基于植被状态指数的甘肃省2000-2019年干旱时空特征分析

Analysis of the Spatial and Temporal Characteristics of Drought in Gansu Province from 2000 to 2019 Based on the Vegetation State Index

农业发展受干旱影响极为敏感。为了为制定科学的应对措施和干旱缓解措施提供科学依据,利用NDVI作为基础数据,将植被状态指数(VCI)作为表征干旱的指标,通过分析VCI的变化趋势、计算干旱频率和干旱面积占比、分析VCI与降水量的相关性,探讨2000—2019年不同空间尺度甘肃省干旱的时空分布特征,并且结合土地利用类型分析了不同用地类型发生不同程度旱情的可能性。结果表明:甘肃省农业干旱高发于春季,其次是秋季;空间上以全域性干旱为主,即研究时段内甘肃省干旱面积占比大于50%为主,并呈现西北高东南低的空间格局;植被状态指数与当月降水量的相关系数最大,达到了0.827;林地和草地发生干旱的比例最低,未利用地发生干旱的比例最高。综上,甘肃省旱情以全域性干旱为主,且时空分布不均,整体旱情呈现逐渐缓解的趋势。

Agricultural development is extremely sensitive to the impact of drought.In order to provide a scientific basis for formulating appropriate scientific response and drought mitigation measures,NDVI was used as the basic data,and the Vegetation Condition Index(VCI)was used as an indicator to characterise drought.By analysing the variation trend of VCI,calculating the drought frequency,the proportion of drought area,and analysing the correlation between VCI and precipitation,the temporal and spatial distribution characteristics of drought in Gansu Province at different spatial scales from 2000 to 2019 were discussed.Combined with land use types,the possibility of different degrees of drought in different land use types were analysed.The results show that:the agricultural drought in Gansu Province is most common in spring,followed by summer;spatially,it is dominated by global drought,that is,the proportion of drought area in Gansu Province was more than 50%during the study period,and the spatial pattern is high in the northwest and low in the southeast;The correlation coefficient between the vegetation state index and the monthly precipitation was the largest,reaching 0.827;the drought rate of forest land and grassland was the lowest,and the drought rate of unused land was the highest.To sum up,the drought in Gansu Province is dominated by global drought,and the spatial and temporal distribution is uneven.