## 4 Results
### Monitoring and Assessing the 2009 Drought in Victoria
For moderate drought stress (\(<\) -0.5\(\sigma\)), the area percentage indicated by SIF (28.1%) was similar to those indicated by APAR\({}_{\text{NDVI}}\) (22.5%) and APAR\({}_{\text{EVI}}\) (20.2%) in January 2009. For severe positive anomaly (\(>\)1\(\sigma\)), however, the area percentage shown by APAR\({}_{\text{NDVI}}\) was 15.6% and the value for APAR\({}_{\text{EVI}}\) was 11.2%, while the values shown by SIF and GPP were 0%. For severe drought stress (\(<\)\(-\)1\(\sigma\)) in February 2009, the area percentage indicated by GPP was 24.7%, and the value for SIF was 27%. On the other hand, the values for APAR\({}_{\text{NDVI}}\) (18.0%) and APAR\({}_{\text{EVI}}\) (11.2%) were much smaller than those revealed by SIF and GPP. SIF showed more similarity to APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) than to GPP for the drought stress of [-1\(\sigma\), 0) in February. The area percentages for severe drought stress shown by APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) were lower than those shown by SIF and GPP in February. In March, the area percentages ofextreme drought stress (\(<\)\(-\)1.5\(\sigma\)) shown by APAR\({}_{\rm NDVI}\) (7.8%) and APAR\({}_{\rm EVI}\) (8.9%) were much higher than those shown by GPP and SIF. Figure 3: The dynamics of the averaged GPP, SIF, APAR\({}_{\rm NDVI}\), APAR\({}_{\rm EVI}\), temperature, precipitation and PAR during the 2009 drought event (from January to March). The changes of all the aforementioned variables for general Victoria region, crop land and evergreen broadleaf forest land are shown in (**a**), (**b**) and (**c**), respectively. The spatial averages of GPP, SIF, APAR\({}_{\rm NDVI}\), APAR\({}_{\rm EVI}\) and PAR are taken from all 0.5\({}^{\circ}\) pixels for each studied region. The blue lines represent the mean level covering the period of 2007–2013. The error bars are the \(\pm\)1 standard deviation, which was obtained from the zonal average of the pixel-wise standard deviation. The spatial averages of temperature and precipitation are obtained from these stations located in each studied region, and the \(\pm\)1 standard deviations of temperature and precipitation were calculated by the spatial averages over 2007–2013 across these stations located in each studied region. Figure 5b,c show the percentages of negative and positive anomaly areas calculated by the pixels located in crop land and evergreen broadleaf forest land, respectively. For crop land, results for SIF, APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) were overall consistent. In February, the area percentage of severe drought stress (\(<\)\(-\)1\(\sigma\)) shown by SIF was higher than those shown by APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\). In March, the area percentages of extreme drought stress (\(<\)\(-\)1.5\(\sigma\)) shown by APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) were 7.8% and 8.9%, respectively, while no extreme drought-stressed area was indicated by GPP or SIF. Figure 4: The spatial and temporal variations of normalized FLUXCOM GPP, SIF, APAR\({}_{\text{NDVI}}\), APAR\({}_{\text{EVI}}\), ECMWF temperature, ET/PET and PAR anomalies in Victoria from January to March 2009. Figure 5: Monthly dynamics of the anomaly area percentages of vegetation activity revealed by GPP, SIF, APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\); \(\sigma\) is the standard deviation of monthly GPP, SIF, APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) over 2007–2013. Red and green columns represent negative and positive anomalies, respectively. The results of general Victoria region, crop land and evergreen broadleaf forest land are shown in (**a**), (**b**) and (**c**), respectively. Regarding evergreen broadleaf forest land, APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\) showed positive anomalies and SIF exhibited a high area percentage for the weak positive anomaly of [0, 1\(\sigma\)) in January. In February, the area percentage of the drought stress (<0) shown by SIF was higher than those shown by APAR\({}_{\text{NDVI}}\) and APAR\({}_{\text{EVI}}\).