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Regional variations in hourly and daily totals of global radiation recorded at automatic weather stations in Estonia

2012; Estonian Academy Publishers; Volume: 18; Issue: 1 Linguagem: Inglês

10.3176/eng.2012.1.06

2228-0820

Klemens Rosin, S Keevallik,

Atmospheric Ozone and Climate

Daily cycles and totals of global radiation, recorded at the automatic weather stations on the coast of Estonia, were compared with those at Tartu-Toravere where the quality of data is guaranteed, as this station belongs to the BSRN (Baseline Surface Radiation Network). The time period for comparison was 2005-2010, but due to the extensive gaps (mostly due to low quality) in the data sets, local differences in the radiation regime were estimated on the basis of shorter time periods. On the annual basis, there is more sunshine on the West-Estonian islands and coast and less on the North- Estonian coast. On the monthly basis, an interesting feature may be noticed concerning two sites on the northern coast: in April the daily totals at Harku are larger than at Narva-Joesuu and in July vice versa. The possibilities of reconstruction of the global radiation in coastal sites from Toravere data are analysed. Linear regression has been checked for afternoon data for two states of cloudiness: clear and overcast. Regression gives good results everywhere when both sites are cloud-free - coefficient of correlation is practically 1.0. In overcast conditions the correlation is over 0.8 for Tiirikoja and Parnu, over 0.7 for Harku and less for the most distant sites Vilsandi and Narva-Joesuu. This might help marine scientists to derive estimates of solar radiation at the seaside from Toravere data. The first analysis of new data from automatic weather stations shows that the quality of data needs attention and situation in the stations needs improvement.