Vegetation Supply Water Index (VSWI) and Temperature Vegetation dryness Index (TVDI) are two most commonly used methods for surface soil moisture (SSM) retrieval using electromagnetic spectrum of visible, near infrared and thermal infrared band. Both of them take into account the effect of vegetation index (VI) and surface temperature (Ts) on SSM. A comparative analysis of the ability and effect of the two methods for SSM retrieval in karst areas was carried out, using the remote sensing data of Landsat 8 OLI_TIRS. The study area is located in Guilin, which is a typical karst area. The experimental results show that TVDI is more suitable for SSM retrieval in karst areas.
The terrestrial water storage changes (TWSC) for global scale as well as area scale can be estimated by GRACE (Gravity Recovery And Climate Experiment) mission, while hydrologic and climate model named GLDAS (Global Land Data Assimilation System) provide variations of soil moisture and snows which can also derive the TWSC. These new technologies provide new methods to monitor global terrestrial water storage variations and climate change. The global monthly TWSC have been derived from GRACE observations and GLDAS model estimates respectively, it shows there have high There have high correlations between TWSC derived from GRACE observations and GLDAS model estimates, while due to lack of information from GLDAS models, TWSC derived from GRACE observations is more reliable. The monthly mean TWSC from April 2002 to August 2011 have been derived from GRACE observations, and there has a steady condition of the global TWSC with a slowly growing rapid of 0.142±0.0028cm/year in this period. while the change range of Northern Hemisphere of TWSC is more obvious than those of Southern Hemisphere. Due to the unbalance of regional rainfall, the TWSC in the middle latitude regions are changing more significantly than those in high-and-low latitude regions. It shows great correlations between global TWSC and global land surface temperature with correlation coefficient of 0.91, while the change of land surface temperature always occurred about two months later than the TWSC, and both of them have obvious change with annual period.
In order to avoid rework and improve the efficiency of GPS static observation, it is very important to control the quality of GPS data in real time. On the basis of analysis of observation data decoding and observation data quality indices, a new program was compiled for decoding the original observation data and calculating and analyzing the quality indices such as the multipath effect and cycle slips etc. and the quality indices can be displayed intuitively by graphics in realtime. Moreover, the experimental verification is carried out with the engineering practice, and the results proved the correctness and reliability of the designed software RTQC, which can provide guidance and help for the practical work.