Solar radiation fluxes at the surface of the Baltic Proper. Part 1. Mean annual cycle and influencing factors

Meteorological observations made on board Voluntary Observing Ships in the period 1980-1992 are used to estimate the climatological characteristics of the solar radiation flux at the surface of the Baltic Proper. A semi-empirical model developed for the Baltic region is used. Monthly and annual means of solar radiation fluxes reaching the sea surface, averaged over the northern, southern and western parts of the Baltic Proper are calculated. Seasonal and interannual variability of the fluxes as well as the impact of both meteorological and astronomical factors on the monthly and annual means of the fluxes are also analysed. The annual mean irradiance for the entire Baltic Proper is estimated at 117 ( ±4) W m-2. The long-term monthly means for this area vary from 12 (±4) W m-2 in December to 241 (±21) W m-2 in June.