Abstract
Abstract. The tropical tropopause layer (TTL; 14–18.5 km) is the gateway for most air entering the stratosphere, and therefore processes within this layer have an outsized influence in determining global stratospheric ozone and water vapor concentrations. Despite the importance of this layer there are few in situ measurements with the necessary detail to resolve the fine-scale processes within this region. Here, we introduce a novel platform for high-resolution in situ profiling that lowers and retracts a suspended instrument 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 vertical resolution. The instrument system integrates proven sensors for water vapor, temperature, pressure, and cloud and aerosol particles with an innovative mechanical reeling and control system. A technical evaluation of the system performance demonstrated the feasibility of this new measurement platform for future missions with minor modifications. Six instruments planned for two upcoming field campaigns are expected to provide over 4000 profiles through the TTL, quadrupling the number of high-resolution aircraft and balloon profiles collected to date. These and future measurements will provide the necessary resolution to diagnose the importance of competing mechanisms for the transport of water vapor across the TTL.
Highlights
Super-pressure balloons are emerging as a practical platform for Earth science observations at altitudes from the upper troposphere to the mid-stratosphere, carrying payloads ranging from a few up to thousands of kilograms with durations ranging from weeks to close to a year
The instrument system consists of three primary assemblies: a reeling system that is contained within the primary balloon gondola, a smaller sub-gondola or profiler that is lowered from the primary gondola, and a suite of sensors within the profiler that measure position, temperature, pressure, water vapor, and aerosol and cloud particles
Reeldown Aerosol Cloud Humidity and Temperature Sensor (RACHuTS) consists of three main subsystems: the reeling system, the profiler gondola, and the profiler sensor suite, consisting of a temperature and pressure sensor (TSEN, Thermodynamical SENsor), water vapor sensor (FLASH-B, Fluorescence Lyman-Alpha Stratospheric Hygrometer), and cloud and aerosol sensor (ROPC, RACHuTS optical particle counter)
Summary
Super-pressure balloons are emerging as a practical platform for Earth science observations at altitudes from the upper troposphere to the mid-stratosphere, carrying payloads ranging from a few up to thousands of kilograms with durations ranging from weeks to close to a year. The Reeldown Aerosol Cloud Humidity and Temperature Sensor (RACHuTS) is an instrument system developed to perform profile measurements of the atmosphere up to 2 km below a super-pressure balloon (Fig. 1). The instrument system consists of three primary assemblies: a reeling system that is contained within the primary balloon gondola, a smaller sub-gondola or profiler that is lowered from the primary gondola, and a suite of sensors within the profiler that measure position, temperature, pressure, water vapor, and aerosol and cloud particles. The RACHuTS instrument was designed for the Stratéole 2 field experiment – a series of long-duration ballooning campaigns to study the tropical tropopause layer (TTL) using a constellation of super-pressure balloons circling the Earth at the Equator (Haase et al, 2018). This work describes the RACHuTS instrument design and operation, the technical performance of the overall instrument system during the Stratéole 2 engineering test campaign, and the scientific performance of the sensors within the profiler
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