Climate-regime cospectrum analysis: shortwave solar irradiance with other meteorological parameters for regionally spaced locales

Open Access
Rayl, Jeffrey Edwin
Graduate Program:
Energy and Mineral Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 11, 2012
Committee Members:
  • Jeffrey Brownson, Thesis Advisor
  • Solar Energy
  • Irradiance
  • Meteorology
  • Power Spectral Density
  • Cospectrum
  • Coherence
  • Phase
Solar irradiance has both short-term (less than 12 hour) and long-term (intra-seasonal) variations. Understanding these fluctuations is crucial for improving solar resource forecasting and evaluating co-production strategies for solar-fossil power technologies. Downwelling shortwave solar irradiance data (DWS; 3-minute averaging) were used for a three-year period from 2007-2009. Six USA sites were selected from the Integrated Surface Irradiance Study (ISIS) and Surface Radiation (SURFRAD) budget network. Power spectral density was used to analyze the short term and long term variations in DWS. To assess the long-term variations, the data was analyzed in seasonal periods: winter, spring, summer, and fall. Additionally, the cospectrum was evaluated to compare the variation between sites. The three pairs of locations included a mid-Atlantic region: Rock Springs, PA with Sterling, VA; a southwest region: Desert Rock, NV with Hanford, CA; and mid-continent region: Fort Peck, MT with Bismarck, ND. The SURFRAD sites were analyzed in greater detail looking at DWS against several other meteorological parameters using the cospectral analysis. Surface observations of Relative humidity (RH), ambient temperature, wind speed, and air pressure were all analyzed with respect to the DWS. The inter-site coherence and phase analysis allows geographic dispersion of the solar resource to be evaluated. The coherence spectra showed high correlation between downwelling solar and relative humidity.