scholarly journals Annual cycle of global distributions of aerosol optical depth from integration of MODIS retrievals and GOCART model simulations

2003 ◽  
Vol 108 (D3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Hongbin Yu ◽  
R. E. Dickinson ◽  
M. Chin ◽  
Y. J. Kaufman ◽  
B. N. Holben ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Annual Cycle ◽  
Model Simulations ◽  
Gocart Model

scholarly journals Ship-based aerosol optical depth measurements in the Atlantic Ocean: Comparison with satellite retrievals and GOCART model

2006 ◽  
Vol 33 (14) ◽  
Author(s):  
A. Smirnov ◽  
B. N. Holben ◽  
S. M. Sakerin ◽  
D. M. Kabanov ◽  
I. Slutsker ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Retrievals ◽  
Gocart Model

Dust-aerosol optical depth in CMIP6 models and implication for PV-power generation

2021 ◽  
Author(s):  
Robert Scheele ◽  
Stephanie Fiedler
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Data ◽  
Power Plants ◽  
Climate Model ◽  
Dust Aerosol ◽  
Model Simulations ◽  
Desert Dust ◽  
Dust Aerosols ◽  
Climate Model Simulations

<p>Renewable energy produced by photovoltaic (PV) power plants strongly depends on the meteorological conditions. Desert-dust aerosols impair the radiative transfer in the atmosphere, but their effect on PV power is poorly understood from a climatological perspective. Past climate model simulations are known to have a large spread in dust-aerosol loading. With the new CMIP6 model simulations now being available, we revisit the climate-model spread in representing desert-dust aerosols for 1985 to 2014, assess the dust-aerosol changes until 2100, and estimate the associated differences in the PV power potential. To this end, we evaluate the dust aerosol optical depth (DOD) in the CMIP6 historical simulations using modern reanalysis and satellite data. Our results highlight the persistent model spread for DOD in CMIP6, but a multi-model mean DOD close to the reanalysis and satellite data. We identify only slight changes in both the global and regional mean DOD in a green scenario (ssp126) at the end of the 21st century. For a future with continued strong warming (ssp245, ssp585), the simulations suggest an increase (decrease) in regional DOD associated with North-African, Transatlantic transport, and Australia (Taklamakan Desert) dust emissions. The differences in simulated DOD imply changes in the PV power potential for regions affected by dust aerosols. We compute the change in the PV power potential from surface irradiance, temperature, and wind speed in the CMIP6 scenarios against present-day. Our results point to a PV power potential for North Africa that is similarly affected by a future increase in temperature and decrease in irradiance associated with more dust aerosols. In mid-latitude regions of the northern hemisphere, a future change in PV power potential is controlled by changes of clouds and temperature. Our PV power estimates underline the impacts of the model uncertainty in DOD, the degree of future warming, and the unclear response of clouds and circulation to the warming.</p>

scholarly journals Stochastic Resonance Observed in Aerosol Optical Depth Time Series

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 502
Author(s):  
Mariarosaria Falanga ◽  
Enza De Lauro ◽  
Salvatore de Martino
Keyword(s):  
Time Series ◽  
Stochastic Resonance ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Annual Cycle ◽  
Geographic Area ◽  
Resonance Phenomenon ◽  
Local Maxima ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Summer Time

We analyzed the aerosol optical depth time series retrieved from daily satellite Moderate-Resolution Imaging Spectroradiometer measurements. The investigated geographic area includes Italy and the Mediterranean Sea. By performing second- and fourth-order statistics analyses, the dynamics can be decomposed into two sources, the main of which is the annual cycle. The residence time distribution is made of local maxima over an exponential behavior. The two successive peaks are located at about 200 and 600 days. This allows us to hypothesize a stochastic resonance phenomenon in the dynamics of aerosol optical depth. The characteristic periodicity of the resonance is on the annual timescale, and the asymmetric double-well potential is provided by two different regimes for the values of the aerosol optical depth in winter and summer time. This means that a simple, although stochastic, differential equation can represent the time evolution of the optical depth, at least concerning its component related to the annual cycle.

scholarly journals Determination of aerosol properties from MAX-DOAS observations of the Ring effect

2009 ◽  
Vol 2 (2) ◽  
pp. 495-512 ◽  
Author(s):  
T. Wagner ◽  
T. Deutschmann ◽  
U. Platt
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Stratospheric Aerosol ◽  
Lower Atmosphere ◽  
Data Sets ◽  
Model Simulations ◽  
Sensitivity Studies ◽  
Comprehensive Test ◽  
Aerosol Properties ◽  
Ring Effect

