Please see the two attached figures; one showing 2m temperature summary plot for error statistics and the other is the timeseries at a specific station. Summary plot shows that there is a positive bias in early morning hours while timeseries plot show that the model underpredicts 2m temperature from evening to early morning hours. If I am not in mistaken, MET_summary.R calculates the bias using (mod-obs) difference. This calculation then makes a positive bias as overprediction while most of the timeseries that I analyzed shows that the model underpredicts 2m temperature. Therefore, I am confused why timeseries plot show underestimation of 2m nighttime temperature while diurnal variation of 2m temperature bias shows that it is overestimated. I understand that summary report is over the modeling domain in focus while timeseries is only at one station. However, I looked at many station timeseries and the model is underestimating the nighttime temperature.
Is my understanding for the calculation of bias correct such that positive bias means overprediction of 2m temperature through (mod-obs) calculation?
Why does the timeseries show an underestimation of 2m temperature while 2m temperature bias show overestimation over the same evening hours ?
I would appreciate if you could help me to understand the plots better by answering these two questions. Thank you Robert.