This data release is the update of the U.S. Geological Survey - ScienceBase data release by Bera and Over (2018), with the data processed through September 30, 2018. The primary data for water year 2018 (a water year is the 12-month period, October 1 through September 30, designated by the calendar year in which it ends) were downloaded from the Argonne National Laboratory (ANL) (Argonne National Laboratory, 2018) and processed following the guidelines documented in Over and others (2010). Daily potential evapotranspiration (PET) is computed from average daily air temperature, average daily dewpoint temperature, daily total wind speed, and daily total solar radiation, and disaggregated to hourly PET by using the Fortran program LXPET (Murphy, 2005). Missing and apparently erroneous data values were replaced with adjusted values from nearby weather stations used as "backup". Temporal variations in the statistical properties of the data resulting from changes in measurement and data storage methodologies were adjusted to match the statistical properties resulting from the data collection procedures that have been in place since January 1, 1989 (Over and others, 2010). The adjustments were computed based on the regressions between the primary data series from ANL and the backup series using data obtained during common periods. The statistical properties of the regressions were used to assign estimated standard errors to values that were adjusted or filled from other series. The Illinois Climate Network (Water and Atmospheric Resources Monitoring Program, 2018) station at St. Charles, Illinois, was used as "backup" for the hourly air temperature, solar radiation and wind speed data. The Midwestern Regional Climate Center (Midwestern Regional Climate Center, 2018) provided the hourly dewpoint temperature and wind speed data collected by the National Weather Service at the station at O'Hare International Airport and used as "backup". Each data source flag is of the form "xyz", which allows the user to determine its source and the methods used to process the data (Over and others, 2010). References Cited: Argonne National Laboratory, 2018, Meteorological data, accessed on October 10, 2018, at http://www.atmos.anl.gov/ANLMET/.
Bera, M., and Over, T.M., 2018, Meteorological Database, Argonne National Laboratory, Illinois, January 1, 1948 - September 30, 2017: U.S. Geological Survey data release, ​https://doi.org/10.5066/F7H1318R. Midwestern Regional Climate Center, 2018, Meteorological data, accessed on October 12, 2018, at https://mrcc.illinois.edu/CLIMATE/.
Murphy, E.A., 2005, Comparison of potential evapotranspiration calculated by the LXPET (Lamoreux Potential Evapotranspiration) Program and by the WDMUtil (Watershed Data Management Utility) Program: U.S. Geological Survey Open-File Report 2005-1020, 20 p., https://pubs.er.usgs.gov/publication/ofr20051020. Over, T.M., Price, T.H., and Ishii, A.L., 2010, Development and analysis of a meteorological database, Argonne National Laboratory, Illinois: U.S. Geological Survey Open-File Report 2010-1220, 67 p., http://pubs.usgs.gov/of/2010/1220/. Water and Atmospheric Resources Monitoring Program. Illinois Climate Network, 2018. Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820-7495. Data accessed on October 30, 2018, at http://dx.doi.org/10.13012/J8MW2F2Q