Estimating the maritime component of aerosol optical depth and its dependency on surface wind speed using satellite data

Lehahn, Yoav; Koren, Ilan; Boss, Emmanuel; Ben-Ami, Y.; Altaratz, Orit

doi:10.5194/acp-10-6711-2010

Cited by 32 publications

(54 citation statements)

References 44 publications

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“… Lehahn et al [2010] reported that, on average, the threshold value of surface wind speed for triggering emission of maritime aerosols is 4.1 ± 0.1 m/s. When wind speed exceeds the threshold value, the coarse‐mode marine aerosols' optical depth is linearly correlated to the surface wind speed, with a consistent slope of 0.009 ± 0.002 m/s [ Lehahn et al , 2010]. Thus, knowledge of wind speed and direction assists in estimating the average background wind‐induced marine aerosol loading in the lower part of SA.…”

Section: Resultsmentioning

confidence: 99%

Aerosol climatology over South Africa based on 10 years of Multiangle Imaging Spectroradiometer (MISR) data

Tesfaye¹,

Sivakumar²,

Botai³

et al. 2011

J. Geophys. Res.

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[1] In this paper, we present a detailed study of the spatial and seasonal aerosol climatology over South Africa (SA), based on Multiangle Imaging Spectroradiometer (MISR) data. We have used 10 years (2000-2009) of MISR monthly mean aerosol extinction (t ext ), absorption (t a ) optical depths at 558 nm, Angstrom exponents in visible (VIS; 446-672 nm) and near-infrared (NIR; 672-866 nm) spectral bands, and the extracted spectral curvature. The study has shown that, in terms of aerosol load level spatial variation, SA can be classified into three parts: the upper, central, and lower, which illustrate high, medium, and low aerosol loadings, respectively. The results for the three parts of SA are presented in detail. The prevailing sources of aerosols are different in each part of SA. The lower part is dominated by the air mass transport from the surrounding marine environment and other SA or neighboring regions, while the central and upper parts are loaded through windablated mineral dust and local anthropogenic activities. During the biomass burning seasons (July-September), the central part of SA is more affected than the rest of SA by the biomassburning aerosols (based on t a , ∼20% higher than the rest of SA). In alignment with the observed higher values of t ext , aerosol size distributions were found to be highly variable in the upper part of SA, which is due to the high population and the industrial/mining/ agricultural activities in this area.

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Section: Resultsmentioning

confidence: 99%

Aerosol climatology over South Africa based on 10 years of Multiangle Imaging Spectroradiometer (MISR) data

Tesfaye¹,

Sivakumar²,

Botai³

et al. 2011

J. Geophys. Res.

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“…Stronger correlations have been observed using the wind speed averaged over some time before the aerosol measurements were made (‘wind speed history’), rather than instantaneous wind speed, as wind changes on timescales shorter than aerosol lifetimes. The strongest correlations are typically found with wind speed averaged for 12–24 hours prior to the AOD measurement [ Gathman , 1983; Hoppel et al , 1990; Smirnov et al , 2003b; Lehahn et al , 2010]. Some of these analyses bin data by wind speed, and then fit binned averages; this binning will naturally lead to stronger correlations than fits using all data points, as the variability is somewhat averaged‐out, so this should be borne in mind when examining regression statistics from different studies.…”

Section: Relationship With Meteorological Parametersmentioning

confidence: 99%

A pure marine aerosol model, for use in remote sensing applications

et al. 2012

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[1] Retrievals of aerosol optical depth (AOD) and related parameters from satellite measurements typically involve prescribed models of aerosol size and composition, and are therefore dependent on how well these models are able to represent the radiative behavior of real aerosols. This study uses aerosol volume size distributions retrieved from Sun-photometer measurements at 11 Aerosol Robotic Network (AERONET) island sites, spread throughout the world's oceans, as a basis to define such a model for pure (unpolluted) maritime aerosol. Volume size distributions are observed to be bimodal and approximately lognormal, although the coarse mode is skewed with a long tail on the low-radius end. The relationship of AOD and size distribution parameters to meteorological conditions is also examined. As wind speed increases, so do coarse-mode volume and radius. The AOD and Ångström exponent show linear relationships with wind speed, although with considerable scatter. Links between aerosol properties and near-surface relative humidity, columnar water vapor, and sea surface temperature are also explored. A recommended bimodal maritime model, which is able to reconstruct the AERONET AOD with accuracy of order 0.01-0.02, is presented for use in aerosol remote sensing applications. This accuracy holds at most sites and for wavelengths between 340 nm and 1020 nm. Calculated lidar ratios are also provided, and are in the range of other studies, although differ more strongly from those currently used in Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) processing.

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“…Some studies suggest a linear relationship [32][33][34][35], while others a power-law relationship [14,36,37] or an exponential relationship [38]. The discrepancy between different relationships is probably attributed to different instrumentations, platforms, locations and periods used in the investigations.…”

Section: Introductionmentioning

confidence: 99%

Effect of Wind Speed on Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth over the North Pacific

et al. 2018

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Abstract:The surface-wind speed influences on aerosol optical depth (AOD), derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua daily observations over the central North Pacific during the period 2003-2016, have been investigated in this study. The cloud coverage is relatively low over the present investigation area compared to other marine areas, which favors AOD derived from passive remote sensing from space. In this study, we have combined MODIS AOD with 2 m wind speed (U 2m ) on a satellite-pixel basis, which has been interpolated from National Centers for Environmental Prediction (NCEP) reanalysis. In addition, daily averaged AOD derived from Aerosol Robotic Network (AERONET) measurements in the free-troposphere at the Mauna Loa Observatory (3397 m above sea level), Hawaii, was subtracted from the MODIS column AOD values. The latter was to reduce the contribution of aerosols above the planetary boundary layer. This study shows relatively strong power-law relationships between MODIS mean AOD and surface-wind speed for marine background conditions in summer, fall and winter of the current period. However, previous established relationships between AOD and surface-wind speed deviate substantially. Even so, for similar marine conditions the present relationship agrees reasonable well with a power-law relationship derived for north-east Atlantic conditions. The present MODIS retrievals of AOD in the marine atmosphere agree reasonably well with ground-based remote sensing of AOD.

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Estimating the maritime component of aerosol optical depth and its dependency on surface wind speed using satellite data

Cited by 32 publications

References 44 publications

Aerosol climatology over South Africa based on 10 years of Multiangle Imaging Spectroradiometer (MISR) data

Aerosol climatology over South Africa based on 10 years of Multiangle Imaging Spectroradiometer (MISR) data

A pure marine aerosol model, for use in remote sensing applications

Effect of Wind Speed on Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth over the North Pacific

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