75 research outputs found
Bayesian Methodology for Ocean Color Remote Sensing
66 pagesThe inverse ocean color problem, i.e., the retrieval of marine reflectance from top-of-atmosphere (TOA) reflectance, is examined in a Bayesian context. The solution is expressed as a probability distribution that measures the likelihood of encountering specific values of the marine reflectance given the observed TOA reflectance. This conditional distribution, the posterior distribution, allows the construction of reliable multi-dimensional confidence domains of the retrieved marine reflectance. The expectation and covariance of the posterior distribution are computed, which gives for each pixel an estimate of the marine reflectance and a measure of its uncertainty. Situations for which forward model and observation are incompatible are also identified. Prior distributions of the forward model parameters that are suitable for use at the global scale, as well as a noise model, are determined. Partition-based models are defined and implemented for SeaWiFS, to approximate numerically the expectation and covariance. The ill-posed nature of the inverse problem is illustrated, indicating that a large set of ocean and atmospheric states, or pre-images, may correspond to very close values of the satellite signal. Theoretical performance is good globally, i.e., on average over all the geometric and geophysical situations considered, with negligible biases and standard deviation decreasing from 0.004 at 412 nm to 0.001 at 670 nm. Errors are smaller for geometries that avoid Sun glint and minimize air mass and aerosol influence, and for small aerosol optical thickness and maritime aerosols. The estimated uncertainty is consistent with the inversion error. The theoretical concepts and inverse models are applied to actual SeaWiFS imagery, and comparisons are made with estimates from the SeaDAS standard atmospheric correction algorithm and in situ measurements. The Bayesian and SeaDAS marine reflectance fields exhibit resemblance in patterns of variability, but the Bayesian imagery is less noisy and characterized by different spatial de-correlation scales, with more realistic values in the presence of absorbing aerosols. Experimental errors obtained from match-up data are similar to the theoretical errors determined from simulated data. Regionalization of the inverse models is a natural development to improve retrieval accuracy, for example by including explicit knowledge of the space and time variability of atmospheric variables
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Sources, sinks, and transatlantic transport of North African dust aerosol: a multimodel analysis and comparison with remote sensing data
This study evaluates model-simulated dust aerosols over North Africa and the North Atlantic from five global models that participated in the Aerosol Comparison between Observations and Models phase II model experiments. The model results are compared with satellite aerosol optical depth (AOD) data from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-viewing Wide Field-of-view Sensor, dust optical depth (DOD) derived from MODIS and MISR, AOD and coarse-mode AOD (as a proxy of DOD) from ground-based Aerosol Robotic Network Sun photometer measurements, and dust vertical distributions/centroid height from Cloud Aerosol Lidar with Orthogonal Polarization and Atmospheric Infrared Sounder satellite AOD retrievals. We examine the following quantities of AOD and DOD: (1) the magnitudes over land and over ocean in our study domain, (2) the longitudinal gradient from the dust source region over North Africa to the western North Atlantic, (3) seasonal variations at different locations, and (4) the dust vertical profile shape and the AOD centroid height (altitude above or below which half of the AOD is located). The different satellite data show consistent features in most of these aspects; however, the models display large diversity in all of them, with significant differences among the models and between models and observations. By examining dust emission, removal, and mass extinction efficiency in the five models, we also find remarkable differences among the models that all contribute to the discrepancies of model-simulated dust amount and distribution. This study highlights the challenges in simulating the dust physical and optical processes, even in the best known dust environment, and stresses the need for observable quantities to constrain the model processes
Critical Evaluations Of Modis And Misr Satellite Aerosol Products For Aerosol Modeling Applications
The study of uncertainties in satellite aerosol products is essential to aerosol
data assimilation and modeling efforts. In this study, with the assistance of ground- based observations, uncertainties in Moderate Resolution Imaging Spectroradiometer (MODIS) collection 5 Deep Blue (DB), Multi-Angle Imaging Spectroradiometer (MISR) version 22 aerosol products, and the newly released collection 6 Dark Target over-ocean and DB products were evaluated. For each product, systematic biases were analyzed against observing conditions. Empirical correction procedures and data filtering steps were generated to develop noise and bias reduced DA-quality aerosol products for modeling related applications.
