Evaluation of dust extinction and vertical profiles simulated by WRF-Chem with CALIPSO and AERONET over North Africa

Chaibou, Abdoul Aziz Saidou; Ma, Xiaoyan; Kumar, K. Raghavendra; Jia, Hui; Tang, Yue; Sha, Tong

doi:10.1016/j.jastp.2020.105213

Cited by 18 publications

(12 citation statements)

References 73 publications

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“…With respect to using a particular dust emission scheme in WRF-Chem, we have chosen AFWA extension to GOCART in our study. A number of other studies using WRF-Chem to model AOD from dust storms have used the AFWA and UoC extensions to GOCART [48] [49] [50]. While used to investigate dust extinction (AOD) over Sahara Desert in North Africa rather than Australia, [37] modelled these coefficients and particle vertical profile in summer 2006 using GOCART, AFWA and UoC in WRF-Chem.…”

Section: Discussionmentioning

confidence: 99%

Dust Transport from Inland Australia and its Impact on Air Quality and Health on the Eastern Coast of Australia during the February 2019 Dust Storm.

Aragnou¹,

Watt²,

H.³

et al. 2020

Preprint

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Dust storms originating from Central Australia and western New South Wales frequently cause high particles concentration at many sites across New South Wales, both inland and along the coast. This study focussed on a dust storm event in February 2019 which affect air quality across the state as detected at many ambient monitoring stations in the Department of Planning, Industry and Environment (DPIE) air quality monitoring network. The WRF-Chem (Weather Research and Forecast Model – Chemistry) model is used to study the formation, dispersion and transport of dust across the state of New South Wales (NSW, Australia). Wildfires also happened in northern NSW at the same time of the dust storm in February 2019, and their emissions are taken into account in WRF-Chem model by using Fire Inventory from NCAR (FINN) as emission input. The model performance is evaluated and is shown to predict fairly accurate the PM2.5 and PM10 concentration as compared to observation. The predicted PM2.5 concentration over New South Wales during 5 days from 11 to 15 February 2019 is then used to estimate the impact of the February 2019 dust storm event on three health endpoints namely mortality, respiratory and cardiac diseases hospitalisation rates. The results show that even though as the daily average of PM2.5 over some parts of the state, especially in western and north western NSW near the centre of the dust storm and wild fires, are very high (over 900 µg/m3), the population exposure is low due to the sparse population. The top five Statistical Area Level 4 regions with the most impact in term of mortality, respiratory diseases hospitalisation and cardiac disease hospitalisation are Far West and Orana, Newcastle and Lake Macquarie, New England and North West, Sydney – Inner South West and either Central Coast (mortality) or Sydney – Parramatta (respiratory diseases hospitalisation) or Sydney – Inner West (cardiac diseases hospitalisation). Generally, the health impact is similar in order of magnitude to that caused by biomass burnings events from wildfires or from hazardous reduction burnings (HRBs) near populous centres such as in Sydney in May 2016. One notable difference is the higher respiratory diseases hospitalisation for this dust event (161) compared to fire event (24).

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Section: Discussionmentioning

confidence: 99%

Dust Transport from Inland Australia and its Impact on Air Quality and Health on the Eastern Coast of Australia during the February 2019 Dust Storm.

Aragnou¹,

Watt²,

H.³

et al. 2020

Preprint

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“…In most desert areas, dust comes from sediments and alluvial deposits found in depressions, sedimentary basins, and ancient valleys. In the WRF-Chem model, dust source function is represented by the availability of loose erodible soil material 78 , 79 , and dust emission is computed as a function of wind energy, soil moisture, and particle size. A similar empirical formula developed 80 is used to calculate the dust emission flux F in the model following expression: where C is a dimensional factor equal to 1 µgs 2 m −5 , S is the source function 64 .…”

