OMI Solar Spectral Irradiance Data ################################## Authors: Sergey Marchenko and Matthew DeLand Contact: sergey.marchenko@ssaihq.com Last revision: 20 January 2020 Data Product ************ This file gives a basic description of the solar spectral irradiance data that we have produced from Aura OMI solar measurements. Detailed discussion of the procedures used and validation steps can be found in the following papers: S. V. Marchenko and M. T. DeLand (2014), "Solar spectral irradiance changes during Cycle 24", Ap. J. 789:117, doi:10.1088/0004-637X/789/2/117. S. V. Marchenko, M. T. DeLand, and J. L. Lean (2016), "Solar spectral irradiance variability in Cycle 24: Observations and models", J. Space Weather Space Climate, 6, A40, doi:10.1051/swsc/2016036. S. V. Marchenko, T. N. Woods, M. T. DeLand, S. Mauceri, P. Pilewskie, and M. Haberreiter (2019), Improved Aura/OMI solar spectral irradiances: Comparisons with independent data sets and model predictions, Earth and Space Sci., in press, doi:10.1029/2019EA000624. Please note that this data set has been revised in three areas, as described in our 2019 paper: 1. We have improved the separation of pixels flagged as noise-affected, which provides more data in the later part of the OMI record. 2. We now use an exponential time dependence for our degradation model, replacing the previous linear function. 3. We now require consistent absolute irradiance levels at the minimum of Cycle 23 and Cycle 24 as a constraint for item (2). Since Cycle 24 may not have reached its full minimum yet, we believe that item (3) currently leads to an underestimate of ~0.1% for solar cycle variability in the UV region (wv < 350 nm), and < 0.05% in the visible region. The revised degradation model now enables us to extrapolate the correction function back to July 2006. This update replaces some samples between 355-380 nm in mid-2006 that were accidentally omitted. No other data have been changed. Data Location ************* The OMI data can be retrieved at the following web site: https://sbuv2.gsfc.nasa.gov/solar/omi/ File Contents ************* The OMI irradiance data, corrected for long-term degradation, are provided in a single HDF file named 'omi_ssi_irradiance_20191125.h5'. All data are originally measured in three spectral channels: UV1 channel, wavelength range = 265.0-309.5 nm UV2 channel, wavelength range = 310.0-355.5 nm VIS channel, wavelength range = 356.0-500.0 nm The datasets presented here combine these data into a single spectral dimension. The first measurement date available in the OMI data product is 2 July 2006, and the last date included in the current data file is 22 November 2019. The HDF file contains the following variables: JulianDateAdj Observation date in adjusted Julian day format [JD-2450000.0] Year Year of measurement DayofYear Day of year of measurement Month Month of measurement Day Day of month of measurement Hour Hour of measurement Minute Minutes of measurement Second Seconds of measurement WavelengthScale Wavelength scale [nm], sample interval = 0.5 nm IrradianceReference Reference irradiance spectrum created by averaging data between April 2007 and September 2009 [mW/m^2/nm] IrradianceDaily Daily spectra [mW/m^2/nm] IrradianceStDev Standard deviation within each spectral and daily bin