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Assessing Temporal Stability for Coarse Scale Satellite Moisture Validation in the Maqu Area, Tibet
Department of Water Resources, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, Hengelosestraat 99, 7514 AE Enschede, The Netherlands
Department of Civil Engineering, NED University of Engineering and Technology, Karachi 75270, Pakistan
Centre of Excellence in Water Resources Engineering, University of Engineering and Technology, Lahore 54890, Pakistan
* Author to whom correspondence should be addressed.
Received: 10 July 2013; in revised form: 8 August 2013 / Accepted: 12 August 2013 / Published: 16 August 2013
Abstract: This study evaluates if the temporal stability concept is applicable to a time series of satellite soil moisture images so to extend the common procedure of satellite image validation. The area of study is the Maqu area, which is located in the northeastern part of the Tibetan plateau. The network serves validation purposes of coarse scale (25–50 km) satellite soil moisture products and comprises 20 stations with probes installed at depths of 5, 10, 20, 40, 80 cm. The study period is 2009. The temporal stability concept is applied to all five depths of the soil moisture measuring network and to a time series of satellite-based moisture products from the Advance Microwave Scanning Radiometer (AMSR-E). The in-situ network is also assessed by Pearsons’s correlation analysis. Assessments by the temporal stability concept proved to be useful and results suggest that probe measurements at 10 cm depth best match to the satellite observations. The Mean Relative Difference plot for satellite pixels shows that a RMSM pixel can be identified but in our case this pixel does not overlay any in-situ station. Also, the RMSM pixel does not overlay any of the Representative Mean Soil Moisture (RMSM) stations of the five probe depths. Pearson’s correlation analysis on in-situ measurements suggests that moisture patterns over time are more persistent than over space. Since this study presents first results on the application of the temporal stability concept to a series of satellite images, we recommend further tests to become more conclusive on effectiveness to broaden the procedure of satellite validation.
Keywords: temporal stability; representative mean soil moisture (RMSM); correlation; advance microwave scanning radiometer (AMSR-E); satellite validation
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Bhatti, H.A.; Rientjes, T.; Verhoef, W.; Yaseen, M. Assessing Temporal Stability for Coarse Scale Satellite Moisture Validation in the Maqu Area, Tibet. Sensors 2013, 13, 10725-10748.
Bhatti HA, Rientjes T, Verhoef W, Yaseen M. Assessing Temporal Stability for Coarse Scale Satellite Moisture Validation in the Maqu Area, Tibet. Sensors. 2013; 13(8):10725-10748.
Bhatti, Haris A.; Rientjes, Tom; Verhoef, Wouter; Yaseen, Muhammad. 2013. "Assessing Temporal Stability for Coarse Scale Satellite Moisture Validation in the Maqu Area, Tibet." Sensors 13, no. 8: 10725-10748.