SUMMARY Availability variability of sunshine hours and total solar radiation at the Santa Maria (RS) region were determined. Data were colected at the Forest Experimental Station located in Boca do Monte, Experimental Station of Júlio de Castilhos and Grass Experimental Station of São Gabriel as well from the standart meteorological station located at the Federal University of Santa Maria. It was concluded that daily sunshine availability and total solar radiation at Júlio de Castilhos was greater than in São Gabriel and Santa Maria and the variability of these elements was high during all months but higher during winter. The probability of occuring more than one day without sunshine and days with global solar radiation less than 100 cal.cm-2 .day-1 and a sequency of more than one consecutive day with these levels was greater during winter month for the Santa Maria region.
solar radiation; sunshine hours; disponibility; variability; probability
