条件植被温度指数干旱监测指标的等级划分

Classification of Drought Grades Based on Vegetation Temperature Condition Index

以每年3月下旬至5月下旬陕西渭北旱塬合阳、蒲城、澄城、永寿县和耀州区5个旱作农业站点以旬为单位的条件植被温度指数(VTCI)为研究对象,根据气象干旱指数的等级划分标准将VTCI分级。结果表明:VTCI被划分为4个等级。VTCI>0.55为无旱,VTCI在0.46～0.55之间为轻旱,VTCI在0.37～0.46之间为中旱,VTCI<0.37为重旱。通过气温、降水等气象资料对VTCI等级划分结果的验证表明,VTCI的干旱监测结果与当地基于气象资料的监测结果相一致,证实了该等级划分结果是可行的。

Drought is a slow-onset natural disaster,an insidious and creeping phenomenon which occurs in all climatic regimes virtually.Drought is characterized by the high occurring frequency,long duration and vast disaster area.Drought impacts generally agriculture and ranks the first in the loss of all kinds of natural disasters.Therefore,it is of great significance to develop the dynamic and real-time drought monitoring approaches.The drought monitoring index is always set up for specific zone and time.The study about drought monitoring approach is focused on the vegetation temperature condition index （VTCI）,which is based on an assumption that the shape of the scatter plots of LST and NDVI is a triangular at a regional level.In this paper,the Guanzhong Plain in the Shaanxi Province,China is selected as the study area,where drought is one of the natural disasters,there is not only the irrigated farming,but also the rain-fed one,which makes it suitable to use VTCI approach for drought monitoring.The data of field-measured soil moisture content and precipitation in the Guanzhong Plain are employed to validate VTCI approach.According to the theory of point-based quantified drought monitoring approaches,the study focuses on developing quantified drought monitoring index by using RS data.Based on the categories of point-based drought monitoring approaches,drought categories for the vegetation temperature condition index were classified and validated in this study.VTCI values of five rain-fed farming areas near meteorological stations,namely Heyang,Pucheng,Chengcheng,Yongshou and Yaozhou in the Weibei Tableland of Shaanxi Province,were selected for the classification.The results show that the VTCI drought intensity can be classified into 4 grades,i.e.the normality or wetness （VTCI0.55）,slight drought （VTCI：0.46-0.55）,moderate drought （VTCI：0.37-0.46） and severe drought （VTCI0.37）.The VTCI drought grades are similar to the field measured results and the precipitation data,which demonstrates that the classification of VTCI is suitable and practical.