Variation of water body in Dongting Lake from in situ measurements and MODIS observations in recent decades

Identifying the spatiotemporal dynamics of the water body in Dongting Lake,the second largest freshwater lake in China,is crucial for water resource management.In this study,the variations of the water body were comprehensively analyzed based on remote sensing images and in situ measurements from 2000 to 2019.Four breakpoint detection approaches were integrated to analyze the change trends and explore the related driving forces behind the changes.The results showed that significant intra-and inter-annual fluctuations of the water body were found from 2000 to 2019.The water area and volume decreased at rates of 1.26 km^(2)/a and 16.65×10^(6)m^(3)/a,respectively.During the entire study period,the outflow at Chenglingji station(CLJ),the inflow from three outlets of the Yangtze River(Inflow2),and the inundation conditions during the last period(Arealag)made the largest relative contributions to the water area variation(around 25%,27%and 24%,respectively).A breakpoint was detected around 2004,corresponding to the operation period of the Three Gorges Dam(TGD).The regulation of TGD profoundly affected the hydrological characteristics at the three outlets and CLJ,and may have indirectly caused the water area to expand by 2.41 km^(2)/a during the dry seasons between 2004 and 2019.These results provide valuable insight into how natural and anthropogenic factors affect water body variation and may offer a practical reference for the local government to adjust management strategies.

A detailed comparison of MYD11 and MYD21 land surface temperature products in China's Mainland

Land surface temperature(LST)is a key parameter in land surface system.The National Aeronautics and Space Administration(NASA)recently released new Moderate Resolution Imaging Spectroradiometer(MODIS)LST products(MOD21 and MYD21).Here,we conducted a detailed comparison between the MYD11 and MYD21 LST data in China's Mainland.The LSTs of MYD21 were approximately 1℃ higher than those of MYD11 averaged for China's Mainland,as MYD21 corrected the cold bias of MYD11.The proportions of the valid value of MYD21 were generally lower than those of MYD11 because the cloud removal method of MYD21 was stricter than that of MYD11.Furthermore,the outliers were less significant in MYD11 than in MYD21 because the outliers in MYD11 were removed using temporal constraints on LST.The outliers in MYD21A2 resulted in a difference of greater than 3℃ in average seasonal surface urban heat island intensity(SUHII)between MYD11A2 and MYD21A2.Finally,using MYD11 may underestimate the slope of long-term trends of SUHII.MYD21 LST data may have some uncertainties in urban areas.This study provided a reference for users for selecting LST products and for data producers to further improve MODIS LST products.