Atmospheric Dynamics from Synoptic to Local Scale During an Intense Frontal Dust Storm over the Sistan Basin in Winter 2019

The Sistan Basin has been recognized as one of the most active dust sources and windiest desert environments in the world. Although the dust activity in Sistan maximizes during the summer, rare but intense dust storms may also occur in the winter. This study aims to elucidate the atmospheric dynamics related to dust emission and transport, dust-plume characteristics, and impacts on aerosol properties and air quality during an intense dust storm over Sistan in February 2019. The dust storm was initiated by strong northerly winds (~20 ms−1) associated with the intrusion of a cold front from high latitudes. The upper-level potential vorticity (PV)-trough evolved into a cut-off low in the mid and upper troposphere and initiated unstable weather over Afghanistan and northern Pakistan. At the surface, density currents emanating from deep convective clouds and further strengthened by downslope winds from the mountains, caused massive soil erosion. The passage of the cold front reduced the temperature by ~10 °C and increased the atmospheric pressure by ~10 hPa, while the visibility was limited to less than 200 m. The rough topography played a major role in modulating the atmospheric dynamics, wind field, dust emissions, and transport pathways. Meso-NH model simulates large amounts of columnar mass dust loading (> 20 g m−2) over Sistan, while the intense dust plume was mainly traveling below 2 km and increased the particulate matter (PM10) concentrations up to 1800 µg m−3 at Zabol. The dust storm was initially moving in an arc-shaped pathway over the Sistan Basin and then it spread away. Plumes of dust covered a large area in southwest Asia, reaching the northern Arabian Sea, and the Thar desert one to two days later, while they strongly affected the aerosol properties at Karachi, Pakistan, by increasing the aerosol optical depth (AOD > 1.2) and the coarse-mode fraction at ~0.7.

Theoretical assessment of the impact of desert aerosols on the dynamical transmission of meningitidis serogroup A

This paper has been motivated by the following biological question: how influential are desert aerosols in the transmission of meningitidis serogroup A (MenA)? A mathematical model for the dynamical transmission of MenA is considered, with the aim of investigating the impact of desert aerosols. Sensitivity analysis of the model has been performed in order to determine the impact of related parameters on meningitis outbreak. We derive the basic reproduction number [Formula: see text]. We prove that there exists a threshold parameter [Formula: see text] such that when [Formula: see text], the disease-free equilibrium is globally asymptotically stable (GAS). However, when [Formula: see text], the model exhibits the phenomenon of backward bifurcation. At the endemic level, we show that the number of infectious individuals in the presence of desert aerosols is larger than the corresponding number without the presence of desert aerosols. In conjunction with the inequality [Formula: see text] where [Formula: see text] is the basic reproduction number without desert aerosols, we found that the ingestion of aerosols by carriers will increase the endemic level, and the severity of the outbreak. This suggests that the control of MenA passes through a combination of a large coverage vaccination of young susceptible individuals and the production of a vaccine with a high level of efficacy as well as respecting the hygienic rules to avoid the inhalation of desert aerosols. Theoretical results are supported by numerical simulations.

The physics of wind-blown sand and dust

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.