Special attention was also directed at the potential low bias in satellite aerosol optical depth (AOD) climatology due to misclassification of aerosols as clouds over Asia. A heavy aerosol identifying system (HAIS) was developed through the combined use of the Ozone Monitoring Instrument (OMI) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) products for detecting heavy smoke aerosol plumes. Upon extensive evaluation, HAIS was applied to one year of collocated OMI, CALIOP, and MODIS data to study the misclassifications related low bias. This study suggests that the misclassification of heavy smoke aerosol plumes by MODIS is rather infrequent and thus introduces an insignificant low bias to its AOD climatology. Still, this study confirms that misclassification happens in both active- and passive- based satellite aerosol products and needs to be studied for forecasting these events
Lidar Measurements for Desert Dust Characterization: An Overview
We provide an overview of light detection and ranging (lidar) capability for describing and characterizing desert dust. This paper summarizes lidar techniques, observations, and fallouts of desert dust lidar measurements. The main objective is to provide the scientific community, including non-practitioners of lidar observations with a reference paper on dust lidar measurements. In particular, it will fill the current gap of communication between research-oriented lidar community and potential desert dust data users, such as air quality monitoring agencies and aviation advisory centers. The current capability of the different lidar techniques for the characterization of aerosol in general and desert dust in particular is presented. Technical aspects and required assumptions of these techniques are discussed, providing readers with the pros and cons of each technique. Information about desert dust collected up to date using lidar techniques is reviewed. Lidar techniques for aerosol characterization have a maturity level appropriate for addressing air quality and transportation issues, as demonstrated by some first results reported in this pape
Desert dust characterization in Northern Africa, Middle East and Europe through regional dust modelling, and satellite-borne and ground-based observations
Tesis doctoral de la Universitat Politècnica de Catalunya. Programa de Doctorat en Enginyeria Ambiental[ES] Una gran cantidad de polvo se moviliza en regiones áridas del planeta y se emite a la atmósfera bajo condiciones meteorológicas favorables. A partir de medidas realizadas en superficie y desde satélite, además de estimaciones obtenidas a partir de modelos, se calcula que en todo el planeta se emiten entre centenares y miles de megatoneladas de polvo cada año. El impacto que tiene el polvo mineral en el clima, los ecosistemas y la calidad del aire,
y por lo tanto, en la salud humana y en las actividades econĂłmicas, representa una cuestiĂłn social y cientĂfica de gran relevancia. La fuente más importante de emisiĂłn de polvo mineral a nivel global es la regiĂłn del Sáhara.[EN] A large amount of mineral dust is mobilized over arid regions and injected into the atmosphere under favourable weather conditions. Estimates of global dust input based on ground based and satellite observations, and modelling studies range from several hundred to thousands megatons per year. The impact of mineral dust upon climate, ecosystems and air quality (and consequently on economic activities and human health) represents a major
scientific and societal issue. The most prominent example of this transport is the export of desert mineral dust from the Saharan region
Desert dust characterization in Northern Africa, Middle East and Europe through regional dust modelling, and satellite-borne and ground-based observations
The impact of mineral dust upon climate, ecosystems and air quality represents a major scientific and societal issue. The aim goals of the present Ph.D. Thesis are to evaluate the behaviour and to improve the forecasting skills of a regional dust model and to characterize the desert dust content in Northern Africa, Europe and Middle East.
