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A Decade of Solar and Terrestrial Radiation Monitoring at Gobabeb for BSRN
Journal
Journal Namibia Scientific Society
Volume
69
Pages / Article-Number
141-157
Abstract
The Gobabeb Baseline Surface Radiation Network (BSRN) location was established a decade ago as part of a global network to provide standardised, high quality surface observations of radiation fluxes under the auspices of the World Meteorological Organisation. The Gobabeb BSRN measures the incoming and outgoing shortwave and longwave radiation at two locations in the Central Namib Desert. With a suite of instruments, radiative fluxes of shortwave downward radiation (SWD), direct solar radiation (DIR), diffuse radiation (DIF), longwave downward radiation (LWD), shortwave upward radiation (SWU) and longwave upward radiation (LWU) are recorded at 1-min intervals, together with relevant meteorological variables directly at the locations. As logistical issues prevent frequent calibration of instruments against World Radiometric standards, the measurements of DIR, SWD and LWD are duplicated to replicate radiation measurements as primary and redundant datasets. The two datasets are compared to each other to identify and exclude questionable data before being deposited in an open-access repository. The Gobabeb BSRN dataset is of very high quality, with less than 1% data missing for downward radiation. The upward radiation dataset has more missing data due to its becoming operational at a later date. As expected, climatic variables have the greatest influences on radiation fluxes at Gobabeb. Due to its location in a hyperarid desert, radiation is generally high throughout the year. Reflected radiation from rare cloud walls during the austral summer may, however, result in very high downward fluxes. The frequent incidence of fog due to onshore advection of stratus cloud banks over the nearby South Atlantic Ocean from August to February is distinctly visible in the dataset. Variation in the radiative fluxes of the different elements provides more detailed information on seasonal and daily incidence of fog, as well as seasonal changes in atmospheric aerosols. We briefly illustrate how high-quality BSRN data are used globally for validating solar energy resource assessments and evaluating differences between modelled predictions and actual surface performance.
