Turbulence characteristics in the atmospheric surface layer during summer monsoon of 1997 over a semi-arid location in India

A land surface processes experiment (LASPEX) was conducted in the semi-arid region of Northwest India during January 1997–February 1998. Analysis of turbulent components of wind and air temperature collected in the surface layer (SL) at Anand (22°35′N, 72°55′E) during the Indian summer monsoon season from June to September 1997 is presented. Turbulent fluctuation of wind components and air temperature observed at Anand varied as a function of terrain features and stability of the surface layer. Under neutral conditions, the standard deviation of vertical velocity ( σ w ) and temperature ( σ T ) were normalized using respective surface layer scaling parameter u * and T * which fitted the expressions σ w / u * = 1.25 and σ T / T * ≈ 4. Micrometeorological spectrum of wind and temperature at 5 m above ground level (AGL) at Anand showed peaks at time scale of 1–3 min at the low-frequency end. The inertial sub-range characteristics (−2/3 slope) of the spectrum are exhibited mostly. However, in some occasions, slope of −1 denoting brown noise was depicted by the wind and temperature spectrum, which indicated anisotropy in turbulence.