DCMEX: The Deep Convective Microphysics EXperiment

DCMEX项目的目标是通过改进全球模式中微物理过程的表示，最终减少平衡气候敏感性方面的不确定性。尤其是热带系统产生的针状物对云的反馈有很大的贡献。砧座的辐射性能、寿命和面积大小是关键参数。DCMEX将确定它们受云微物理影响甚至控制的程度，包括组成砧座的冰粒的习性、浓度和大小，这反过来又取决于云混合相区的微物理过程以及发生在砧座本身的微物理过程。近年来，全球气候模式的复杂性有了迅速的进步。然而，一些用于表示微物理过程的方程式是基于比预期更差的物理理解。例如，Gettelman和Sherwood(2016)指出，由于微物理过程的不确定性，如冰过程的处理，在确定不同全球模型的云反馈方面存在显著差异。Ceppi等人。(2017)还得出结论，在全球模型中准确表示云及其辐射效应仍然具有挑战性，部分原因是很难表示云的微物理，以及微物理和动力学之间的相互作用。控制热带砧木云不透明度和面积覆盖率的微物理和辐射过程和动力学在全球气候模式中没有得到很好的代表。DCMEX将在真实世界的实验室对流云系-混合相区和砧座-中对云微物理进行新的测量，并改进和测试模式，然后将其应用于全球热带深对流系统。我们建议部署FAAM飞机以及两个双极化、多普勒雷达和机载和地面气溶胶测量，以研究新墨西哥州一个孤立山脉上空形成的深对流云。重点将放在冰成核颗粒(INP)(初级冰生产)和涉及现有冰颗粒(次级冰颗粒生产)的过程中形成冰，例如碰撞。这些观测将被用来测试和进一步改进气候模型中冰川过程的表示。我们的方法认识到，为了准确地表示云反馈，模型需要准确地表示系统中的各个流程。因此，证明该模式能够再现观测到的云的演变是准确预测云反馈的必要条件。DCMEX的研究将有一条从新的野外活动到更准确的气候敏感性估计的稳健途径。这条途径由四个部分组成：新的观测；利用这些观测和过程建模得出新的参数；利用现有的热带深对流中的山丘现场数据和卫星观测来验证模型；以及利用获得的知识改进和测试气候模型中微物理的代表性。特别是，DCMEX将建立在我们小组在改进微物理表示方面的经验的基础上。一套无缝的Met Office模型将用于对流解析模拟和带有参数对流的全球模拟。最后，将进行简化的气候变化(强制变暖环境)实验，以了解不同的微物理过程对云反馈的作用。

The goal of the DCMEX project is to ultimately reduce the uncertainty in equilibrium climate sensitivity by improving the representation of microphysical processes in global models. It is the anvils produced by tropical systems in particular that contribute significantly to cloud feedbacks. The anvil radiative properties, lifetimes and areal extent are the key parameters. DCMEX will determine the extent to which these are influenced, or even controlled by the cloud microphysics including the habits, concentrations and sizes of the ice particles that make up the anvils, which in turn depend on the microphysical processes in the mixed-phase region of the cloud as well as those occurring in the anvil itself.There has been a rapid advancement in the sophistication of global climate models in recent years. Yet some of the equations used to represent microphysics processes are based on a poorer physical understanding than desired. Gettelman and Sherwood (2016), for example pointed out that there is significant spread in determining cloud feedbacks across different global models due to uncertainties in microphysical processes, such as the treatment of ice processes. Ceppi et al. (2017) also concluded that accurately representing clouds and their radiative effects in global models remains challenging partly due to the difficulty in representing the cloud microphysics, as well as the interactions between microphysics and dynamics. The microphysical and radiative processes and dynamics that control the opacity and areal coverage of tropical anvil clouds are not well represented in global climate models.DCMEX will make novel measurements of cloud microphysics in a real-world laboratory convective cloud system - both the mixed-phase region and anvil - as well as improve and test models and then apply them globally to tropical deep convective systems. We propose to deploy the FAAM aircraft along with two dual-polarisation, Doppler radars and airborne and ground-based aerosol measurements to study the deep convective clouds that form over an isolated mountain range in New Mexico. The focus will be on the formation of ice from ice nucleating particles (INPs) (primary ice production) and by processes involving existing ice particles (secondary ice particle production), such as collisions. These observations will be used to test and further refine the representation of ice processes in climate models. Our approach recognises that in order to represent cloud feedbacks accurately a model needs to represent the individual processes within the system accurately. Demonstrating that the model is able reproduce the observed evolution of these clouds is therefore a necessary condition for the accurate prediction of cloud feedbacks.The research in DCMEX will have a robust pathway from a novel field campaign to more accurate estimates of climate sensitivity. This pathway is built with four integrated parts: new observations; the use of these observations and process modelling to derive new parametrisations; the use of existing in-situ data and satellite observations of anvils in tropical deep convection to validate the model; and use of the knowledge gained to improve and test the representation of microphysics in climate models. In particular, DCMEX will build on the experience of our groups in improving microphysical representation. A seamless suite of Met Office models will be used for convection- resolving simulations and global simulations with parametrised convection. Finally, simplified climate change (imposed warmer environment) experiments will be carried out to understand the role of the different microphysical processes on cloud feedbacks.