author = "Silva, Abel Antonio and Echer, Mariza Pereira de Souza",
          affiliation = "{Instituto de Estudos Avan{\c{c}}ados (IEAv)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)}",
                title = "Ground-based observations of clouds through both an automatic 
                         imager and human observation",
              journal = "Meteorological Applications",
                 year = "2016",
               volume = "23",
               number = "1",
                pages = "150--157",
                month = "Jan.",
             keywords = "clouds, cloud cover, automatic imager, human observation.",
             abstract = "The routine to determine the local cloud cover (LCC) drawn from 
                         sky images obtained using a ground-based automatic imager is 
                         validated. Almost 3 years of daily data of LCC and cloud cover 
                         measurements by ground-based human observation (CCHO) were 
                         compared for two Brazilian stations set 6km apart. The linear 
                         fitting between daily values showed a co-efficient of 
                         determination (r(2)) and a percent scattering of points (SD%) of 
                         approximate to 0.77 and approximate to 19.4% respectively. These 
                         results are evidence for the significant similarity between the 
                         two sets of data. On the other hand, the level of difference found 
                         can be explained by the fact that (1) the data refer to 
                         independent micro-scale observations of the sky from stations set 
                         a few kilometres apart and (2) the data were drawn from 
                         interpretations of cloud cover by an automatic imager and a human 
                         observer. The monthly average values of LCC and CCHO showed better 
                         linear fitting parameters r(2)=0.95 and SD%=6.3%. Average 
                         differences of approximate to-10% from LCC to CCHO were found. 
                         These average differences may reflect a systematic bias between 
                         the two processes of measuring cloud cover.",
                  doi = "10.1002/met.1542",
                  url = "http://dx.doi.org/10.1002/met.1542",
                 issn = "1350-4827",
             language = "en",
           targetfile = "silva_ground.pdf",
        urlaccessdate = "24 jan. 2021"