Monday, April 2, 2012

Sunlight on the tundra

Out at CARL (Cake Eater Atmospheric Research Laboratory), we have a fine array of instruments measuring all sorts of things, from blowing snow to sunlight. Here’s a brief description on how we set these instruments up and what they actually do. (Post by graduate student Melinda Webster, Univ. of Washington)

To begin, we had to do some manual labor. We dug snow pits for placing two towers in to provide them with stability in the chance that it becomes really, really windy. We needed a place with level ground so that the anemometers (the instruments that measure wind speed and direction) wouldn’t give us weird measurements. You can imagine having a pinwheel facing the wind works better than facing sideways to the wind. Our snow pits ended up being ~70 centimeters deep. Here’s our dig:  

After digging, we set up the actual towers themselves. After bolts and pieces, running wires through freezing metal tubes, testing the instruments with success, we were good to go! Once we had the towers up and standing, we piled snow back into the pits and set up wires bolted between the towers and the ground (again, for stability).

Closest to CARL is our radiometer tower which measures the sun’s energy each day. It tells us how much shortwave (Gamma, Xrays, UV) and longwave (Infrared, Microwaves, Radiowaves) radiation reaches the Earth’s surface. This is a great way to count the number of sunny and cloudy days, which can then be compared to the daily changes in air temperature and air chemistry.
The second tower is the meteorological station. It tells us four very useful things: air temperature, humidity, wind speed, and wind direction. The tower provides continuous information on the local atmospheric changes, like if it’s getting windier and colder, or warmer or calmer. It also provides a great comparison for other meteorological data measured around Barrow. 

We also compare these measurements to data from the Surface Velocity Profiler (SVP) buoys and Thermocrons. The SVP buoys measure air temperature and air pressure at hourly intervals. The Thermocrons are these thumb-sized devices which measure surface temperature every 5 minutes.  They are used to validate satellite-derived surface temperatures.
Thank you to graduate student Melinda Webster (Univ. of Washington) for this great post!

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