Raman Lidar for Boundary-layer temperature profiling

大气边界层（ABL）是直接受地球表面影响的一层空气，高度一般在100米至3公里之间。因此，了解它是如何发展的是非常重要的，因为它将包含和化学处理所有排放到它的污染物。已知会发生某些过程，其中气团可以提升到ABL上方并运输到偏远地区。在这里，它们可以混合回ABL，并影响下游很长一段路（在某些情况下数百英里）的污染物浓度。一种类型的ABL被称为夜间边界层（NBL），顾名思义，它发生在夜间。在NBL中，温度分布很重要，因为它们决定了稳定性。正是这种稳定性影响了NBL的发展方式，包括雾的形成，之前被污染的空气的混合。本提案中提出的研究将有助于了解这些事件形成的过程，最终可能导致更准确的天气或污染预报。为了观察这些温度分布，可以使用气象气球，但要常规观察边界层的温度，这将是非常昂贵的。因此，一种不同的技术可以用来测量大气温度，具有足够高的时间分辨率，以观察混合过程。这种遥感技术被称为激光雷达（光探测和测距），它可以通过用光探测来远程测量大气的特性。激光雷达可用于测量微量气体，如臭氧、二氧化硫和水蒸气，以及大气的物理特性，如风、湿度和温度。因此，提出了一种激光雷达系统，该系统将能够测量夜间边界层发展过程中边界层温度分布的演变。该项目将测试使用现有激光雷达系统测量温度剖面的技术，该系统将进行修改。这将导致设计出一种紧凑、低功耗的激光雷达，可用于现场实验来测量NBL。激光雷达系统将使用一种新型二极管泵浦固体激光器，与传统的耗电脉冲激光器相比，该激光器最终将提供更高的温度曲线时间分辨率。

The atmospheric boundary layer (ABL) is the layer of air which is directly affected by the Earth's surface and generally is between 100 metres to 3 kilometres high. It is therefore very important to understand how it develops as it will contain and chemically process all pollutants emitted in to it. Certain processes are known to occur whereby air masses can be lifted above the ABL and transported to remote locations. Here they can be mixed back in to the ABL and affect the pollutant concentration a long way downstream (in some cases several hundred miles). One type of ABL is known as the nocturnal boundary layer (NBL) which as its name suggests takes place during the night. In the NBL, temperature profiles are important as they determine the stability. It is this stability that affects the way the NBL develops which could include fog formation, mixing in of previously polluted air. The research suggested in this proposal will help understand the processes involved in the formation of these events which may ultimately lead to more accurate weather or pollution forecasts. To observe these temperature profiles it is possible to use weather balloons, but to routinely observe the temperature of the boundary layer this would be prohibitively expensive. A different technology can therefore be used to measure the temperature of the atmosphere with a high enough time resolution to observe mixing processes. This remote sensing technique is known as LIDAR (LIght Detection And Ranging) and it can be used to remotely measure properties of the atmosphere by probing it with light. Lidar can be used to measure trace gases like ozone, sulphur-dioxide and water vapour as well as physical properties of the atmosphere like wind, humidity and temperature. A lidar system is therefore proposed that will be able to measure the evolution of boundary layer temperature profiles during the development of the nocturnal boundary layer. The project will involve testing the technology to measure temperature profiles using a pre-existing lidar system which will be modified. This will result in the design of a compact and low power consumption lidar that can be used in field experiments to measure the NBL. The lidar system will use a new diode pumped solid state laser which will ultimately allow a higher time resolution of temperature profiles compared to traditional power hungry pulsed laser.