Accuracy of Wind Velocity Determinations with Doppler Sodars

Self Cite

Convective plume patterns, characteristic of clear sky and light wind daytime boundary layers over land, were observed for two nights with a &i-axial Doppler sodar operated in the central area of Rome during the summer of 1994. An urban heat island effect, combined with a continuation of a breeze from the sea late into night during both days, is believed to be responsible for the observed nocturnal convection. Estimates of the surface heat flux and the vertical velocity scaling parameter are obtained from profiles of vertical velocity variance, and the Raman lidar water vapor measurements are used to obtain the humidity scaling parameter. Convective scaling results for vertical wind and humidity fairly agree with the results of other experiments and models. On the basis of available measurements, it appears that mixed-layer similarity formulations used to characterize the daytime convective boundary layer over horizontally homogeneous surfaces can also be applied to the nocturnal urban boundary layer during periods of reasonable convective activity.

Section: Methodsmentioning

confidence: 99%

Convective characteristics of the nocturnal urban boundary layer as observed with Doppler sodar and Raman lidar

Casadio

Sarra

Fiocco³

et al. 1996

Self Cite

“…The data processing algorithms and electronics have been described by Mastrantonio and Fiocco (1982) and Elisei et al (1986). This sodar emits acoustic bursts into the atmosphere with durations of 0.1 s at different frequencies, 1750, 2000, and 2250 Hz, one for each channel-antenna, simultaneously in three directions, at a repetition rate of 6 s. The height range of measurements is from 44 to 1000 m with a step of about 27 m. The backscattered signals received by the antennae are sampled after appropriate filtering, and a fast Fourier transform is performed.…”

Section: Area Of Study and Instrumentationmentioning

confidence: 99%

Local Circulation Diurnal Patterns and Their Relationship with Large-Scale Flows in a Coastal Area of the Tyrrhenian Sea

Petenko

Mastrantonio

Viola

et al. 2011

In order to characterise the local low-level circulation in the Tyrrhenian Sea coastal area near Rome, the wind field observed by conventional anemometers, Doppler sodar, and rawinsonde has been analysed. The prevailing diurnal behaviour of wind speed and direction as a function of season was highlighted, and the existence of two different patterns of the local circulation, mainly due to land and sea breezes and to the drainage flow from the mouth of the Tiber valley, revealed. The comparison between the low-level circulation and synoptic flow allowed us to determine the influence of the large-scale flow on nocturnal currents that are observed at the Pratica di Mare site and the way that wind direction evolves during the day. Numerical simulations are consistent with experimental data and depict the main features of the low-level wind field in the area

“…Fewer than 5% of the data were affected in these ways. The velocity estimates were obtained from the mean Doppler shift calculated from the rotary signal spectrum, defined as the bin of maximum amplitude plus two bins on either of the maximum, using methods similar to those of Mastrantonio and Fiocco (1982). The raw signal amplitudes were calculated as the integrated intensities within the same region of the spectrum.…”

Section: Initial Data Processingmentioning

confidence: 99%

A case study of turbulence in the stable nocturnal boundary layer

Coulter

1990

Velocity and signal intensity data during stable conditions in the nocturnal boundary layer (NBL) were obtained with a minisodar on two consecutive nights with similar mean conditions. There was little turbulence activity during the first night, but during the second night, continuous background Kelvin-Helmholtz waves and instabilities having a 2-min period grew and penetrated above the mean NBL height at approximately 60-min intervals. Enhanced ozone concentrations at the surface occurred during the active periods even though most mean meteorological parameters were unchanged. Vertical profiles of vertical velocity standard deviation, dissipation rate, and temperature variance destruction rate in the NBL were measured and analyzed separately according to levels of turbulence activity. Well-defined differences between inactive and active periods of a factor of two to four were found for each parameter. The temperature structure parameter flux was large and in opposite directions in the upper and lower part of the NBL during active periods of turbulence, but small during other periods.