SMAP Satellite Soil Moisture Products: a preliminary evaluation against COSMOS-UK estimates in Great Britain

Quinn, Nevil; Horswell, Michael; West, Harry; Newton, Chris

Abstract

Satellite-based soil moisture monitoring has matured, notably as a result of the Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) missions. Whilst spatial resolutions fall short of those ideal for field-scale monitoring, there are several ‘value-added’ RS soil moisture products available at the regional (e.g. SMOS: 25km, SMAP: 36km) to meso-scale (e.g. SMAP: 9km) resolution. Challenges arise as sensors only measure surface moisture (0-5cm), but frequent repasses (2-3days), global coverage and low latency offer other advantages. Evaluation against ground-based measurements in the USA and elsewhere is encouraging, but little evaluation has been undertaken in the UK. We make a start by evaluating these products against COSMOS-UK soil moisture at ~40 sites corresponding to a variety of climatic, soil and land cover settings. These cosmic ray sensors integrate soil moisture over an area of ~12ha, and while not matching the spatial scale or soil depth of satellite measurements, do at least avoid some of the field-scale heterogeneity issues associated with point-based measurement. COSMOS-UK sites were installed from 2013 onwards, so records are short and a consistent temporal analysis is not possible. For each site, soil moisture corresponding to the overlapping grid square of the satellite product was extracted. Time series were correlated and evaluated using the Pearson correlation coefficient, unbiased root-mean square error and mean bias. Reasons for spatio-temporal variations in correlations are proposed including reference to including reference to soil profile characteristics and properties at each site, as well as vegetation and climatic setting.

• Presentation Conference Type: Conference Paper (unpublished)
• Conference Name: International Union of Geodesy & Geophysics General Assembly
• Start Date: Jul 8, 2019
• End Date: Jul 18, 2019
• Acceptance Date: Feb 1, 2019
• Publication Date: Jul 10, 2019
• Peer Reviewed: Peer Reviewed
• Public URL: https://uwe-repository.worktribe.com/output/1491940
• Additional Information: Title of Conference or Conference Proceedings : International Union of Geodesy & Geophysics General Assembly