Turbulence Characteristics in the Atmospheric Surface Layer Over a Heterogeneous Cultivated Surface in a Tropical Region

The description of atmospheric turbulence on heterogeneous surfaces and more specifically during stable stratification conditions, remains nowadays a relevant and open issue in micrometeorology. To partially remedy this problem, we investigate in this study, the behaviour of turbulence above a heterogeneous cultivated surface during stable and unstable conditions. The analyses were realized according to seasons using almost seven years of eddy covariance measurements acquired at 4.95 m height. The results showed that the turbulence kinetic energy per unit mass was on average less than 0.5 m2 s−2 at night but increased during the day. It hits around local noon a peak value ~ 1.6 m2 s−2 on average. The peak value is relatively lower (~ 0.92 m2 s−2) during the wet season compared to other periods (1.6 m2 s−2). The average value of turbulence intensities are Iu = 0.44, Iv = 0.50 and Iw = 0.22 following u, v, w wind speed directions. During stable conditions, there are turbulent movements when the flux Richardson number is less than a critical value estimated approximately to 0.17. The flux-variance similarity functions that characterize the behaviour of turbulence are seasonally dependent, especially under stable conditions. However, each of these functions obey the Monin–Obukhov Similarity Theory whatever the stratification except those of temperature under near-neutral conditions. The results obtained indicate that the atmospheric turbulence is relative to the type of ecosystem and the height of measurement. This process is led by aerodynamic parameters and wind speed.