Maintains the original model variability for both monthlies and dailies. To look at daily extremes, you are better off using the HCN data for the historical period and the HCN data combined with model deltas for the future. Use direct GCM dailies for looking at extremes in temperature and precipitation. GCM dailies will incorporate variability changes due to global warming, though since the GCMs don't include all processes upon which daily variability depends, the results are uncertain and should be viewed as only one possible scenario. Ultimately you may want to look at both measure of variability.
Temperature is computed as an instantaneous value at each model time step.
Therefore the mean screen temperatures will not equal the mean of the minimum and maximum temperatures, even though this is the case in the real world where records of minimum and maximum temperatures are the primary temperature observations. Mearns, L. O., Rosenzweig, C., and R. Goldberg. The effect of changes in daily and interannual climatic variability on Ceres-Wheat. a sensitivity study.