Intercomparison between multi-angle imaging spectroradiometer (MISR) and sunphotometer aerosol optical thickness in dust source regions over China: implications for satellite aerosol retrievals and radiative forcing calculations

Abstract. Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to −0.0234 and −0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude–longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2 and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day−1 between 3 and 5 km, dropped to 1.5 K day−1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day−1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of −0.1 K day−1 at 6 km.

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Dust vertical profile impact on global radiative forcing estimation using a coupled chemical-transport–radiative-transfer model

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7097-2013 ◽

2013 ◽

Vol 13 (14) ◽

pp. 7097-7114 ◽

Cited By ~ 35

Author(s):

L. Zhang ◽

Q. B. Li ◽

Y. Gu ◽

K. N. Liou ◽

B. Meland

Keyword(s):

Heating Rate ◽

Vertical Profile ◽

Radiative Forcing ◽

Asian Dust ◽

Dust Particles ◽

Radiative Transfer Model ◽

Transfer Model ◽

Vertical Profiles ◽

Dust Source ◽

Source Regions

Abstract. Atmospheric mineral dust particles exert significant direct radiative forcings and are important drivers of climate and climate change. We used the GEOS-Chem global three-dimensional chemical transport model (CTM) coupled with the Fu-Liou-Gu (FLG) radiative transfer model (RTM) to investigate the dust radiative forcing and heating rate based on different vertical profiles for April 2006. We attempt to actually quantify the sensitivities of radiative forcing to dust vertical profiles, especially the discrepancies between using realistic and climatological vertical profiles. In these calculations, dust emissions were constrained by observations of aerosol optical depth (AOD). The coupled calculations utilizing a more realistic dust vertical profile simulated by GEOS-Chem minimize the physical inconsistencies between 3-D CTM aerosol fields and the RTM. The use of GEOS-Chem simulated vertical profile of dust extinction, as opposed to the FLG prescribed vertical profile, leads to greater and more spatially heterogeneous changes in the estimated radiative forcing and heating rate produced by dust. Both changes can be attributed to a different vertical structure between dust and non-dust source regions. Values of the dust vertically resolved AOD per grid level (VRAOD) are much larger in the middle troposphere, though smaller at the surface when the GEOS-Chem simulated vertical profile is used, which leads to a much stronger heating rate in the middle troposphere. Compared to the FLG vertical profile, the use of GEOS-Chem vertical profile reduces the solar radiative forcing at the top of atmosphere (TOA) by approximately 0.2–0.25 W m−2 over the African and Asian dust source regions. While the Infrared (IR) radiative forcing decreases 0.2 W m−2 over African dust belt, it increases 0.06 W m−2 over the Asian dust belt when the GEOS-Chem vertical profile is used. Differences in the solar radiative forcing at the surface between the use of the GEOS-Chem and FLG vertical profiles are most significant over the Gobi desert with a value of about 1.1 W m−2. The radiative forcing effect of dust particles is more pronounced at the surface over the Sahara and Gobi deserts by using FLG vertical profile, while it is less significant over the downwind area of Eastern Asia.

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Improved estimate of global dust radiative forcing using a coupled chemical transport-radiative transfer model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-2415-2013 ◽

2013 ◽

Vol 13 (1) ◽

pp. 2415-2456 ◽

Cited By ~ 3

Author(s):

L. Zhang ◽

Q. B. Li ◽

Y. Gu ◽

K. N. Liou ◽

B. Meland

Keyword(s):

Radiative Transfer ◽

Vertical Profile ◽

Radiative Forcing ◽

Chemical Transport ◽

Dust Particles ◽

Radiative Transfer Model ◽

Transfer Model ◽

Vertical Profiles ◽

Dust Source ◽

Source Regions

Abstract. Atmospheric mineral dust particles exert significant direct radiative forcings and are critical drivers of climate change. Here, we use the GEOS-Chem global three-dimensional chemical transport model (3-D CTM) coupled online with the Fu-Liou-Gu (FLG) radiative transfer model (RTM) to investigate the dust radiative forcing and heating rates based on different dust vertical profiles. The coupled calculations using a realistic dust vertical profile simulated by GEOS-Chem minimize the physical inconsistencies between 3-D CTM aerosol fields and the RTM. The use of GEOS-Chem simulated aerosol optical depth (AOD) vertical profiles as opposed to the FLG prescribed AOD vertical profiles leads to greater and more spatially heterogeneous changes in estimated radiative forcing and heating rate produced by dust. Both changes can be attributed to a different vertical structure between dust and non-dust source regions. Values of the dust AOD are much larger in the middle troposphere, though smaller at the surface when the GEOS-Chem simulated AOD vertical profile is used, which leads to a much stronger heating rate in the middle troposphere. Compared to FLG vertical profile, the use of GEOS-Chem vertical profile reduces the solar radiative forcing effect by about 0.2–0.25 W m−2 and the Infrared (IR) radiative forcing over the African and Asia dust source regions by about 0.1–0.2 W m−2. Differences in the solar radiative forcing at the surface between using the GEOS-Chem vertical profile and the FLG vertical profile are most significant over the Gobi desert with a value of about 1.1 W m−2. The radiative forcing effect of dust particles is more pronounced at the surface over the Sahara and Gobi deserts by using FLG vertical profile, while it is less significant over the downwind area of Eastern Asia.

