气候变化领域集成服务门户(CCPortal): Time-variant error characterization of SMAP and ASCAT soil moisture using Triple Collocation Analysis

CCPortal

DOI	10.1016/j.rse.2021.112324
	Time-variant error characterization of SMAP and ASCAT soil moisture using Triple Collocation Analysis
	Wu K.; Ryu D.; Nie L.; Shu H.
发表日期	2021
ISSN	00344257
卷号	256
英文摘要	Knowledge about spatiotemporal error characteristics of remotely sensed soil moisture (SM) products is essential for correctly interpreting observational information and optimally assimilating them into hydrological models. This work aims to (i) investigate the relative difference between time-invariant and time-variant daily SM errors of Advanced Scatterometer (ASCAT) and Soil Moisture Active Passive (SMAP) products and (ii) analyze correlation of the daily SM errors with surface biomass quantified by the Leaf Area Index (LAI) and rainfall. The time-invariant error denotes an aggregate error magnitude during the whole investigation period and the time-variant error at daily time scale also refers to an aggregate error magnitude but for the period of the 100-day time window centered at the day to be processed. The time-invariant and daily SM errors are estimated using the Triple Collocation Analysis (TCA) applied to ASCAT and SMAP SM retrievals along with the Global Land Data Assimilation System version 2.1 (GLDAS2) SM product for the period of April 2015 – January 2020. Results indicate the relative difference between time-invariant and time-variant daily errors is notable for both ASCAT and SMAP SM products. The relative difference in units percentage denotes the ratio of difference value between time-invariant and daily errors to time-invariant error itself. The daily TCA error fluctuated at 43% value from time-invariant error for ASCAT SM and at 47% value for SMAP SM on a global average. When averaged globally, temporal mean of time-variant daily errors was relatively smaller than time-invariant error by -27% for ASCAT SM and -18% for SMAP SM, respectively. In tropical areas, the relative difference between time-invariant and daily errors is large during the dry season and becomes small when rainy season comes. When the peak lagged correlation is used, daily errors exhibit a stronger correlation with rainfall than they do with LAI in 61% of landmass pixels for ASCAT SM and 66% of landmass pixels for SMAP SM. LAI cannot be used to predict temporal variability of time-variant SM errors in barren land. Lagged correlation analysis reveals rainfall peak coincides with SM error peak in areas featured with low vegetation cover, including barren land, grasslands, and open shrublands. By contrast, the LAI peak comes after the SM error peak in all cases. Savannas and woody savannas are a special case as SM error peak comes first, followed by rainfall then LAI peaks. In summary, ASCAT and SMAP time-variant error varies with a large deviation from time-invariant errors and its temporal variation shows a stronger association with rainfall than changing LAI. © 2021 Elsevier Inc.
英文关键词	ASCAT; SMAP; soil moisture; time-variant error; Triple Collocation Analysis
语种	英语
scopus关键词	Aggregates; Meteorological instruments; Pixels; Rain; Soil moisture; Tropics; Correlation analysis; Error characteristics; Error characterizations; Hydrological models; Land data assimilation systems; Remotely sensed soil moisture; Soil moisture active passive (SMAP); Temporal variability; Errors; ASCAT; correlation; dry season; error analysis; leaf area index; savanna; shrubland; soil moisture; spatiotemporal analysis; temporal variation
来源期刊	Remote Sensing of Environment
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/178926
作者单位	State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan, 430079, China; Dept of Infrastructure Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia
推荐引用方式 GB/T 7714	Wu K.,Ryu D.,Nie L.,et al. Time-variant error characterization of SMAP and ASCAT soil moisture using Triple Collocation Analysis[J],2021,256.
APA	Wu K.,Ryu D.,Nie L.,&Shu H..(2021).Time-variant error characterization of SMAP and ASCAT soil moisture using Triple Collocation Analysis.Remote Sensing of Environment,256.
MLA	Wu K.,et al."Time-variant error characterization of SMAP and ASCAT soil moisture using Triple Collocation Analysis".Remote Sensing of Environment 256(2021).