Section: Methodsmentioning

confidence: 99%

Dust radiative forcing and its impact on surface energy budget over West Africa

Chaibou

Sha

2020

Sci Rep

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Dust is the dominant aerosol type over West Africa (WA), and therefore accurate simulation of dust impact is critical for better prediction of weather and climate change. the dust radiative forcing (DRf) is estimated using two sets of experiments in this study: one without and the other with dust aerosol and its feedbacks with the Weather Research and forecasting with chemistry model (WRf-chem). Results show that DRF presents a net warming effect at the top-of-atmosphere (TOA) and in the atmosphere (ATM), and cooling at the surface (SFC). The net DRF over WA is estimated to be 9 W/m 2 at the TOA, 23 W/m 2 in the ATM, and − 13 W/m 2 at the Sfc. furthermore, dust-induced a reduction of sensible heat up to 24 W/m 2 and SFC temperature up to 2 °C cooling over WA, an increase of latent heat up to 12 W/m 2 over Sahara, a decrease up to 24 W/m 2 over the vegetated surfaces and an increase in the surface energy balance up to 12 W/m 2 over WA. The presence of dust significantly influences the surface energy budget over WA, suggesting that dust effects should be considered in more climate studies to improve the accuracy of climate predictions. Aerosols play a vital role in the climate system and have been among the major uncertainties in predictions of future climate change 1. West Africa (WA) is one of the most vulnerable regions to climate change, with the Sahara desert as the major source of dust aerosols in the world 2-5. The vulnerability is higher in the Sahel region, which has experienced a long period of drought in the late 1960s and 1980s. Numerous studies have pointed out that dust loading over the Sahel has increased significantly between the 1960s and 1980s, and is the consequence of drying of the region 6-13. Since the 1990s, better rainfall conditions appear to occur in the Sahel region 14-16. On this basis, a comprehensive investigation of dust impact on climate variability and drought in WA is essential, where the economy depends mostly on rainfed agriculture and transhumant livestock 11,15,17-19. To improve our understanding, the scientific community has launched several field campaigns, such as SaHAran Dust Experiments (SHADE) 20 , SAharan Mineral dUst experiMent (SAMUM) 21 , African Monsoon Multidisciplinary Analysis (AMMA) 22 , etc. Dust aerosols emitted from the Sahara and Sahel are considerably higher than any other desert in the world. The surface wind speed is the primary controlling factor of the emission and transport of dust particles into the atmosphere to great distances by convective events that develop actively in the desert 2,3,5,23,24. More than half of dust deposited in the oceans comes from elsewhere in North Africa. Saharan dust contains nutrients that fertilize soils and water, block or reflect sunlight, affect the formation of clouds and cyclones 25-27. Interactions of dust particles with radiation in the troposphere (absorption, scattering, etc.) are the basis in changing atmospheric state parameters, which may induce significant changes in climate. Dust aerosols influence many proces...

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“…For example, most dust models simply assume constant values of aerodynamic roughness length and soil clay fraction (Ginoux et al, 2001;Tegen et al, 2002;Zender et al, 2003), ignoring their temporal and spatial variability, which may cause uncertainties in the estimated surface friction velocity and threshold friction velocity. During recent decades, with the development of observation technology, detailed information on the surface characteristics appropriate for global and regional models has been provided (Laurent et al, 2005(Laurent et al, , 2008Prigent et al, 2005Prigent et al, , 2012Shangguan et al, 2014;Perlwitz et al, 2015a, b). Therefore, adopting more accurate and detailed soil datasets is expected to improve the dust model performance.…”

Section: R Tian Et Al: a Revised Mineral Dust Emission Scheme In Gementioning

confidence: 99%

“…However, as stated above, M clay is assumed to be a constant equal to 20 % in the original scheme, which can cause uncertainty in dust prediction. In the improved scheme, we employ the gridded data of clay content from the Global Soil Dataset for use in Earth System Models (GSDE) (Shangguan et al, 2014), which is based on the Digital Soil Map of the World (FAO, 1995(FAO, , 2003 and various regional and national soil databases. Figure 2 shows the updated M clay from Shangguan et al 2014with a horizontal resolution of 2 • × 2.5 • at the global scale.…”

Section: Soil Type and Soil Texture Datamentioning

confidence: 99%

A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

Tian

Zhao

2021

Atmos. Chem. Phys.

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Abstract. Mineral dust plays a significant role in climate change and air quality, but large uncertainties remain in terms of dust emission prediction. In this study, we improved treatment of the dust emission process in a global 3-D chemical transport model (GEOS-Chem v12.6.0), by incorporating the geographical variation of aerodynamic roughness length (Z0), smooth roughness length (Z0s) and soil texture and by introducing the Owen effect and the formulation of the sandblasting efficiency α by Lu and Shao (1999). To investigate the impact of the modifications incorporated in the model, several sensitivity simulations were performed for a severe dust storm during 27 March to 2 April 2015 over northern China. Results show that simulated threshold friction velocity is very sensitive to the updated Z0 and Z0s field, with the relative difference ranging from 10 % to 60 % compared to the original model with a uniform value. The inclusion of the Owen effect leads to an increase in surface friction velocity, which mainly occurs in the arid and semi-arid regions of northwest China. The substitution of a fixed value of α assumed in the original scheme with one varying with friction velocity and soil texture based on observations reduces α by 50 % on average, especially over regions with sand texture. Comparisons of sensitivity simulations and measurements show that the revised scheme with the implementation of updates provides more realistic threshold friction velocities and PM10 mass concentrations. The performance of the improved model has been evaluated against surface PM10 observations as well as MODIS aerosol optical depth (AOD) values, showing that the spatial and temporal variation of mineral dust are better captured by the revised scheme. Due to the inclusion of the improvement, average PM10 concentrations at observational sites are more comparable to the observations, and the average mean bias (MB) and normalized mean bias (NMB) values are reduced from −196.29 µg m−3 and −52.79 % to −47.72 µg m−3 and −22.46 % respectively. Our study suggests that the erodibility factor, sandblasting efficiency and soil-related properties which are simply assumed in the empirical scheme may lack a physical mechanism and spatial–temporal representativeness. Further study and measurements should be conducted to obtain a more realistic and detailed map of these parameters in order to improve dust representation in the model.

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Evaluation of dust extinction and vertical profiles simulated by WRF-Chem with CALIPSO and AERONET over North Africa

Cited by 18 publications

References 73 publications

Dust Transport from Inland Australia and its Impact on Air Quality and Health on the Eastern Coast of Australia during the February 2019 Dust Storm.

Dust Transport from Inland Australia and its Impact on Air Quality and Health on the Eastern Coast of Australia during the February 2019 Dust Storm.

Dust radiative forcing and its impact on surface energy budget over West Africa

A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

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