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Estimating radiative forcing efficiency of dust aerosol based on direct satellite observations: case studies over the Sahara and Taklimakan Desert

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-11669-2021 ◽

2021 ◽

Vol 21 (15) ◽

pp. 11669-11687

Author(s):

Lin Tian ◽

Lin Chen ◽

Peng Zhang ◽

Lei Bi

Keyword(s):

Radiative Forcing ◽

Complex Refractive Index ◽

Satellite Observations ◽

Dust Aerosol ◽

Taklimakan Desert ◽

Dust Source ◽

Dust Aerosols ◽

Microphysical Properties ◽

Source Regions ◽

The Taklimakan Desert

Abstract. The direct radiative forcing efficiency of dust aerosol (DRFEdust) is an important indicator to measure the climate effect of dust. The DRFEdust is determined by the microphysical properties of dust, which vary with dust source regions. However, there are only sparse in situ measurements of them, such as the distribution of the dust aerosol particle size and the complex refractive index in the main dust source regions. Furthermore, recent studies have shown that the non-spherical effect of the dust particle is not negligible. The DRFEdust is often evaluated by estimating given microphysical properties of the dust aerosols in the radiative transfer model (RTM). However, considerable uncertainties exist due to the complex and variable dust properties, including the complex refractive index and the shape of the dust. The DRFEdust over the Taklimakan Desert and Sahara is derived from the satellite observations in this paper. The advantage of the proposed satellite-based method is that there is no need to consider the microphysical properties of the dust aerosols in estimating the DRFEdust. For comparison, the observed DRFEdust is compared with that simulated by the RTM. The differences in the dust microphysical properties in these two regions and their impacts on DRFEdust are analyzed. The DRFEdust derived from the satellite observation is -39.6±10.0 W m-2τ-1 in March 2019 over Tamanrasset in the Sahara and -48.6±13.7 W m-2τ-1 in April 2019 over Kashi in the Taklimakan Desert. According to the analyses of their microphysical properties and optical properties, the dust aerosols from the Taklimakan Desert (Kashi) scatter strongly. The RTM-simulated results (−41.5 to −47.4 W m-2τ-1 over Kashi and −32.2 to −44.3 W m-2τ-1 over Tamanrasset) are in good agreement with the results estimated by satellite observations. According to previous studies, the results in this paper are proven to be reasonable and reliable. The results also show that the microphysical properties of the dust can significantly influence the DRFEdust. The satellite-derived results can represent the influence of the dust microphysical properties on the DRFEdust, which can also validate the direct radiative effect of the dust aerosol and the DRFEdust derived from the numerical model more directly.

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Synergy of satellite-based aerosol optical thickness analysis and trajectory statistics for determination of aerosol source regions

International Journal of Remote Sensing ◽

10.1080/01431161.2019.1612117 ◽

2019 ◽

Vol 40 (22) ◽

pp. 8450-8464

Author(s):

A. Szkop ◽

A. Pietruczuk

Keyword(s):

Optical Thickness ◽

Aerosol Optical Thickness ◽

Source Regions ◽

Aerosol Source

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Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-625-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 625-636 ◽

Cited By ~ 11

Author(s):

T. Elias ◽

J.-L. Roujean

Keyword(s):

Optical Thickness ◽

Temporal Variability ◽

Radiative Forcing ◽

Ground Level ◽

Aerosol Optical Thickness ◽

Reference Level ◽

Urban Site ◽

Spatial And Temporal Variability ◽

Aerosol Radiative Forcing ◽

Aerosol Radiative

Abstract. A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF), as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiative transfer computations. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments: an urban site near Paris and a continental background site located South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6 in magnitude). The method reproduces measurements of DSSF within an accuracy assessment of 20 W m−2 (5% in relative) in 70% of the situations, and within 40 W m−2 in 90% of the situations, for the two case studies considered here. Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT): sensitivity is included between 120 and 160 W m−2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

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A new method for deriving aerosol solar radiative forcing and its first application within MILAGRO/INTEX-B

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-7829-2010 ◽

2010 ◽

Vol 10 (16) ◽

pp. 7829-7843 ◽

Cited By ~ 15

Author(s):

K. S. Schmidt ◽

P. Pilewskie ◽

R. Bergstrom ◽

O. Coddington ◽

J. Redemann ◽

...