Abstract. The first quantitative comparison of MAX-DOAS observations of the Ring effect with model simulations is presented. It is performed for a large variety of viewing geometries (solar zenith angles: 45° to 90°, elevation angles: 3°, 6°, 10°, 18°, 90°; three different azimuth angles), which allows a comprehensive test of our capabilities to measure and simulate the Ring effect. In addition to the Ring effect, also the observed O4 absorptions (optical densities) and radiances are compared with model simulations. In general good agreement is found for all measured quantities. From several sensitivity studies it is found that for most measurement situations, the aerosol optical depth has usually the strongest influence on the observed quantities, but also other aerosol properties like e.g. the vertical distribution have a significant effect. In some aspects, the qualitative dependence of the Ring effect on aerosol properties is similar to that of the O4 absorption. This can be understood, since both quantities depend strongly on the light path length in the lower atmosphere. However, since the Ring effect depends also on the properties of the scattering processes, in specific cases observation of the Ring effect can provide complementary information to that retrieved from the O4 observations. This is e.g. possible for measurements at small relative azimuth angles, from which information on the aerosol phase function can be derived. Observations at large solar zenith angle might allow the retrieval of stratospheric aerosol properties, even in cases with very low aerosol optical depths. In addition, Ring effect observations in zenith direction are rather sensitive to the aerosol optical depth (in contrast to O4 observations), which might allow to retrieve information on aerosol properties from existing zenith UV data sets prior to the MAX-DOAS era.

scholarly journals An observationally constrained estimate of global dust aerosol optical depth

2016 ◽  
Vol 16 (23) ◽  
pp. 15097-15117 ◽  
Author(s):  
David A. Ridley ◽  
Colette L. Heald ◽  
Jasper F. Kok ◽  
Chun Zhao
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Global Climate ◽  
Middle Eastern ◽  
Dust Emission ◽  
Dust Aerosol ◽  
Model Simulations ◽  
State Of The Science

Abstract. The role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model median (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.

scholarly journals Improved representation of the global dust cycle using observational constraints on dust properties and abundance

2021 ◽  
Vol 21 (10) ◽  
pp. 8127-8167
Author(s):  
Jasper F. Kok ◽  
Adeyemi A. Adebiyi ◽  
Samuel Albani ◽  
Yves Balkanski ◽  
Ramiro Checa-Garcia ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Current Model ◽  
Dust Emission ◽  
Surface Concentration ◽  
Inverse Model ◽  
Dust Aerosol ◽  
Observational Constraints ◽  
Model Errors ◽  
Model Simulations

Abstract. Even though desert dust is the most abundant aerosol by mass in Earth's atmosphere, atmospheric models struggle to accurately represent its spatial and temporal distribution. These model errors are partially caused by fundamental difficulties in simulating dust emission in coarse-resolution models and in accurately representing dust microphysical properties. Here we mitigate these problems by developing a new methodology that yields an improved representation of the global dust cycle. We present an analytical framework that uses inverse modeling to integrate an ensemble of global model simulations with observational constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth. We then compare the inverse model results against independent measurements of dust surface concentration and deposition flux and find that errors are reduced by approximately a factor of 2 relative to current model simulations of the Northern Hemisphere dust cycle. The inverse model results show smaller improvements in the less dusty Southern Hemisphere, most likely because both the model simulations and the observational constraints used in the inverse model are less accurate. On a global basis, we find that the emission flux of dust with a geometric diameter up to 20 µm (PM20) is approximately 5000 Tg yr−1, which is greater than most models account for. This larger PM20 dust flux is needed to match observational constraints showing a large atmospheric loading of coarse dust. We obtain gridded datasets of dust emission, vertically integrated loading, dust aerosol optical depth, (surface) concentration, and wet and dry deposition fluxes that are resolved by season and particle size. As our results indicate that this dataset is more accurate than current model simulations and the MERRA-2 dust reanalysis product, it can be used to improve quantifications of dust impacts on the Earth system.

scholarly journals How should we aggregate data? Methods accounting for the numerical distributions, with an assessment of aerosol optical depth

2019 ◽  
Vol 19 (23) ◽  
pp. 15023-15048 ◽  
Author(s):  
Andrew M. Sayer ◽  
Kirk D. Knobelspiesse
Keyword(s):  
Standard Deviation ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Spatial Scales ◽  
Geometric Mean ◽  
Arithmetic Mean ◽  
Observation System ◽  
Data Sets ◽  
Model Simulations ◽  
Log Normal

