SGP/QCRAD/E1 - Intermittently missing downwelling diffuse
Starting on or about 10/26/2005 the downwelling diffuse hemispheric irradiance (Eppley 8-48) instrument had intermittent missing values. Technicians found a loose wire on the instrument connector and repaired it on 4/4/2006. This means that Best Estimate Global can't be calculated from the sum of direct and diffuse. It also means that some quality checks can't be done. Problem documented in instrument DQR D060331.2.
Use MFRSR diffuse or global shortwave hemispheric (PSP) component - normal incident component (CosZA*NIP) to calulate diffuse component. Comparison of absolute difference between actual and computed diffuse component values and diffuse standard deviations > 1-2 W/m2 can help filter the noisy diffuse data. There is no standard method.