...
The correlation is more homogeneous, even though many of the low KGE areas also show low correlation, with exceptions, such as the upstream part of the Niger river basin, or some catchments in the Nile basin, which show high correlation but at the same time really high positive bias and some larger variability errors.
Figure 3. Bias ratio error of the GloFAS v4 simulation.
...
Still, some pattern emerges and generally the errors are more negative than positive, i.e. the GloFAS v4.0 river discharge simulation is too early in the signal, so peaks happen earlier than in the observations. This is the case in many of the catchments in the higher latitudes, in Amazonia or in Australia. In terms of magnitude, the larger errors mean 5-10 days or even over 10 days timing problem.
Figure 6. Timing error of the GloFAS v4 simulation.
...
Figure 7. KGE error difference maps between GloFAS v4 and v3 simulations (top row) and cumulative distributions of KGE for both v4 and v3. Using all all points (1st column), using only calibration points for both models without larger reservoir or lake influence (2nd column) and non-calibration points for both models without larger reservoir or lake influence (3rd column).
...
Absbias ratio
The bias, measured by the absolute value of the 0-centred version of the KGE's bias ratio component (abspbiasabsbias), is very clearly largely contributing to the improved KGE by drastically reduced bias errors in v4 (Figure 8). This is generally the same with all the stations (Figure 8 1st column), of the calibrated (Figure 8 2nd column) or non-calibrated stations (Figure 8 3rd column). The geographical distribution of the errors is very similar to the KGE's picture in Figure 7, with the tropics in general showing very large bias improvement, often more than halving the bias ratio error of v3 by v4.
The cumulative distributions of the absbias errors highlight that the high 0.43 in v3 decreased to only 0.12 in v4, with -0.22 as the median of the abspbias absbias difference values. The same values are 0.16 to 0.07, with -0.09 as the median of the abspbias absbias difference for the the calibration stations, while 1.92 to 0.50, with -0.88 as the median of the abspbias absbias differences for the non-calibrated case. This confirms the same picture seen for the KGE, with the calibrated stations showing much smaller improvement in pbias bias than the non-calibrated stations.
Figure 8. Abspbias error difference maps between GloFAS v4 and v3 simulations (top row) and cumulative distributions of abspbias for both v4 and v3. Using all all points (1st column), using only calibration points for both models without larger reservoir or lake influence (2nd column) and non-calibration points for both models without larger reservoir or lake influence (3rd column).
...