Abstract
Persistence is an important feature of soil moisture, which affects many important processes such as land–air interaction and ecohydrological processes. Soil moisture datasets from reanalysis, remote-sensing observations and land surface models have been widely used in various ecohydrological studies, however, due to the complexity of hydrological processes, the essential features of soil moisture such as spatial-temporal characteristics and persistence still need to be further quantified. This study focused on the Australia region and used in situ observation from fourteen International Soil Moisture Network sites to evaluate soil moisture from six gridded products, including satellite remote-sensing records (ESA CCI), output of reanalysis (ERA5-Land) and land surface models (GLDAS and GLEAM). High correlation coefficients between observations and the other soil moisture datasets were gotten. Regional averaged inter-annual variations of soil moisture were relatively large with some dry periods (2002–2010, 2013–2016) and wet periods (2011–2012) indicated by these gridded products. General coherent spatial patterns were found in long-term soil moisture with large differences in the lateral inflow area of the Great Artesian Basin. The coefficient of variation of these soil moisture datasets generally decreased from northwest to southeast, but the enhanced vegetation index coefficient of variation was larger in the southwest corner, northeast (non-coastal areas) and the lateral inflow area. Persistence calculated from various soil moisture datasets had quite large differences compared with measurements. Meanwhile, little coherence was gotten among different surface soil moisture datasets, the persistence of deep soil moisture seemed to be significantly overestimated. Therefore, models still need to improve the temporal characteristics with the persistence rather than the correlation coefficient.
Highlights
Introduction published maps and institutional affilSoil moisture (SM) is one of the essential variables of the terrestrial water cycle, ecohydrology and land–air interactions [1]
SM persistence (SMP) plays a vital role [3] in land–air interaction, and the study of SM dynamics and its persistence is of great significance for improving land surface models (LSMs)
SM data from 0–0.08 m at 10 sites on the Australian Ozark Network Communications (OZNET) network were applied to evaluate the LSMs and remotely sensed surface SM
Summary
Soil moisture (SM) is one of the essential variables of the terrestrial water cycle, ecohydrology and land–air interactions [1]. SM has a typical characteristic of red noise with memory, called persistence. SMP can be calculated by autocorrelation coefficient (AC) methods and is quantified by lag (in days). SMP plays a vital role [3] in land–air interaction, and the study of SM dynamics and its persistence is of great significance for improving land surface models (LSMs). As SM involves complex water processes, scientists are committed to continuously improving SM datasets from both observation and simulation. SM data from site observation is sparsely distributed and has poor time continuity, and it is difficult to apply it in large-scale and long-term analysis.
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