is used instead of optical depth. Constraints used in the retrieval of aerosol optical thickness 22 as mentioned above, the separation of aerosol scattering and land surface reflectance requires additional information. Aerosol optical depth aod is a quantitative estimate of the amount of aerosol present in the. The misr standard aerosol retrieval algorithm runs in an operational, fully automatic mode. Examples of aerosols include windblown dust, sea salts, volcanic ash, smoke from fires, and pollution from factories. Aerosols released into the atmosphere from anthropogenic activity cars, industry and natural events fires, dust storms affect human health, reduce visibility, and alter earths radiation budget. Index termsaerosol optical depth aod, aerosol robotic net work aeronet, bayesian, merging, moderate resolution imag. Trends in aerosol optical depth over indiantrends in aerosol optical depth over indian region.
Use of satellitebased aerosol optical depth and spatial clustering to predict ambient pm 2. Generally, aerosol optical depth aod is used as a proxy for the aerosol concentrations in a vertically distributed column in the atmosphere koren et al. Intercomparison of multisatellites and aeronet aod over. A geostatistical data fusion technique for merging remote. Retrieval of aerosol optical depth from surface solar. Aerosol optical depth over land from avhrr pathfinder. Depending upon their size, type, and location, aerosols can either cool the surface, or warm it. Aerosol optical depth as a measure of particulate exposure using imputed censored data, and relationship with childhood asthma hospital admissions for 2004 in athens, greece gary higgs, 1 david a sterling, 2 subhash aryal, 3 abhilash vemulapalli, 3 kostas n priftis. Aerosol optical depth michigan technological university. Collection 6 edeep bluedark target comparison and merged aerosol products 1. These data allow the optical depth representing the aerosol amount of coarse and fine radius p1. A geostatistical data fusion technique for merging remote sensing and ground. Aerosol optical thickness is the degree to which aerosols prevent the transmission of light in the atmoshpere. In this paper, based on sensitivity of total dsr to aerosol physical optical parameters, a method is proposed to determine the 0.
The constraints used in this method are 1 to require that the wavelength dependence of the aerosol optical thickness is a smooth nonlinear function of. The average depth of the pacific is 14,040 feet 4,280 meters. Exploring aerosol optical thickness using modis satellite. Discrepancies exist between aerosol optical depth aod products due to differences in their.
In this study, focusing on improving estimates of aerosol information on large scale, we develop a data synergy technique based on the ensemble kalman filter enkf to effectively combine these two types of measurements and yield a monthly mean aerosol optical depth aod product with global coverage and improved accuracy. However, factors such as human observation differences and local meteorological conditions often impair the spatial consistency of the visibility converted aod dataset. Esrl global monitoring laboratory global radiation group. The size distribution of aerosols can be estimated from spectral aerosol optical depth, typically from 440nm to 870nm. Impact of elevated aerosol layers on aerosol optical depth. Misr global aerosol optical depth validation based on two. Merging regional and global aerosol optical depth records from major available satellite products. Extended coverage to vegetated surfaces, as well as bright land. Trends in aerosol optical depth over indiantrends in. Eps aerosol optical depth aod algorithm theoretical.
Will continue to merge the responsibilities across the. A comprehensive set of aerosol optical depth aod data, produced by a merger of aod product data from the moderate resolution imaging spectroradiometer. The tcap data set will be used to evaluate regional and global models. In order to merge the fmf from satellite and groundbased products, the theoretical. Modis dark target products collection 6 and onward to collection 7 robert levy nasagsfc.
Simulated aerosol optical depth with the large size mode improve the agreements with observations, especially in high. Bayesian merging of misr and modis aerosol optical depth. Merging regional and global aerosol optical depth records. Aerosols at ten sites in northwestern china are classified in this study. First longterm study on aod trend was evaluated over iran.
Huttunen et al retrieval of aerosol optical depth from surface solar radiation measurements the current forcing of anthropogenic aerosol. Pdf merging regional and global aerosol optical depth. In other words, particles in the atmosphere dust, smoke, pollution can. The aerosol in the elevated layers had enhanced amounts of rbc, biomass burning aerosol, sulfate and nitrate. Aod tells us how much direct sunlight is prevented from reaching the ground by these aerosol particles. Merging aerosol optical depth aod and aod trend estimation from. Jpss assistt overview and star enterprise algorithm. The pacific ocean has a surface area of over 60 million square miles. Bell, c and petros koutrakis a a exposure, epidemiology, and risk program, department of environmental health, harvard school of public health, boston, ma 02215. Retrieval of aerosol optical thickness over land surfaces. Aerosol optical depth measurements by airborne sun. New regression method to merge different modis aerosol.
The air mass backtrajectory clustering analysis was combined with aerosol optical depth aod of fine mode, coarse mode and fine mode fraction in order to evaluate the longrange effects of transportation patterns of trajectories for the ground. Aerosol optical depth measurements by means of groundbased sun photometry were made in bern, switzerland during two and a half years primarily to provide quantitative corrections for atmospheric effects in remotely sensed data in the visible and nearinfrared spectral region. The remote sensing technology can accurate inverse the aerosol optical depth so as to demonstrate the haze distribution. In other words, particles in the atmosphere dust, smoke, pollution can block sunlight by absorbing or by scattering light. The aerosol algorithm is applied to every pixel at moderate resolution 0. Recently, a new technique to converting visibility measurements to aerosol optical depth aod has been developed on a stationtostation basis lin et al. Several approaches were then investigated to merge the aod records from different satellites and. How to generate a histogram of calipso feature aerosol. Aerosol optical depth and burden of sea salt aerosol with the large size mode are studied in community earth system model. It reports aerosol optical thickness aot and aerosol type at 17. Aerosol optical depths typically decrease with increasing wavelength and are much smaller for longwave radiation than for shortwave radiation.
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