Solving the Coarse Dust Conundrum: What Processes Cause Large-scale Models to Underestimate Coarse Dust Transport?

在任何给定的时间，我们的大气层都含有数千万吨的沙漠尘埃。这些尘埃播撒云层，散射和吸收阳光，当它离开我们的大气层时，会使生态系统肥沃，并使冰雪变暗。基础物理学预测，粗大的尘埃颗粒--仍然不会超过人类头发的厚度--很快就会从大气层中沉淀出来。然而，测量表明情况并非如此；相反，粗尘埃可以在大气中停留数天，并从源头移动数千公里。因此，这些尘埃有更多的时间影响地球及其天气和气候。这使得确定导致尘埃停留在大气中的时间超过预期的过程变得至关重要，并在气候和天气模型中解释这些缺失的过程。该项目使用大涡模拟(LES)和其他技术来测试有助于保持粗尘埃漂浮的过程性质的三个假设。具体地说，该项目测试尘埃的非球形性、带电和/或尘埃层中的湍流是否使尘埃保持在高空，以抵御重力沉降的作用。该项目将导致尘埃重力沉降的参数化，其中包括这些缺失的过程，并可用于天气和气候模型。这将使这些模型能够更准确地表示大气中的沙漠沙尘及其对地球系统的影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

At any given time, our atmosphere contains tens of millions of metric tons of desert dust. This dust seeds clouds and scatters and absorbs sunlight and, when it settles from our atmosphere, fertilizes ecosystems and darkens snow and ice. Basic physics predicts that coarse dust particles - still no larger than the thickness of a human hair - quickly settle out of the atmosphere. However, measurements indicate that this is not the case; instead, coarse dust can remain in the atmosphere for days and travel thousands of kilometers from its source. This dust therefore has more time to impact the Earth and its weather and climate. This makes it critical to determine the processes that cause dust to stay in the atmosphere longer than expected, and account for these missing processes in climate and weather models.This project uses Large Eddy Simulations (LES) and other techniques to test three hypotheses of the nature of the process(es) that help keep coarse dust aloft. Specifically, this project tests whether dust asphericity, electrification, and / or turbulence in dusty layers keep dust aloft against the action of gravitational settling. The project will result in a parameterization of dust gravitational settling that includes these missing processes and that can be used in weather and climate models. This will allow these models to more accurately represent desert dust in the atmosphere and its impact on the Earth system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.