TITLE: 	Model Atmospheric Land Exchange (ALEXI) generated land surface energy
	fluxes: Sensible Heat, Latent Heat, Ground Heat and Net Radiation.
	John Mecikalski
	1225 West Dayton Street
	Madison, WI 53706

	Kenneth Davis
	512 Walker Building
	University Park, PA 16802
	The Atmosphere-Land Exchange Inverse (ALEXI) model is a coupled two
	source land surface one dimensional atmospheric boundary layer (ABL) 
	model. The lower boundary conditions for the two source model are 
	provided by thermal IR observations taken at two times during the 
	morning hours.  The ABL model then relates the rise in air temperature 
	above the canopy and the growth of the ABL to the time integrated influx
	of sensible heating from the surface.  ALEXI was developed as an
	auxiliary means for estimating surface fluxes over large regions using
	primarily remote-sensing data.  No precipitation data or moisture
	storage capacity is required to run the model.  This information is
	deduced from a change in the radiometric temperature detected by the
	GOES-8 satellite.  The most practical flux data is the daytime
	integrated surface flux.  The model requires clear skies to derive the
	surface fluxes. 
	This ALEXI model daily integrated surface flux data is available from
	2002135 to Present over the entire IHOP region.  

	See published methods in references below.

	The ALEXI model is run once a day at 5km horizontal resolution (5km x
	5km).  During IHOP, it used GOES-08 Satellite images collected once an
	hour during daylight hours, about 15 images total per day, to compute
	the time change in brightness temperature in the 10.7 um infrared
	channel.  Other model inputs besides these GOES images are USGS bi-weekly 
	composited NDVI (to compute fraction cover), the USGS landcover classification,
	surface ASOS/AWOS data (for wind speed), and GOES Visible data derived solar 
	insolation.  The outputs from the model are the estimated Sensible, 
	Latent, Ground and Net Fluxes.  These fluxes are derived by differencing
	the radiometric temperature from two different times, one hour after local
	sunrise and one and a half hours before local solar noon, at each ALEXI pixel. 
	Flux partitioning is effectively determined as a function of the radiometric
	temperature changes in concert with knowledge of vegetation cover.  If a 
	particular pixel is cloudy at either of the times, it isn't processed because 
	an accurate radiative temperature difference cannot be derived.   

	The data is in ASCII format.  The files will be named
	AlexiFlux_IHOPyyyydoy.txt  yyyy=year and doy= Julian day of year. 
	2002135=May 15, 2002 for example.  There is one file per day with the
	integrated surface fluxes.  The header descriptions:
	I= row
	J= column
	TIME= in UTC 
	LAT= latitude in degrees North
	LON= longitude in degrees
	H=  Sensible Heat Flux in Watts/meter2 range from 0.0-800.0
	LE= Latent Heat Flux in Watts/meter2 range from 0.0-800.0
	G= Ground Heat Flux in Watts/meter2 range from 0.0-800.0
	RNET= Net Radiation in Watts/meter2 range from 0.0-1000.0
	This information was recalculated with the correct NDVIs and reran May 
	5, 2003.
	Values of -9999.00 indicate missing fluxes.

	The days 2002160, 2002161, and 2002175 are all missing due to loss of
	satellite images and initial processing material from those days.
	Data can be viewed on any text reader.

	Anderson, M.C., Norman, J.M., Diak, G.R., Kustas, W.P., and Mecikalski,
	J.R., 1997. "A two-source time-integrated model for estimating surface 
	fluxes using thermal infrared remote sensing", Remote Sensing Environ.,
	60, 195-216.
	Mecikalksi, J.R., Diak, G.R., Anderson, M.C., and Norman, J.M., 1999. 
	"Estimating fluxes on continental scales using remotely-sensed data in 
	an atmospheric-land exchange model", J. Appl. Meteorol., 35, 1352-1369.