DCMEX -- 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的不确定性。特别是由热带系统产生的风暴对云反馈的贡献很大。抗辐射性能、寿命和面积范围是关键参数。DCMEX将确定这些受云微物理影响的程度，甚至由云微物理控制，包括构成冰柱的冰粒的习性、浓度和大小，这反过来又取决于云混合相区域的微物理过程以及发生在冰柱本身的微物理过程。近年来，全球气候模型的复杂程度有了迅速的提高。然而，一些用来表示微物理过程的方程是基于对物理的理解比期望的要差。例如，Gettelman和Sherwood（2016）指出，由于微物理过程（如冰过程的处理）的不确定性，在确定不同全球模型的云反馈方面存在显著的差异。Ceppi等人（2017）还得出结论，在全球模型中准确地表示云及其辐射效应仍然具有挑战性，部分原因是难以表示云微物理，以及微物理和动力学之间的相互作用。控制热带砧状云不透明度和面积覆盖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体现。DCMEX将在现实世界的实验室对流云系统中进行云微物理的新测量，包括混合相位区域和砧状云，并改进和测试模型，然后将其应用于全球热带深层对流系统。我们建议部署faam飞机以及两个双偏振，多普勒雷达和机载和地面气溶胶测量来研究在新墨西哥州一个孤立的山脉上形成的深层对流云。重点将放在由冰成核粒子（初级冰的产生）和通过涉及现有冰粒子的过程（次级冰粒子的产生），如碰撞形成冰。这些观测结果将用于测试和进一步改进气候模式中的代表处过程。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内的各个过程。因此，证明该模式能够再现观测到的这些云的演变是准确预测云反馈的必要条件。DCMEX的研究将为从新的野外活动到更准确的气候敏感性估计提供一条强有力的途径。这条路径由四个组成部分组成：新的观测；利用这些观测和过程建模来推导新的参数化；利用现有的热带深层对流地温资料和卫星观测资料对模型进行验证；并利用所获得的知识来改进和测试气候模型中的微物理表征。特别是，DCMEX将以我们团队在改进微物理表示方面的经验为基础。英国气象局的一套无缝模型将用于对流解析模拟和对流参数化的全球模拟。最后，将进行简化的气候变化（强加的变暖环境）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 sensi-tivity by improving the representation of microphysical processes in global models. It is the anvilsproduced by tropical systems in particular that contribute significantly to cloud feedbacks. The anvilradiative properties, lifetimes and areal extent are the key parameters. DCMEX will determine theextent to which these are influenced, or even controlled by the cloud microphysics including thehabits, concentrations and sizes of the ice particles that make up the anvils, which in turn dependon the microphysical processes in the mixed-phase region of the cloud as well as those occurring inthe anvil itself.There has been a rapid advancement in the sophistication of global climate models in recentyears. Yet some of the equations used to represent microphysics processes are based on a poorerphysical understanding than desired. Gettelman and Sherwood (2016), for example pointed outthat there is significant spread in determining cloud feedbacks across different global models dueto 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 modelsremains challenging partly due to the difficulty in representing the cloud microphysics, as well as theinteractions 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 modelsand then apply them globally to tropical deep convective systems. We propose to deploy the FAAMaircraft along with two dual-polarisation, Doppler radars and airborne and ground-based aerosolmeasurements to study the deep convective clouds that form over an isolated mountain range inNew Mexico. The focus will be on the formation of ice from ice nucleating particles (INPs) (primaryice 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 ofice 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 thereforea 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 accurateestimates 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 ofexisting in-situ data and satellite observations of anvils in tropical deep convection to validate themodel; and use of the knowledge gained to improve and test the representation of microphysicsin climate models. In particular, DCMEX will build on the experience of our groups in improvingmicrophysical representation. A seamless suite of Met Office models will be used for convection-resolving simulations and global simulations with parametrised convection. Finally, simplified climatechange (imposed warmer environment) experiments will be carried out to understand the role of thedifferent microphysical processes on cloud feedbacks.