Keyword(s):

Optical Thickness ◽

Radiative Forcing ◽

Field Experiments ◽

Single Scattering ◽

Aerosol Optical Thickness ◽

Spectral Irradiance ◽

New Method ◽

Horizontal Gradient ◽

Aerosol Radiative Forcing ◽

Aerosol Forcing

Abstract. We introduce a method for deriving aerosol spectral radiative forcing along with single scattering albedo, asymmetry parameter, and surface albedo from airborne vertical profile measurements of shortwave spectral irradiance and spectral aerosol optical thickness. The new method complements the traditional, direct measurement of aerosol radiative forcing efficiency from horizontal flight legs below gradients of aerosol optical thickness, and is particularly useful over heterogeneous land surfaces and for homogeneous aerosol layers where the horizontal gradient method is impractical. Using data collected by the Solar Spectral Flux Radiometer (SSFR) and the Ames Airborne Tracking Sunphotometer (AATS-14) during the MILAGRO (Megacity Initiative: Local and Global Research Observations) experiment, we validate an over-ocean spectral aerosol forcing efficiency from the new method by comparing with the traditional method. Retrieved over-land aerosol optical properties are compared with in-situ measurements and AERONET retrievals. The spectral forcing efficiencies over ocean and land are remarkably similar and agree with results from other field experiments.

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Uncertainty in modeling dust mass balance and radiative forcing from size parameterization

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-19649-2013 ◽

2013 ◽

Vol 13 (7) ◽

pp. 19649-19700 ◽

Cited By ~ 1

Author(s):

C. Zhao ◽

S. Chen ◽

L. R. Leung ◽

Y. Qian ◽

J. Kok ◽

...

Keyword(s):

Mass Balance ◽

Radiative Forcing ◽

Dust Emission ◽

Dust Particles ◽

Mass Loading ◽

Dust Source ◽

Deposition Fluxes ◽

Source Regions ◽

Dust Mass ◽

The Difference

Abstract. This study examines the uncertainties in simulating mass balance and radiative forcing of mineral dust due to biases in the dust size parameterization. Simulations are conducted quasi-globally (180° W–180° E and 60° S–70° N) using the WRF-Chem model with three different approaches to represent dust size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or 4-bin approaches against a relatively more accurate 8-bin approach in simulating dust mass balance and radiative forcing are identified. Compared to the 8-bin approach, the 4-bin approach simulates similar but coarser size distributions of dust particles in the atmosphere, while the 3-mode approach retains more fine dust particles but fewer coarse dust particles due to its prescribed σg of each mode. Although the 3-mode approach yields up to 10 days longer dust mass lifetime over the remote oceanic regions than the 8-bin approach, the three size approaches produce similar dust mass lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the global dust mass lifetime is mainly determined by the dust mass lifetime near the dust source regions. With the same global dust emission (∼6000 Tg yr-1), the 8-bin approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust mass loading, respectively. The difference in dust mass loading between the 8-bin approach and the 4-bin or 3-mode approaches has large spatial variations, with generally smaller relative difference (<10%) near the surface over the dust source regions. The three size approaches also result in significantly different dry and wet deposition fluxes and number concentrations of dust. The difference in dust aerosol optical depth (AOD) (a factor of 3) among the three size approaches is much larger than their difference (25%) in dust mass loading. Compared to the 8-bin approach, the 4-bin approach yields stronger dust absorptivity, while the 3-mode approach yields weaker dust absorptivity. Overall, on quasi-global average, the three size parameterizations result in a significant difference of a factor of 2∼3 in dust surface cooling (-1.02∼-2.87 W m-2) and atmospheric warming (0.39∼0.96 W m-2) and in a tremendous difference of a factor of ∼10 in dust TOA cooling (-0.24∼-2.20 W m-2). An uncertainty of a factor of 2 is quantified in dust emission estimation due to the different size parameterizations. This study also highlights the uncertainties in modeling dust mass and number loading, deposition fluxes, and radiative forcing resulting from different size parameterizations, and motivates further investigation of the impact of size parameterizations on modeling dust impacts on air quality, climate, and ecosystem.

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