Monitoring Of Agricultural Drought Based On Temporal Series Of GLASS LAI Anomaly In Northeast Of China

Drought has become widespread occurrence natural disasters, threatening the foodsecurity of nation and causing the great losses of economy. It is an important scientific issuein the fields of food security and global changing that how to monitor the drought timely andextensivelyLots of research works on drought has been done in the domestic and foreign counters.In the previous period, several drought indices were constructed in terms of differentrequirements to apply to the real researches and the monitoring data were generally obtainedfrom monitoring ground sites of precipitation and temperature. Although these studies havemade some progresses, it was still difficult to obtain meteorological data and some factorsmight bring troubles to drought monitoring because of the point-like data. In recent years,with the development of remote sensing technology, this technology provides new avenuesto monitor drought because it has some advantages such as its large coverage and timelydrought monitoring. Researchers used different vegetation indices, such as the realization ofthe energy balance of drought monitoring to achieve series of goals. LAI (Leaf Area Index)acts as an important structural parameter on land vegetation. Crop growth and developmentwill be inhibited when the crop is lack of water caused by drought, so that its LAI will belower than the normal one, and then we can monitor the drought degree based on thechanges of LAI finding the difference from the average.LAI data used in this article is made of863projects “The Study on Global LandSurface Characteristic Parameters Products and its Application "(hereinafter referred GLASSLAI). GLASS LAI have higher time resolution because of those pretreatment have be doneincluding the removing of atmospheric correction, geometric correction, the cloud shadowand snow shadow，and the filling of the missing pixels.Without the affected by rainfall, the vegetation types is an important role for the changeof LAI as well. In this paper, the author used MODIS land classification data (MOD12Q1)classified the Northeast region as the final crop experimental area. In the study, the authorused Google Earth to filter out31qualifying sites, and collected sites’ Palmer DroughtSeverity Index (the abbreviation PDSI). The anomaly percentage of LAI (Lap) is anindicator to vegetation growth status, which defined based on the GLASS LAI. And thenanalyzed the correlations between Lap and anomaly percentage of rainfall (Pa), thecorrelations Lap and PDSI, also studied the hysteresis quality. The author defined fivedifferent level of drought according to Lap, and monitored the drought of the crop innortheast of China in May of2009to October of2009.The results show that: Pa and Lap have relatively good correlation and the correlationcoefficient close to0.5, when the ground covered by crops and the crop growth is relativelystrong season; while PDSI and Lap have weak correlation with the correlation coefficientless than0.3. The regular lag time cannot be determined in the hysteresis quality research. Inorder to validate the distribution situation of the study area of drought by using PalmerDrought Severity Index, the results showed that: Lap which defined based on GLASS LAImight well reflect the drought events that occurred in the study area, while the space-timecontinuum of GLASS LAI can overcome the problem of uneven distribution in the space ofrainfall data, using of which can improve the accuracy of monitoring drought in crop, therefore, GLASS LAI has a wide application prospects.