This data has been encrypted; to obtain key please write to David Hollinger
at davidh@christa.unh.edu.

Howland Eddy Correlation 1996 Data Set 


SITE DESCRIPTION:
     Surface flux measurements were made at the Northern Experimental Forest study site near
Howland Maine. The site is located at approximately 45deg 12min N latitude and 68deg 08min W
longitude.Vegetation consists of northern hardwood transitional species including aspen-birch,
hemlock-spruce-fir, and hemlock-hardwood mixtures. Topographically, the region varies from flat
to gently rolling with a maximum elevation change of less than 68m. Eddy correlation
measurements were made from a 25.5-m walk-up platform tower. The forest around the tower is
relatively uniform in height with a mean height of 19.5 m and living biomass density of 43 kg/m2.
Leaf area index was approximately 5.3. 


INSTRUMENTATION:
     Measurements of CO2, H2O and sensible heat and latent heat fluxes were obtained by
eddy correlation using a three axis ATI sonic anemometer with a closed-path CO2/H2O (LICOR
6262) analyzer. Additional measurements included net radiation, ground heat flux,
photosynthetically active photon flux density, rainfall and soil temperature. The flux due to the
change in storage of CO2 below the above canopy sensors was determined with a profile system
which successively sampled air from four heights.


DATA FORMAT:
The file is in ascii comma delimited text format. Missing values are represented by "-9999".


DATA FILE HEADER:

"Rep","JD","HourMin","FCO2","Fstorage","NEE","Rn","H","LE","G","PPT","Tair","PPFD","P
PFDstd", "Tsoil","ubar","ustar","wnddir","ea"

where

JD = Julian Day (Jan 1 = 1)
HourMin = hour and minute of measurement (1730 = 5:30 p.m.)
FCO2 = above canopy CO2 flux (umol/m2s)
Fstorage = storage flux (umol/m2s)
NEE  = net ecosystem exchange = FCO2 + Fstorage (umol/m2s)
Rn = net radiation (W/m2) *NOTE* The net radiation values were consistently high but a second 
     radiometer (UMaine) was in operation since the beginning of August. To provide net 
     radiation for the whole year, our net radiation data was adjusted to fit the values from the 
     UMaine radiometer
H = sensible heat flux (W/m2)
LE = latent heat flux (W/m2)
G = ground heat flux (W/m2)
PPT = precipitation (mm)
Tair = air temperature (C) *NOTE* derived from sonic anemometer measurements except
     when the sonic anenemometer data was unavailable (i.e. during rain) in which case
     air temperature probe measurements were substituted.
PPFD = photosynthetically active photon flux density (umol/m2s)
PPFDstd = standard deviation in PPFD (umol/m2s)
Tsoil = soil temperature (C) at 5 cm depth
ubar = mean horizontal wind speed (m/s)
ustar = mean friction velocity (m/s)
wnddir = mean wind direction (degrees)
ea = mean water vapor mol fraction (mmol H2O/mol air)


                         
                                                  2/10/97