## 4 Results of the Experiment
### Analysis of Spatial Variability in Drought  
#### 4.4.1 Month-by-Month Drought Changes in Vegetation in Laibin City  
Based on the inverse calculation of the month-by-month drought monitoring results of Laibin City in 2021, 2022, and 2023, the mean TVDI values of the month-by-month data were calculated to complete the analysis of the month-by-month drought changes in the vegetation areas of Laibin City. As illustrated in Figure 18, there was no significant change in the monthly mean TVDI values in January, February, and March of 2021. The monthly mean TVDI values were 0.42, 0.49, and 0.50, respectively, showing a relatively gradual change. The drought conditions were essentially normal in January, and mild drought conditions were observed in February and March. The TVDI value for April increased compared to March, reaching 0.76, marking the most severe drought month in 2021. The average TVDI values for May and June showed minimal fluctuations, at 0.51 and 0.60, respectively, indicating light drought conditions. However, there was a noticeable contrast between June and July, with signs of worsening conditions. The average TVDI values for July, August, September, October, and November remained relatively stable, indicating five consecutive months of moderate drought. In December, the drought conditions improved significantly compared to the previous months, reducing the drought level to mild.The data is basically consistent with the temperature and precipitation changes shown in Figures 2 and 3. Figure 17: Map of changes in the percentage of drought area of vegetation in Laibin by year. Figure 18: Changes in mean TVDI values of vegetation areas in Laibin by month in the last three years. In 2022, the drought conditions in January and February remained basically unchanged, both classified as mild droughts. The mean TVDI value in March slightly increased compared to February, also categorized as a mild drought. The changes in mean TVDI values in March and April were minimal, with values of 0.52 and 0.60, respectively, both indicating mild drought conditions. May showed slight improvement compared to April, with mean TVDI values approaching normal levels. However, in June, drought conditions worsened significantly, with a mean TVDI value of 0.85, marking the most severe drought in a single month in 2022 and the highest level in the past three years, classified as a severe drought. July saw considerable improvement compared to June, with the mean TVDI value dropping to 0.54, indicating mild drought conditions. Drought conditions deteriorated in August, September, October, and November, with moderate drought conditions in all months except for September. By December, the mean TVDI value decreased, leading to an improvement in drought conditions, which were reduced to a mild drought. In 2023, the drought conditions varied throughout the year. In January, conditions were normal. By February, the mean TVDI value sharply increased to 0.70, indicating moderate drought. In March, conditions improved significantly, characterized as mild drought. April saw a significant increase in TVDI value, still in the mild drought range but nearing moderate levels. By May, conditions worsened, reaching the year's TVDI threshold for moderate drought. June, July, and August maintained the moderate drought status. September saw improvement, dropping to light drought. October and November remained at a light drought level. December showed a fluctuation, starting as a moderate drought but then increasing again to moderate levels. Over the period spanning 2021 to 2023, Laibin City experienced varying degrees of drought conditions, with 19 months classified as light drought, 15 months as moderate drought, 1 month as severe drought, and 1 month as normal. The prevailing pattern of drought in Laibin City oscillates between light, moderate, and severe categories, with the months from April to October witnessing frequent drought occurrences.