Thermal regime of warm-dry permafrost in relation to ground surface temperature in the Source Areas of the Yangtze and Yellow rivers on the Qinghai-Tibet Plateau, SW China

Luo, Dejun; Wu, Qingbai; Bense, Victor; He, Ruixia; Ma, Qiang; Gao, Shanxing; Jin, Xiaoying; Lü, Lanzhi

doi:10.1016/j.scitotenv.2017.09.083

Cited by 105 publications

(55 citation statements)

References 44 publications

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“…For example, the solar radiation arriving on some unobstructed south-facing slopes would far exceed that on a horizontal plane, and it would be much diminished in valleys or on north facing slopes (Aguilar et al, 2010). A spatial interpolation method based on few sparsely installed stations cannot effectively capture the spatial heterogeneity of solar radiation in a mountainous area, which will exert significant influences on the spatial distribution of air and ground temperatures, ET, snowmelt, and mass balance of mountainous glaciers (Gruber et al, 2017;Harris et al, 2009;Hasler et al, 2015;Hoffman et al, 2016;Luo, Jin, Marchenko, et al, 2018;Luo, Jin, Wu, et al, 2018;van Pelt et al, 2012). According to observations in the Antarctica dry valley, the ground surface temperature dropped by about 10°C in less than 4 hr following the onset of topographic shadows (Katurji et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Influences of Topographic Shadows on the Thermal and Hydrological Processes in a Cold Region Mountainous Watershed in Northwest China

Zhang

Cheng

et al. 2018

J Adv Model Earth Syst

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The solar radiation incident in a mountainous area with a complex terrain has a strong spatial heterogeneity due to the variations in slope orientation (self‐shading) and shadows cast by surrounding topography agents (topographic shading). Although slope self‐shading has been well studied and considered in most land surface and hydrological models, topographic shading is usually ignored, and its influence on the thermal and hydrological processes in a cold mountainous area remains unclear. In this study, a topographic solar radiation algorithm with consideration for both slope self‐shading and topographic shadows has been implemented and incorporated into a distributed hydrological model with physically based descriptions for the energy balance. A promising model performance was achieved according to a vigorous evaluation. In a control model without considering the topographic shadows, the simulated solar radiation incident in the study area was about 14.3 W/m2 higher on average, which in turn led to a higher simulated annual mean ground temperature at 4 m (by 0.41 °C) and evapotranspiration (by 16.1 mm/a), and a smaller permafrost extent (reduced by about 8%), as well as smaller maximal snow depth and shorter snow duration. Although the simulation was not significantly improved for discharge hydrograph in the base model, higher river runoff peaks and an increased runoff depth were obtained. In areas with a rugged terrain and deep valleys, the influences of topographic shadows would even be stronger in reality than the presented results, which cannot be ignored in the simulation of the thermal and hydrological processes, especially in a refined model.

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Section: Introductionmentioning

confidence: 99%

Influences of Topographic Shadows on the Thermal and Hydrological Processes in a Cold Region Mountainous Watershed in Northwest China

Zhang

Cheng

et al. 2018

J Adv Model Earth Syst

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“…Owing to the thermal dampening effect of dense vegetation and close‐adhered peat substrates, mean annual GST ( MAGST ) showed a slight increasing trend. The surface offset, the difference between MAAT and MAGST (Luo, Jin, Wu, et al, ), was averaged at 3.2 ± 0.3 °C. It even showed a decreasing trend of −0.16 °C ( p = 0.07), supposedly due to the pronounced warming of T a and relatively stable GST.…”

Section: Resultsmentioning

confidence: 99%

Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau

Luo

Jin

et al. 2018

JGR Atmospheres

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Increase of surface temperatures has long been recognized as an unequivocal response to radiative forcing and one of the most important implications for global warming. However, it remains unclear whether the variation of ground surface temperature (GST) and soil temperatures is consistent with simultaneous changes of the near‐surface air and land (or skin) surface temperatures (Ta and LST). In this study, a seven‐year continuous observation of GST, Ta, and surface water and heat exchange was carried out at an elevational permafrost site at Chalaping, northeastern Qinghai‐Tibet Plateau. Results showed a distinct retarding of warming on the ground surface and subsurface under the presence of dense vegetation and moist peat substrates. Mean annual Ta and LST increased at noteworthy rates of 0.22 and 0.32 °C/a, respectively, while mean annual GST increased only at a rate of 0.057 °C/a. No obvious trends were detected for the four radiation budgets except the soil heat flux (G), which significantly increased at a rate of 0.29 W · m−2 · a−1, presumably inducing the melting of ground ice and resulted in much higher moisture content through the summers of 2015 and 2016 than preceding years and subsequent 2017 at the depths between 80 and 120 cm. However, no noticeable immediate variations of soil temperatures occurred owing to the large latent heat effect (thermal inertia) and the extending zero‐curtain period. We suggest that a better protected eco‐environment, particularly the surface vegetation, helps preserving the underlying permafrost, and thus to mitigates the potential degradation of elevational permafrost on the Qinghai‐Tibet Plateau.

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“…The forest stands are more open or sparsely vegetated than the unburned area. In summer, destruction of the vegetation and SOM layer after forest fires result in compromised insulation and shading effects of solar radiation onto the ground surface, and thus in weakening of thermal offsets and enhancing of surface offsets, and in increases in surface albedo and thermal conductivity of the soils …”

Section: Discussionmentioning

confidence: 99%

Effects of forest fires on the permafrost environment in the northern Da Xing'anling (Hinggan) mountains, Northeast China

Jin

et al. 2019

Permafrost & Periglacial

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Forest fires have significantly impacted the permafrost environment, and many research programs looking at this have been undertaken at higher latitudes. However, their impacts have not yet been systematically studied and evaluated in the northern part of northeast China at mid‐latitudes. This study simultaneously measured ecological and geocryological changes at various sites in the boreal forest at different stages after forest fires (chronosequence approach) in the northern Da Xing'anling (Hinggan) Mountains, Northeast China. We obtained results through field investigations, monitoring and observations, remote sensing interpretations, and laboratory tests. The results show that forest fires have resulted in a decreased Normalized Difference Vegetation Index (NDVI) and soil moisture contents in the active layer, increased active layer thickness (ALT) and ground temperatures, and the release of a large amount of C and N from the soils in the active layer and at shallow depths of permafrost. NDVI and species biodiversity have gradually increased in the years since forest fires. However, the vegetation has not fully recovered to the climax community structures and functions of the boreal forest ecosystems. For example, ground temperatures, ALT, and soil C and N contents have been slowly recovering in the 30 years after the forest fires, but they have not yet been restored to pre‐fire levels. This study provides important scientific bases for assessment of the impacts of forest fires on the boreal forest ecosystems in permafrost regions, environmental restoration and management, and changes in the carbon stock of soils at shallow (<3 m) depths in the Da Xingan'ling Mountains in northeast China.

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Thermal regime of warm-dry permafrost in relation to ground surface temperature in the Source Areas of the Yangtze and Yellow rivers on the Qinghai-Tibet Plateau, SW China

Cited by 105 publications

References 44 publications

Influences of Topographic Shadows on the Thermal and Hydrological Processes in a Cold Region Mountainous Watershed in Northwest China

Influences of Topographic Shadows on the Thermal and Hydrological Processes in a Cold Region Mountainous Watershed in Northwest China

Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau

Effects of forest fires on the permafrost environment in the northern Da Xing'anling (Hinggan) mountains, Northeast China

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