Saharan - West African Monsoon Multi-scale Analysis (SWAMMA)

西非季风对数百万人的生计至关重要，但仍然是天气和气候预测的主要挑战。季风为大规模雷暴系统提供了水分，这些雷暴系统为萨赫勒地区提供了年降雨量。季风是由夏季大陆上的热量驱动的。撒哈拉沙漠夏季气温最高，众所周知，季风对撒哈拉和萨赫勒地区的加热很敏感。撒哈拉沙漠的热量由灰尘、云和来自撒哈拉沙漠边缘的冷空气的通风控制。众所周知，模型在这一地区表现出重大差异，这对季风爆发很重要，但历史上一直缺乏评估模型的数据。最近的研究表明，季风，沙尘和风暴系统形成一个完全耦合的系统，全球模式在这个系统内的耦合表现出重大的偏差。业务模型未能捕捉季风雨的组织，位置和时间，这导致风暴系统和季风之间的不正确耦合。业务模式也未能代表由风暴系统产生的哈布布沙尘暴，这可能是夏季沙尘排放的主要驱动力。这意味着，即使是包含沙尘的业务模型也无法准确捕捉沙尘对气象的影响，因为模型中缺少一个主要的沙尘排放机制。最近的研究还表明，撒哈拉沙漠上空存在比以前观测到的更大的尘埃颗粒，这将影响加热速率，反馈到气象学上。SWAMMA将汇集一个最近开发的模型，该模型可以首次捕获这些耦合与最近从这个高度数据稀疏的区域获得的数据（在NERC资助的AMMA和Fennec项目期间收集）。因此，SWAMMA将首次将联合收割机与能够代表季风系统夏季能量收支关键特征的模型相结合，并提供足以评估这种模型的第一批数据。SWAMMA将评估新模型，量化在撒哈拉和萨赫勒产生沙尘的风。它将利用新的数据分析尘埃颗粒大小变化的影响。SWAMMA将使用AMMA和Fennec的模型和观测结果评估季风系统的能量收支。SWAMMA将量化季风系统的耦合过程如何响应季风边界条件的季节演变，以控制季风降雨的季节稳定性及其变化。通过将最近获得的数据和新模型与现有的天气和气候模型结合起来，该项目将评估业务模型中的过程误差如何导致西非和全球预测的系统性误差。该项目将为业务模型必须捕捉的过程提供度量标准，以便捕捉西非季风系统的关键过程和耦合。

The West African Monsoon is critical to the livelihoods of millions, but remains a major challenge for weather and climate prediction. The monsoon provides moisture for large systems of thunderstorms that provide the annual rainfall in the Sahel. The monsoon is driven by the summertime heating over the continent. The Sahara exhibits the highest summertime temperatures and it is known that the monsoon is sensitive to the heating in the Sahara and the Sahel. The heating in the Sahara is controlled by dust, cloud and ventilation by colder air from the Sahara's margins. It is known that models exhibit major differences in this region, which is for example important for monsoon onset, but historically there has been an absence of data with which to evaluate models. Recent research has shown that the monsoon, dust and the storm-systems form a fully coupled system and that global models exhibit major biases in the couplings within this system. Operational models fail to capture the organisation, location and timing of the monsoon rains and this leads to incorrect coupling between the storm systems and the monsoon. Operational models also fail to represent the haboob dust storms generated by the storm systems, which are likely the main driver of dust emission in the summer. This means that even operational models which include dust fail to accurately capture the impacts of the dust on the meteorology, since a major dust emission mechanism is missing in the models. Recent research has also shown the existence of larger dust particles over the Sahara than previously observed, which will affect heating rates, feeding back on to the meteorology. SWAMMA will bring together a recently-developed model that can for the first time capture these couplings with recently-acquired data from this highly data-sparse region (collected during the NERC-funded AMMA and Fennec projects). SWAMMA will therefore combine for the first time a model that should be able to represent the key features of the summertime energy budget of the monsoon system with the first data sufficient to evaluate such a model. SWAMMA will evaluate the new model, quantifying the winds that generate dust uplift in the Sahara and Sahel. It will use the new data to analyse the impacts of variations in the sizes of dust particles. SWAMMA will evaluate the energy budgets of the monsoon system using both models and observations from AMMA and Fennec. SWAMMA will quantify how the coupled processes of the monsoon system respond to the seasonal evolution of the monsoon's boundary conditions to control the seasonal stability of the monsoon rainfall and its variability. By bringing together the recently-acquired data and the new model with existing weather and climate models the project will evaluate how process errors in operational models lead to systematic errors in predictions, both over West Africa and globally. The project will provide metrics for the processes that must be captured by operational models for them to capture the key processes and couplings in the West African monsoon system.