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  1. Abstract In situ observations and output from a numerical model are utilized to examine three dust outbreaks that occurred in the northwestern Sonoran Desert. Via analysis of these events, it is shown that trapped waves generated in the lee of an upwind mountain range produced high surface wind speeds along the desert floor and the observed dust storms. Based on analysis of observational and model output, general characteristics of dust outbreaks generated by trapped waves are suggested, including dust-layer depths and concentrations that are dependent upon wave phase and height above the surface, emission and transport associated with the presence of a low-level jet, and wave-generated high wind speeds and thus emission that occurs far downwind of the wave source. Trapped lee waves are ubiquitous in Earth’s atmosphere and thus it is likely that the meteorological aspects of the dust storms examined here are also relevant to understanding dust in other regions. These dust outbreaks occurred near the Salton Sea, an endorheic inland body of water that is rapidly drying due to changes in water-use management. As such, these findings are also relevant in terms of understanding how future changes in size of the Salton Sea will impact dust stormsmore »and air quality there. Significance Statement Dust storms are ubiquitous in Earth’s atmosphere, yet the physical processes underlying dust emission and subsequent transport are not always understood, in part due to the wide variety of meteorological processes that can generate high winds and dust. Here we use in situ measurements and numerical modeling to demonstrate that vertically trapped atmospheric waves generated by air flowing over a mountain are one such mechanism that can produce dust storms. We suggest several features of these dust outbreaks that are specific to their production by trapped waves. As the study area is a region undergoing rapid environmental change, these results are relevant in terms of predicting future dust there.« less
    Free, publicly-accessible full text available March 1, 2024
  2. The condition of the Salton Sea, California's largest lake, has profound implications for people and wildlife both near and far. Colorado River irrigation water has supported agricultural productivity in the basin's Coachella and Imperial valleys since the Sea formed over 100 years ago, bringing billions of dollars per year to the region and helping to feed households across the United States. The runoff, which drains into the Sea, has historically maintained water levels and supported critical fish and migratory bird habitats. However, since 2018, a large portion of the water previously allocated for agriculture has been diverted to urban regions, causing the Sea to shrink and become increasingly saline. This poses major threats to the Sea's ecology, as well as risks to human health, most notably in the noxious dust produced by the drying lakebed. To ensure continued agricultural and ecological productivity and protect public health, management of the Sea and surrounding wetlands will require increased research and mitigation efforts.
  3. Understanding of the fundamental chemical and physical processes that lead to the formation and evolution of secondary organic aerosol (SOA) in the atmosphere has been rapidly advancing over the past decades. Many of these advancements have been achieved through laboratory studies, particularly SOA studies conducted in environmental chambers. Results from such studies are used to develop simplified representations of SOA formation in regional- and global-scale air quality models. Although it is known that there are limitations in the extent to which laboratory experiments can represent the ambient atmosphere, there have been no systematic surveys of what defines atmospheric relevance in the context of SOA formation. In this work, GEOS-Chem version 12.3 was used to quantitatively describe atmospherically relevant ranges of chemical and meteorological parameters critical for predictions of the mass, composition, and physical properties of SOA. For some parameters, atmospherically relevant ranges are generally well represented in laboratory studies. However for other parameters, significant gaps exist between atmospherically relevant ranges and typical laboratory conditions. For example, cold winter (less than 0 °C) and humid (greater than 70% RH) conditions are relatively common on the Earth’s surface but are poorly represented in published chamber data. Furthermore, the overlap in relative humiditymore »and organic aerosol mass between chamber studies and ambient conditions is almost nonexistent. For parameters with significant gaps, extended laboratory studies and/or mechanistic models are needed to bridge these gaps.« less