Validation of SMOS L3 AND L4 Soil Moisture Products In The Remedhus (SPAIN) AND CEMADEN (BRAZIL) Networks

Spatafora, Luciana Rossato; Vall-llossera, M.; Camps, Adriano; Chaparro, David; Alvalá, Regina Célia dos Santos; Barbosa, Humberto Alves

doi:10.26848/rbgf.v13.2.p691-712

Cited by 6 publications

(3 citation statements)

References 21 publications

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“…Comparing the stations from REMEDHUS in Figure 12c shows that Carretoro had a greater overestimation trend than the other stations throughout all years. All REMEDHUS stations are dominated by cropland, but Carretoro contains a greater proportion of sand content in the soil and has the lowest soil water retention capacity (Spatafora et al., 2020). Hence, the SMAP SM data were not sensitive enough to represent the relatively lower SM true values in Carretoro.…”

Section: Analysis and Discussionmentioning

confidence: 99%

A global 1‐km downscaled SMAP soil moisture product based on thermal inertia theory

Fang

Lakshmi

Cosh

et al. 2022

Vadose Zone Journal

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Microwave remote sensing technology has been applied to produce soil moisture (SM) retrievals on a global scale for various studies and applications. However, due to the limitations of current technology, the native spatial resolution of currently available passive microwave SM products is on the order of tens of kilometers, and this resolution cannot be used to characterize SM variability on a regional scale. To overcome this limitation, a downscaling algorithm based on the thermal inertia theory–derived relationship between SM and temperature difference was developed using outputs from the Global Land Data Assimilation System–Noah Land Surface Model and the land long‐term data record–Advanced Very High Resolution Radiometer normalized difference vegetation index (NDVI) dataset and applied to the Aqua Moderate Resolution Imaging Spectroradiometer land surface temperature/NDVI data to produce a downscaled 1‐km Soil Moisture Active Passive (SMAP) radiometer daily SM product, respectively, at 6:00 a.m. and 6:00 p.m. on a global scale from 2015 to 2020. The evaluation results reveal that the downscaling model performs better in the middle or low latitudes than in high latitudes. It also performs better in warm months than in cold months. The in situ SM observations from dense networks around the world were used to validate the 1‐km and enhanced 9‐km SMAP SM data. The validation metrics indicated that both the 1‐km and 9‐km SM data have overall overestimation trends, and the unbiased RMSE (0.063 m3 m–3 on average), mean absolute error (0.052 m3 m–3 on average), and spatial standard deviation (0.025 m3 m–3 on average) of the 1 km data are generally more accurate than the metrics of the 9‐km SM data, which indicates that the downscaled data provide reliable observed SM information.

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Section: Analysis and Discussionmentioning

confidence: 99%

A global 1‐km downscaled SMAP soil moisture product based on thermal inertia theory

Fang

Lakshmi

Cosh

et al. 2022

Vadose Zone Journal

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“…A short summary of the main features of this product is provided in [59]. The choice of this product was based on its acceptable performance in the identification of drought when compared to in situ measurements in the study area [60].…”

Section: Smos Surface Soil Moisture Datamentioning

confidence: 99%

Flash Drought and Its Characteristics in Northeastern South America during 2004–2022 Using Satellite-Based Products

