NSA evaluation of heated ventilators in the Arctic

Description

Due to the harsh conditions at the ARM North Slope of Alaska site, the broadband radiometers have been equipped with electric heaters inside the ventilators to keep hoarfrost and snow from accumulating on the pyranometer domes and affecting the measurements. The amount of heat used and the location of the heater within the sensor housing, to date, have been chosen based on limited tests of ventilators and sensor heating performed prior to the Surface Heat Budget of the Arctic (SHEBA, 1997–1998) project. The NSA Evaluation of Heated Ventilators in the Arctic field campaign was designed to gain a more complete understanding of the effects of ventilator heaters on domed radiometric measurements. Throughout the field campaign various combinations of heater type, ventilator flow, and AC- vs. DC-powered ventilator fans were performed to optimize the ARM broadband measurement strategy for the NSA site. In an effort to eliminate the hazards posed by 110 V AC electricity, lower-voltage DC fans were tested as a replacement. The field campaign was targeted at improving both our understanding and the quality and accuracy of the ARM NSA radiometer measurements. This field campaign built on the results of the "NSA Pyranometer IR Loss Study" field campaign conducted from August 2006 to July 2007. Information from Daily Rounds as well as digital pictures will be combined with heater and fan configuration information and synoptic weather information to show which configurations are most effective at eliminating errors due to frost buildup on the radiometer domes.