NDVI Data Files and Images for the Walnut River Watershed and Immediate Surrounding Area During CASES97 Data were collected with an Argonne ground station from NOAA polar-orbiting satellite high-resolution picture transmissions for the first five intensive operations periods of CASES97. The data were processed to produce data files and images. The data files and associated information are as follows: Solar zenith View zenith Assumed visibility ASCII file Satellite MM/DD/YY angle (deg) angle (deg) (km) 97119cor.dat NOAA14 04/29/97 32.75 4 90 97124cor.dat NOAA12 05/04/97 63.75 35 280 97130cor.dat NOAA14 05/10/97 27.25 34 120 97136cor.dat NOAA14 05/16/97 32.25 18 35 97140cor.dat NOAA14 05/20/97 24.25 44.5 110 The ASCII files contain six columns of data: 1. longitude 2. latitude 3. reflectance in AVHRR channel 1 corrected for atmospheric effect using LOWTRAN7 4. reflectance in AVHRR channel 2 corrected for atmospheric effect using LOWTRAN7 5. NDVI calculated from the above corrected reflectances 6. surface brightness temperature by averaging the brightness temperatures derived from corrected AVHRR channels 4 and 5 Each file contains 89 rows and 75 columns in increments of 0.01151882 deg and 0.01151882 deg longitude and latitude, respectively. The whole frame corresponds to the following longitudes and latitudes: ULX=-97.3270 ULY=38.1670 LRX=-96.4746 LRY=37.1533 The values for visibility were chosen by iterative comparisons of the transmittances calculated with LOWTRAN7 for selected wavelengths with optical depths in five narrow bands measured with the multifilter rotating shadowband radiometer at the central facility of the Atmospheric Radiation Measurement Program's southern Great Plains Cloud and Radiation Testbed site (ARM/SGP/CART). Because the CART central faciility is located approximately 100 km from the Walnut River Watershed, this matching of calculated transmittances to measured optical depths led to only rough estimates of visibility. On all days selected except May 16, a one-to-one correspondence could be obtained. On May 16, a value of visibility was chosen to give a maximum value of NDVI for the scene that was between the maxima found on May 10 and May 20. For further information, contact Jie Song jsong@prospero.er.anl.gov or jsong@geog.niu.edu 630-252-6114 or 815-753-6837 or Marv Wesely mlwesely@anl.gov 630-252-5827 6/15/98