An aerosol characterization was performed using long-term series of aerosol optical depth (AOD) from AERONET sun photometers. The results showed that mineral dust was the most important constituent in Northern Africa and Arabia. Small particles were abundant in sites close to urban and industrial areas of Continental and Eastern Europe and Middle East, and important contributions of biomass burning were observed in the sub-Sahel region in winter. Desert dust transport to Southern Europe was observed from spring to autumn and decreasing with latitude with contributions above 40% to the aerosol column load.
Dust models are essential to complement dust-related observations, understand the dust processes and predict the impact of dust on air quality. Despite that the BSC-DREAM8b model has reached a level of delivering reliable operational dust forecasts, it is necessary to conduct an extensive evaluation of its behaviour. The BSC-DREAM8b and the original DREAM models and different research model versions were evaluated over Northern Africa, Mediterranean and Middle East using AERONET measurements and seasonal averages from satellite aerosol products. The model evaluation highlighted that BSC-DREAM8b and DREAM strongly underestimated the dust fields in the Sahel during winter and overestimated dust concentrations during spring rainy events in the Mediterranean. The introduction of new dry deposition scheme and an updates in the wet deposition scheme improved the long-range transport, although significant underestimation remained in the Sahel in winter. The inclusion of a preferential source mask improved the localization of the main North African sources and the long-range dust transport to Europe and Atlantic regions. The inclusion of a more physically-based dust emission scheme with a new soil texture database led to reasonably good results at source areas and subsequent long-range transport. In this case, the use of a preferential source mask didnÂżt introduce significant improvements.
The long-range dust transport over Europe was evaluated and analysed with an annual simulation of the CALIOPE air quality modelling system. CALIOPE includes CMAQ which calculates biogenic, anthropogenic and sea salt aerosol; and BSC-DREAM8b which provides desert dust. For the evaluation, we used daily PM10, PM2.5 and aerosol components from the EMEP/CREATE network; total, coarse and fine AOD from AERONET and seasonal averages from satellite aerosol products. Overall CALIOPE could reproduce reasonably well the daily variability of the main components and the seasonal aerosol patterns in Europe. However, the PM and AOD levels were underestimated. The most underestimated aerosol components were carbonaceous matter and secondary inorganic aerosols (SIA). A simple model bias correction based on the chemical composition observations was applied to the model simulation to provide an estimation of the spatial and seasonal distribution of aerosols over Europe. The simulated aerosol concentrations presented maximum values over the industrialized and populated areas of the Po Valley and the Benelux regions. SIA were dominant in the fine fractions representing up to 80% of the aerosol budget in latitudes beyond 40ÂşN. A second maximum was detected over Eastern and Southern Europe. High values in Southern Europe were linked to Saharan dust transport which contributed up to 40% of the total aerosol mass. Maxima dust seasonal concentrations were found between spring and early autumn. These results showed that desert dust is the main responsible of the exceedances of the PM10 EU air quality threshold in large areas south of 45ÂşN.Una gran quantitat de pols que Ă©s mobilitzada en les regions Ă rides del planeta, Ă©s injectada a l’atmosfera sota condicions meteorològiques favorables. A partir de mesures terrestres i de satèl·lit, a mĂ©s a mĂ©s d’estimacions obtingudes a partir de models, es calcula que en tot el planeta s’emeten entre centenars i milers de megatones de pols per any. L’impacte que tĂ© la pols mineral en el clima, els ecosistemes i la qualitat de l’aire, i per tant, en la salut humana i les activitats econòmiques, representa una qĂĽestiĂł social i cientĂfica de gran rellevĂ ncia. La font mĂ©s important d’emissiĂł de pols mineral a nivell global Ă©s la regiĂł del SĂ hara.
