A method for simultaneous broadband solar radiation calibration and aerosol optical depth retrieval

A method is presented to calibrate pyrheliometer and pyranometer data using in-situ measurements of Direct Solar Radiation (DSR) and Global Solar Radiation (GSR). A key point in the method is directly using World Radiation Reference (WRR, 1367.07w/m²) as calibration standard, and it can be used to estimate or correct historical radiation records. Another key technique is simultaneous pyranometer calibration and aerosol optical depth (AOD) retrieval. The method suitableness is analyzed through numerical simulations as well as comparisons of the AOD retrievals with SIMEL AOD measurements. The method is used in estimating accuracies of radiation measurements at three meteorological observatories of Beijing, Urumqi and Gomuld in China. Furthermore, this method is used to re-calibrate DSR data and then retrieve AOD, yielding trendily smaller (compared with no corrected case) AOD retrievals at these three sites during 1960-2004.