Abstract. Many applications of geophysical data – whether from surface observations, satellite retrievals, or model simulations – rely on aggregates produced at coarser spatial (e.g. degrees) and/or temporal (e.g. daily and monthly) resolution than the highest available from the technique. Almost all of these aggregates report the arithmetic mean and standard deviation as summary statistics, which are what data users employ in their analyses. These statistics are most meaningful for normally distributed data; however, for some quantities, such as aerosol optical depth (AOD), it is well-known that distributions are on large scales closer to log-normal, for which a geometric mean and standard deviation would be more appropriate. This study presents a method of assessing whether a given sample of data is more consistent with an underlying normal or log-normal distribution, using the Shapiro–Wilk test, and tests AOD frequency distributions on spatial scales of 1∘ and daily, monthly, and seasonal temporal scales. A broadly consistent picture is observed using Aerosol Robotic Network (AERONET), Multiangle Imaging SpectroRadiometer (MISR), Moderate Resolution Imagining Spectroradiometer (MODIS), and Goddard Earth Observing System Version 5 Nature Run (G5NR) data. These data sets are complementary: AERONET has the highest AOD accuracy but is sparse, and MISR and MODIS represent different satellite retrieval techniques and sampling. As a model simulation, G5NR is spatiotemporally complete. As timescales increase from days to months to seasons, data become increasingly more consistent with log-normal than normal distributions, and the differences between arithmetic- and geometric-mean AOD become larger, with geometric mean becoming systematically smaller. Assuming normality systematically overstates both the typical level of AOD and its variability. There is considerable regional heterogeneity in the results: in low-AOD regions such as the open ocean and mountains, often the AOD difference is small enough (<0.01) to be unimportant for many applications, especially on daily timescales. However, in continental outflow regions and near source regions over land, and on monthly or seasonal timescales, the difference is frequently larger than the Global Climate Observation System (GCOS) goal uncertainty in a climate data record (the larger of 0.03 or 10 %). This is important because it shows that the sensitivity to an averaging method can and often does introduce systematic effects larger than the total goal GCOS uncertainty. Using three well-studied AERONET sites, the magnitude of estimated AOD trends is shown to be sensitive to the choice of arithmetic vs. geometric means, although the signs are consistent. The main recommendations from the study are that (1) the distribution of a geophysical quantity should be analysed in order to assess how best to aggregate it, (2) ideally AOD aggregates such as satellite level 3 products (but also ground-based data and model simulations) should report a geometric-mean or median AOD rather than (or in addition to) arithmetic-mean AOD, and (3) as this is unlikely in the short term due to the computational burden involved, users can calculate geometric-mean monthly aggregates from widely available daily mean data as a stopgap, as daily aggregates are less sensitive to the choice of aggregation scheme than those for monthly or seasonal aggregates. Furthermore, distribution shapes can have implications for the validity of statistical metrics often used for comparison and evaluation of data sets. The methodology is not restricted to AOD and can be applied to other quantities.

scholarly journals Determination of aerosol properties from MAX-DOAS observations of the Ring effect

2009 ◽  
Vol 2 (2) ◽  
pp. 725-779 ◽  
Author(s):  
T. Wagner ◽  
T. Deutschmann ◽  
U. Platt
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Stratospheric Aerosol ◽  
Lower Atmosphere ◽  
Data Sets ◽  
Model Simulations ◽  
Sensitivity Studies ◽  
Comprehensive Test ◽  
Aerosol Properties ◽  
Ring Effect

Abstract. The first quantitative comparison of MAX-DOAS observations of the Ring effect with model simulations is presented. It is performed for a large variety of viewing geometries (solar zenith angles: 45° to 90°, elevation angles: 3°, 6°, 10°, 18°, 90°; three different azimuth angles), which allows a comprehensive test of our capabilities to measure and simulate the Ring effect. In addition to the Ring effect, also the observed O4 absorptions (optical densities) and radiances are compared with model simulations. In general good agreement is found for all measured quantities. From several sensitivity studies it is found that for most measurement situations the aerosol optical depth has usually the strongest influence on the observed quantities, but also other aerosol properties like e.g. the vertical distribution have a significant effect. Typically, the qualitative dependence of the Ring effect on aerosol properties is very similar to that of the O4 absorption. This can be understood, since both quantities depend strongly on the light path length in the lower atmosphere. However, in specific cases, the observation of the Ring effect can provide complementary information to that retrieved from the O4 observations. This is e.g. possible for measurements at small relative azimuth angles, from which information on the asymmetry parameter can be derived. Observations at large solar zenith angle allow the retrieval of stratospheric aerosol properties, even in cases with very low aerosol optical depths. In addition, Ring effect observations in zenith direction are rather sensitive to the aerosol optical depth (in contrast to O4 observations), which might allow to retrieve information on aerosol properties from existing zenith UV data sets prior to the MAX-DOAS era.

Refined Use of Satellite Aerosol Optical Depth Snapshots to Constrain Biomass Burning Emissions in the GOCART Model

2017 ◽  
Vol 122 (20) ◽  
pp. 10,983-11,004 ◽  
Author(s):  
Mariya Petrenko ◽  
Ralph Kahn ◽  
Mian Chin ◽  
James Limbacher
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Biomass Burning ◽  
Gocart Model
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