Contribution of IASI to the observation of the dust aerosol diurnal cycle over Sahara

2020 ◽  
Author(s):  
virginie capelle ◽  
alain chedin ◽  
Noelle Scott ◽  
Martin Todd
Keyword(s):  
Diurnal Cycle ◽  
Deep Convection ◽  
Dust Emission ◽  
Saharan Dust ◽  
Dust Aerosols ◽  
Source Regions ◽  
Resolution Model ◽  
High Resolution Model ◽  
Dust Distribution ◽  
Realistic Information

<p>The Infrared Atmospheric Sounder Interferometer (IASI) is well suited for monitoring of dust aerosols because of its capability to determine both AOD and altitude of the dust layer, and because of the good match between the IASI times of observation (9.30 am and pm, local time) and the time of occurrence of the main Saharan dust uplift mechanisms. Here, starting from IASI-derived dust characteristics for an 11-year period, we assess the capability of IASI to bring realistic information on the dust diurnal cycle. We first show the morning and nighttime climatology of IASI-derived dust AOD for two major dust source regions of the Sahara: The Bodele Depression and the Adrar region. Compared with simulations from a high resolution model, permitting deep convection to be explicitly resolved, IASI performs well. In a second step, a Dust Emission Index specific to IASI is constructed, combining simultaneous information on dust AOD and mean altitude, with the aim of observing the main dust emission areas, daytime and nighttime. Comparisons are then made with other equivalent existing results derived from ground based or other satellite observations. Results demonstrate the capability of IASI to improve the documentation of dust distribution over Sahara over a long period of time. Associating observations of dust aerosols in the visible, on which a majority of aerosol studies are so far based, and in the infrared thus appears as a way to complement the results from other satellite instruments in view of improving our knowledge of their impact on climate.</p>

scholarly journals Saharan dust transport and deposition towards the tropical northern Atlantic

2009 ◽  
Vol 9 (4) ◽  
pp. 1173-1189 ◽  
Author(s):  
K. Schepanski ◽  
I. Tegen ◽  
A. Macke
Keyword(s):  
Dust Emission ◽  
Source Area ◽  
Saharan Dust ◽  
Dust Deposition ◽  
Deposition Rates ◽  
Dust Transport ◽  
Tropical North Atlantic ◽  
Different Seasons ◽  
Northern Atlantic ◽  
Dust Distribution

Abstract. We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.

scholarly journals Profiling of Saharan dust from the Caribbean to West Africa, Part 2: Shipborne lidar measurements versus forecasts

2017 ◽  
Author(s):  
Albert Ansmann ◽  
Franziska Rittmeister ◽  
Ronny Engelmann ◽  
Sara Basart ◽  
Angela Benedetti ◽  
...  
Keyword(s):  
Mass Concentration ◽  
Dust Emission ◽  
Saharan Dust ◽  
Light Extinction ◽  
Tropical Atlantic ◽  
Anthropogenic Aerosol ◽  
Dust Transport ◽  
Source Regions ◽  
Dust Sources ◽  
Lidar Measurements

Abstract. A unique 4-week ship cruise from Guadeloupe to Cabo Verde in April–May 2013 (see part 1, Rittmeister et al., 2017) is used for an in-depth comparison of dust profiles observed with a polarization/Raman lidar aboard the German research vessel Meteor over the remote tropical Atlantic and respective dust forecasts of a regional (SKIRON) and two global atmospheric (dust) transport models (NMMB/BSC-Dust, MACC/CAMS). New options of model-observation comparisons are presented. We analyze how well the modeled fine dust (submicrometer particles) and coarse dust contributions to light extinction and mass concentration match respective lidar observations, and to what extent models, adjusted to aerosol optical thickness observations, are able to reproduce the observed layering and mixing of dust and non-dust (mostly marine) aerosol components over the remote tropical Atlantic. Based on the coherent set of dust profiles at well defined distances from Africa (without any disturbance by anthropogenic aerosol sources over the ocean) we investigate how accurately the models handle dust removal at distances of 1500 km to more than 5000 km west of the Saharan dust source regions. It was found that (a) dust predictions are of acceptable quality for the first several days after dust emission up to 2000 km west of the African continent, (b) the removal of dust from the atmosphere is too strong for large transport paths in the global models, and (c) the simulated fine-to-coarse dust ratio (in terms of mass concentration and light extinction) is too high in the models compared to the observations. This deviation is already given close to the dust sources and then increases with distance from Africa.

