Improved Wind and Turbulence Measurements Using a Low-Cost 3-D Sonic Anemometer at a Low-Wind Site

Abstract

A year of data from sonic anemometer and mechanical wind sensors was analyzed and compared at a low-wind site. Results indicate that 15-minute average and peak 1-second wind speeds (u) from the sonic agree well with data derived from a co-located cup anemometer over a wide range of speeds. Wind direction data derived from the sonic also agree closely with those from a wind vane except for very low wind speeds. Values of standard deviation of longitudinal wind speed ( u ) and wind direction fluctuations ( ) from the sonic and mechanical sensors agree well for times with u > 2 ms -1 but show significant differences with lower u values. The most significant differences are associated with the standard deviation of vertical wind fluctuations ( w ): the co-located vertical propeller anemometer yields values increasingly less than those measured by the sonic anemometer as u decreases from 2.5 approaching 0 ms -1 . The combination of u over-estimation and under-estimation of w from the mechanical sensors at low wind speeds causes considerable underestimation of the standard deviation of vertical wind angle fluctuations ( ), an indicator of vertical dispersion. Calculations of from sonic anemometer measurements are typically 5° to 10° greater than from the mechanical sensors when the mechanical instruments indicate that < 5° or so. The errors with the propeller anemometer, cup anemometer and wind vane, caused by their inability to respond to higher frequency (smaller scale) turbulent fluctuations, can therefore lead to large (factors of 2 to 10 or more) errors in both the vertical and horizontal dispersion during stable conditions with light winds. The sonic anemometer clearly provides more accurate and reliable wind data than the mechanical wind sensor with u < 2.5 ms -1 .

Validating Salinity From SMAP With Saildrones and Research Vessel Data During EUREC4A-OA/ATOMIC

“…This variability seems to dominate in the vicinity of buoy 46086, which the saildrone only circumnavigated for less than a day, which provides a small sample size. This phenomenon is not synonymous with this campaign as Gilhousen [21] and Bowen [22] found similar results. Bowen [22] suggests that this variability may be due to the wind vane response not being as effective at low wind speeds.…”

“…This phenomenon is not synonymous with this campaign as Gilhousen [21] and Bowen [22] found similar results. Bowen [22] suggests that this variability may be due to the wind vane response not being as effective at low wind speeds.…”

Biases in Wind Speed Measurements Due to Anemometer Changes

“…New 2-and 3-axis sonic wind devices represent an improvement compared to mechanical cup anemometers assessed in this study, and greater effects may be anticipated as these can accurately measure weak wind speeds. Therefore, sonic devices can reduce the frequency of calm periods that are registered by cup anemometers, which are less sensitive to weak winds (Bowen, 2008). However, even though the high accuracy and excellent reliability and low maintenance of new sonic sensors, errors in wind measurements may also be associated with other factors, such as the data encoding issues.…”

The Micrometeorology of the Haifa Bay Area and Mount Carmel during the Summer

“…The over-speeding effect was noticeable in speeds up to 2 m/s, where the median bias was 0.13 m/s. Wind directions differences were within ±5 • 80% of the time [15]. Based on these results, the time averaged horizontal wind data from the weather stations network were used for the spatio-temporal analysis of the flow field in the HBA.…”

“…The ultrasonic anemometer specifications (http://www.youngusa. com/products/6/3.html accessed on 16 Several field studies have compared co-located ultrasonic and mechanical anemometers, such as propeller-vane anemometers [14][15][16]. The main disadvantage of the later is over-speeding which occurs when an anemometer responds quicker to an increase in wind speed than to a decrease of the same magnitude [17,18].…”