Upscaling sparse ground‐based soil moisture observations for the validation of coarse‐resolution satellite soil moisture products

Abstract

The contrast between the point-scale nature of current ground-based soil moisture instrumentation and the ground resolution (typically >10 2 km 2) of satellites used to retrieve soil moisture poses a significant challenge for the validation of data products from current and upcoming soil moisture satellite missions. Given typical levels of observed spatial variability in soil moisture fields, this mismatch confounds mission validation goals by introducing significant sampling uncertainty in footprint-scale soil moisture estimates obtained from sparse ground-based observations. During validation activities based on comparisons between ground observations and satellite retrievals, this sampling error can be misattributed to retrieval uncertainty and spuriously degrade the perceived accuracy of satellite soil moisture products. This review paper describes the magnitude of the soil moisture upscaling problem and measurement density requirements for ground-based soil moisture networks. Since many large-scale networks do not meet these requirements, it also summarizes a number of existing soil moisture upscaling strategies which may reduce the detrimental impact of spatial sampling errors on the reliability of satellite soil moisture validation using spatially sparse ground-based observations. © 2012 by the American Geophysical Union

Microwave remote sensing of short‐term droughts during crop growing seasons

“…This not only suggests the deficiency in modeling or remote sensing of soil moisture but also may indicate the mismatch in spatial scales between in situ observations and the reanalysis or retrieval products that makes the comparison difficult. Point-scale soil moisture has a stronger temporal dynamics [Rodriguez-Iturbe et al, 1995;Crow et al, 2012] than the large-scale (satellite or model) estimation. To testify the sensitivity of the results to spatial scales, we repeat the analysis with resolution coarser than 0.25°.…”

Application of Remote Sensing Data to Constrain Operational Rainfall-Driven Flood Forecasting: A Review

“…While in-situ probes provide continuous soil moisture measurements with a satisfactory level of accuracy, it has been widely admitted that these point measurements lack representativeness of regional soil water conditions [117]. Remote sensing techniques provide the opportunity to obtain spatial information on land surface soil moisture, compensating for the shortage of in-situ measuring techniques.…”

Land surface model performance using cosmic-ray and point-scale soil moisture measurements for calibration

“…The soil properties and processes at this scale can however differ from those at the LSM grid cell sizes, which are often as large as hundreds to tens of thousands of square kilometres (Pitman, 2003). Due to the different governing processes, upscaling the soil hydraulic properties from soil core scale to field scale is nontrivial (Vinnikov et al, 1996;Crow et al, 2012).…”