Hunga Tonga-Hunga Ha'apai: a paradigm-changing eruption

2022年的Hunga Tonga-Hunga Ha'apai火山喷发（HT-HH）是30年来最强烈的火山喷发。这次喷发挑战了许多关于火山羽流对大气和气候影响的先入之见，并呼吁人们采用新的、更全面的方法来研究火山羽流。这将提高未来的监测能力，加强对羽流动力学和影响的了解。监测火山羽流很重要，原因有很多，包括它们对气候的影响。这种气候影响通常是由二氧化硫（SO2）的排放驱动的。这种气体可以转化为硫酸盐气溶胶，使入射的太阳辐射偏转，导致地球变冷。尽管喷发强度很大，但HT-HH只排放了少量的二氧化硫，不足以导致冷却。然而，由于它是海底火山，喷发向大气中注入了大量的水蒸气。水蒸气是一种温室气体，与“正常的”火山喷发对气候的影响不同，这次火山喷发预计会对对流层产生变暖效应：放大人为驱动的气候变化。在以前的火山-大气-气候相互作用的研究中，水蒸气在很大程度上被忽视了，需要进一步的研究。它还有一个额外的作用，即引起硫酸盐气溶胶的迅速出现：可能是通过加速二氧化硫向硫酸盐的转化，或者更直接地从海水中的硫酸盐转化。硫酸盐的早期形成也在其他火山喷发中被发现。无论形成机制如何，硫酸盐气溶胶的早期出现意味着单靠二氧化硫的测量（传统方法）不足以量化向大气中排放的硫。研究火山羽流的另一个动机是它们的危险性，尤其是对航空的危险性。火山灰会对飞机造成重大损害，在某些情况下，严重到会导致发动机故障，甚至可能危及生命。火山气体也会损坏飞机。因此，监测这些羽流对于尽量减少它们带来的危害至关重要。卫星数据在监测和研究火山羽流方面起着重要作用。HT-HH火山爆发已经确定了一些需要改进的地方，这些地方可以通过使用新的仪器进行频繁的全球观测来解决（过去的火山爆发无法使用）。该项目将开发用于量化火山羽流特性的下一代卫星检索。这些将用于红外大气探测干涉仪（IASI）：一种对多种类型的火山羽流敏感的气象卫星仪器。新的检索将更加全面：同时获取有关水蒸气、二氧化硫、硫酸盐和火山灰的信息，而不是单独处理它们。这将使它们成为检测危害和提供数据以快速评估气候影响的宝贵工具。与英国气象局密切合作，将确保新开发的工具可用于未来的火山喷发事件，从而确保项目的持久影响。随着这些检索的发展，它们将与其他数据集一起应用于详细研究HT-HH。气候影响模型和季节预报将根据新卫星数据的结果初始化，用于研究这次喷发对气候和大气动力学的未来影响。这将有助于更好地理解这一不寻常的事件。其影响超出了这次喷发，因为将这些检索结果应用于研究其他喷发事件将有助于提高对火山羽流动力学的理解。HT-HH喷发引发了许多关于火山羽流的问题。这很可能会对未来几十年的研究方向产生持久的影响，而这个项目将在其中发挥关键作用。

The 2022 eruption of Hunga Tonga-Hunga Ha'apai (HT-HH) is the most intense volcanic eruption in 30 years. The eruption challenges many preconceptions about the impact of volcanic plumes on the atmosphere and climate, and calls for new, more comprehensive methods for studying volcanic plumes. These would improve future monitoring capability and enhance understanding of plume dynamics and impacts. Monitoring volcanic plumes is important for a number of reasons including their climatic impact. This climate impact is usually driven by the emission of sulphur dioxide (SO2). This gas can be converted to sulphate aerosol which deflects incoming solar radiation and causes planetary cooling. Despite the intensity of the eruption, HT-HH emitted only small quantities of SO2: not sufficient to cause cooling. However, due to it being a submarine volcano, the eruption injected significant quantities of water vapour into the atmosphere. Water vapour is a greenhouse gas and in contrast to 'normal' eruption-climate impacts, the eruption is expected to have a warming effect in the troposphere: amplifying anthropogenically driven climate change. Water vapour has been largely neglected in previous studies of volcano-atmosphere-climate interactions and requires significant further study. It has an additional effect of causing the rapid emergence of sulphate aerosol: possibly through accelerating the conversion of SO2 to sulphate, or more directly from sulphate in seawater. Early formation of sulphate has also been identified during other eruptions. Regardless of the formation mechanism, early emergence of sulphate aerosol means that measurements of SO2 alone (the conventional approach), are not sufficient for quantifying the emission of sulphur to the atmosphere. Another motive for studying volcanic plumes is their hazardous nature, in particular, to aviation. Volcanic ash can cause significant damage to aircraft, in some cases so severe that it causes engine failure and potentially life-threatening circumstances. Volcanic gases can also damage aircraft. Monitoring these plumes is therefore essential to minimize the hazard they present. Satellite data plays an important part of monitoring and studying volcanic plumes. The HT-HH eruption has identified a number of areas for improvement which can be adressed with new instrumentation making frequent global observations (unavailable for past eruptions). This project will develop the next generation of satellite retrievals for the quantification of volcanic plume properties. These will be developed for the Infrared Atmospheric Sounding Interferometer (IASI): a meteorological satellite instrument with sensitivity to multiple types of volcanic plumes. The new retrievals will be more comprehensive: simultaneously obtaining information about water vapour, SO2, sulphate and volcanic ash, rather than treating them separately. This will make them valuable tools for both hazard detection and providing data to rapidly assess climate impacts. Working closely with the UK Met Office will ensure the newly developed tools can be used operationally for future eruptive events, so ensuring a lasting impact from the project. Following the development of these retrievals, they will be applied, along with other datasets, to study the HT-HH in detail. Climate impact models and seasonal forecasts, initialized with results from the new satellite data, will be used to study the future impact of this eruption on climate and atmospheric dynamics. This will build a better understanding of this unusual event. The impact goes beyond this eruption, as applying the retrievals to study other eruptive events will help to improve understanding of volcanic plume dynamics. The HT-HH eruption has raised numerous questions about volcanic plumes. It is likely that this will have a lasting impact on the direction of research over the next few decades, with this project playing a key role in this.