Evaluation for short-duration freeze-thaw events of seasonally frozen soil in the headstreams of Nujiang River
- Article
- Figures
- Metrics
- Preview PDF
- Reference
- Related
- Cited by
- Materials
Abstract:
Seasonally frozen soil is widely distributed in Qinghai-Tibet Plateau and soil freeze-thaw events occur frequently in the headstream of Nujiang River. Due to the large altitude difference and the asynchrony of meteorological changes between different regions in the headstream region, the occurrence of freeze-thaw events has different characteristics and certain regularities in time and space.To explore the characteristics of freeze-thaw in seasonally frozen soil, the short-duration freeze-thaw events that occurred in the 5 cm surface soil of 4 typical experimental fields of the headstream region were selected. The connotation of the short-duration freeze-thaw events was clarified and a specific identification method for these events was proposed. The characteristics of events were evaluated and the evaluation was formed by five aspects: The start and end time, the total duration, the total number of times, the cycle frequency, and the intensity. In the intensity evaluation, the Copula function method was used to combine three single indexes of temperature difference, humidity difference, and duration to construct a more comprehensive and efficient comprehensive index, and the two different processes of freeze and freeze-thaw are evaluated separately.The evaluation results showed that from September 1, 2019, to August 31, 2020, the short-duration freeze-thaw events in the 4 typical experimental fields had a maximum difference of 45 days in the start time and 64 days in the end time. The maximum difference in the total duration, the total number of times and the cycle frequency can reach 112 days, 79 times, and 0.058 times/day, respectively. The maximum difference in the cumulative intensity and the maximum intensity can reach 50.991 and 0.034 for the freezing process, 50.991 and 0.034 for the freeze-thaw process.The characteristics of short-duration freeze-thaw events in different geographical locations in the headstream of Nujiang River are different. The events in the middle-altitude area ( 4 500 - 5 000 m.a.s.l.) showed regularity with a longer total duration, higher total number of times, cycle frequency, and accumulation intensity than the events in the low-altitude area (< 4500 m.a.s.l.) and the high-altitude area (> 5 000 m.a.s.l.). High-frequency or high-intensity events can greatly affect or even destroy the soil environment. In this regard, more attention should be paid to freeze-thaw monitoring and protection in the northern part of the basin. Freeze and freeze-thaw were two processes with different intensity effects, and evaluated respectively can avoid the problem of weakened strength. The results are conducive to clarifying the freeze-thaw characteristics of seasonally frozen soil in the plateau alpine region, and reflecting the impact of short-duration freeze-thaw events, providing support for water and soil conservation, frost heaving, thaw collapsing hazards prevention and control in the headstream.
Keywords:
Project Supported:
Clc Number:
Mobile website
® 2024 All Rights Reserved
冀公网安备13010502002656号
冀公网安备13010502002656号