2:30 PM - 2:45 PM
[AAS06-04] Investigation of the effects of wind speed and direction on atmospheric pressure probe observations
Keywords:CFD, atmospheric pressure fluctuations, atmospheric pressure observation
In recent years, high attention is focused on global warming, and the behaviour of greenhouse gases on the Earth's surface, which are one of the causes, is required. Carbon dioxide (CO2) is one kind of greenhouse gas and increasing rapidly due to human economic activities. The elucidation of CO2 dynamics is an urgent issue.
CO2 is constantly exchanged between the oceans, which account for 70% of the earth's surface, and the atmosphere. Many researchers have observed the amount of CO2 (CO2 flux) as an important factor influencing changes in atmospheric CO2 concentration. In general, the CO2 flux is evaluated by the eddy covariance technique, which enables direct measurement of momentum, heat and trace fluxes. Open-path gas analysers are often used in this technique, but open-path gas analysers require the correction for removal of the effects of air density fluctuations. The WPL correction proposed by Webb et al. is commonly used to remove the effects of air density fluctuations. However, Kondo et al. reported that significant CO2 fluxes between an asphalt surface and the atmosphere were observed when they measured trace fluxes on an asphalt surface where there should be no CO2 exchange with the atmosphere. And They concluded that WPL correction may cause the overestimation of CO2 fluxes. WPL correction ignores the effect of atmospheric pressure fluctuations, and it is conceivable that this is one of the factors which cause the overestimation.
Atmospheric pressure fluctuations are generally observed using atmospheric pressure probes that are designed to reduce the effects of wind-induced dynamic pressure. However, it is difficult to eliminate this effect, and the wind speed and direction significantly affect the observation values. To improve observation accuracy, this study clarifies the effects of wind speed and direction on atmospheric pressure probe observation by wind tunnel experiments and CFD analysis.
CO2 is constantly exchanged between the oceans, which account for 70% of the earth's surface, and the atmosphere. Many researchers have observed the amount of CO2 (CO2 flux) as an important factor influencing changes in atmospheric CO2 concentration. In general, the CO2 flux is evaluated by the eddy covariance technique, which enables direct measurement of momentum, heat and trace fluxes. Open-path gas analysers are often used in this technique, but open-path gas analysers require the correction for removal of the effects of air density fluctuations. The WPL correction proposed by Webb et al. is commonly used to remove the effects of air density fluctuations. However, Kondo et al. reported that significant CO2 fluxes between an asphalt surface and the atmosphere were observed when they measured trace fluxes on an asphalt surface where there should be no CO2 exchange with the atmosphere. And They concluded that WPL correction may cause the overestimation of CO2 fluxes. WPL correction ignores the effect of atmospheric pressure fluctuations, and it is conceivable that this is one of the factors which cause the overestimation.
Atmospheric pressure fluctuations are generally observed using atmospheric pressure probes that are designed to reduce the effects of wind-induced dynamic pressure. However, it is difficult to eliminate this effect, and the wind speed and direction significantly affect the observation values. To improve observation accuracy, this study clarifies the effects of wind speed and direction on atmospheric pressure probe observation by wind tunnel experiments and CFD analysis.