Andrea Mazzoldi

Validation of surface current measurements in the Northern Adriatic Sea from High-Frequency radars

Abstract The performances of a shore-based high-frequency (HF) radar network deployed along the coast of the Venice lagoon (northern Adriatic Sea) are discussed based on a comparison with a single bottom-mounted ADCP deployed in the shallow-water area offshore of the lagoon for a 40-day period in August–September 2005. The analyses, carried out using currents representative of the first meter for the HF radars and 2.5 m for the ADCP, gave rms differences of radial currents in the range of 8.7–14.7 cm s−1 (correlation 0.37– 0.82) for the ideal pattern and 8.4–20.5 cm s−1 (correlation 0.14–0.84) for the measured pattern. Good correlation was found between surface current vectors and moored data (scalar correlation up to R = 0.83, vector correlation ρ = 0.78, veering angle 6°). Comparison metrics were improved for the low-passed currents. Angular offsets ranged between +6° and +11°. Differences depended primarily on the geophysical variability within the water column. Bearing offsets also contributed because...

Measuring water exchange between the Venetian Lagoon and the open sea

Almost 15 centuries ago, people fleeing civil disorder and barbarian invasions after the collapse of the Roman Empire began building houses on low-lying islands in the middle of a lagoon. These islands later on—in the 10th century—became the city of Venice, the center of the long-lived Venetian Republic. Surrounded by water, the republic flourished for more than 7 centuries thanks to its strategic position. It fell into decline only at the end of the eighteenth century after being occupied by Napoleon. The early Venetians who built their city on the water to defend it from attacks would never have expected that the water would become the citys most dangerous enemy. In fact, this is what has been going on during the last century Venice risks being destroyed by the very waters that once served as its defense.

A Real-Time and Offline Quality Control Methodology for SeaSonde High-Frequency Radar Currents

AbstractA near-real-time and offline quality control methodology for SeaSonde systems is proposed. It is applied on radial current maps and is based on the determination of the signal-to-noise ratio (SNR) values of the Doppler lines that contribute to the hourly radial current at each range-bearing (R, θ) pair, under the assumption that SNR is a proxy for radar data quality. The retrieval of the sequence of Doppler lines is performed through a minimization procedure that takes advantage of the statistical descriptors output in the short-term radial maps. The separation of the contributing Doppler velocities into valid observations and anomalous velocities is based on their spectral quality factor and on a range-dependent noise threshold derived from statistics (average and standard deviation) of the signal amplitudes in the tails of the Doppler spectra. The final product of the quality control procedure is a radial current map, in which Doppler velocities are weighted by their SNR values and their spectra...