Long-term (2003-2017) Trends of Vegetation Condition Index (VCI) in Guangdong Using Modis Data and Implications for Drought Assessment

Drought will affect ecological environment and cause economic losses. Guangdong Province has been suffering from seasonal drought for a long time. Traditional drought assessment mainly relies on site-scale soil moisture content data or meteorological-related data. The spatial representativeness of this drought assessment method based on single point is poor. The high temporal and spatial resolution of remote sensing images is more conducive to our assessment of long-term and large-scale drought changes. Soil moisture and dryness can affect the growth of vegetation. In vegetation-covered areas, indicators reflecting vegetation status can also be used for drought assessment to a certain extent. We calculated Vegetation Condition Index (VCI) using an 8-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) from 2003 to 2017. The spatial and temporal distribution of drought in Guangdong Province in recent years was analyzed based on VCI. The following main conclusions are obtained: 1) the results of remote sensing drought assessment by using VCI are consistent with the actual situation. The annual average VCI in Guangdong Province in 2005, 2006 and 2010 was lower than in other years. According to the meteorological data of Guangdong Province, severe drought occurred from late 2004 to early 2005, from late 2005 to early 2006 and from late 2010 to early 2011. 2) On a long-term trend, the drought situation tends to decrease year by year in Guangdong. Compared with other areas in Guangdong, drought occurrence in eastern Guangdong is less frequent and milder. 3) Spring drought and autumn-winter drought of different severity usually occur in Guangdong Province. Spring drought is usually the most serious in Western Guangdong and the lightest in eastern Guangdong.