Evaluation of Clouds in the E3SM Atmosphere Model with Satellite Simulators

2020 ◽  
Author(s):  
Yuying Zhang ◽  
Shaocheng Xie ◽  
Wuyin Lin ◽  
Stephen A. Klein ◽  
Mark Zelinka ◽  
...  
Keyword(s):  
Deep Convection ◽  
Model Performance ◽  
Supercooled Liquid ◽  
The Arctic ◽  
Cmip5 Models ◽  
Model Errors ◽  
Tropical Deep Convection ◽  
Resolution Model ◽  
High Resolution Model ◽  
Atmosphere Model

<div> <div> <div> <div> <div> <div>This study systematically evaluates clouds simulated by the Energy Exascale Earth System Model (E3SM) Atmosphere Model version one (EAMv1) against satellite cloud observations. The simulator package, COSP, is used to facilitate a meaningful “apples-to-apples” comparison between model and observation by considering the different definitions of geophysical quantities among models and observations and the limitations/features of the observing process. EAMv1 is configured at two horizontal resolutions (1<span>º</span> and 0.25<span>º</span>) and one vertical resolution of 72 layers for different scientific applications. To provide a more complete picture of the model performance in simulating clouds and insights into modeled cloud biases, the evaluation is performed by utilizing unique features of individual instrument contained in COSP in observing different aspects of clouds.</div> <div> </div> <div>Both low (1deg) and high (0.25deg) resolution EAMv1 configurations generally underestimat clouds in low and midlatitudes and overestimate clouds in the Arctic although the error is smaller in the high-resolution model. The underestimate of clouds is due to the underestimate of optically thin to intermediate clouds, as EAMv1 generally overestimates optically intermediate to thick clouds. Other model errors include the largely under-predicted marine stratocumulus along the coasts and high clouds over the tropical deep convection regions. The underestimate of thin clouds results in too much LW radiation being emitted to space and too little SW radiation being reflected back to space while the overestimate of optically intermediate and thick clouds leads to too little LW radiation being emitted to space and too much SW radiation being reflected back to space. EAMv1 shows better skill in reproducing the observed distribution of clouds and their properties and has smaller radiatively relevant errors in the distribution of clouds than most of the CFMIP1 and CFMIP2 models. It produces more supercooled liquid cloud fraction than CAM5 and most CMIP5 models primarily due to a new ice nucleation scheme and secondarily due to a reduction of the ice deposition growth rate.</div> </div> </div> </div> </div> </div>

scholarly journals Numerical Simulations of the 1 May 2012 Deep Convection Event over Cuba: Sensitivity to Cumulus and Microphysical Schemes in a High-Resolution Model

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Yandy G. Mayor ◽  
Michel D. S. Mesquita
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
Deep Convection ◽  
Added Value ◽  
Cumulus Parameterization ◽  
Lateral Boundary Condition ◽  
Verification Method ◽  
Cumulus Scheme ◽  
Resolution Model ◽  
High Resolution Model

This paper evaluates the sensitivity to cumulus and microphysics schemes, as represented in numerical simulations of the Weather Research and Forecasting model, in characterizing a deep convection event over the Cuban island on 1 May 2012. To this end, 30 experiments combining five cumulus and six microphysics schemes, in addition to two experiments in which the cumulus parameterization was turned off, are tested in order to choose the combination that represents the event precipitation more accurately. ERA Interim is used as lateral boundary condition data for the downscaling procedure. Results show that convective schemes are more important than microphysics schemes for determining the precipitation areas within a high-resolution domain simulation. Also, while one cumulus scheme captures the overall spatial convective structure of the event more accurately than others, it fails to capture the precipitation intensity. This apparent discrepancy leads to sensitivity related to the verification method used to rank the scheme combinations. This sensitivity is also observed in a comparison between parameterized and explicit cumulus formation when the Kain-Fritsch scheme was used. A loss of added value is also found when the Grell-Freitas cumulus scheme was activated at 1 km grid spacing.

