Observed development of the vertical structure of the marine boundary layer during the LASIE experiment in the Ligurian Sea

Abstract

Abstract. In the marine environment, complete datasets describing the surface layer and the vertical structure of the Marine Atmospheric Boundary Layer (MABL), through its entire depth, are less frequent than over land, due to the high cost of measuring campaigns. During the seven days of the Ligurian Air-Sea Interaction Experiment (LASIE), organized by the NATO Undersea Research Centre (NURC) in the Mediterranean Sea, extensive in situ and remote sensing measurements were collected from instruments placed on a spar buoy and a ship. Standard surface meteorological measurements were collected by meteorological sensors mounted on the buoy ODAS Italia1 located in the centre of the Gulf of Genoa. The evolution of the height (z i ) of the MABL was monitored using radiosondes and a ceilometer on board of the N/O Urania.Here, we present the database and an uncommon case study of the evolution of the vertical structure of the MABL, observed by two independent measuring systems: the ceilometer and radiosondes. Following the changes of surface flow conditions, in a sequence of onshore -offshoreonshore wind direction shifting episodes, during the mid part of the campaign, the overall structure of the MABL changed.Correspondence to: A. M. Sempreviva (am.sempreviva@isac.cnr.it) Warm and dry air from land advected over a colder sea, induced a stably stratified Internal Boundary Layer (IBL) and a consequent change in the structure of the vertical profiles of potential temperature and relative humidity.

Air–Sea Interaction in the Ligurian Sea: Assessment of a Coupled Ocean–Atmosphere Model Using In Situ Data from LASIE07

“…6b) shows similar multiday trends in model and observations, explaining the high correlations (0.63 in CAO, 0.64 in UA, see Table 2a), and the small mean bias (less than 3 W m 22 ), but there are large differences on subdaily time scales, so that the rmse is 24 W m 22 for both runs. Ceilometer measurements from R/V Urania confirmed the presence of clouds below 2000 m on these days (Sempreviva et al 2010). 6b).…”

Seasonal Variability of Wind Sea and Swell Waves Climate along the Canary Current: The Local Wind Effect

“…The frontal storms are responsible for very high wind speed events, usually from the south-west, before the cold front passage, veering to the north-west sector after the front. In JJA the situation is different [77]. The extreme wave heights in the area are now clearly dominated by wind sea (H s s < H w s ), from west Iberia to Mauritania, with the exception of an area west of the Gulf of Cadiz, North of the Madeira Islands, reflecting the particular characteristics of the wind and wave climates along the EBCCS due to the influx of Mediterranean water and to the Azores Current [78].…”

The ODAS Italia 1 buoy: More than forty years of activity in the Ligurian Sea

“…The radiosonde and ceilometer LASIE data were jointly analysed with buoy data. It was clearly shown experimentally, for the first time in the Mediterranean area, how the vertical structure of the MABL (Marine Atmospheric Boundary Layer) changes according to the synoptic conditions (Sempreviva et al, 2010). On the first day of the campaign (16 June), the wind was from SouthWest, speed higher than 6 m s À1 , the sky was covered and the sea was rough.…”