Far-IR cirrus cloud radiative properties from CAESAR observations

能够预测气候是现代科学的一项非常重要的任务。例如，在短期内，水手和农民需要知道明天或下周的天气情况。从中期来看，能源公司需要知道冬天是特别寒冷还是特别温和。从长远来看，气候变化是一个关键问题。在所有这些时间尺度上，同样的基本物理原理支配着气候。地球被阳光加热，这些热量通过风和海洋分布在全球各地，并以热量的形式重新释放回太空。加热和再排放（冷却）之间的平衡对保持气候稳定至关重要。作为气象学家和气候科学家，我们使用复杂的计算机模型来预测气候。虽然这些是世界上最大的计算机模拟，需要最先进的超级计算机来运行，但这些模型仍然是对真实情况的极大简化。为了使用这些模型，并确保它们给出正确的答案，我们需要用现实世界中记录的观察结果来测试它们。以云为例；云对大气有加热和冷却的作用。云将阳光反射回太空，从而冷却地球表面。但它们也会捕获地表散发的热量（因为它们很冷，向太空释放的能量比同等的无云天空少），并使地球变暖。这两种影响中哪一种最重要取决于云的高度和厚度，它是由水还是冰构成的，以及云中单个粒子的大小和形状。通过测量云散发的热量及其内部特性（或“微物理”），我们可以确定两者之间的联系，从而确定云对气候的总体影响。让事情变得更复杂的是，云发出的热量具有与可见光相似的光谱。就像彩色玻璃窗只允许某些颜色通过每块面板一样，云层比其他云层更能传输红外线（热）光谱的某些部分。如果你想象热光谱覆盖等效的红-紫可见光谱，我们对黄色到紫色部分了解很多，但对红色和橙色部分一无所知。因此，在气候模型中，我们不得不对光谱的这一部分做出有根据的猜测。我们现在有了一种新的仪器（叫做TAFTS），可以测量红外光谱的未知部分，所以在这个项目中，我们计划测量全红外光谱以及卷云微物理，最终完全了解两者在整个红外光谱中的联系。通过这一切，我们将更好地了解云对全球气候的影响，并将结果输入用于为水手、农民、能源公司和科学家预测天气的气候模型中。

Being able to predict the climate is a very important task for modern science. In the short term, sailors and farmers, for example, need to know what the weather will be like tomorrow, or next week. In the medium term, energy companies need to know if the winter will be particularly cold or mild. In the longer term, climate change is a key issue. On all these time scales the same basic physics governs the climate. The planet is heated by sunlight, this heat is distributed around the globe by the winds and the oceans and re-emitted as heat back into space. It is the balance between the heating and re-emission (cooling) that is critical in keeping our climate stable. As meteorologists and climate scientists, we use complicated computer models to predict the climate. Although these are some of the biggest computer simulations in the world and require state-of-the-art supercomputers to run, these models are still a vast simplification of what is really happening. To use these models, and be sure they give the right answers, we need to test them against observations recorded in the real world. Take clouds, for example; a cloud has both a heating and cooling effect on the atmosphere. Clouds reflect sunlight back into space, thus cooling the Earth's surface. But they also trap the heat emitted by the surface (as they are cold and emit less energy to space than an equivalent cloud-less sky) and warm the planet. Which of these two effects is the most important depends on how high and thick the cloud is, whether it is made of water or ice and the size and shape of the individual particles in the cloud. By measuring both the heat emitted by the cloud and its internal properties (or 'microphysics') we can determine the link between the two, and hence the overall effect the cloud is having on the climate. To make things more complicated the heat emitted by a cloud has a spectrum similar to visible light. And in the same way that a stained-glass window only allows certain colours through each panel, clouds transmit certain parts of the infrared (heat) spectrum better than others. If you imagine the heat spectrum to cover the equivalent red-violet visible spectrum, we know lots about the yellow to violet section, but nothing about the red and orange bit. Consequently, in the climate models we have had to make an educated guess about this section of the spectrum. We now have a new instrument (called TAFTS) that can measure the unknown parts of the infrared spectrum, so in this project we plan to measure the full infrared spectrum as well as the cirrus cloud microphysics to finally fully understand the link between the two throughout the infrared spectrum. By doing all this, we will have a better understanding of the effect of clouds on the global climate and feed the results into the climate models used to predict the weather for the sailors, farmers, energy companies and scientists.