基于温度植被干旱指数的关中地区旱情监测

Monitoring drought in Guanzhong areas using temperature-vegetation drought index

及时准确地进行区域尺度的干旱监测对于保障农业生产和保护粮食安全具有重要指导意义。该研究基于2001—2020年的MOD11A2地表温度8 d合成产品与MOD13A1植被指数16 d合成产品,通过地表温度(land surface temperature,LST)和归一化植被指数(normalized difference vegetation index,NDVI)数据构建NDVI-LST特征空间,获取关中地区2001—2020年20 a时间序列的温度植被干旱指数(temperature vegetation dryness index,TVDI),分析关中地区干旱时空分布演变特征和干旱影响成因,探索其未来演变趋势。结果表明:1)关中地区近20 a来TVDI平均值为0.57,干旱类型整体上属于正常的干旱状态,82.00%的地区干旱变化状况为稳定不变,渭河冲积平原干旱程度较为严重,其次是渭北旱塬地区,南部秦岭地区较为湿润;2)关中地区未来干旱情况有所缓解,7.71%的研究区将持续变湿,36.24%的地区由干变湿;3)关中地区的TVDI值与海拔、坡度、降水量呈现负相关,与气温呈现正相关关系,林地、草地覆盖对缓解干旱具有积极意义。温度植被干旱指数从区域尺度上实现了干旱状况的定量化表征,在关中地区具有较好的适用性,遥感干旱监测结果可为关中地区抗旱对策的制定提供理论基础和科学依据。

Drought is one of the most serious natural disasters with the widest distribution,the highest frequency,and the greatest economic losses in the world.A grave threat has been posed to agricultural production,food security,and socio-economic development.It is of great significance to timely and accurately monitor the drought at the regional scale.In this study,the NDVI-LST feature space was constructed using the MOD11A2 surface temperature 8-d synthetic product and MOD13A1 vegetation index 16-d synthetic product.The data was collected from the land surface temperature(LST)and normalized difference vegetation index(NDVI).Temperature vegetation dryness index(TVDI)was captured from the Guanzhong areas in a 20-year time series from 2001 to 2020.The spatial and temporal distribution of drought was analyzed to determine the causes and future trends of natural disasters.The results show that:1)It was feasible to carry out drought monitoring on a regional scale using the TVDI remote sensing index.The average TVDI was 0.57 over the past 20 years.The drought type was in a normal state in general.The highest annual average TVDI was found in 2013 and the lowest in 2006.The average TVDI value fluctuated greatly during the 20-year period.Drought also shared strong regional characteristics,indicating a spatial distribution pattern of wet in the southwest,dry in the center and northeast,and normal in the north.2)The spatial and temporal trends of drought showed that 82.00%of the areas had relatively stable droughts,and only 8.05%of the areas were with improved droughts.As such,there was a relatively small variation in the drought condition;Combined with the Hurst index,the future trend of drought was characterized by a relatively small amount of change.There was an anti-sustainable trend of drought in the future;Combined Hurst index and TVDI trend,7.71%of the study area was continuously wet in the future,and 36.24%of the area was changed from drought to wet.3)The TVDI value was positively correlated with the air temperature,while negatively correlated with the precipitation.There was a similar spatial distribution pattern of the 20-year average TVDI and the annual average air temperature.The air temperature and precipitation shared a similar distribution in the spatial pattern.The degree of drought depended mainly on the air temperature and precipitation.Meanwhile,the degree of aridity was negatively correlated with both elevation and slope.The arid and more arid types were mainly distributed in the central plains with low elevations and small slopes.While the moist and more moist types occupied a larger area in the mountainous areas south of the Qinling Mountains with high elevation.The TVDI values varied with months in the different land use types in the study area.The cropland and construction land presented the highest TVDI values,with the annual mean values of 0.76 and 0.75,respectively,whereas,the woodland was the smallest TVDI value,with an annual mean value of 0.45.Therefore,the woodland and grassland cover can be expected to positively mitigate the drought.The TVDI can be used to quantify the drought conditions from the regional scale.Remote sensing drought monitoring can also provide a theoretical foundation and scientific basis for the formulation of drought countermeasures in Guanzhong areas.