Comparison of Moderate Resolution Imaging Spectroradiometer ocean aerosol retrievals with ship-based Sun photometer measurements from the Around the Americas expedition

Adames, Ángel F.; Reynolds, M.; Smirnov, A.; Covert, D. S.; Ackerman, Thomas P.

doi:10.1029/2010jd015440

Cited by 16 publications

(12 citation statements)

References 49 publications

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“…Additional products like fine mode fraction (fine mode AOT divided by total AOT) have been evaluated by Anderson et al (2005), Kleidman et al (2005) and Bréon et al (2011) and the aerosol effective size by Remer et al (2002) and Remer et al (2005). For a comparison to the Maritime Aerosol Network (MAN) data (see Smirnov et al, 2011;Adames et al, 2011). The main conclusion from these papers is that MODIS level 2 AOT over ocean shows significant correlation with AERONET observations.…”

Section: Introductionmentioning

confidence: 87%

Validation and empirical correction of MODIS AOT and AE over ocean

2013

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Abstract. We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness) and AE (Ångström exponent) over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork) sites for the years [2003][2004][2005][2006][2007][2008][2009]. We show that MODIS (MODerate-resolution Imaging Spectroradiometer) AOT exhibits significant biases due to wind speed and cloudiness of the observed scene, while MODIS AE, although overall unbiased, exhibits less spatial contrast on global scales than the AERONET observations. The same behaviour can be seen when MODIS AOT is compared against Maritime Aerosol Network (MAN) data, suggesting that the spatial coverage of our datasets does not preclude global conclusions. Thus, we develop empirical correction formulae for MODIS AOT and AE that significantly improve agreement of MODIS and AERONET observations. We show these correction formulae to be robust. Finally, we study random errors in the corrected MODIS AOT and AE and show that they mainly depend on AOT itself, although small contributions are present due to wind speed and cloud fraction in AOT random errors and due to AE and cloud fraction in AE random errors. Our analysis yields significantly higher random AOT errors than the official MODIS error estimate (0.03 + 0.05 τ ), while random AE errors are smaller than might be expected. This new dataset of bias-corrected MODIS AOT and AE over ocean is intended for aerosol model validation and assimilation studies, but also has consequences as a stand-alone observational product. For instance, the corrected dataset suggests that much less fine mode aerosol is transported across the Pacific and Atlantic oceans.

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Section: Introductionmentioning

confidence: 87%

Validation and empirical correction of MODIS AOT and AE over ocean

2013

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“…MODIS AOT values are calculated by retrieval algorithms based on lookup tables for different particles which depend on scattering geometries (Tanre et al, 1997). Error estimations of MODIS AOT retrievals have been investigated by comparison with ground-based AERONET (e.g., Remer et al, 2005;Bréon et al, 2011) and MAN observations (e.g., Adames et al, 2011;Smirnov et al, 2011;Schutgens et al, 2013). Here we use the Naval Research Laboratory (NRL) L3 Shi et al, 2011) data that are derived from MODIS L2 observations through additional quality checks and empirical correction formulae.…”

Section: Observational Data Sets For Model Evaluationmentioning

confidence: 99%

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

et al. 2015

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Abstract. Wildfires represent a major source for aerosols impacting atmospheric radiation, atmospheric chemistry and cloud micro-physical properties. Previous case studies indicated that the height of the aerosol-radiation interaction may crucially affect atmospheric radiation, but the sensitivity to emission heights has been examined with only a few models and is still uncertain. In this study we use the general circulation model ECHAM6 extended by the aerosol module HAM2 to investigate the impact of wildfire emission heights on atmospheric long-range transport, black carbon (BC) concentrations and atmospheric radiation. We simulate the wildfire aerosol release using either various versions of a semiempirical plume height parametrization or prescribed standard emission heights in ECHAM6-HAM2. Extreme scenarios of near-surface or free-tropospheric-only injections provide lower and upper constraints on the emission height climate impact. We find relative changes in mean global atmospheric BC burden of up to 7.9 ± 4.4 % caused by average changes in emission heights of 1.5-3.5 km. Regionally, changes in BC burden exceed 30-40 % in the major biomass burning regions. The model evaluation of aerosol optical thickness (AOT) against Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol RObotic NETwork (AERONET) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations indicates that the implementation of a plume height parametrization slightly reduces the ECHAM6-HAM2 biases regionally, but on the global scale these improvements in model performance are small. For prescribed emission release at the surface, wildfire emissions entail a total sky top-of-atmosphere (TOA) radiative forcing (RF) of −0.16 ± 0.06 W m −2 . The application of a plume height parametrization which agrees reasonably well with observations introduces a slightly stronger negative TOA RF of −0.20 ± 0.07 W m −2 . The standard ECHAM6-HAM2 model in which 25 % of the wildfire emissions are injected into the free troposphere (FT) and 75 % into the planetary boundary layer (PBL), leads to a TOA RF of −0.24 ± 0.06 W m −2 . Overall, we conclude that simple plume height parametrizations provide sufficient representations of emission heights for global climate modeling. Significant improvements in aerosol wildfire modeling likely depend on better emission inventories and aerosol process modeling rather than on improved emission height parametrizations.

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“…Satellite-derived and coast or island acquired AODs have been studied by Mulcahy et al (2008), Glantz et al (2009), Lehahn et al (2010), Huang et al (2010), O'Dowd et al (2010), Kiliyanpilakkil and Meskhidze (2011), Grandey et al (2011), Adames et al (2011), and Sayer et al (2012). Power-law and linear relationships between AOD and wind speed were established although sampling issues, uncertainties in retrieval algorithms, and/or influence of the chosen island locations gave an indication that the problem is far from being solved and there is not yet consensus.…”

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confidence: 99%

Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

et al. 2012

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Abstract. The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (∼0.004-0.005), even for strong winds over 10 m s −1 . The relationships show significant scatter (correlation coefficients typically in the range 0.3-0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used.

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Comparison of Moderate Resolution Imaging Spectroradiometer ocean aerosol retrievals with ship-based Sun photometer measurements from the Around the Americas expedition

Cited by 16 publications

References 49 publications

Validation and empirical correction of MODIS AOT and AE over ocean

Validation and empirical correction of MODIS AOT and AE over ocean

Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

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