Seite - 386 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 1 Relation between study area, monitoring stations and NOAA raster data 3. METHODS 3.1. NOAA FORECAST DATA / BIAS CORRECTION Bias correction was performed using two different methods: quantile mapping and formation of monthly factors. The monthly factors were calculated for each calendar month. First, average values for each month were calculated for each observation station and forecast grid over the entire time period for which observed and forecasted datasets are available. This was the time period from 2011 to 2016. Then, the correction factor was calculated for each month by computing the ratio between the observed and the forecasted values. The correction factors are specific to each combination of observation station and forecast grid. Bias corrected forecasts could then be obtained by multiplying each value of the forecasted time series with the appropriate monthly correction factor. 386