The seasonal characteristics of the breeze circulation at a coastal Mediterranean site in South Italy

Abstract

Abstract. We present a study on the characteristics of the sea breeze flow at a coastal site located in the centre of the Mediterranean basin at the southern tip of Italy. This study is finalized to add new data on breeze circulations over a narrow peninsula and present a unique experimental coastal site at about 600 m from the coastline in a flat open area at the foot of a mountain chain located in a region of complex orography. We study the seasonal behaviour of the sea-land breeze circulation by analysing two years of hourly data of wind speed and direction, temperature, radiation and relative humidity from a surface meteorological station, eighteen-months data from a wind profiler, and two-year data from the ECMWF analysis.Results show that breezes dominate the local circulation and play a major role for the local climate. They are modulated by the season, through the sea-land temperature difference and the large-scale flow. The large-scale forcing acts in phase with the diurnal breeze and opposes the nocturnal breeze.In summer, the daytime difference between the land surface temperature and the SST (Sea Surface Temperature) reaches its maximum, while the nigh-time difference has its minimum. This causes a strong, frequent and intense diurnal breeze and a weak nocturnal breeze.In winter and fall the nocturnal difference between the sea and land surface temperature reaches a maximum value, while the diurnal difference is at its minimum value. This causes a strong, frequent and intense nocturnal breeze despite of the large-scale forcing that is usually opposed to local-scale flow.

Investigation of reactive gases and methane variability in the coastal boundary layer of the central Mediterranean basin

“…As already observed at CGR, the magnitude of the morning NO peak increased sharply during summer: this suggested an increased influence of anthropogenic emissions (probably related to vehicular traffic) to NO variability during warm months, due to tourist activities in the region. However, the morning peak is maximized (4.7 ppb) in winter (December), as expected due to increase NO lifetime during cold months and more stable PBL conditions in the region (Federico et al, 2010). For all the seasons, after the onset of the sea breeze, decreasing NO values were observed until 12, followed by stable values close to detection limit until 18, when the land breeze usually start to affect LMT.…”

“…Moderate wind breezes from the sea (NW-SW) were mainly observed (55% of hourly occurrence) during daytime, while NE gentle wind breezes from land mainly (50% of occurrence) affected the nighttime period. The diurnal cycle of wind speed ( Figure S1) is enhanced during summer when the synoptic scale forcing during nighttime (Federico et al, 2010) leads to higher wind speed. In agreement with CGR, a significant increase in the average water vapor concentration was observed at LMT from winter (by up to 1.5%) to summer (by more than 2.3%).…”

Preliminary lightning observations over Greece

“…These events are strongly regulated by the local‐scale topography and low‐level circulation such as sea breeze and humidity. [ Kotroni et al , 2001; Federico et al , 2010]. Despite the fact that summer thunder days are of continental origin, large continental areas southern of the 38°N parallel (such as the island of Crete; see Figure 1a) over the Aegean Sea are nearly void of lightning presence.…”

Three-model ensemble wind prediction in southern Italy

“…Spring and fall share characteristics with both summer and winter and wind speeds have values between those of summer and winter. Figure 5 also shows a diurnal cycle in all seasons due to the thermally forced local circulations (Federico et al, 2010;Mangia et al, 2004). The amplitude of the cycle is largest in summer and smallest in winter because of both the greater insolation in summer and the larger number of cyclones that cross southern Italy in winter.…”