Moisture structure in the dry intrusion origin region and its inflow - impact of diabatic processes (NAWDIC-DImoist)

• Applicant: Professorin Dr. Annette Miltenberger
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552800876

Extratropical cyclones are defining feature of mid-latitude weather and climate and are as well as the associated fronts also responsible for significant and high-impact weather. The flow pattern constituting extratropical cyclones features several distinct coherent airstreams including the warm-conveyor belt and the dry intrusion. These airstreams connect the boundary layer to the upper troposphere and vice-versa. Thereby they provide a pathway of propagation of forecast errors between upper- and lower troposphere. Noticeably this includes also transport of trace constituents such as water vapor and ozone as well as forecast uncertainties in their geographical distribution. It is well-established that moist processes strongly impact the dynamics of extratropical cyclones and associated airstream. Nevertheless, meso- and synoptic-scale variability of humidity in the upper troposphere and lower stratosphere (UTLS) is poorly characterized and its representation in current reanalysis products has known biases. The central aim of the NAWDIC-DImoist is (i) a characterization of UTLS water vapor variability with a focus on the dry intrusion origin region and (ii) an understanding of the impacts of UTLS moisture structure on the flow evolution and predictability. We first characterize the climatological UTLS moisture structure and its variability in the dry intrusion origin region based on existing reanalysis and observational data. The physical processes responsible for the formation of the moisture structure are investigated. Secondly, we combine high-resolution modeling with in-situ observations from NAWDIC-HALO and its US partner missions to establish a detailed representation of the UTLS moisture structure in the dry intrusion inflow and descent region. The targeted in-situ observations constitute a much needed information source due to general sparsity of high-quality moisture data in the UTLS. Advanced Lagrangian diagnostics will be used to link different observations in the North Atlantic region in a physically consistent manner and provide an additional interpretation framework for the observations. Finally, we will quantify the impact of the UTLS moisture structure on the larger-scale thermodynamic state of the atmosphere, including radiative heating profiles and diabatic modifications of the large-scale flow. The impact of (mis-)representing the UTLS moisture structure for forecasting the dry intrusion dynamics as well as the evolution of downstream upper tropospheric flow features is analyzed. NAWDIC-DImoist thereby combines advanced high-resolution modeling with detailed insitu observations to develop a comprehensive view of the physical processes shaping upper tropospheric humidity structures in relation with the dry intrusion as well as its impact on the flow dynamics. This contributes to the understanding of UTLS, which is known to be a key region in assessing future changes in the humidity distribution and associated radiative forcing.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1294: Atmospheric and Earth System Research with the "High Altitude and Long Range Research Aircraft" (HALO)
• Co-Investigators: Professorin Dr. Corinna Hoose; Dr. Annika Oertel