hourly-averaged CO2 mixing ratio from towers:
WLEF (at 76m)
Sylvania (at 36m)
Brule  (at 76m)
Fence (at 76 m)
Location of the towers can be found at
http://rflux.psu.edu/sites/sites.htm

data format:

column number,
	0-- year
	1-- month
	2-- day
	3-- hour (UT)
	4-- day of year (jday)
	5-- fractional day (fjday)
	6-- CO2 mixing ratio at 76m of WLEF tower      ppm
	7-- CO2 mixing ratio at 36m of Sylvania tower  ppm
	8-- CO2 mixing ratio at 76m of Brule tower     ppm
	9-- CO2 mixing ratio at 76m of Fence tower     ppm
	>10-- empty, filled as  -999 ; add more data at other towers soon