Els principals objectius de la present tesi doctoral sĂłn el d'avaluar el comportament i el de millorar les capacitats de predicciĂł d'un model regional de pols aixĂ com el de caracteritzar el contingut de pols desèrtica en el nord d'Ă€frica, Orient MitjĂ i Europa. En aquest marc de treball, el model regional de pols BSC-DREAM8b i els fotòmetres de la xarxa internacional AERONET sĂłn les principals eines que serĂ n utilitzades en el transcurs de la present investigaciĂł. La comparaciĂł entre valors observats i simulats no pot ser adequadament entesa si les mesures no estan separades en els seus components fonamentals. AixĂ, es va dur a terme una caracteritzaciĂł d'aerosols per al nord d'Ă€frica, Europa i Orient MitjĂ . Aquesta caracteritzaciĂł estĂ basada en sèries d'espessor òptic d'aerosols (AOD; Aerosol Optical Depth en anglès) dels fotòmetres de la xarxa AERONET. L'anĂ lisi d'aquesta base de dades es va realitzar aplicant el mètode de Gobbi i co-autors. Aquest mètode grĂ fic permet deduir diferents propietats òptiques i fĂsiques dels aerosols (com sĂłn el radi efectiu del mode fi i la contribuciĂł de les fraccions fines i gruixudes a l’AOD), a mĂ©s a mĂ©s, de diferenciar entre diferents processos que fan augmentar el valor de l’AOD com sĂłn la humidificaciĂł i/o coagulaciĂł de les fraccions fines o l'increment de partĂcules mĂ©s gruixudes a causa de la
presència de nĂşvols. Els resultats van mostrar que la pols mineral Ă©s l'aerosol mĂ©s important al nord d'Ă€frica i ArĂ bia. En estacions properes a zones urbanes i industrials de regions continentals i de l'est d'Europa i Orient MitjĂ es van observar partĂcules fines associades a fonts antropogèniques. TambĂ© es van detectar importants contribucions en les fraccions fines degudes a la crema de biomassa a la zona del sub-Sahel durant l'hivern. El transport de pols desèrtica cap al sud d'Europa estĂ associat a determinats patrons meteorològics estacionals. Com a resultat, en zones del sud d'Europa, la pols desèrtica es va observar entre primavera i tardor, i la seva contribuciĂł (que va arribar superar el 40%) decreixia cap a latituds mĂ©s al nord. En aquest darrer cas, la pols desèrtica acostumava a trobar-se barrejada amb altres tipus d'aerosols d'origen antropogènic Els models de pols sĂłn essencials per complementar les observacions, entendre els processos associats al cicle de la pols i predir el seu impacte en les concentracions en superfĂcie del material particulat (PM; Particulate Matter en anglès). En particular, els models regionals sĂłn adequats per a la simulaciĂł d'episodis individuals d’instrusiĂł de pols desèrtica. Actualment, el model de pols BSC-DREAM8b Ă©s mantingut i desenvolupat en el Barcelona Supercomputing Center – Centre Nacional de SupercomputaciĂł (BSC-CNS). En els darrers anys, el model ha proporcionat prediccions diĂ ries de concentracions de pols desèrtica en dos dominis: Nord d'Ă€frica-Europa – Europa - Orient MitjĂ i Ă€sia. A pesar que el BSCDREAM8b ha arribat a aconseguir una qualitat de pronòstic operacional capaç de
reproduir els episodis d'intrusió saharians més importants que afecten al Mediterrani i Europa, és necessari avaluar el seu comportament en regions font de pols.
