A Differential Absorption LiDAR for Measurement of Greenhouse Gases

我们这个时代一个悬而未决的重大科学问题是——我们排放到大气中的所有碳都去了哪里？考虑到海洋、森林和农业等一系列可能的候选者，这是一个难以回答的问题。我们所知道的是，不确定性是存在的，我们在全球碳平衡中有一个“缺失的碳汇”。如果我们想要通过控制碳的自然来源和汇来减缓全球变化，我们需要知道碳平衡和碳在陆地-海洋-大气系统中的命运。碳循环科学的新学科才刚刚开始，我们的DIAL系统是观察和理解从陆地和水系统进入和离开大气的各种形式的碳的理想场所。DIAL MGG的相对低成本和自主运行意味着许多可以部署在偏远地区，覆盖世界上目前没有观测的部分地区。DIAL MGG可以作为美国、欧洲和日本科学网络现有测量的补充技术。科学家们目前使用天气模型，通过测量经过观测点仪器的碳来确定碳的来源；这样就可以估算出大气中高达5-7公里的碳含量，然后他们就可以计算出区域和大陆尺度上的碳交换。DIAL MGG也是对卫星观测的补充，因为卫星不能在大气层较低的几公里范围内解决非常详细的问题，只能给出列积分值。DIAL MGG可以在低层大气中每隔几百米返回一次CO2和CH4的浓度。经过一段时间的评估，当DIAL MGG根据当前的方法和技术进行校准后，我们认为DIAL MGG可能最终取代当前的方法。了解碳在大气中的流向具有经济和政治价值。碳交易仍处于起步阶段，但一系列DIAL MGG仪器，例如，放置在热带森林的上风和下风处，作为碳信用额支付的碳汇，将明确证明该森林的碳汇（或源）强度。类似地，任何拟议的页岩气地点的泄漏都可以通过DIAL MGG仪器独立和定量地观察到。在这个项目中部署的STFC专业知识对成功至关重要的例子包括：-指定适当的望远镜组件以产生期望的性能；-设计和制造一个定制的光学系统，使激光发射与望远镜对齐；-探测器的对准。

One of the great unanswered science questions of our time is - just where does all the carbon go that we emit into the atmosphere? It is a surprisingly difficult question to answer given there are a range of possible candidates such as oceans, forests and agriculture. What we do know is that uncertainty exists and we have a 'missing carbon sink' in the global carbon balance. We need to know the carbon balance and the fate of carbon in our land-ocean-atmosphere system if we can ever aim to mitigate global change by manipulating natural sources and sinks of carbon. The new discipline of Carbon Cycle Science is just beginning and our DIAL system is ideally placed to observe and understand carbon in various forms moving, from terrestrial and water systems, into and out of the atmosphere. The relatively low-cost and autonomous operation of the DIAL MGG means that many can be deployed in remote areas, covering parts of the world where no observations are currently made. The DIAL MGG can be used as a complementary technique to existing measurements covered by scientific networks in the USA, Europe and Japan. Scientists currently use weather models to determine where the carbon comes from by measuring carbon that passes an instrument at an observation point; this allows estimates of carbon up to 5-7 km in the atmosphere and they can then work out carbon exchange on regional and continental scales.DIAL MGG is also complementary to satellite observations since satellites cannot resolve great detail within the lower several kilometres of the atmosphere and can only give column-integrated values. The DIAL MGG can return CO2 and CH4 concentrations every few hundred metres in the lower atmosphere. After a period of assessments when DIAL MGG is calibrated against current methods and technology we believe that the DIAL MGG may ultimately replace current methods. There is economic and political value in knowing where carbon is flowing in the atmosphere. Carbon trading is still in its infancy but a series of DIAL MGG instruments, for instance, located upwind and downwind of a tropical forest being offered as a carbon sink for payment of Carbon credits, would prove unequivocally what the sink (or source) strength was for that forest. Similarly, leakage from any proposed shale gas site could be observed independently and quantitatively by a number of DIAL MGG instruments.Examples of the STFC expertise being deployed on this project which are critical to success include:- Specifying appropriate telescope components to produce the desired performance;- Designing and manufacturing a bespoke optical system to launch the laser in alignment with the telescope;- Alignment of the Detector.