author = "Silva Filho, Paulo Cavalcante and Silva, Francisco Raimundo da and 
                         Corso, G.",
          affiliation = "Instituto Federal de Educa{\c{c}}{\~a}o, Ci{\^e}ncia e 
                         Tecnologia Do Rio Grande Do Norte (IFRN) and {Instituto Nacional 
                         de Pesquisas Espaciais (INPE)} and {Universidade Federal do Rio 
                         Grande do Norte (UFRN)}",
                title = "Autocorrelation in ultraviolet radiation measured at ground level 
                         using detrended fluctuation analysis",
              journal = "Physica A: Statistical Mechanics and its Applications",
                 year = "2016",
               volume = "453",
                pages = "264--270",
                month = "July",
             keywords = "Climate, Detrended fluctuation analysis, Long-range correlation, 
                         Solar radiation, Ultraviolet radiation.",
             abstract = "In this study, we analyzed the autocorrelation among four 
                         ultraviolet (UV) radiation data sets obtained at 305 nm, 320 nm, 
                         340 nm, and 380 nm. The data were recorded at ground level at the 
                         INPE climate station in Natal, RN, Brazil, which is a site close 
                         to the equator. The autocorrelations were computed by detrended 
                         fluctuation analysis (DFA) to estimate the index \α. We 
                         found that the fluctuations in the UV radiation data were fractal, 
                         with scale-free behavior at a DFA index \α\≃0.7. In 
                         addition, we performed a power law spectral analysis, which showed 
                         that the power spectrum exhibited a power law behavior with an 
                         exponent of \β\≃0.45. Given that the theoretical 
                         result is \β=2\α-1, these two results are in good 
                         agreement. Moreover, the application of the DFA method to the UV 
                         radiation data required detrending using a polynomial with an 
                         order of at least eight, which was related to the complex daily 
                         solar radiation curve obtained at ground level in a tropical 
                         region. The results indicated that the \α exponent of UV 
                         radiation is similar to other climatic records such as air 
                         temperature, wind, or rain, but not solar activity.",
                  doi = "10.1016/j.physa.2016.01.039",
                  url = "http://dx.doi.org/10.1016/j.physa.2016.01.039",
                 issn = "0378-4371",
             language = "en",
           targetfile = "silva_autocorrelation.pdf",
        urlaccessdate = "27 nov. 2020"