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)。水蒸气是红外能量的强吸收者，额外的水蒸气会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，这会对气候变化后降水量的变化产生全球影响。存在重大的知识差距，阻碍了对全球降水对气候变化的反应的深入了解。ASPIC将通过一项范围广泛的研究来填补其中的一些空白，研究重点是水蒸气吸收红外辐射的一个重要但不确定的成分，即所谓的“连续体”。根据ASPIC，将利用最新的技术发展来开发一种新的实验室设备，用于测量水蒸气连续体。然后，这个新的设备将被用来进行一系列新颖的测量。然后，这些测量将进入最先进的详细计算，该计算将检查实验室测量对我们对气候和气候变化的理解所产生的影响；这些新的详细计算还将纳入该地区的其他最新发展，以促进全面评估。目前实验室对所谓的近红外波长区域的水蒸气连续吸收的相当少的测量显示出明显的分歧，而对这些差异的满意解释被证明是难以捉摸的。此外，这种吸收如何随温度变化存在很大的不确定性，而且现有的测量结果都没有扩展到“室温”以下，达到大气中普遍经历的温度。在试点项目取得成功之后，将利用新颖的“超连续”激光与其他进展一起，在近红外波长区域和比以前的测量更接近大气的温度范围内进行高精度测量。两种互补的光谱技术将被用来对结果进行交叉检查。这些结果将被纳入详细的辐射传输计算中，这些计算将被用来显著提高对大气中太阳辐射的吸收将如何随着气候变暖和水蒸气浓度增加而变化的理解。现有的计算使用了不太详细的方法，表明了强烈的不确定性，这会对气候变暖时降雨量将如何变化的预测产生影响。考虑到在受控的实验室条件下测量相对较弱的红外吸收的困难，以及需要开发一种超越当前现状的先进的新测量系统，拟议的测量本身就存在风险。然而，ASPIC建立在STFC资助的一个试点项目的基础上，该项目于2015年完成，由主要和联合调查员参与：“使用超连续谱源测量微弱的水蒸气吸收”对于清楚地展示在这类工作中使用超连续谱激光的可行性，从而降低ASPIC的总体风险非常重要。雷尔空间(将在那里开发光谱仪和进行测量)在开发新的光谱技术方面的丰富经验也为排除出现的任何困难提供了重要资源。尽管存在这种风险，但成功这样做的收益将是巨大的，不仅从气候角度来看，而且对于使用相同波长区域来监测气溶胶、云和地球表面的测量技术也是如此。它们还将有助于理解水蒸气的基本光谱性质。

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.