基于NDVI-Ts特征空间的黑龙江省干旱监测

Drought Monitoring in Heilongjiang Province Based on NDVI-Ts Space

NDVI-Ts特征空间方法结合了卫星遥感地表反射率和热红外特性,能较好地反映一定时空尺度的地表干旱状况,该文基于Terra-MODIS归一化植被指数(NDVI)和地表温度(LST)产品,构建NDVI-Ts三角形特征空间,采用植被温度状态指数结合MODIS地表分类产品IGBP对黑龙江省2007年夏季干旱进行监测和分析。结果显示:此次夏季干旱的空间分布广,持续时间长,干旱程度重,西部松嫩平原和东部三江平原等地主要农作物产区普遍发生干旱,且旱情严重。结合同期地面气象观测的月降水量数据对监测结果进行验证和评估表明:植被温度状态指数是一项近实时的干旱监测指标,不仅与当地最近的降水事件有关,而且与前期一段时间内的总体降水事件相关,可以较真实地反映当地干旱发生、发展的动态过程。

Combining the spectral vegetation index with thermal infrared information,the triangular space of NDVI-Ts based on satellite remote sensing data provides an effective method for monitoring surface dryness at large spatial scales.Vegetation-Temperature Condition Index（VTCI） based on the triangular space of MODIS NDVI-Ts is applied to monitoring summer drought in Heilongjiang Province in 2007.The VTCI is based on satellite derived information only,and therefore the index is potential for operational application. The Terra-MODIS NDVI（MOD13A2） V005,LST（MOD11A2） V005 and the land cover product （MOD12Q1） V004 products,at 1-kilometer spatial resolution,are used as the indicators for the monitoring and analysis.The monitoring period is from 10 June to 12 August 2007.It＇s found that the space of NDVI-Ts for the whole study area is typically triangular because the monitored area is large enough to make the value of NDVI and soil moisture vary in a very large scope.Then,a linear regression analysis is conducted to get the equations of the dry and wet line from the triangular space for the whole area,and the VTCI for the Heilongjiang Province is extracted.Combined with MODIS land cover product IGBP and frequency distribution of the VTCI,the spatial pattern and temporal evolution of the drought are also analyzed. At last,the ground-measured precipitation data at the same periods are used to validate the drought monitoring measurements. The result shows that the drought widely distributed in spatial scale and is very serious.It is more serious in main crop-producing areas,especially in the western Songnen Plain and the west of eastern Sanjiang Plain.From 10 June to 25 June the drought is heavier than the other 3 monitoring periods.Some fluctuations occur in July,then the drought weakens in most areas in August,except the Daxinganling Mountains in northwest where the drought enhances to some extent.The correlation analysis between VTCI and ground-based measured precipitation indicates that there is a significant linear correlation between VTCI and total monthly precipitation.The VTCI and cumulative total monthly precipitation are also linearly correlated from the monitoring month to the previous months.Obvious correlation is also found between VTCI and the percentage of departure from normal monthly precipitation in the monitoring month, and between VTCI and the cumulative percentage of departure from normal monthly precipitation from the monitoring month to the previous months.The result suggests that VTCI is not only correlated with recent rainfall but also correlated with past cumulative rainfall.So it is a reasonable simplification of the NDVI-Ts space and can monitor drought instantly,which is proved adaptive in Heilongjiang Province.