Heatwaves are a consequence of a quasi-stationary anticyclone. Their effect might be mitigated along the coasts, at least temporarily, by the sea breeze. From June to November 2021 in the site of Soverato (38°41′16′′ N 16° 33′ 00′′E), the MEditerranean Sea Salt And Dust Ice Nuclei (MESSA-DIN) campaign was carried out by CNR-IMAA. The ground based remote sensing equipment measuring during the campaign included a Doppler wind lidar (Päschke 2015). Wind data have been analyzed to investigate the land-sea breeze variability at Soverato considering the effect of the synoptic circulation, marine aerosol transport and Saharan dust outbreaks.
2. EXTENDED ABSTRACT
The data analysis reveals the prevailing land-sea breeze regime during July, August and September: in the latter month, a less marked breeze dynamics and the beginning of its breakup are evident. In summer months, ventilation follows the same pattern: the breeze is established at 05:00-06:00 in the morning with winds coming from the South East. This structure from a few meters a.g.l. reaches its maximum height (about 750 m a.g.l.) in the midday. At the same time, while winds blow from sea to land in the first 500 m of altitude, from 1 km up to the top of the boundary layer, a circulation coming from west - south west is triggered. During the night, a reversal of the circulation is observed and below 1 km the prevailing directions are from the south-west, while above the direction returns from the south-east.
In October and November, the land-sea breeze regime looks missing, with prevalent winds from South, probably due to a low pressure system insisting over southern Italy in the early autumn months.
For what concern the horizontal wind speeds, again following the monthly analysis, it is evident that during the summer months the wind speeds are moderate, between 0 and 10 m s-1 in the first 2 km of the atmosphere, while the highest speed is around 20 m s-1 at the top of the boundary layer.
The analysis was also correlated to Saharan dust intrusions and observations of marine aerosol by a co-located UV Raman lidar. The analysis allowed us to indentify 13 days with dust intrusions and 27 days dominated by marine aerosol.
During dust intrusions, the wind dynamic showed a marked presence of land-sea breeze circulation in the first 2 km of the atmosphere, while from 3 to 5 km, in the afternoon and evening hours, wind directions are from South-West. By comparing wind directions with air mass back-trajectories calculated with the HYSPLIT model (https://www.ready.noaa.gov) , it can be seen that winds, coming from Sahara desert, intrude the boundary layer following the breeze regime, while above the ABL the preferential intrusion direction is South West following the trend of the synoptic circulation coupled with the orography of the site (Avolio 2017, Falasca 2021). For marine aerosol cases, the wind dynamic is characterized by a strong circulation of land-sea breeze previously described for the summer months.
We also investigated the climatological evolution of the land-sea breeze in the site comparing the campaign data with the ERA5 reanalysis: in a global warming scenario, it should be top-priority the study of local atmospheric circulation and its implication in the mitigation of the effect of temperature extremes.
3. REFERENCES
Päschke, E., R. Leinweber, and V. Lehmann. "An assessment of the performance of a 1.5 μm Doppler lidar for operational vertical wind profiling based on a 1-year trial." Atmospheric Measurement Techniques 8.6 (2015): 2251-2266.
Avolio, E., et al. "Sensitivity analysis of WRF model PBL schemes in simulating boundary-layer variables in southern Italy: An experimental campaign." Atmospheric Research 192 (2017): 58-71.
Falasca, Serena, et al. "Sensitivity of near-surface meteorology to PBL schemes in WRF simulations in a port-industrial area with complex terrain." Atmospheric Research 264 (2021): 105824.
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