Friday, October 23, 2009

Met tower set-up


The meteorological tower (aka "met tower") is set up to hold the instruments that monitor weather, and will later hold the inlet for the instrument that measures N2O5. In order to completely understand the lifetimes and cycles of N2O5, we need to monitor air temperature and wind speeds. Temperature will affect the rate of chemical reactions happening in the air, while wind speeds and directions will dictate the source of our air flow.


The tower consists of two identical levels, each at different heights. In the photo above, each level holds a wind vane (black), cup anemometer (black), sonic anemometer (silver), and temperature probe (white cylinder). Sonic anemometers use sound waves to measure wind speeds in all three dimensions, while the cup anemometers catch the air like ice cream scoops and spin relative to wind speed.

Typical nighttime wind flow at the Quist Farm site is from the northeast (~45 degrees). This typically occurs as a "drainage flow" from the city area of Fairbanks. Cold air is more dense than warm air, and will flow like water through terrain. The Quist Farm sits just downstream of Fairbanks in a valley. As cold air drains from the city at night it generates this general flow pattern. The above graph was made using the cup anemometer and wind vane data from the upper wind vane. It shows drainage flow on the night of 10/21/09. Keep in mind we use UTC standard time, so everything is synchronized. Therefore, 6AM on Oct. 22 (UTC standard) corresponds to 10PM on Oct. 21 (AK daylight).

Saturday, October 17, 2009

Quist Farm Field Site

GPS exact location of Field Site: N64 45.558 W148 06.371 543 ft

Our sub-Arctic field site is 20miles NNE of Fairbanks. We tracked our route out to the field site and the exact location. To identify the main wind flow direction and speed we used previous data to choose the location. Once we learned the primary wind direction was NNE from 0 to 90 degrees we choose this spot in the following video. The key characteristics of this site for the meteorology of this study are:
1- Unobstructed path of wind flow in the NNE direction.
2- Flat undisturbed field with wind direction and flow coming from downtown Fairbanks (NNE of site).

video
This video shows the initial visit to the Quist Farm site. In order to avoid car traffic on this road, and obstruction in the path of the main wind direction NNE, we decided to use the Hut out in the middle of the field on a flat part of the land. We ran power from the post in the end of the video out to the final position of the Hut through conduit pipe that runs underneath the driveway. Pictures of the final position for the instruments will follow in upcoming posts.

Start of our Fall 2009 Field study: the hut

Patrick and Ben helped load the cold winter research hut up on the trailer using a ratchet system. We work with CRREL (Cold Regions Research and Engineering Laboratory) on Ft. Wainwright to obtain several key instruments and equipment for this project. Tom Douglas and Art Gelvin were instrumental to the field campaign by letting us use their meteorological tower and hut. We thank them for helping us with this project.