A data set of quality checked daily sunshine duration measurements was collected from 104 Italian sites over the 1936 to 2013 period. Monthly mean values were homogenized, projected onto a grid, and subjected to principle component analysis, which identified two significantly different regions: North and South. Sunshine duration temporal evolution is presented, and possible reasons for differences between the two regions are discussed in the light of a comparison with the trends found in observations of total cloud cover and with results from two neighboring regions: the Alps and Spain. In addition, trends for irradiance records, estimated from sunshine duration records using the Ångström-Prescott formula, are presented too. The major feature of the trends, an increase in sunshine duration from the mid-1980s, was common to both northern and southern Italy; the decrease in the preceding 30 year period was not, as northern Italy had a lower rate of decrease than southern Italy. The few records available during the earliest period of the data set indicate that sunshine duration in Italy increased from the mid-1930s to the mid-1950s. The further steps needed to identify and quantify the mechanisms giving rise to the observed trends and to the reported regional differences in dimming and brightening are outlined.
|Titolo:||Sunshine duration variability and trends in Italy from homogenized instrumental time series (1936-2013)|
MANARA, VERONICA (Primo)
|Parole Chiave:||data homogenization; global dimming/global brightening; Italy; sunshine duration; trends|
|Settore Scientifico Disciplinare:||Settore FIS/06 - Fisica per il Sistema Terra e Il Mezzo Circumterrestre|
|Data di pubblicazione:||2015|
|Digital Object Identifier (DOI):||10.1002/2014JD022560|
|Appare nelle tipologie:||01 - Articolo su periodico|