Advanced Spectroscopy for improved characterisation of the near-Infrared water vapour Continuum (ASPIC)

例如，由二氧化碳浓度变化驱动的气候变化导致大气中水蒸气浓度的进一步变化（或反馈）。水蒸气是红外线能量的强吸收剂，额外的水蒸气导致原本会发生的变暖增加50-100%。它还导致大气和地表吸收的能量分配发生重大变化。众所周知，这会对气候变化后的降水变化产生全球影响。存在着重大的知识差距，妨碍了对全球降水对气候变化的反应的深入了解。ASPIC将通过一项广泛的研究来解决其中的一些差距，重点关注水蒸气吸收红外辐射的一个重要但不确定的组成部分，即“连续统”。在ASPIC下，将利用最新的技术发展来开发一种新的实验室设施，用于测量水蒸气连续体。然后，这个新设施将用于进行一组新的测量。然后，这些测量结果将被纳入详细的最先进的计算，这将研究实验室测量结果对我们了解气候和气候变化的影响;这些新的详细计算还将纳入该地区的其他最新发展，现有的相当少的实验室测量的水蒸气连续吸收在所谓的近-红外波长区域显示出明显差异，且对这些差异的令人满意的解释已被证明是难以捉摸的。此外，在这种吸收如何随温度变化方面存在很大的不确定性，并且现有的测量方法都没有在“室温”以下扩展到大气中广泛经历的温度。在一个成功的试点项目之后，将利用新型“超连续”激光器以及其他先进技术，在近红外波长区域和比以前的测量更与大气相关的温度范围内进行高精度测量。将使用两种互补的光谱技术对结果进行交叉核对，然后将这些结果纳入详细的辐射转移计算，这些计算将用于大大提高对大气中太阳辐射吸收如何随着气候变暖和水蒸气浓度增加而变化的认识。现有的计算，使用不太详细的方法，显示出很强的不确定性，对气候变暖下降雨量将如何变化的预测产生影响。鉴于在受控实验室条件下测量相对较弱的红外吸收的困难以及开发超越当前现状的先进新测量系统的需要，拟议的测量具有固有的风险。然而，ASPIC建立在STFC资助的试点项目的基础上，该项目涉及2015年完成的主要研究者和共同研究者：“使用超连续光源测量弱水蒸气吸收”对于明确证明在此类工作中使用超连续激光的可行性非常重要，因此可以减轻ASPIC的整体风险。RAL Space在开发新型光谱技术方面的丰富经验（光谱仪将在那里开发并进行测量）也为解决出现的任何困难提供了重要资源。尽管存在这种风险，但成功做到这一点不仅从气候角度来看，而且对于使用同一波长区域监测气溶胶、云和地球表面的测量技术来说，都是非常重要的。它们还将有助于了解水蒸气的基本光谱特性。

Climate change driven by, for example, changes in concentrations of carbon dioxide, leads to further changes (or feedbacks) in the concentration of water vapour in the atmosphere. Water vapour is a strong absorber of infrared energy and the additional water vapour leads to a 50-100% increase in the warming that would otherwise occur. It also leads to significant changes in the partitioning of energy absorbed by the atmosphere and surface. This is known to exert a global-level influence on the change in precipitation following climate change. There are major knowledge gaps which inhibit a robust understanding of the global precipitation response to climate change. ASPIC will tackle some of these gaps via a wide-ranging study focusing on one important, but uncertain, component of absorption of infrared radiation by water vapour, known as the "continuum". Under ASPIC, latest technological developments will be exploited to develop a new laboratory facility for measuring the water vapour continuum. This new facility will then be used to make a novel set of measurements. These measurements will then feed into detailed state-of-the-art calculations, which will examine the implications arising from the laboratory measurements for our understanding of climate and climate change; these new detailed calculations will also incorporate other recent developments in the area, facilitating a rounded assessment.The rather few existing laboratory measurements of water vapour continuum absorption in the so-called near-infrared wavelength region show marked disagreements, and a satisfactory explanation of these differences has proved elusive. Further, there are large uncertainties in how this absorption varies with temperature, and none of the existing measurements extend below "room temperature" to the temperatures widely experienced in the atmosphere. Following a successful pilot project, novel "super-continuum" lasers will, together with other advances, be exploited to make measurements of high-accuracy across the near-infrared wavelength region and across a temperature range more relevant to the atmosphere than earlier measurements. Two complementary spectroscopic techniques will be used to allow cross-checking of the results.These results will then be incorporated into detailed radiative transfer calculations that will be used to significantly improve understanding of how absorption of solar radiation in the atmosphere will change as the climate warms, and water vapour concentrations increase. Existing calculations, which have used less-detailed methods, indicate strong uncertainties, with consequences for predictions of how rainfall will change in a warming climate. The proposed measurements are inherently risky, given the difficulty of measuring the relatively weak infrared absorption under controlled laboratory conditions and the need to develop an advanced new measurement system which goes beyond the current status quo. However, ASPIC builds on an STFC-funded pilot project involving the Principal and Co-Investigator that was completed in 2015: "Measuring weak water vapour absorption using a super-continuum source" was important in clearly demonstrating the feasibility of using super-continuum lasers in such work, and therefore in mitigating the overall risk in ASPIC. The depth of experience at RAL Space (where the spectrometers will be developed and the measurements made) in developing novel spectroscopic techniques also provides an important resource for troubleshooting any difficulties that arise. Despite this risk, the gain from doing so successfully would be significant not only from a climate perspective, but also for measurement techniques that use this same wavelength region to monitor aerosols, clouds and the Earth's surface. They would also contribute to understanding the fundamental spectroscopic properties of water vapour.