TITLE: Model Atmospheric Land Exchange (ALEXI) generated land surface energy fluxes: Sensible Heat, Latent Heat, Ground Heat and Net Radiation. AUTHORS: John Mecikalski 1225 West Dayton Street Madison, WI 53706 (608)262-1023 firstname.lastname@example.org http://biscayne.ssec.wisc.edu/~johnm Kenneth Davis 512 Walker Building University Park, PA 16802 (814)863-8601 email@example.com http://www.meteo.psu.edu/~davis/ DATA SET OVERVIEW: 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. http://emily.soils.wisc.edu/~anderson/alexi/alexi.html INSTRUMENT DESCRIPTION: See published methods in references below. DATA COLLECTION AND PROCESSING: 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. DATA FORMAT: 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. DATA REMARKS: 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. REFERENCES: 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.