Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau
The knowledge of soil apparent thermal diffusivity (k) is important for investigating soil surface heat transfer and temperature. Long-term k determined using the near-surface soil temperature is limited on the Tibetan Plateau (TP). The main objective of this study is to determine k with a conductio...
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MDPI AG
2022-08-01
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| author | Bing Tong Hui Xu Robert Horton Lingen Bian Jianping Guo |
| author_facet | Bing Tong Hui Xu Robert Horton Lingen Bian Jianping Guo |
| author_sort | Bing Tong |
| collection | DOAJ |
| description | The knowledge of soil apparent thermal diffusivity (k) is important for investigating soil surface heat transfer and temperature. Long-term k determined using the near-surface soil temperature is limited on the Tibetan Plateau (TP). The main objective of this study is to determine k with a conduction–convection method using the near-surface soil temperature measured at three sites during 2014–2016 on the TP. The hourly, daily, and monthly k values of the 0.0 m to 0.20 m layer were obtained. The hourly and daily k values ranged from 0.3 × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> to 1.9 × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> at the wet site, and from 1.0 × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> to 4.0 × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> at the two dry sites. For the monthly timescale, k ranged from 0.4 (±0.0) × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> to 1.1 (±0.2) × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> at the wet site, and varied between 1.7 (±0.0) × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> and 3.3 (±0.2) × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> at the two dry sites. The k was not constant over a day, and it varied seasonally to different degrees at different sites and years. The variation of k with soil moisture (θ) appeared to be roughly similar for unfrozen soil at these sites and years, namely, k increased sharply before reaching the peak as θ increased, and then it tended to be stable or varied slightly with further increases in θ. This variation trend was consistent with previous studies. However, the relationship between k and θ changed when soil temperature was below 0 °C, because ice had higher k than water. The correlation coefficients (r) between k and θ ranged from 0.37 to 0.80, and 0.80 to 0.92 on hourly and monthly timescales, respectively. The monthly and annual k values were significantly correlated (r: 0.73~0.93) to the Normalized Difference Vegetation Index (NDVI). The results broaden our understanding of the relationship between in situ k and θ. The presented values of k at various timescales can be used as soil parameters when modeling land–atmosphere interactions at these TP regions. |
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| spelling | doaj.art-c999077c185d41c3ba4154ba053a31d72023-11-23T14:03:16ZengMDPI AGRemote Sensing2072-42922022-08-011417423810.3390/rs14174238Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan PlateauBing Tong0Hui Xu1Robert Horton2Lingen Bian3Jianping Guo4State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, ChinaState Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, ChinaAgronomy Department, Iowa State University, Ames, IA 50011, USAChinese Academy of Meteorological Sciences, Beijing 100081, ChinaState Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, ChinaThe knowledge of soil apparent thermal diffusivity (k) is important for investigating soil surface heat transfer and temperature. Long-term k determined using the near-surface soil temperature is limited on the Tibetan Plateau (TP). The main objective of this study is to determine k with a conduction–convection method using the near-surface soil temperature measured at three sites during 2014–2016 on the TP. The hourly, daily, and monthly k values of the 0.0 m to 0.20 m layer were obtained. The hourly and daily k values ranged from 0.3 × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> to 1.9 × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> at the wet site, and from 1.0 × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> to 4.0 × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> at the two dry sites. For the monthly timescale, k ranged from 0.4 (±0.0) × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> to 1.1 (±0.2) × 10<sup>−6</sup> m<sup>2</sup> s<sup>−1</sup> at the wet site, and varied between 1.7 (±0.0) × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> and 3.3 (±0.2) × 10<sup>−7</sup> m<sup>2</sup> s<sup>−1</sup> at the two dry sites. The k was not constant over a day, and it varied seasonally to different degrees at different sites and years. The variation of k with soil moisture (θ) appeared to be roughly similar for unfrozen soil at these sites and years, namely, k increased sharply before reaching the peak as θ increased, and then it tended to be stable or varied slightly with further increases in θ. This variation trend was consistent with previous studies. However, the relationship between k and θ changed when soil temperature was below 0 °C, because ice had higher k than water. The correlation coefficients (r) between k and θ ranged from 0.37 to 0.80, and 0.80 to 0.92 on hourly and monthly timescales, respectively. The monthly and annual k values were significantly correlated (r: 0.73~0.93) to the Normalized Difference Vegetation Index (NDVI). The results broaden our understanding of the relationship between in situ k and θ. The presented values of k at various timescales can be used as soil parameters when modeling land–atmosphere interactions at these TP regions.https://www.mdpi.com/2072-4292/14/17/4238soil thermal diffusivityconduction–convection methodsoil temperaturesoil water contentNormalized Difference Vegetation Index (NDVI) |
| spellingShingle | Bing Tong Hui Xu Robert Horton Lingen Bian Jianping Guo Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau Remote Sensing soil thermal diffusivity conduction–convection method soil temperature soil water content Normalized Difference Vegetation Index (NDVI) |
| title | Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau |
| title_full | Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau |
| title_fullStr | Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau |
| title_full_unstemmed | Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau |
| title_short | Determination of Long-Term Soil Apparent Thermal Diffusivity Using Near-Surface Soil Temperature on the Tibetan Plateau |
| title_sort | determination of long term soil apparent thermal diffusivity using near surface soil temperature on the tibetan plateau |
| topic | soil thermal diffusivity conduction–convection method soil temperature soil water content Normalized Difference Vegetation Index (NDVI) |
| url | https://www.mdpi.com/2072-4292/14/17/4238 |
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