Barbosa

2023

Atmosphere

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The term flash drought describes a special category of drought with rapid onset and strong intensity over the course of days or weeks. To characterize the impact of flash droughts on vegetation coverage, this study assessed the influence of soil water deficits on vegetation dynamics in the northeastern South America region by combining time series of vegetation index, rainfall, and soil moisture based on satellite products at a daily time scale. An 18-year analysis, from 2004 to 2022, of the Normalized Difference Vegetation Index (NDVI), Standard Precipitation Index (SPI), and surface soil moisture (SSM) was performed based on three different satellite remote sensing estimates: the spinning enhanced visible and infrared imager (SEVIRI) and the integrated multi-satellite retrievals algorithm (IMERG), and the soil moisture and ocean salinity (SMOS). The results revealed that flash drought events exerted dramatic impacts on terrestrial ecosystems in the study region during the first two decades of the 2000s, with changes in seasonal and regional vegetation dynamics. Further, the fixed-threshold values to characterize flash drought events were suggested as the timing when the water deficit was less than −1.0 units and vegetation index reached the value equal to +0.3 during five consecutive weeks or more, coupled with soil moisture rates below 40% percentile, leading to a strong region-wide drought throughout the entire region. Additionally, the results of linear least squares trend analyses revealed a negative trend in the pentad-SEVIRI radiance for the solar channel 1 within the semiarid ecosystems of the study region (i.e., the Caatinga biome) that was suggested as a reduction in clouds in the 18 years of the study. Developing combined threshold measures of flash drought based on satellite remote sensing may lead to an accurate assessment of flash drought mitigation.

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“…This product was averaged considering its ascending and descending orbits to minimize the influence of the radio frequency interference (RFI) on retrieved SSM values [58]. The choice of this product was based on its acceptable performance in the identification of agricultural drought when compared to in situ measurements in the SFRB [7,59].…”

Section: Satellite-based Data Smos Surface Soil Moisture Datamentioning

confidence: 99%

Drought Assessment in the São Francisco River Basin Using Satellite-Based and Ground-Based Indices

Paredes‐Trejo¹,

Barbosa²,

Giovannettone³

et al. 2021

Remote Sensing

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The São Francisco River Basin (SFRB) plays a key role for the agricultural and hydropower sectors in Northeast Brazil (NEB). Historically, in the low part of the SFRB, people have to cope with strong periods of drought. However, there are incipient signs of increasing drought conditions in the upper and middle parts of the SFRB, where its main reservoirs (i.e., Três Marias, Sobradinho, and Luiz Gonzaga) and croplands are located. Therefore, the assessment of the impacts of extreme drought events in the SFRB is of vital importance to develop appropriate drought mitigation strategies. These events are characterized by widespread and persistent dry conditions with long-term impacts on water resources and rain-fed agriculture. The purpose of this study is to provide a comprehensive evaluation of extreme drought events in terms of occurrence, persistence, spatial extent, severity, and impacts on streamflow and soil moisture over different time windows between 1980 and 2020. The Standardized Precipitation-Evapotranspiration Index (SPEI) and Standardized Streamflow Index (SSI) at 3- and 12-month time scales derived from ground data were used as benchmark drought indices. The self-calibrating Palmer Drought Severity Index (scPDSI) and the Soil Moisture and Ocean Salinity-based Soil Water Deficit Index (SWDIS) were used to assess the agricultural drought. The Water Storage Deficit Index (WSDI) and the Groundwater Drought Index (GGDI) both derived from the Gravity Recovery and Climate Experiment (GRACE) were used to assess the hydrological drought. The SWDISa and WSDI showed the best performance in assessing agricultural and hydrological droughts across the whole SFRB. A drying trend at an annual time scale in the middle and south regions of the SFRB was evidenced. An expansion of the area under drought conditions was observed only during the southern hemisphere winter months (i.e., JJA). A marked depletion of groundwater levels concurrent with an increase in soil moisture content was observed during the most severe drought conditions, indicating an intensification of groundwater abstraction for irrigation. These results could be useful to guide social, economic, and water resource policy decision-making processes.

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Validation of SMOS L3 AND L4 Soil Moisture Products In The Remedhus (SPAIN) AND CEMADEN (BRAZIL) Networks

Cited by 6 publications

References 21 publications

A global 1‐km downscaled SMAP soil moisture product based on thermal inertia theory

A global 1‐km downscaled SMAP soil moisture product based on thermal inertia theory

Flash Drought and Its Characteristics in Northeastern South America during 2004–2022 Using Satellite-Based Products

Drought Assessment in the São Francisco River Basin Using Satellite-Based and Ground-Based Indices

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