Scaling IEC turbulence to Exact Standard Deviations

I was using latest version of Turbsim for generating wind field for Class IA onshore site and was interested to know the ‘physical’ differences between the three options provided (I read that the manual says to choose 0, if unsure).

But I was not aware as to how reasonable is it, to use a constant standard deviation (‘2’ option). Are there any good/bad scenarios for using these options in a smart and a rationale way?

Thanks and Warm Regards,
Fraunhofer IWES, Germany

I think this topic is discussed in .
Wish that will help.