or inputs.     DHI must be &gt;=0.</li><li><b><tt>GHI</tt></b> - a scalar or vector of global horizontal irradiance in W/m^2. If GHI     is a vector it must be of the same size as all other vector inputs.     GHI must be &gt;=0.</li><li><b><tt>SunZen</tt></b> - a scalar or vector of apparent (refraction-corrected) zenith     angles in decimal degrees. If SunZen is a vector it must be of the     same size as all other vector inputs. SunZen must be &gt;=0 and &lt;=180.</li></ul></div><h2>Outputs<a name="5"></