In order to perform detailed calculations of dynamic loads on wind turbines due to turbulence, a precise wind simulator is needed. International standards give guidelines to generate a synthetic wind for a flat terrain in the absence of wakes. Measurements in complex terrain and under wake effects have been analysed with the purpose of establishing some modifications to those guidelines that improve the simulated wind turbulence characteristics. A modification of the spectrum shape is proposed for locations affected by wind turbine wakes. Modifications are also proposed for the ratios of standard deviations and the turbulence lengths, which give a tendency to turbulence isotropy, as the complexity of the terrain and wake effects become more relevant. The parameter called normalized turbulence intensity (NTI) is introduced to quantify the ‘complexity’ of a location. Copyright © 2011 John Wiley & Sons, Ltd.