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 (22A degrees 35'N, 72A degrees 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 (sigma (w) ) and temperature (sigma (T) ) were normalized using respective surface layer scaling parameter u (*) and T (*) which fitted the expressions sigma (w) /u (*) = 1.25 and sigma (T) /T (*) a parts per thousand 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.