En aquest context, el model BSC-DREAM8b i la seva versiĂł original, DREAM, aixĂ com diferents versions experimentals, van ser avaluats per a un cicle estacional complet utilitzant les dades de la xarxa AERONET i promitjos estacionals de productes d'aerosols de diferents satèl·lits pel Nord d'Ă€frica, Orient MitjĂ i Europa. Els resultats de l'avaluaciĂł del model van mostrar que tant el BSC-DREAM8b com el DREAM subestimaven les concentracions de pols a la regiĂł del Sahel durant l'estaciĂł hivernal del Harmattan. Per contra, importants sobreestimacions en l'oest del Mediterrani es van detectar coincidint amb episodis plujosos a la primavera. L’inclusiĂł d'un nou esquema de deposiciĂł seca a mĂ©s de l'actualitzaciĂł de la relaciĂł de rentat en l'esquema de deposiciĂł humida del model, van aconseguir millores en el transport a llarga distĂ ncia, en particular sobre el Mediterrani malgrat que les subestimacions a la zona del Sahel van continuar sent persistents a l'hivern. La introducciĂł d'una mĂ scara de fonts preferents basada en la topografia del terreny en l'esquema d'emissiĂł va millorar la localitzaciĂł de les principals regions font en el Nord d'Ă€frica. Com a conseqüència, es van observar millores en el transport de llarga distĂ ncia cap a Europa i les regions AtlĂ ntiques. La inclusiĂł d'un nou esquema d'emissiĂł (que inclou parametritzacions fĂsiques mĂ©s complexes) a mĂ©s d'una nova base de dades de textura de sòls va aconseguir bons resultats en regions font aixĂ com en regions afectades pel transport de pols a llarga distĂ ncia. En aquest cas, l’introducciĂł d'una mĂ scara de fonts preferents en l'esquema d'emissiĂł no va mostrar significants millores en comparaciĂł dels valors observats.
A Europa, es poden trobar diferents tipus d'aerosols associats a diferents fonts d'emissiĂł (tant naturals com antropogèniques) que s’han de tenir en compte quan s'analitzen les contribucions dels aerosols sobre el continent europeu. El transport de pols sahariana cap a sud d'Europa va ser avaluat i analitzat mitjançant una simulaciĂł del sistema de modelitzaciĂł de qualitat de l'aire CALIOPE. El sistema de modelitzaciĂł CALIOPE integra un conjunt de models dels quals el BSC-DREAM8b i el model fotoquĂmic CMAQ proporcionen les estimacions d'aerosols. Per a l'avaluaciĂł de CALIOPE es van utilitzar diverses fonts de dades de xarxes en superfĂcie (com la xarxa europea de qualitat de l'aire EMEP/CREATE i la xarxa de AERONET) i mitjanes estacionals de productes d'aerosols de satèl.lits. L'avaluaciĂł va mostrar que malgrat subestimar les concentracions d'aerosols, CALIOPE va ser capaç de capturar les variabilitats diĂ ries observades en les estacions en superfĂcie aixĂ com reproduir els patrons estacionals observats en els productes de satèl·lit. L'avaluaciĂł dels aerosols per components va mostrar que les espècies quĂmiques amb major subestimaciĂł pel que fa a les observacions estaven associades a les fraccions fines de carbĂł elemental i orgĂ nic aixĂ com els aerosols secundaris inorgĂ nics (nitrats, sulfats i amoni). Com a resultat, es va aplicar un senzill mètode de correcciĂł de l’error als resultats de la simulaciĂł basat en les observacions de la composiciĂł quĂmica per tal de mostrar una
estimaciĂł espaial i temporal de la distribuciĂł dels diferents aerosols presents a Europa.
