Elevated Moist Layers – Using HALO during EUREC4A to explore a blind spot in the global satellite observing system

前两次HALO活动（NARVAL-1和NARVAL-2）的数据表明，在热带对流层低层，升高的湿层并不罕见。升高的湿层迄今没有得到更多的关注，其主要原因可能是它们难以在卫星湿度廓线测量中探测到。全球观测系统中的这一盲点是气候研究的一个重要问题，因为它会使平均湿度廓线看起来比实际情况更接近底部，从而影响气候敏感性估计，因为气候敏感性的很大一部分差异可以用海洋上空对流层低层内湿度垂直混合的模式多样性来解释，平均垂直湿度廓线是一个很好的诊断方法。为什么像SAPHIR和IASI这样的被动探测器在探测高湿层方面如此之差，这一点一点也不明显。该项目将检验这一假设，即它与往往伴随着潮湿层的逆温有关。利用EUREC 4A活动数据，它将量化和分析这个问题，并在此分析的基础上，试图开发一个新的IASI湿度廓线数据产品，更好地代表高架潮湿层。HALO活动数据也将用于确认新产品。此外，该项目还将有助于改进整个活动区域的卫星湿度分布图，供欧洲区域经济合作第四阶段A项目和国际科学界使用。

Data from two previous HALO campaigns (NARVAL-1 and NARVAL-2) indicate that elevated moist layers are not uncommon in the tropical lower troposphere. Perhaps the main reason why elevated moist layers have hitherto not received more attention is that they are difficult to detect in satellite humidity profile measurements. This blind spot in the global observing system is an important issue for climate research, since it would make humidity profiles on average appear more bottom-heavy than they are in reality, which would affect climate sensitivity estimates, since a large part of the variance in climate sensitivity can be explained by model diversity in the vertical mixing of moisture within the lower troposphere over oceans, for which the mean vertical moisture profile is a good diagnostic.It is not at all obvious why passive sounders like SAPHIR and IASI are so poor in detecting elevated moist layers. The project will test the hypothesis that it is related to the temperature inversions that tend to accompany moist layers. Using the EUREC4A campaign data, it will quantify and analyse the problem, and on the basis of this analysis attempt to develop a new IASI humidity profile data product that better represents the elevated moist layers. The HALO campaign data will also be used to validate the new product. Furthermore, the project will contribute improved satellite humidity profiles across the entire campaign area for use by other EUREC4A projects and the international scientific community.