Winds of Change: Exploring the Meteorological Drivers of Global Dust

从干燥的土地上扬起的矿物粉尘占空气中颗粒物的很大一部分，据估计占全球颗粒物气溶胶负担的三分之二。大气中粉尘多的一个原因是，自工业革命以来，大气中的粉尘浓度急剧增加，这可能是由于开垦、耕作、农业用地的扩大。尘埃作为大气气溶胶的突出表现及其随时间的急剧增加促使人们对其气候效应进行研究，其中包括通过将阳光反射回空间而使地球变冷，通过捕获外出的红外辐射而使地球变暖，以及由于尘埃对云的影响而产生的间接影响。但是，当强风吹过干燥的土壤时，矿物粉尘就会进入大气，因此，偶尔发生在小地区的极端风事件可能会对全球负担造成巨大影响，这使得此类研究变得复杂。小规模极端事件的突出对理解沙尘在气候系统中的作用的努力提出了挑战，特别是那些依赖于长期全球气候模式模拟的努力，这些模式缺乏捕捉小规模风暴所需的分辨率和动力学复杂性。该奖项下的研究考虑了两种类型的风事件在全球粉尘排放中的作用：山区的下坡风暴和habos，由崩塌雷暴的下突引起的强直线风事件。这两种类型的风事件都与强粉尘排放有关，并且都是由当前全球气候模型未捕获的小尺度动力学驱动的。该项目利用了跨尺度预测模型（MPAS）的40天模拟，该模型具有精细尺度分辨率（3.75公里网格间距）和下坡风暴和海涌所需的更复杂的动力学。来自MPAS模拟的地面风被作为离线粉尘排放模型的输入，以确定这些事件排放的粉尘量。第二项研究调整了一个最先进的气候模型，即社区地球系统模型版本（CESM），以复制离线粉尘排放实验中产生的粉尘。CESM模拟被“微调”以符合观测到的大气环流，以便将尘埃气溶胶浓度及其气候影响与实际测量结果进行比较。鉴于空气中粉尘的潜在气候影响、这些影响的巨大不确定性以及人类活动可能在多大程度上引起粉尘浓度的巨大变化，这项工作具有社会和科学意义。大气中的粉尘还有其他影响，例如，它降低了空气质量，但它也为海洋生态系统提供了铁和其他营养物质的来源。该项目还包括与圣地亚哥县教育办公室合作，为加州高中科学教师开发教学活动。此外，该项目还为研究生和博士后提供支持和培训，从而为该研究领域的未来劳动力提供支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Mineral dust kicked up from dry land accounts for a remarkably large portion of the particulate matter in the air, by some estimates as much as two thirds of the global particulate aerosol burden. One reason for the dustiness of the atmosphere is that atmospheric dust concentration has increased dramatically since the Industrial Revolution, possibly due to the expansion of cleared, tilled, agricultural land. The prominence of dust as an atmospheric aerosol and its dramatic increase over time motivate research on its climatic effects, among them cooling by reflecting sunlight back to space, warming by trapping outgoing infrared radiation, and indirect effects due to the influence of dust on clouds. But such research is complicated by the fact that mineral dust enters the atmosphere when strong winds blow over dry soil, thus extreme wind events occurring sporadically and over small areas can make an outsized contribution to the global burden. The prominence of small-scale extreme events challenges efforts to understand the role of dust in the climate system, especially efforts that rely on long simulations of global climate models which lack the resolution and dynamical sophistication needed to capture small-scale windstorms.Research under this award considers the role of two types of wind events in global dust emissions: downslope windstorms in mountainous regions and haboobs, strong straight-line wind events caused by the downbursts of collapsing thunderstorms. Both types of wind events are associated with strong dust emissions and both are driven by small-scale dynamics that are not captured by current global climate models. The project takes advantage of 40-day simulations of the Model for Predication Across Scales (MPAS), which has the fine-scale resolution (3.75km grid spacing) and more sophisticated dynamics needed for downslope windstorms and haboobs. The surface winds from the MPAS simulations are taken as inputs to an offline dust emission model to determine the amount of dust emitted by these events. A second line of research adjusts a state-of-the-art climate model, the Community Earth System Model version (CESM), to replicate the dust generated in the offline dust emission experiments. The CESM simulations are "nudged" to conform to observed atmospheric circulation so that the dust aerosol concentration and its climate effects can be compared against real-world measurements.The work is of societal as well as scientific interest given the potential climatic effects of airborne dust, the large uncertainty as to those effects, and the extent to which human activity could cause large changes in dust concentration. The dustiness of the atmosphere has other effects, for instance it reduces air quality but it also provides a source of iron and other nutrients for marine ecosystems. The project also includes a collaboration with the San Diego County Office of Education to develop teaching activities for California high school science teachers. In addition, the project provides support and training to a graduate student and a postdoc, thereby providing for the future workforce in this research area.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.