WITN TV tower observatory - ITN
Latitude: 35.37° N,
Longtitude: 77.39° W
Elevation: 9 m
The WITN station is the first site instrumented by the Measurements of Anthropogenic Gases and Natural Emissions from Tall Towers (MAGNETT) program of NOAA/CMDL. WITN is located in eastern North Carolina, about 3 km east of Grifton (pop. 2500). The area surrounding WITN is mixed agricultural and forest, with some light industry. Forests cover about half of the surrounding three-county region (Pitt, Lenoir and Greene counties). The most common crops are corn, soybeans, tobacco, wheat and peanuts. The site utilizes a 610 m high television transmission tower as the sampling platform. Air from three levels (51, 123, and 496 m) on the tower is continuously pumped into the base laboratory, where it is analyzed for fourteen different trace gases. Wind direction and speed, temperature and relative humidity are measured at 51, 123, and 404 m on the tower. Incident photosynthetically active radiation (PAR), rainfall and surface pressure are also monitored. Since June, 1992, CO2 and 222Rn mixing ratios and several meteorological parameters have been monitored on a continuous basis at each of the three sampling levels on the WITN tower. A weekly flask sampling program was initiated in July, 1992; filled flask pairs are returned to our Boulder laboratory and analyzed for CH4, CO, H2, CO2, and 13C/12C and 18O/16O isotope ratios in CO2. In October, 1994, an automated 4-channel gas chromatograph (GC) was installed at the site to measure H2, CO, CH4, N2O, SF6, CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (CCl2F-CClF2), CH3CCl3, CCl4, CHCl3, and C2Cl4. Every hour, the GC analyzes the air at each of the three sampling levels and performs a two-point calibration.
Instrumentation at ITN. The blue case on the bottom of the main rack contains the gas chromatograph, three CO2 sensors, four Rn detectors, an optical disc drive for data backup, and several computers are also part of this rack. The rack to the left contains all flowcontrollers for sample intake and a refrigerator (on top) for water removal from the sampling lines.
We are indebted to American Family Broadcasting for the very generous donation of space on the commercial transmitter tower and in the transmitter building, and especially to Mr. A. Manning, chief engineer at WITN-TV, for invaluable assistance and advice.