Clouds at Arctic Atmospheric Observatories. Part II: Thermodynamic Phase Characteristics
Open Access
- 1 March 2011
- journal article
- research article
- Published by American Meteorological Society in Journal of Applied Meteorology and Climatology
- Vol. 50 (3), 645-661
- https://doi.org/10.1175/2010jamc2468.1
Abstract
Cloud phase defines many cloud properties and determines the ways in which clouds interact with other aspects of the climate system. The occurrence fraction and characteristics of clouds distinguished by their phase are examined at three Arctic atmospheric observatories. Each observatory has the basic suite of instruments that are necessary to identify cloud phase, namely, cloud radar, depolarization lidar, microwave radiometer, and twice-daily radiosondes. At these observatories, ice clouds are more prevalent than mixed-phase clouds, which are more prevalent than liquid-only clouds. Cloud ice occurs 60%–70% of the time over a typical year, at heights up to 11 km. Liquid water occurs at temperatures above −40°C and is increasingly more likely as temperatures increase. Within the temperature range from −40° to −30°C, liquid water occurs in 3%–5% of the observed cloudiness. Liquid water is found higher in the atmosphere when accompanied by ice; there are few liquid-only clouds above 3 km, although liquid in mixed-phase clouds occurs at heights up to about 7–8 km. Regardless of temperature or height, liquid water occurs 56% of the time at Barrow, Alaska, and at a western Arctic Ocean site, but only 32% of the time at Eureka, Nunavut, Canada. This significant difference in liquid occurrence is due to a relatively dry lower troposphere during summer at Eureka in addition to warmer cloud temperatures with more persistent liquid water layers at the far western locations. The most persistent liquid clouds at these locations occur continuously for more than 70 h in the autumn and more than 30 h in the winter. Ice clouds persist for much longer than do liquid clouds at Eureka and occur more frequently in the winter season, leading to a total cloud occurrence annual cycle that is distinct from the other observatories.Keywords
This publication has 55 references indexed in Scilit:
- Accelerated decline in the Arctic sea ice coverGeophysical Research Letters, 2008
- High Spectral Resolution LidarPublished by Springer Science and Business Media LLC ,2006
- Liquid fraction in stratiform mixed‐phase clouds from in situ observationsQuarterly Journal of the Royal Meteorological Society, 2004
- Two case studies of winter continental‐type water and mixed‐phase stratocumuli over the sea 1. Microphysical and optical propertiesJournal of Geophysical Research: Solid Earth, 2002
- Full-Time, Eye-Safe Cloud and Aerosol Lidar Observation at Atmospheric Radiation Measurement Program Sites: Instruments and Data ProcessingJournal of Atmospheric and Oceanic Technology, 2002
- Evolution of the cloudy boundary layer during the autumnal freezing of the Beaufort SeaJournal of Geophysical Research: Solid Earth, 1997
- Overview of Arctic Cloud and Radiation CharacteristicsJournal of Climate, 1996
- The sensitivity of climate simulations to the specification of mixed phase cloudsClimate Dynamics, 1996
- Measurement of Stratus Cloud and Drizzle Parameters in ASTEX with a Kα-Band Doppler Radar and a Microwave RadiometerJournal of the Atmospheric Sciences, 1995
- Occurrence and characteristics of lower tropospheric ice crystals in the arcticInternational Journal of Climatology, 1990