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  1. Abstract

    Atmospheric waves in the tropical tropopause layer are recognized as a significant influence on processes that impact global climate. For example, waves drive the quasi‐biennial oscillation (QBO) in equatorial stratospheric winds and modulate occurrences of cirrus clouds. However, the QBO in the lower stratosphere and thin cirrus have continued to elude accurate simulation in state‐of‐the‐art climate models and seasonal forecast systems. We use first‐of‐their‐kind profile measurements deployed beneath a long‐duration balloon to provide new insights into impacts of fine‐scale waves on equatorial cirrus clouds and the QBO just above the tropopause. Analysis of these balloon‐borne measurements reveals previously uncharacterized fine‐vertical‐scale waves (<1 km) with large horizontal extent (>1000 km) and multiday periods. These waves affect cirrus clouds and QBO winds in ways that could explain current climate model shortcomings in representing these stratospheric influences on climate. Accurately simulating these fine‐vertical‐scale processes thus has the potential to improve sub‐seasonal to near‐term climate prediction.

  2. Abstract. The tropical tropopause layer (TTL; 14–18.5 km) is the gateway formost air entering the stratosphere, and therefore processes within thislayer have an outsized influence in determining global stratospheric ozoneand water vapor concentrations. Despite the importance of this layer thereare few in situ measurements with the necessary detail to resolve the fine-scale processes within this region. Here, we introduce a novel platform forhigh-resolution in situ profiling that lowers and retracts a suspendedinstrument package beneath drifting long-duration balloons in the tropics.During a 100 d circumtropical flight, the instrument collected over a hundred 2 km profiles of temperature, water vapor, and aerosol at 1 m resolution, yielding unprecedented geographic sampling and verticalresolution. The instrument system integrates proven sensors for water vapor,temperature, pressure, and cloud and aerosol particles with an innovativemechanical reeling and control system. A technical evaluation of the systemperformance demonstrated the feasibility of this new measurement platformfor future missions with minor modifications. Six instruments planned fortwo upcoming field campaigns are expected to provide over 4000 profilesthrough the TTL, quadrupling the number of high-resolution aircraft andballoon profiles collected to date. These and future measurements willprovide the necessary resolution to diagnose the importance of competingmechanisms for the transport of water vapor across the TTL.