The Role of Coarse Mineral Dust Particles in the Climate System

矿物尘埃颗粒被强烈的地表风从沙漠地区吹升到大气层中，在那里它们可以被带到世界各地数千公里的地方。撒哈拉沙漠是世界上最大的沙尘源，沙尘经常从这里向西穿越大西洋，远至亚马逊雨林和加勒比海。每年有几次，天气模式将撒哈拉的灰尘输送到北方欧洲，在那里，当灰尘沉积在汽车上时，经常可以观察到。沙尘在通过大气输送的过程中，对气候系统和人类产生重要影响。例如，尘埃颗粒可以改变云中冰的性质，改变云的范围和寿命。当尘埃颗粒沉积到海洋中时，它为海洋浮游植物提供了营养来源，而海洋浮游植物本身可以调节大气中的二氧化碳水平。尘埃颗粒也为亚马逊雨林提供了营养。沙尘暴使颗粒物水平升高，对靠近沙尘源的健康产生影响，例如在北非，但也对数千公里以外的地方，例如在加勒比地区产生影响。灰尘也对航空业构成危害，并通过遮挡太阳来降低太阳能发电场的效率。尘埃粒子与太阳光和红外辐射相互作用，这是地球能量平衡的组成部分。例如，尘埃颗粒将阳光反射回太空，并向地球表面重新发射红外辐射。这些相互作用扰乱了地球的能量平衡。这种扰动的具体大小和符号取决于许多复杂的因素，其中包括所讨论的尘埃颗粒的大小。因此，沙尘颗粒影响区域大气环流和降水。例如，撒哈拉沙尘影响数百万人赖以生存的西非季风降水，也可能影响大西洋飓风的发展。由于矿物粉尘具有如此广泛的影响，因此能够在天气和气候模型中准确地表示粉尘非常重要。尽管如此，目前的模型无法充分代表粉尘过程。这在很大程度上是由于对尘埃颗粒大小的描述不足。最近由NERC资助的飞机在撒哈拉中部进行的测量显示，存在比以前认为的大得多的“巨型”尘埃颗粒，它们在大气中停留了几天，影响了辐射平衡。其他实地测量证实，“粗”颗粒也存在于远离尘源的尘埃中。气候模型并不代表这些粗糙或巨大的颗粒，尽管它们对能量平衡和随后的环流变化很重要。卫星对尘埃的测量必须对尘埃的性质做出假设，而且这些假设也不包括粗糙和巨大尘埃颗粒的代表。该研究金旨在提供最近和未来飞机测量的尘埃特性，针对气候模型和卫星检索算法进行定制，并充分纳入粗颗粒和巨颗粒。将评估这些粗颗粒对卫星反演的影响，以期改进卫星反演的尘埃，这本身就用于气候模型的验证。大颗粒对辐射平衡的影响将被充分量化，以确定气候模型因不代表粗颗粒而忽略了哪些辐射效应。这将通过使用专门的飞机进行从地方到全球范围的现场观测和以往和今后测量活动的辐射测量观测、散射和辐射计算以及卫星和地面观测来完成。总的来说，这将导致改进卫星对尘埃的测量，并量化适用于气候模型的粗尘和巨尘颗粒的辐射重要性。

Mineral dust particles are uplifted from desert regions by strong surface winds and lofted into the atmosphere, where they can be transported over thousands of kilometres around the world. The Sahara is the world's largest source of dust, and from here dust is frequently transported westwards across the Atlantic Ocean, as far as the Amazon rainforest and the Caribbean. Several times a year weather patterns transport Saharan dust towards Northern Europe, where dust is often observed when deposited on cars. While being transported by the atmosphere, dust exerts important effects on the climate system and humans. For example, dust particles can change the properties of ice in clouds, altering cloud extent and lifetime. When deposited to the ocean, dust particles provide a source of nutrients to oceanic phytoplankton, which in themselves can modulate atmospheric carbon dioxide levels. Dust particles also provide a supply of nutrients to the Amazon rainforest. Dust storms raise particulate matter levels which have an effect on health close to dust sources, such as in North Africa, but also thousands of kilometres away such as in the Caribbean. Dust also poses a hazard for aviation, and can decrease the effectiveness of solar energy farms by obscuring the sun. Dust particles interact with both sunlight and infrared radiation which are components of the Earth's energy balance. For example, dust particles reflect sunlight back to space, and re-emit infrared radiation back towards the Earth's surface. These interactions perturb the Earth's energy balance. The specific magnitude and sign of this perturbation are dependent on many complex factors, which include the size of the dust particles in question. As a result, dust particles affect regional atmospheric circulation and precipitation. For example Saharan dust affects West African Monsoon precipitation, upon which millions of people depend, and can also affect Atlantic hurricane development. Since mineral dust exerts such wide-ranging impacts, it is of great importance to be able to accurately represent dust in weather and climate models. Despite this, current models are unable to adequately represent dust processes. Much of this is due to inadequate representations of the size of dust particles. Recent NERC-funded aircraft measurements over the central Sahara have revealed the presence of much larger 'giant' dust particles than previously considered, which remain in the atmosphere for several days, influencing the radiation balance. Other field measurements have confirmed that 'coarse' particles are also present in dust transported far away from dust sources. Climate models do not represent these coarse or giant particles, despite their importance for the energy balance and subsequent circulation changes. Satellite measurements of dust must make assumptions of dust properties, and these also do not include a representation of coarse and giant dust particles. This fellowship aims to provide dust properties from recent and future aircraft measurements, tailored towards both climate models and satellite retrieval algorithms, with full incorporation of coarse and giant particles. The impact of these coarse particles on satellite retrievals will be assessed, with a view to improving satellite retrievals of dust, which in themselves are used for climate model validation. The impact of the large particles on the radiation balance will be fully quantified to determine what radiative effect climate models omit by not representing coarse particles. This will be done by using specialist aircraft in-situ and radiometric observations from previous and future measurement campaigns, scattering and radiation calculations and satellite and ground-based observations, from local to global scales. Overall this will lead to an improvement of satellite measurements of dust and a quantification of the radiative importance of coarse and giant dust particles applicable to climate models.