Ground‐based remote sensing measurements from the Atmospheric Radiation Measurement Program (ARM) West Antarctic Radiation Experiment (AWARE) campaign at the McMurdo station and the ARM North Slope of Alaska (NSA) Utqiaġvik site are used to retrieve and analyze single‐layer stratiform mixed‐phase cloud macrophysical and microphysical properties for these different polar environments. Single‐layer stratiform mixed‐phase clouds have annual frequencies of occurrence of ~14.7% at Utqiaġvik and ~7.3% at McMurdo, with the highest occurrences in early autumn. Compared to Utqiaġvik, stratiform mixed‐phase clouds at McMurdo have overall higher and colder cloud‐tops, thicker ice layer depth, thinner liquid‐dominated layer depth, and smaller liquid water path. These properties show clear seasonal variations. Supercooled liquid fraction at McMurdo is greater than at Utqiaġvik because, at a given temperature, McMurdo clouds have comparable liquid water paths but smaller ice water paths. Analyses of retrieved cloud microphysical properties show that compared to Utqiaġvik, stratiform mixed‐phase clouds at McMurdo have greater liquid droplet number concentration, smaller layer‐mean effective radius, and smaller ice water content and ice number concentration at a given cloud‐top temperature. These relationships may be related to different aerosol loading and chemical composition, and environment dynamics. Results presented in this study can be used as observational constraints for model representations of stratiform mixed‐phase clouds.
Evaluation of ARM tethered-balloon system instrumentation for supercooled liquid water and distributed temperature sensing in mixed-phase Arctic clouds
Abstract. A tethered-balloon system (TBS) has been developed and is beingoperated by Sandia National Laboratories (SNL) on behalf of the U.S.Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) UserFacility in order to collect in situ atmospheric measurements withinmixed-phase Arctic clouds. Periodic tethered-balloon flights have beenconducted since 2015 within restricted airspace at ARM's Advanced MobileFacility 3 (AMF3) in Oliktok Point, Alaska, as part of the AALCO (AerialAssessment of Liquid in Clouds at Oliktok), ERASMUS (Evaluation of RoutineAtmospheric Sounding Measurements using Unmanned Systems), and POPEYE(Profiling at Oliktok Point to Enhance YOPP Experiments) field campaigns. Thetethered-balloon system uses helium-filled 34 m3 helikites and 79 and104 m3 aerostats to suspend instrumentation that is used to measureaerosol particle size distributions, temperature, horizontal wind, pressure,relative humidity, turbulence, and cloud particle properties and tocalibrate ground-based remote sensing instruments. Supercooled liquid water content (SLWC) sondes using the vibrating-wireprinciple, developed by Anasphere Inc., were operated at Oliktok Point atmultiple altitudes on the TBS within mixed-phase clouds for over 200 h.Sonde-collected SLWC data were compared with liquid water content derivedfrom 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-distributedtemperature sensing and supercooled liquid water measurements are inreasonably good agreement with remote sensing and radiosonde-basedmeasurements of both properties. From these measurements and sensorevaluations, tethered-balloon flights are shown to offer an effective methodof collecting data to inform and constrain numerical models, calibrate andvalidate remote sensing instruments, and characterize the flight environmentof unmanned aircraft, circumventing the difficulties of in-cloud unmanned aircraft flights such as limited flight time and in-flight icing.
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- NSF-PAR ID:
- 10131281
- Date Published:
- Journal Name:
- Atmospheric Measurement Techniques
- Volume:
- 12
- Issue:
- 12
- ISSN:
- 1867-8548
- Page Range / eLocation ID:
- 6845 to 6864
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/amt-12-6845-2019
