| Paper: | TH-A2.27 |
| Session: | Applications of Radiometry II |
| Time: | Thursday, March 29, 09:00 - 10:20 |
| Presentation: |
Poster
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| Topic: |
Theory, physical principles and electromagnetic models: |
| Title: |
Improvement of vegetation water content estimation over the Tibetan Plateau using field measurements |
| Authors: |
Menglei Han; Tsinghua University | | |
| | Hui Lu; Tsinghua University | | |
| | Kun Yang; Tsinghua University | | |
| | Jiancheng Shi; Institute of Remote Sensing and Digital Earth | | |
| Abstract: |
Vegetation water content (VWC) is an essential variable in the tau-omega model which is adopted to deal with the vegetation effects in many standard soil moisture retrieval algorithms. Currently, VWC is derived from NDVI with considering land cover map and stem factors and then used as an input to estimate the vegetation opacity in both SMOS and SMAP algorithm. This method and corresponding datasets are developed on the basis of field experiments conducted mainly in U.S. However, the reliability and accuracy of this method have never been evaluated over the Tibetan Plateau, where unique climate and vegetation coverage located. The objectives of this study, therefore, are: (1) Intercomparison of VWC data sets among SMAP, SMOS and AMSR2 over the Tibetan Plateauļ¼(2)evaluation of the VWC against ground observation collected at Maqu site; (3)development of a new VWC data set with using an accurate and high resolution land cover map and considering the effects of vegetation fractional coverage.
The intercomparison results demonstrate that the three VWC data sets are generally in good agreement, while SMAP VWC shows more clearly variations. Comparing to the ground observations, all VWC values from three data sets are larger than the in situ measurements. One possible reason is the stem factor is too large over this region, where the height of dominate grass is generally less than 10cm and the stem component of VWC should be very small. Based on the comparison results, we revised the VWC estimation equation with considering the vegetation fractional coverage effect while removing the contribution of stem components. The VWC estimated with the new equation agrees well with ground measurements and also shows reasonable spatial and temporal variation over the Tibetan Plateau. This new VWC data set could be input into soil moisture algorithms and then improve the performance of soil moisture production over this region.
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