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，在热带对流层下层，潮湿层的升高并不罕见。高湿层迄今未受到更多关注的主要原因可能是它们难以在卫星湿度剖面测量中被探测到。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剖面看起来比实际情况更重，这将影响气候敏感性的估计，因为气候敏感性的很大一部分差异可以用海洋对流层下层水汽垂直混合的模式多样性来解释，平均垂直湿度剖面是一个很好的诊断。为什么像sapir和IASI这样的被动测深仪在探测升高的潮湿层方面如此糟糕，这一点也不明显。该项目将测试这一假设，即它与伴随潮湿层的温度逆温有关。使用EUREC4A活动数据，它将量化和分析问题，并在此分析的基础上尝试开发新的IASI湿度剖面数据产品，以更好地代表升高的潮湿层。HALO活动数据也将用于验证新产品。此外，该项目将改善整个活动区域的卫星湿度剖面，供其他EUREC4A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.