CLouds and Aerosol Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)

生物质燃烧气溶胶(BBA)通过显著反射和吸收太阳光而影响区域辐射收支，从而对气候产生重大影响，其成核特性扰乱云的微物理特性，从而影响云的辐射特性、降水和云寿命。然而，BBA是一种复杂且鲜为人知的气溶胶物种，因为它由有机碳和无机化合物与黑碳混合而成，因此在气溶胶-辐射-相互作用和气溶胶-云-相互作用中都存在很大的不确定性，这些不确定性限制了我们当前气候模型准确重建过去气候和预测未来气候变化的能力。非洲大陆是BBA的全球最大来源(约占全球排放量的50%)，这些BBA通过底层的半永久性云层输送到近海，使东南大西洋成为BBA集中的区域热点。虽然全球气候模型一致认为这是一个区域热点，但在试图评估气溶胶-辐射-相互作用和气溶胶-云-相互作用时，它们的结果截然不同。因此，该地区对气候模式提出了非常严格的测试，不仅需要获取气溶胶的地理、垂直、吸收和散射特性，而且还需要获取云的地理分布、垂直范围和云的反射特性。同样，为了充分捕捉气溶胶-云--相互作用，云在背景条件下的敏感性；气溶胶的激活过程；关于生物气溶胶在何时何地进入海洋边界层的不确定性，以及这种夹带对云的微物理和辐射特性的影响导致了很大的不确定性。BBA覆盖的云层还导致卫星对云层属性的反演产生偏差，这可能导致层积云亮度的错误表示；这已被证明在世界其他地区造成偏差，例如巴西通过知之甚少的全球遥相关过程产生的降水偏差。现在是解决这些挑战的时候了，因为测量方法和高分辨率模型能力在过去几年中都得到了快速发展，现在已经足够先进，可以充分限制BBA的过程和性质。这种测量/高分辨率模式组合可以用来挑战较高分辨率数值天气预报(NWP)和气候模式中气溶胶-辐射-相互作用和气溶胶-云-相互作用的表示。该地区以前的测量仅限于在Safari-2000期间进行的基本测量，当时限制复杂的云-气溶胶-辐射所需的高级测量尚未开发出来，高分辨率模拟还处于起步阶段。因此，我们正在提议一个主要的财团计划，Clarity-2016，一个由5个大学合作伙伴和英国气象局组成的财团，它将提供一套地面和飞机测量，以测量、了解、评估和改进：a)物理、化学、BBAsb的光学和辐射特性)层积云的物理特性)天气和气候模式中气溶胶-辐射相互作用的表示d)一系列模式尺度上的气溶胶-云相互作用的表示。主要的现场实验将于2016年9月在纳米比亚的沃尔维斯湾进行。英国大型研究飞机(FAAM)将用于测量现场和遥感的气溶胶和云以及属性，而飞机上的先进辐射计将测量气溶胶和云的辐射影响。虽然该提案是独立编写的，但我们正在与NASA先知计划(5个NASA中心，8所美国大学)和NSF资助的ONFIRE计划(22个美国研究所)密切合作和协调。

Biomass burning aerosol (BBA) exerts a considerable impact on climate by impacting regional radiation budgets as it significantly reflects and absorbs sunlight, and its cloud nucleating properties perturb cloud microphysics and hence affect cloud radiative properties, precipitation and cloud lifetime. However, BBA is a complex and poorly understood aerosol species as it consists of a complex cocktail of organic carbon and inorganic compounds mixed with black carbon and hence large uncertainties exist in both the aerosol-radiation-interactions and aerosol-cloud-interactions, uncertainties that limit the ability of our current climate models to accurately reconstruct past climate and predict future climate change. The African continent is the largest global source of BBA (around 50% of global emissions) which is transported offshore over the underlying semi-permanent cloud decks making the SE Atlantic a regional hotspot for BBA concentrations. While global climate models agree that this is a regional hotspot, their results diverge dramatically when attempting to assess aerosol-radiation-interactions and aerosol-cloud-interactions. Hence the area presents a very stringent test for climate models which need to capture not only the aerosol geographic, vertical, absorption and scattering properties, but also the cloud geographic distribution, vertical extent and cloud reflectance properties. Similarly, in order to capture the aerosol-cloud-interactions adequately, the susceptibility of the clouds in background conditions; aerosol activation processes; uncertainty about where and when BBA aerosol is entrained into the marine bundary layer and the impact of such entrainment on the microphysical and radiative properties of the cloud result in a large uncertainty. BBA overlying cloud also causes biases in satellite retrievals of cloud properties which can cause erroneous representation of stratocumulus cloud brightness; this has been shown to cause biases in other areas of the word such as biases in precipitation in Brazil via poorly understood global teleconnection processes. It is timely to address these challenges as both measurement methods and high resolution model capabilities have developed rapidly over the last few years and are now sufficiently advanced that the processes and properties of BBA can be sufficiently constrained. This measurement/high resolution model combination can be used to challenge the representation of aerosol-radiation-interaction and aerosol-cloud-interaction in coarser resolution numerical weather prediction (NWP) and climate models. Previous measurements in the region are limited to the basic measurements made during SAFARI-2000 when the advanced measurements needed for constraining the complex cloud-aerosol-radiation had not been developed and high resolution modelling was in its infancy.We are therefore proposing a major consortium programme, CLARIFY-2016, a consortium of 5 university partners and the UK Met Office, which will deliver a suite of ground and aircraft measurements to measure, understand, evaluate and improve:a) the physical, chemical, optical and radiative properties of BBAsb) the physical properties of stratocumulus cloudsc) the representation of aerosol-radiation interactions in weather and climate models d) the representation of aerosol-cloud interactions across a range of model scales. The main field experiment will take place during September 2016, based in Walvis Bay, Namibia. The UK large research aircraft (FAAM) will be used to measure in-situ and remotely sensed aerosol and cloud and properties while advanced radiometers on board the aircraft will measure aerosol and cloud radiative impacts. While the proposal has been written on a stand-alone basis, we are closely collaborating and coordinating with both the NASA ORACLES programme (5 NASA centres, 8 USA universities) and NSF-funded ONFIRE programme (22 USA institutes).