scholarly journals Saharan dust transport and deposition towards the Tropical Northern Atlantic

2008 ◽  
Vol 8 (4) ◽  
pp. 16061-16096 ◽  
Author(s):  
K. Schepanski ◽  
I. Tegen ◽  
A. Macke
Keyword(s):  
Dust Emission ◽  
Source Area ◽  
Saharan Dust ◽  
Dust Deposition ◽  
Deposition Rates ◽  
Dust Transport ◽  
Tropical North Atlantic ◽  
Different Seasons ◽  
Northern Atlantic ◽  
Dust Distribution

Abstract. We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three exemplary months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.

scholarly journals Investigation of June 2020 Giant Saharan Dust Storm Using Remote Sensing Observations and Model Reanalysis

2021 ◽  
Author(s):  
A. Asutosh ◽  
V. Vinoj ◽  
M. Nuncio
Keyword(s):  
Dust Storm ◽  
Radiative Forcing ◽  
Climate Models ◽  
Satellite Observation ◽  
Saharan Dust ◽  
Resolution Model ◽  
High Resolution Model ◽  
Dust Events ◽  
Index Value

This paper investigates the characteristics and impact of a major Saharan dust storm during June 14th -19th 2020 to atmospheric radiative and thermodynamics properties over the Atlantic Ocean. The event witnessed the highest ever aerosol optical depth (close to 2 during the peak of the storm) for June since 2002. The satellites and high-resolution model reanalysis products well captured the origin, spread and the effects of the dust storm. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) profiles, lower angstrom exponent values (~ 0.12) and higher aerosol index value (> 4) tracked the presence of elevated dust. It was found that the dust AOD was as much as 250-300% higher than their climatology resulting in an atmospheric radiative forcing ~200% larger. As a result, elevated warming ( 8-16 %) was observed, followed by a drop in relative humidity(2-4%) in the atmospheric column, as evidenced by both in-situ and satellite measurements. Quantifications such as these for extreme dust events provide significant insights that may help in understanding their climate effects, including improvements to dust simulations using chemistry-climate models

scholarly journals New developments in the representation of Saharan dust sources in the aerosol-climate model ECHAM6-HAM2

2015 ◽  
Vol 8 (9) ◽  
pp. 7879-7910 ◽  
Author(s):  
B. Heinold ◽  
I. Tegen ◽  
K. Schepanski ◽  
J. R. Banks
Keyword(s):  
Climate Model ◽  
Dust Emission ◽  
Source Area ◽  
Saharan Dust ◽  
Moist Convection ◽  
Dust Source ◽  
New Developments ◽  
Dust Sources ◽  
Dust Events ◽  
Dust Distribution

Abstract. In the aerosol-climate model ECHAM6-HAM2, dust source activation (DSA) observations from Meteosat Second Generation (MSG) satellite are proposed to replace the original source area parameterization over the Sahara Desert. The new setup is tested in nudged simulations for the period 2007 to 2008. The evaluation is based on comparisons to dust emission events inferred from MSG dust index imagery, AERONET sun photometer observations, and satellite retrievals of aerosol optical thickness (AOT). The model results agree well with AERONET measurements. Good correlations between model results and MSG-SEVIRI dust AOT as well as Multi-angle Imaging Spectro-Radiometer (MISR) AOT indicate that also the spatial dust distribution is well reproduced. ECHAM6-HAM2 computes a more realistic geographical distribution and up to 20 % higher annual Saharan dust emissions, using the MSG-based source map. The representation of dust AOT is partly improved in the southern Sahara and Sahel. In addition, the spatial variability is increased towards a better agreement with observations depending on the season. Thus, using the MSG DSA map can help to circumvent the issue of uncertain soil input parameters. An important issue remains the need to improve the model representation of moist convection and stable nighttime conditions. Compared to sub-daily DSA information from MSG-SEVIRI and results from a regional model, ECHAM6-HAM2 notably underestimates the important fraction of morning dust events by the breakdown of the nocturnal low-level jet, while a major contribution is from afternoon-to-evening emissions.

