Global survey and statistics of radio-frequency interference in AMSR-E land observations

Njoku, E. G.; Ashcroft, Peter; Chan, T. K.; Li, Li

doi:10.1109/tgrs.2004.837507

Cited by 304 publications

(188 citation statements)

References 8 publications

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“…The traditional spectral difference indices method (Njoku et al, 2005) was used to detect RFI and with this method no RFI signals were found for AMSR-E. Because ASCAT is a real aperture radar backscatter instrument it is not affected by RFI. Figure 1 shows the geographical locations of the six NVE in situ stations used in this study.…”

Section: The Advanced Microwave Scanning Radiometer -Earth Observing mentioning

confidence: 99%

Evaluation of satellite soil moisture products over Norway using ground-based observations

Griesfeller

Lahoz

Dorigo

et al. 2016

International Journal of Applied Earth Observation and Geoinfor

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Abstract.In this study we evaluate satellite soil moisture products from the Advanced SCATterometer (ASCAT) and the Advanced Microwave Scanning Radiometer -Earth Observing System (AMSR-E) over Norway using ground-based observations from the Norwegian Water Resources and Energy Directorate. The ASCAT data are produced using the change detection approach of Wagner et al. (1999), and the AMSR-E data are produced using the VUA-NASA algorithm (Owe et al., 2001(Owe et al., , 2008. Although satellite and ground-based soil moisture data for Norway have been available for several years, hitherto, such an evaluation has not been performed. This is partly because satellite measurements of soil moisture over Norway are complicated owing to the presence of snow, ice, water bodies, orography, rocks, and a very high coastline-to-area ratio. This work extends the European areas over which satellite soil moisture is validated to the Nordic regions. Owing to the challenging conditions for soil moisture measurements over Norway, the work described in this paper provides a stringent test of the capabilities of satellite sensors to measure soil moisture remotely. We show that the satellite and in situ data agree well, with averaged correlation (R) values of 0.72 and 0.68 for 2 ASCAT descending and ascending data vs in situ data, and 0.64 and 0.52 for AMSR-E descending and ascending data vs in situ data for the summer/autumn season (1 June -15 October), over a period of 3 years (2009)(2010)(2011). This level of agreement indicates that, generally, the ASCAT and AMSR-E soil moisture products over Norway have high quality, and would be useful for various applications, including land surface monitoring, weather forecasting, hydrological modelling, and climate studies. The increasing emphasis on coupled approaches to study the Earth System, including the interactions between the land surface and the atmosphere, will benefit from the availability of validated and improved soil moisture satellite datasets, including those over the Nordic regions.

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Section: The Advanced Microwave Scanning Radiometer -Earth Observing mentioning

confidence: 99%

Evaluation of satellite soil moisture products over Norway using ground-based observations

Griesfeller

Lahoz

Dorigo

et al. 2016

International Journal of Applied Earth Observation and Geoinfor

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“…Draper et al (2009) illustrated that the soil moisture retrievals by an algorithm developed by Vrije Universiteit Amsterdam, in collaboration with NASA (hereafter VUA-NASA) had better correspondence to in situ data over south-eastern Australia than other retrievals. In addition, no apparent radio frequency interference on AMSR-E C-band brightness temperature was observed over Australia (Njoku et al, 2005), making this a useful test-bed to analyze retrievals from this band. Therefore, the VUA-NASA product is applied in this study.…”

Section: Amsr-e Soil Moisturementioning

confidence: 99%

Influence of cracking clays on satellite estimated and model simulated soil moisture

Liu

Evans

McCabe

et al. 2010

Hydrol. Earth Syst. Sci.

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Abstract. Vertisols are clay soils that are common in the monsoonal and dry warm regions of the world. One of the characteristics of these soil types is to form deep cracks during periods of extended dry, resulting in significant variation of the soil and hydrologic properties. Understanding the influence of these varying soil properties on the hydrological behavior of the system is of considerable interest, particularly in the retrieval or simulation of soil moisture. In this study we compare surface soil moisture (θ in m 3 m −3 ) retrievals from AMSR-E using the VUA-NASA (Vrije Universiteit Amsterdam in collaboration with NASA) algorithm with simulations from the Community Land Model (CLM) over vertisol regions of mainland Australia. For the threeyear period examined here (2003)(2004)(2005), both products display reasonable agreement during wet periods. During dry periods however, AMSR-E retrieved near surface soil moisture falls below values for surrounding non-clay soils, while CLM simulations are higher. CLM θ are also higher than AMSR-E and their difference keeps increasing throughout these dry periods. To identify the possible causes for these discrepancies, the impacts of land use, topography, soil properties and surface temperature used in the AMSR-E algorithm, together with vegetation density and rainfall patterns, were investigated. However these do not explain the observed θ responses. Qualitative analysis of the retrieval model suggests that the most likely reason for the Correspondence to: Y. Y. Liu (yi.y.liu@csiro.au) low AMSR-E θ is the increase in soil porosity and surface roughness resulting from cracking of the soil. To quantitatively identify the role of each factor, more in situ measurements of soil properties that can represent different stages of cracking need to be collected. CLM does not simulate the behavior of cracking soils, including the additional loss of moisture from the soil continuum during drying and the infiltration into cracks during rainfall events, which results in overestimated θ when cracks are present. The hydrological influence of soil physical changes are expected to propagate through the modeled system, such that modeled infiltration, evaporation, surface temperature, surface runoff and groundwater recharge should be interpreted with caution over these soil types when cracks might be present. Introducing temporally dynamic roughness and soil porosity into retrieval algorithms and adding a "cracking clay" module into models are expected to improve the representation of vertisol hydrology.

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“…The AMSR-E brightness temperature at 6.9 GHz is sensitive to soil moisture from the top surface layer (~2 cm), vegetation water content, and surface effective temperature ). However, possible Radio-Frequency Interference (RFI) has been observed at 6.9 GHz over many areas, most of which are densely concentrated in the United States, Japan, and the Middle East and sparsely concentrated in Europe (Li et al, 2004;Njoku et al, 2005). In other areas, the accuracy of the measured brightness temperature is better than 1 K.…”

Section: Amsr-e Satellite Datamentioning

confidence: 99%

Evaluation of the Community Microwave Emission Model Coupled with the Community Land Model over East Asia

Jia¹,

Xie

2011

Atmospheric and Oceanic Science Letters

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Global survey and statistics of radio-frequency interference in AMSR-E land observations

Cited by 304 publications

References 8 publications

Evaluation of satellite soil moisture products over Norway using ground-based observations

Evaluation of satellite soil moisture products over Norway using ground-based observations

Influence of cracking clays on satellite estimated and model simulated soil moisture

Evaluation of the Community Microwave Emission Model Coupled with the Community Land Model over East Asia

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