The “Ora del Garda” is a coupled lake and valley breeze, which flows very regularly, during clear-sky days in the warm season, from the northern shorelines of Lake Garda. Hence it propagates into the valleys nearby, until it reaches, through an elevated saddle, the River Adige Valley north of the city of Trento, where it interacts with the local up-valley winds, producing a strong and gusty flow. Typical features of this wind are outlined by means of a climatologic analysis of data from two representative surface weather stations – one located on the shores of lake Garda, and one 30 km inland – covering a 10-year period. Furthermore, to assess the impact of the synoptic wind on the development of the lake breeze, wind speed and direction at 850 hPa level from reanalysis are analysed. Clear lake-breeze days are identified in the period April-September by means of a set of objective criteria, based on the analysis of surface radiation and observations of wind speed and direction at the two surface stations. It is found that the Ora del Garda develops on the shores of the lake in about 70% of the days from April to September, with higher values in summertime. Moreover in about 90% of days in which the lake breeze develops on the lake shores, it also reaches the inland weather station. Average wind strengths on Lake Garda shores are in the order of 4-6 m s-1, with maximum intensities reaching frequently 10 m s-1. The wind typically starts blowing on average at 1100-1200 LST (but the onset time is progressively delayed from spring to summer), and lasts until 1700-2000 LST (with earlier cessation times occurring more frequently in April and September). The lake breeze takes on average 3.5 h to get to the inland weather station, where it lasts until 2000-2100 LST. The analysis of wind speed and direction at 850 hPa from reanalysis highlights that the lake breeze is on average stronger and its duration is slightly longer when the synoptic wind blows onshore. Moreover the lake breeze propagates faster, and arrives earlier at the inland weather station, under synoptic winds blowing onshore.
A climatological analysis of the “Ora del Garda” wind in the Alps
Giovannini, Lorenzo;Laiti, Lavinia;Zardi, Dino;De Franceschi, Massimiliano
2013-01-01
Abstract
The “Ora del Garda” is a coupled lake and valley breeze, which flows very regularly, during clear-sky days in the warm season, from the northern shorelines of Lake Garda. Hence it propagates into the valleys nearby, until it reaches, through an elevated saddle, the River Adige Valley north of the city of Trento, where it interacts with the local up-valley winds, producing a strong and gusty flow. Typical features of this wind are outlined by means of a climatologic analysis of data from two representative surface weather stations – one located on the shores of lake Garda, and one 30 km inland – covering a 10-year period. Furthermore, to assess the impact of the synoptic wind on the development of the lake breeze, wind speed and direction at 850 hPa level from reanalysis are analysed. Clear lake-breeze days are identified in the period April-September by means of a set of objective criteria, based on the analysis of surface radiation and observations of wind speed and direction at the two surface stations. It is found that the Ora del Garda develops on the shores of the lake in about 70% of the days from April to September, with higher values in summertime. Moreover in about 90% of days in which the lake breeze develops on the lake shores, it also reaches the inland weather station. Average wind strengths on Lake Garda shores are in the order of 4-6 m s-1, with maximum intensities reaching frequently 10 m s-1. The wind typically starts blowing on average at 1100-1200 LST (but the onset time is progressively delayed from spring to summer), and lasts until 1700-2000 LST (with earlier cessation times occurring more frequently in April and September). The lake breeze takes on average 3.5 h to get to the inland weather station, where it lasts until 2000-2100 LST. The analysis of wind speed and direction at 850 hPa from reanalysis highlights that the lake breeze is on average stronger and its duration is slightly longer when the synoptic wind blows onshore. Moreover the lake breeze propagates faster, and arrives earlier at the inland weather station, under synoptic winds blowing onshore.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione
