Sensitivity of the WRF-Chem (V3.6.1) model to different dust emission parametrisation: assessment in the broader Mediterranean region

Abstract

Abstract. In this study we aim to assess the WRF-Chem model capacity to reproduce dust transport over the eastern Mediterranean. For this reason, we compare the model aerosol optical depth (AOD) outputs to observations, focusing on three key regions: North Africa, the Arabian Peninsula and the eastern Mediterranean. Three sets of four simulations have been performed for the 6-month period of spring and summer 2011. Each simulation set uses a different dust emission parametrisation and for each parametrisation, the dust emissions are multiplied with various coefficients in order to tune the model performance. Our assessment approach is performed across different spatial and temporal scales using AOD observations from satellites and ground-based stations, as well as from airborne measurements of aerosol extinction coefficients over the Sahara.Assessment over the entire domain and simulation period shows that the model presents temporal and spatial variability similar to observed AODs, regardless of the applied dust emission parametrisation. On the other hand, when focusing on specific regions, the model skill varies significantly. Tuning the model performance by applying a coefficient to dust emissions may reduce the model AOD bias over a region, but may increase it in other regions. In particular, the model was shown to realistically reproduce the major dust transport events over the eastern Mediterranean, but failed to capture the regional background AOD. Further comparison of the model simulations to airborne measurements of vertical profiles of extinction coefficients over North Africa suggests that the model realistically reproduces the total atmospheric column AOD. Finally, we discuss the model results in two sensitivity tests, where we included finer dust particles (less than 1 µm) and changed accordingly the dust bins' mass fraction.

Simulation of Severe Dust Events over Egypt Using Tuned Dust Schemes in Weather Research Forecast (WRF-Chem)

“…2.0) is investigated in Figure 4. Both PM 10 and PM 2.5 maps confirm their high values within the domain D1, and particularly D3, with significantly higher value of PM 10 . The average PM 10 and PM 2.5 within the D1 domain are 1.10 × 10 4 and 2.22 × 10 3 µg/m 3 , respectively.…”

“…The dust emission in DS3 is calculated only when the erosion factor is non-zero. This constraint is presented in [10]. As mentioned before, the four subdomains D1, D2, D3, and D4 ( Figure 1) are used to support the interpretation and validation of the model's results.…”

“…The following three parameters from the model output are used to examine the intensity of the dust plume; the dust load, the density of PM 2.5 , and of PM 10 . The term "Coeff" in the following refers to the value of the tuning parameter in the dust emission scheme.…”

Multimodel simulations of a springtime dust storm over northeastern China: implications of an evaluation of four commonly used air quality models (CMAQ v5.2.1, CAMx v6.50, CHIMERE v2017r4, and WRF-Chem v3.9.1)

“…Depending on the extent to which human activities are involved, dust emissions can be classified as natural or anthropogenic. Natural dust emissions are activated by wind from undisturbed surface in arid or semiarid areas, such as the Sahara in North Africa (Formenti et al, 2011), alluvial plains and deserts in western Asia and Central Asia (Cao et al, 2015;Xi and Sokolik, 2015), deserts and sandy lands in East Asia (Laurent et al, 2005), various desert landforms in Australia (Revel-Rolland et al, 2006), and deserts in the southwest USA (Gillette et al, 1996;Zhao et al, 2012). Anthropogenic dust emissions are either activated by mechanical forces (tilling, mining, etc.…”

“…Numerical dust models are often used to assess the magnitude of windblown dust emission and to predict its effects on air quality and climate. Several dust schemes to estimate the dust flux into the atmosphere and other relevant parameters have been proposed in the past 20 years; some have been coupled with air quality models, such as WRF-Chem (Kang et al, 2011;Su and Fung, 2015;Flaounas et al, 2017), CMAQ Foroutan et al, 2017), CAMx (Klingmüller et al, 2018), CHIMERE (Menut et al, 2013a;Mailler et al, 2017), ALADIN-SURFEX (Mokhtari et al, 2012), LOTOS-EUROS (Manders-Groot et al, 2016), EMEP MSC-W (Simpson et al, 2012), NAQPMS (Li et al, 2012), and CUACE/Haze . These models are widely used to study the air quality and climate effects of dust emissions.…”