L'anĂ lisi de d’aquesta simulaciĂł va mostrar que les mĂ ximes concentracions d'aerosols es localitzen a les zones poblades i industrialitzades del Benelux i de la Vall del Po. Aquests mĂ xims estan associats a les fraccions fines compostes d'aerosols secundaris inorgĂ nics (observant-se contribucions de mĂ©s del 80%). MĂ xims secundaris es van detectar a l'est i sud d'Europa. Les altes concentracions en el sud d'Europa s’associaven al transport de pols sahariana que contribuĂŻa en mĂ©s d'un 40% al total de la massa en columna. Prop de la superfĂcie, les mĂ ximes concentracions estacionals associades al transport de pols (> 30 microg/m3) van ser observades entre primavera i estiu. A mĂ©s a mĂ©s, els resultats de la simulaciĂł anual d'aerosols per Europa va mostrar que el transport de pols sahariana Ă©s el principal responsable de la superaciĂł del lĂmit diari de PM10 establert per la UniĂł Europea
(50 microg/m3) en extenses Ă rees al sud dels 45ÂşN.Postprint (published version
Satellite remote sensing of aerosols using geostationary observations from MSG-SEVIRI
Aerosols play a fundamental role in physical and chemical processes affecting regional and global climate, and have adverse effects on human health. Although much progress has been made over the past decade in understanding aerosol-climate interactions, their impact still remains one of the largest sources of uncertainty in climate change assessment. The wide variety of aerosol sources and the short lifetime of aerosol particles cause highly variable aerosol fields in both space and time. Groundbased measurements can provide continuous data with high accuracy, but often they are valid for a limited area and are not available for remote areas. Satellite remote sensing appears therefore to be the most appropriate tool for monitoring the high variability of aerosol properties over large scales. Passive remote sensing of aerosol properties is based on the ability of aerosols to scatter and absorb solar radiation. Algorithms for aerosol retrieval from satellites are used to derive the aerosol optical depth (AOD), which is the aerosol extinction integrated over the entire atmospheric column. The aim of the work described in this thesis was to develop and validate a new algorithm for the retrieval of aerosol optical properties from geostationary observations with the SEVIRI (Spinning Enhanced Visible and Infra-Red Imager) instrument onboard the MSG (Meteorological Second Generation) satellite. Every 15 minutes, MSG-SEVIRI captures a full scan of an Earth disk covering Europe and the whole African continent with a high spatial resolution. With such features MSG-SEVIRI offers the unique opportunity to explore transport of aerosols, and to study their impact on both air quality and climate. The SEVIRI Aerosol Retrieval Algorithm (SARA) presented in this thesis, estimates the AOD over sea and land surfaces using the three visible channels and one near-infrared channel of the instrument. Because only clear sky radiances can be used to derive aerosol information, a stand-alone cloud detection algorithm was developed to remove cloud contaminated pixels. The cloud mask was generated over Europe for different seasons, and it compared favorably with the results from other cloud detection algorithms - namely the cloud mask algorithm of Meteo-France for MSG-SEVIRI, and the MODIS (Moderate Resolution Imaging Spectroradiometer) algorithm. The aerosol information is extracted from cloud-free scenes using a method that minimizes the error between the measured and the simulated radiance. The signal observed at the satellite level results from the complex combination of the surface and the atmosphere contributions. The surface contribution is either parameterized (over sea), or based on a priori values (over land). The effects of atmospheric gases and aerosols on the radiance are simulated with the radiative transfer model DAK (Doubling-Adding-KNMI) for different atmospheric scenarios. The algorithm was applied for various case studies (i.e. forest fires, dust storm, anthropogenic pollution) over Europe, and the results were validated against groundbased measurements from the AERONET database, and evaluated by comparison with aerosol products derived from other space-borne instruments such as the Terra/- Aqua-MODIS sensors. In general, for retrievals over the ocean, AOD values as well as their diurnal variations are in good agreement with the observations made at AERONET coastal sites, and the spatial variations of the AOD obtained with the SARA algorithm are well correlated with the results derived from MODIS. Over land, the results presented should be considered as preliminary. They show reasonable agreement with AERONET and MODIS, however extra work is required to improve the accuracy of the retrievals based on the proposed metho
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A review of coarse mineral dust in the Earth system
