Ultraviolet solar radiation in tropical central Andes (12.0°S)

Abstract

Ultraviolet (UV) solar irradiance measurements at 1-min intervals performed in central Andes, Huancayo, Peru (12.0ºS, 75.3ºW, 3313 m asl) between January 2003 and December 2006, were used to analyze daily, monthly and annual cycles of UV solar irradiance. The measurements were performed with a GUV-511 multi-channel filter radiometer at four wavelengths: 305, 320, 340 and 380 nm. UV irradiance data under clear sky and all sky conditions were separated by a procedure based on calculation of normalized irradiance. In February, the highest hourly mean value at noon for the UV Index reached 18.8 for clear sky conditions and 15.5 for all sky conditions, with outlier peaks close to UVI=28. In addition, the highest mean value for daily erythemal dose was found also in February, reaching 7.5 KJ m⁻² d⁻¹ with a maximum outlier value close to 10.1 KJ m⁻² d⁻¹. Comparisons between clear sky GUV measurements and TUV model estimations were evaluated with statistical quantities showing values of R$^{2}$ around to 0.98. Total ozone column and trace gases were obtained from OMI. Aerosol parameters were obtained from MODIS. The enhancements of clouds of spectral irradiance at 340 nm referred to cloudless sky reach maxima of 20%. These results indicate that tropical central Andes has among the highest incident ultraviolet solar radiation in the world.