Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index
Among the indirect estimation approaches of soil water content in the upper layer of the soil, the “triangle method” is one of the most common that relies on the simple relationship between the optical and thermal features sensed via Earth Observation. These features are controll...
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| Format: | Article |
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MDPI AG
2020-01-01
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| Series: | Geosciences |
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| Online Access: | https://www.mdpi.com/2076-3263/10/1/23 |
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| author | Fulvio Capodici Carmelo Cammalleri Antonio Francipane Giuseppe Ciraolo Goffredo La Loggia Antonino Maltese |
| author_facet | Fulvio Capodici Carmelo Cammalleri Antonio Francipane Giuseppe Ciraolo Goffredo La Loggia Antonino Maltese |
| author_sort | Fulvio Capodici |
| collection | DOAJ |
| description | Among the indirect estimation approaches of soil water content in the upper layer of the soil, the “triangle method” is one of the most common that relies on the simple relationship between the optical and thermal features sensed via Earth Observation. These features are controlled by water content at the surface and within the root zone but also by meteorological forcing including air temperature and humidity, as well as solar radiation. Night- and day-time MODIS composites of land-surface temperature (<i>LST</i>) allowed applying a version of the triangle method that takes into account the temporal admittance of the soil. In this study, it has been applied to a long time-series of pair images to analyze the seasonal influence of the meteorological forcing on a triangle method index (or temperature−vegetation index, <i>TVX</i>), as well as to discuss extra challenges of the diachronic approach including seasonality effects and the variability of environmental forcing. The Imera Meridionale basin (Sicily, Italy) has been chosen to analyze the method over a time-series of 12 years. The analysis reveals that, under these specific environmental and climatic conditions (strong seasonality and rainfall out of phase with vegetation growth), Normalized Difference Vegetation Index (<i>NDVI</i>) and <i>LST</i> pairs move circularly in time within the optical vs. thermal feature space. Concordantly, the boundaries of the triangle move during the seasons. Results showed a strong correlation between <i>TVX</i> and rainfall normalized amplitudes of the power spectra (<i>r</i><sup>2</sup> ~0.8) over the range of frequencies of the main harmonics. |
| first_indexed | 2024-04-13T13:35:21Z |
| format | Article |
| id | doaj.art-f52f2a1d86f8416790f35db01f89b619 |
| institution | Directory Open Access Journal |
| issn | 2076-3263 |
| language | English |
| last_indexed | 2024-04-13T13:35:21Z |
| publishDate | 2020-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Geosciences |
| spelling | doaj.art-f52f2a1d86f8416790f35db01f89b6192022-12-22T02:44:48ZengMDPI AGGeosciences2076-32632020-01-011012310.3390/geosciences10010023geosciences10010023Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation IndexFulvio Capodici0Carmelo Cammalleri1Antonio Francipane2Giuseppe Ciraolo3Goffredo La Loggia4Antonino Maltese5Dipartimento di Ingegneria, Università degli Studi di Palermo, 90133 Palermo, ItalyEuropean Commission, Joint Research Centre, 21027 Ispra, ItalyDipartimento di Ingegneria, Università degli Studi di Palermo, 90133 Palermo, ItalyDipartimento di Ingegneria, Università degli Studi di Palermo, 90133 Palermo, ItalyDipartimento di Ingegneria, Università degli Studi di Palermo, 90133 Palermo, ItalyDipartimento di Ingegneria, Università degli Studi di Palermo, 90133 Palermo, ItalyAmong the indirect estimation approaches of soil water content in the upper layer of the soil, the “triangle method” is one of the most common that relies on the simple relationship between the optical and thermal features sensed via Earth Observation. These features are controlled by water content at the surface and within the root zone but also by meteorological forcing including air temperature and humidity, as well as solar radiation. Night- and day-time MODIS composites of land-surface temperature (<i>LST</i>) allowed applying a version of the triangle method that takes into account the temporal admittance of the soil. In this study, it has been applied to a long time-series of pair images to analyze the seasonal influence of the meteorological forcing on a triangle method index (or temperature−vegetation index, <i>TVX</i>), as well as to discuss extra challenges of the diachronic approach including seasonality effects and the variability of environmental forcing. The Imera Meridionale basin (Sicily, Italy) has been chosen to analyze the method over a time-series of 12 years. The analysis reveals that, under these specific environmental and climatic conditions (strong seasonality and rainfall out of phase with vegetation growth), Normalized Difference Vegetation Index (<i>NDVI</i>) and <i>LST</i> pairs move circularly in time within the optical vs. thermal feature space. Concordantly, the boundaries of the triangle move during the seasons. Results showed a strong correlation between <i>TVX</i> and rainfall normalized amplitudes of the power spectra (<i>r</i><sup>2</sup> ~0.8) over the range of frequencies of the main harmonics.https://www.mdpi.com/2076-3263/10/1/23diachronic mappingthermal admittancefast fourier-transformseasonal effects |
| spellingShingle | Fulvio Capodici Carmelo Cammalleri Antonio Francipane Giuseppe Ciraolo Goffredo La Loggia Antonino Maltese Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index Geosciences diachronic mapping thermal admittance fast fourier-transform seasonal effects |
| title | Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index |
| title_full | Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index |
| title_fullStr | Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index |
| title_full_unstemmed | Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index |
| title_short | Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index |
| title_sort | soil water content diachronic mapping an fft frequency analysis of a temperature vegetation index |
| topic | diachronic mapping thermal admittance fast fourier-transform seasonal effects |
| url | https://www.mdpi.com/2076-3263/10/1/23 |
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