I am performing Gaussian geostatistical simulation (conditional). But, the mean and minimum output rasters have some negative values. Some simulated maps have negative values. Does anybody have some idea why this is happening? Could it mean that my ajusted model in the simple kriging is not good? Thanks.

It is simulating from a Gaussian distribution, and negative values are valid simulations from this model. The phenomenon that you are interpolating may not be able to be negative (like rainfall or pollution levels), but the model doesn't know this, and some of the simulations will likely contain negative values just due to chance. I only know…