scholarly journals Dust Lidar Ratios Retrieved from the CALIOP Measurements Using the MODIS AOD as a Constraint

2020 ◽  
Vol 12 (2) ◽  
pp. 251 ◽  
Author(s):  
Man-Hae Kim ◽  
Sang-Woo Kim ◽  
Ali H. Omar
Keyword(s):  
Saharan Dust ◽  
Orthogonal Polarization ◽  
Dust Aerosols ◽  
Deep Blue ◽  
Source Regions ◽  
Modis Aod ◽  
Moderate Resolution ◽  
Lidar Ratio ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Lidar ratio for dust aerosols is retrieved from a synergetic use of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Total Attenuated Backscatter coefficients and the Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depths (AODs) for 5 years from 2007 to 2011. MODIS AODs from the Dark Target (DT) algorithm over ocean and from the Deep Blue (DB) algorithm over land are used as a constraint for the retrieval. The dust lidar ratio is retrieved larger over land (46.6 ± 36.3 sr) than ocean (39.5 ± 16.8 sr) and shows distinct regional variation. Lidar ratio for Saharan dust (49.5 ± 36.8 sr) is larger than Arabian dust (42.5 ± 26.2 sr). Lidar ratios for dust aerosols transported to Mediterranean Sea (44.4 ± 15.9 sr), Mid Atlantic (40.3 ± 12.4 sr), and Arabian Sea (37.5 ± 12.1 sr) show lower values relative to their source regions. Retrieved dust lidar ratios for Taklamakan and Gobi Deserts region (35.0 ± 31.1 sr) and Australia (35.4 ± 34.4 sr) are slightly lower than the above-mentioned regions. AOD comparison between CALIOP and MODIS shows that the CALIOP AOD is biased low. When including clear air AOD for CALIOP, however, AODs from two sensors become more comparable.

scholarly journals How well do the CMIP6 models simulate dust aerosols?

2021 ◽  
Author(s):  
Alcide Zhao ◽  
Claire L. Ryder ◽  
Laura J. Wilcox
Keyword(s):  
Dust Emission ◽  
Coupled Model ◽  
Radiation Budget ◽  
Seasonal Cycles ◽  
Dust Aerosols ◽  
Ensemble Mean ◽  
Simulated Surface ◽  
Intercomparison Project ◽  
Dust Distribution ◽  
The Relationship

Abstract. Mineral dust impacts key processes in the Earth system, including the radiation budget, clouds, and nutrient cycles. We evaluate dust aerosols in 16 models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) against multiple reanalyses and satellite observations. Most models, and particularly the multi-model ensemble mean (MEM), capture the spatial patterns and seasonal cycles of global dust processes well. However, large uncertainties and inter-model diversity are found. For example, global dust emissions, primarily driven by model-simulated surface winds, vary by a factor of 5 across models, while the MEM estimate is double the amount in reanalyses. The ranges of CMIP6 model-simulated global dust emission, deposition, burden and optical depth (DOD) are larger than previous generations of models. Models present considerable disagreement in dust seasonal cycles over North China and North America. Here, DOD values are overestimated by most CMIP6 models, with the MEM estimate 1.2–1.7 times larger compared to satellite and reanalysis datasets. Such overestimates can reach up to a factor of 5 in individual models. Models also fail to reproduce some key features of the regional dust distribution, such as dust accumulation along the southern edge of the Himalayas. Overall, there are still large uncertainties in CMIP6 models’ simulated dust processes, which feature inconsistent biases throughout the dust lifecycle between models, particularly in the relationship connecting dust mass to DOD. Our results imply that modelled dust processes are becoming more uncertain as models become more sophisticated. More detailed output relating to the dust cycle in future intercomparison projects will enable better constraints of global dust cycles, and enable the potential identification of observationally-constrained links between dust cycles and optical properties.

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