Mineral dust particles suspended in the atmosphere span more than three orders of magnitude in diameter, from <0.1 µm to more than 100 µm. This wide size range makes dust a unique aerosol species with the ability to interact with many aspects of the Earth system, including radiation, clouds, hydrology, atmospheric chemistry, and biogeochemistry. This review focuses on coarse and super-coarse dust aerosols, which we respectively define as dust particles with a diameter of 2.5–10 µm and 10–62.5 µm. We review several lines of observational evidence indicating that coarse and super-coarse dust particles are transported farther than previously expected and that the abundance of these particles is substantially underestimated in current global models. We synthesize previous studies that used observations, theories, and model simulations to highlight the impacts of coarse and super-coarse dust aerosols on the Earth system, including their effects on dust-radiation interactions, dust-cloud interactions, atmospheric chemistry, and biogeochemistry. Specifically, coarse and super-coarse dust aerosols produce a net positive direct radiative effect (warming) at the top of the atmosphere and can modify temperature and water vapor profiles, influencing the distribution of clouds and precipitation. In addition, coarse and super-coarse dust aerosols contribute a substantial fraction of ice-nucleating particles, especially at temperatures above –23 °C. They also contribute a substantial fraction to the available reactive surfaces for atmospheric processing and the dust deposition flux that impacts land and ocean biogeochemistry by supplying important nutrients such as iron and phosphorus. Furthermore, we examine several limitations in the representation of coarse and super-coarse dust aerosols in current model simulations and remote-sensing retrievals. Because these limitations substantially contribute to the uncertainties in simulating the abundance and impacts of coarse and super-coarse dust aerosols, we offer some recommendations to facilitate future studies. Overall, we conclude that an accurate representation of coarse and super-coarse properties is critical in understanding the impacts of dust aerosols on the Earth system
RETRIEVAL OF TROPOSPHERIC AEROSOL PROPERTIES OVER LAND FROM INVERSION OF VISIBLE AND NEAR-INFRARED SPECTRAL REFLECTANCE: APPLICATION OVER MARYLAND
Aerosols are major components of the Earth's global climate system, affecting the radiation budget and cloud processes of the atmosphere. When located near the surface, high concentrations lead to lowered visibility, increased health problems and generally reduced quality of life for the human population. Over the United States mid-Atlantic region, aerosol pollution is a problem mainly during the summer. Satellites, such as the MODerate Imaging Spectrometer (MODIS), from their vantage point above the atmosphere, provide unprecedented coverage of global and regional aerosols over land. During MODIS' eight-year operation, exhaustive data validation and analyses have shown how the algorithm should be improved. This dissertation describes the development of the 'second-generation' operational algorithm for retrieval of global tropospheric aerosol properties over dark land surfaces, from MODIS -observed spectral reflectance. New understanding about global aerosol properties, land surface reflectance characteristics, and radiative transfer properties were learned in the process. This new operational algorithm performs a simultaneous inversion of reflectance in two visible channels (0.47 and 0.66 μm) and one shortwave infrared channel (2.12 μm), thereby having increased sensitivity to coarse aerosol. Inversion of the three channels retrieves the aerosol optical depth (τ) at 0.55 μm, the percentage of non-dust (fine model) aerosol (η) and the surface reflectance. This algorithm is applied globally, and retrieves τ that is highly correlated (y = 0.02 + 1.0x, R=0.9) with ground-based sunphotometer measurements. The new algorithm estimates the global, over-land, long-term averaged τ ~ 0.21, a 25% reduction from previous MODIS estimates. This leads to reducing estimates of global, non-desert, over-land aerosol direct radiative effect (all aerosols) by 1.7 W·m-2 (0.5 W·m-2 over the entire globe), which significantly impacts assessment of aerosol direct radiative forcing (contribution from anthropogenic aerosols only). Over the U.S. mid-Atlantic region, validated retrievals of τ (an integrated column property) can help to estimate surface PM2.5 concentration, a monitored criteria air quality property. The 3-dimensional aerosol loading in the region is characterized using aircraft measurements and the Community Multi-scale Air Quality Model (CMAQ) model, leading to some convergence of observed quantities and modeled processes
Laboratory for Atmospheres 2010 Technical Highlights
The 2010 Technical Highlights describes the efforts of all members of the Laboratory for Atmospheres. Their dedication to advancing Earth Science through conducting research, developing and running models, designing instruments, managing projects, running field campaigns, and numerous other activities, is highlighted in this report
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