Evaluation of ARM tethered-balloon system instrumentation for supercooled liquid water and distributed temperature sensing in mixed-phase Arctic clouds

Abstract

Abstract. A tethered-balloon system (TBS) has been developed and is being operated by Sandia National Laboratories (SNL) on behalf of the U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) User Facility in order to collect in situ atmospheric measurements within mixed-phase Arctic clouds. Periodic tethered-balloon flights have been conducted since 2015 within restricted airspace at ARM's Advanced Mobile Facility 3 (AMF3) in Oliktok Point, Alaska, as part of the AALCO (Aerial Assessment of Liquid in Clouds at Oliktok), ERASMUS (Evaluation of Routine Atmospheric Sounding Measurements using Unmanned Systems), and POPEYE (Profiling at Oliktok Point to Enhance YOPP Experiments) field campaigns. The tethered-balloon system uses helium-filled 34 m3 helikites and 79 and 104 m3 aerostats to suspend instrumentation that is used to measure aerosol particle size distributions, temperature, horizontal wind, pressure, relative humidity, turbulence, and cloud particle properties and to calibrate ground-based remote sensing instruments. Supercooled liquid water content (SLWC) sondes using the vibrating-wire principle, developed by Anasphere Inc., were operated at Oliktok Point at multiple altitudes on the TBS within mixed-phase clouds for over 200 h. Sonde-collected SLWC data were compared with liquid water content derived from a microwave radiometer, Ka-band ARM zenith radar, and ceilometer at the AMF3, as well as liquid water content derived from AMF3 radiosonde flights. The in situ data collected by the Anasphere sensors were also compared with data collected simultaneously by an alternative SLWC sensor developed at the University of Reading, UK; both vibrating-wire instruments were typically observed to shed their ice quickly upon exiting the cloud or reaching maximum ice loading. Temperature sensing measurements distributed with fiber optic tethered balloons were also compared with AMF3 radiosonde temperature measurements. Combined, the results indicate that TBS-distributed temperature sensing and supercooled liquid water measurements are in reasonably good agreement with remote sensing and radiosonde-based measurements of both properties. From these measurements and sensor evaluations, tethered-balloon flights are shown to offer an effective method of collecting data to inform and constrain numerical models, calibrate and validate remote sensing instruments, and characterize the flight environment of unmanned aircraft, circumventing the difficulties of in-cloud unmanned aircraft flights such as limited flight time and in-flight icing.

Assessing the vertical structure of Arctic aerosols using balloon-borne measurements

“…In this paper, we provide some unique perspectives on the distribution of aerosol properties in the lower Arctic atmosphere collected using TBS at Oliktok Point, Alaska, between spring 2016 and summer 2019 de Boer et al, 2015;Dexheimer et al, 2019). Oliktok Point is a unique Arctic site as it has been shown to be influenced by aerosols from local oilfield activity in addition to the other more ubiquitous Arctic aerosol sources (Creamean et al, 2018b, c;Maahn et al, 2017 Boer et al, 2019a, b).…”

“…Flights occurred at altitudes up to 1.5 km a.m.s.l. and with durations from 1 to 9 h in various atmospheric conditions, including clear sky, broken to overcast clouds, rain, sleet, and snow (Dexheimer et al, 2019). Typical profiles included the following procedures: (1) a gradual ascent, hovering at a desired altitude, then a gradual descent; (2) if already airborne, a gradual descent, hovering at a desired altitude, then gradual ascent; (3) a quick ascent and descent; (4) a quick ascent followed by hovering at a desired altitude, then quick descent; and (5) a stepwise path up or down.…”

Assessing the vertical structure of Arctic aerosols using tethered-balloon-borne measurements

“…Two different balloons were used, including a 34 m 3 helikite (Allsopp Helikites Ltd.) and a 79 m 3 aerostat (SkyDoc™ and Drone Aviation Corp.). The helikite ( Figure 1c) uses lighter-than-air principles to obtain its initial lift and a kite-like structure to achieve stability and dynamic lift, while the larger aerostat uses a skirt instead of a kite to achieve stability in flight Dexheimer, 2018;Dexheimer et al, 2019). The helikite was typically used for flights with desired altitudes up to 700 m above the ground, had a maximum payload of < 10 kg, and could be operated in wind speeds < 11 m s -1 .…”

“…In this paper, we provide some unique perspectives on the distribution of aerosol properties in the lower Arctic atmosphere collected using TBS at Oliktok Point, Alaska between spring 2016 and summer 2019 de Boer et al, 2015;Dexheimer et al, 2019). These flights generally occurred between the months of May and October under various field campaigns, including the Inaugural Campaigns for ARM Research using Unmanned Systems (ICARUS; , Aerosol Vertical Profiling at Oliktok Point (AVPOP; Creamean et al, 2018a) and Profiling at Oliktok Point to Enhance Year of Polar Prediction (YOPP) Experiments (POPEYE; de Boer et al, 2019a;de Boer et al, 2019b).…”

“…Flights occurred to altitudes up to 1.5 km a.m.s.l. and with durations from 1 to 9 h in various atmospheric conditions including clear sky, broken to overcast clouds, rain, sleet, and snow (Dexheimer et al, 2019). Typical profiles included: (1) a gradual ascent, hovering at a desired altitude, then a gradual descent, (2) if already airborne, a gradual descent, hovering at a desired altitude, then gradual ascent, (3) quick ascent and descent, (4) quick ascent followed by hovering at a desired altitude, then quick descent, and (5) a stepwise path up or down.…”