Caracterización de la turbulencia atmosférica en una gran zona verde de una megaciudad andina tropical

The turbulence produced by surface-atmosphere interactions and its dissipation largely determine the dispersion of pollutants and, therefore, their public health impact. Turbulence parameterizations in pollutant transport and dispersion models have been observationally obtained and validated mainly for mid-latitudes, but very little for the tropics. In this article, we report the statistical characterization of the atmospheric turbulence at a representative site of the Metropolitan Area of Bogota – Colombia (4°39’30.48”N, 74°5’2.38”W, 2577 m ASL), a tropical Andean megacity, using high frequency measurements obtained with a 3-axis ultrasonic anemometer validated for exposure and operated at 10 Hz, at 7.8 m height between August and November 2014. Our analysis reveals that during the measurement period the lateral turbulence in Bogota, expressed as standard deviation, was high and comparable to the longitudinal turbulence (σv ≅ σu ≈ 0.2-1.3 m s-1), which characterizes its atmosphere as horizontally isotropic. The turbulent intensities observed (Iu ≈ Iv ≈ 0.6, Iw ≈ 0.3) were ~2 to ~3 times higher than those reported for mid-latitudes at the low wind speeds at Bogota. The spectral analysis was consistent with the statistical one, with longitudinal and vertical spectra comparable to those reported for neutral to slightly unstable conditions, and lateral spectra with peak frequencies an order of magnitude lower than the reported in the literature, which indicates high production of lateral turbulence. We estimate that the eddies at the beginning of the energy cascade had characteristic lengths of ~120 m and ~10 m in the horizontal and vertical, respectively. © 2019. Acad. Colomb. Cienc. Ex. Fis. Nat.