条件植被温度指数及其在干旱监测中的应用

Vegetation-Temperature Condition Index and Its Application for Drought Monitoring

  • 摘要: 应用NOAA -AVHRR数据,在用条件植被指数、条件温度指数和距平植被指数进行年度间相对干旱程度监测的基础上,提出了条件植被温度指数的概念,它适用于监测某一特定年内某一时期(如旬)区域级的相对干旱程度。条件植被温度指数的定义既考虑了区域内归一化植被指数的变化,又考虑了在归一化植被指数值相同条件下土地表面温度的变化。陕西省关中平原地区2000年3月下旬干旱的监测结果表明,条件植被温度指数能较好地监测该区域的相对干旱程度,并可用于研究干旱程度的空间变化特征,对干旱的监测结果与用土壤热惯量模型反演的土壤表层含水量的结果基本吻合。

     

    Abstract: Most previous applications of the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer (NOAA-AVHRR) remotely sensed data for drought monitoring were based on vegetation condition index (VCI),temperature condition index (TCI),and/or anomaly vegetation index (AVI),which extracted from AVHRR derived normalized difference vegetation index (NDVI) and brightness temperature data.These indices were often applied to monitor drought occurrence at a large scale or a regional level by comparing the indices' inter-annual changes for a special period of the covering years.On basis of the above drought monitoring results,an index called vegetation-temperature condition index (VTCI) was developed for drought monitoring in this study.The index can be used to monitor drought occurrence at a regional level for a special period (e.g.10 days) of a year,and to capture spatial variations of drought occurrences within the region.The new drought monitoring index is not only related to NDVI changes in a region,but also gives emphasis on land surface temperature changes of pixels which have the same NDVI value.The value of VTCI is from 0 to 1.The lower value of VTCI,the heavier the drought occurrence is.The index is site-specific and time-specific. A pilot study was carried out for drought monitoring for the last tenDays of March 2000 in the Guanzhong Plain area of Shanxi Province,China.The results showed that VTCI had betterFK(W15?40ZQ performances in classifying the relative drought occurrence levels and in studying the distribution of drought occurrences.There are different levels of drought occurrences in the Plain.The boundary between the Plain and Qingling Mountain,which is located in the south of the studied area,was clearly showed in the VTCI image.There was a strip area just to the north of this boundary with relatively heavy drought occurrence where VTCI values were less than 0.4.The other centralized heavy drought occurrence areas were the area at banks of the Yellow River valley,the area around Chengcheng county which is located in the Weibei tablelands,and the area to the north of Yangling city.The scattered drought occurrence pixels can also be found in the study area.In General,the monitoring results were accorded with soil surface (0~10 cm) moisture distribution which was simulated by using soil real thermal inertia model developed by the authors.For future development of the drought index,robust methods have to be found to enable estimation of the VTCI parameters for a long time series of data,and the index should be tested in more dryness areas.

     

/

返回文章
返回