## 3 Results
### SIF Response to Henan Drought in 2019  
#### 3.2.1 Spatial and Temporal Patterns of Drought  
Henan suffered a severe drought in July 2019 when there was a precipitation deficit of 10-90% across Henan compared to the multi-year average while temperatures were 0.1-3.2 \({}^{\circ}\)C above the multi-year average in most areas of Henan. Autumn grain production  
Figure 14: Time series of TSIF in California. The land cover types were from the MCD12Q1.006 land cover dataset (IGBP) classification. Croplands, evergreen needleleaf forests, and grasslands mean the TSIF is calculated using the TSIF pixels of croplands, evergreen needleleaf forests, and grasslands, respectively. Statewide mean _SIF_ means the TSIF is calculated using all the TSIF pixels in California.  
Figure 13: Scatterplots of GPP and TSIF from six eddy covariance sites of AmeriFlux over four different ecosystems (corn, woody savanna, grassland, and wetland) (**a–f**). The GPP was temporally aggregated to 16-day to match the temporal resolution of TSIF. Red lines are the regression lines.  
decreased by 2.8% compared to the previous year 2018. The drought was alleviated by extreme precipitation in early-mid August of the same year ([[http://henan.weather.com.cn/](http://henan.weather.com.cn/)]([http://henan.weather.com.cn/](http://henan.weather.com.cn/)) (accessed on 2 November 2021)). The drought and extreme precipitation provide an ideal opportunity to explore the ability of our TSIF for drought monitoring.  
As shown in Figure 15a,b, SPEI shows a severe meteorological drought in July 2019, when the northwestern, western, and southern parts of Henan suffered severe or extreme drought, while the other parts suffered moderate drought. The drought continued in August in the southern part of Henan. As shown in Figure 16a,b, we calculated the monthly precipitation anomalies using Chirps2 monthly precipitation data from 1981 to 2021. The precipitation deficit across Henan in July was also observed with negative precipitation anomalies, and spatial patterns of the drought characterized by the precipitation anomalies were similar to those characterized by SPEI. In August, the western, northwestern, and northern parts of Henan received more precipitation than the multi-year average, with positive precipitation anomalies indicating the drought in these areas was alleviated to some extent. The central and southern parts of Henan showed negative precipitation anomalies, indicating that the precipitation deficit continued in August in these areas. As shown in Figure 15c,d, SPEI shows that no drought event occurred in July 2018; the western part of Henan suffered severe or extreme drought and the other parts show no drought in August 2018; precipitation anomalies show a precipitation deficit in the central, eastern, and southern parts of Henan in July 2018, and the western part and southern part of Henan in August 2018 (Figure 16c,d).  
Figure 15: Spatial and temporal patterns of drought characterized by SPEI for July (**a,c**) and August (**b,d**) of 2018 and 2019. The abbreviations are as follows: EW, extremely wet; SW, severely wet; MW, moderately wet; NN, near normal; MD, moderately dry; SD, severely dry; ED, extremely dry.