Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015)
Other literature type
Siebesma, A. Pier
(issn: 1680-7324, eissn: 1680-7324)
A 50-year hourly dataset of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to trends in all-sky radiation. The trend in all-sky radiation was expressed as a linear combination of trends in fractional cloudiness, clear-sky radiation and cloud-base radiation (radiation emanating from the bottom of clouds). All three trends were derived from the data records. The results indicate that trends in all three components contribute significantly to the observed trend in all-sky radiation. Trends (per decade) in fractional cloudiness, all-sky, clear-sky and cloud-base radiation were respectively 0.0097 ± 0.0062, 1.81 ± 1.07 W m<sup>−2</sup>, 2.78 ± 0.50 W m<sup>−2</sup>, and 3.43 ± 1.17 W m<sup>−2</sup>. Radiative transfer calculations using the aerosol optical thickness derived from visibility observations indicate that Aerosol Radiation Interaction (ARI) is a strong candidate to explain the upward trend in the clear-sky radiation. Aerosol Cloud Interaction (ACI) may have some impact on cloud-base radiation, but it is suggested that decadal changes in cloud thickness and synoptic scale changes in cloud amount also play an important role.