Frost events during the active growth period of plants can cause extensive frost damage with tremendous economic losses and dramatic ecological consequences. A common assumption is that climate ...warming may bring along a reduction in the frequency and severity of frost damage to vegetation. On the other hand, it has been argued that rising temperature in late winter and early spring might trigger the so called “false spring”, that is, early onset of growth that is followed by cold spells, resulting in increased frost damage. By combining daily gridded climate data and 1,489 k in situ phenological observations of 27 tree species from 5,565 phenological observation sites in Europe, we show here that temporal changes in the risk of spring frost damage with recent warming vary largely depending on the species and geographical locations. Species whose phenology was especially sensitive to climate warming tended to have increased risk of frost damage. Geographically, compared with continental areas, maritime and coastal areas in Europe were more exposed to increasing occurrence of frost and these late spring frosts were getting more severe in the maritime and coastal areas. Our results suggest that even though temperatures will be elevated in the future, some phenologically responsive species and many populations of a given species will paradoxically experience more frost damage in the future warming climate. More attention should be paid to the increased frost damage in responsive species and populations in maritime areas when developing strategies to mitigate the potential negative impacts of climate change on ecosystems in the near future.
This study examined the well‐known “increased frost damage” hypothesis by Cannell (1985), based on long‐term phenological records and climate data. Temporal changes in the risk of spring frost damage with recent warming vary largely depending on the species and geographical locations. Species whose phenology was especially sensitive to climate warming tended to have increased risk of frost damage. Geographically, compared with continental areas, maritime and coastal areas in Europe were more exposed to increasing occurrence of frost and these late spring frosts were getting more severe in the maritime and coastal areas.
This paper first presents a simple frost heave model. Frost heave is assumed to be caused by the formation of ice lenses in a freezing soil. The formation of ice lenses is governed by the Clapeyron ...equation of thermodynamics and relies on the existence of a frozen fringe between the frozen and unfrozen zones. Both unfrozen water and ice co-exist in pores of the frozen fringe. The suction at the water–ice interface is the driving force for the water flow that feeds the growth of the ice lens. The initiation of a new ice lens is governed by a simple effective stress concept. The frost heave model contains only a few soil parameters and can be used to compute frost heave and frost penetration in stratified soil profiles. The second part of the paper illustrates the application of the frost heave model in assessing the frost susceptibility of different soils. It is shown that the frost susceptibility of a soil must be assessed together with environmental conditions such as overburden pressure, temperature gradient, cooling rate and the depth of groundwater table. A soil that is only mildly susceptible to frost according to classification can still generate a significant amount of heave or heaving pressure under favourable environmental conditions.
•A simple frost heave model based on the rigid ice concept is proposed in this paper.•The model simulates the formation of discrete ice lenses in freezing soils.•It has relatively few parameters and all parameters have clear physical meaning.•The frost heave model is used to analyse the frost susceptibility of different soils.•It is shown that the frost susceptibility depends on environmental conditions.
The tea tree (Camellia sinensis L. O. Kuntze) is a perennial cash crop, whose tender shoots and young leaves are used in tea production. Tea tree buds that have burst but have not yet been plucked ...may be damaged by frost, resulting in severe economic losses. And frost disasters in spring bring a serious threat to tea production in China. However, the impacts of frost disasters on tea production are not well evaluated. To address this gap, we quantified temporal and spatial changes of frost risk in the Yuezhou Longjing tea production area, which is China’s largest site of green tea production. Accordingly, we developed a new frost risk index based on the percentage of frost-damaged tea buds in relation to all tea buds and its probability. The results showed that elevation was the main factor associated with frost risk. Applying the Mann Kendall test, the effects of elevation on the tea frost risk in plain areas (50–250 m) and hilly areas (251–450 m) were determined. In plain areas, the frost risks and trends for the percentage of all frost-damaged tea buds did not change significantly with elevation. In hilly areas, the frost risks increased significantly with the increasing of elevations. However, the temporal change of percentage of frost-damaged tea buds decreased significantly, and this change showed a significant decreasing trend with increasing elevation in hilly areas. This trend is conducive to tea production in the hills, which are the main Longjing tea production areas. Our findings provide a better understanding of frost risk in tea production and could offer valuable references for frost risk prevention in tea production.
•Dynamic modelling can be used to estimate accurately tea buds growth.•Percentage of tea buds frost injured can be used to evaluate frost risk.•Frost risk didn’t change significantly with elevation and time in plain areas.•Frost risk increased with elevation in hilly areas.•Frost risk of single sites decreased in hilly areas during 2007–2022.
Frost events are a climatic phenomenon of great severity, exerting profound impacts on agricultural production and human endeavours. From 1961 to 2017, China experienced a reduction in frost days ...(FDs) and elongation of frost‐free periods (FFPs) across most regions. Many factors contribute to the variation of frost events, highlighting the urgent need to scrutinize the intrinsic factors driving these climatic frost events' inter‐annual and interdecadal fluctuations. This work analysed the temporal and spatial attributes of FDs and FFPs, using statistical methods to dissect daily minimum temperature data collected from ground observation stations from 1961 to 2017. The results reveal a declining trajectory in annual FDs and an ascending trend in FFPs. However, the interannual and interdecadal variations do not consistently align with the climatological course. The spatial distribution of the first four modes of EOF exhibits a persistent variation, north–south, monopole and east–west pattern for FDs and FFPs. In comparison, the modes of FFPs exhibit many complexities and diversities. Moreover, this study considers geographical location, altitude and proximity to the ocean, as well as atmospheric circulation factors, including circulation indices, ocean indices and other relevant indices, to elucidate their influence on frost events. In conjunction with the role of greenhouse gases in propelling global warming, we elucidate that the intensity of the Atlantic–European polar vortex, the area of the Indian Ocean warm pool, and the spatial positioning and extent of the subtropical high emerge as preeminent internal oscillations instigating interdecadal shifts in frost events. This study provides valuable scientific insights into the formation mechanisms and evolving patterns of frost events.
The most important modal types of frost days and frost‐free periods in China are spatial consistent, north–south, monopole and east–west type. The Atlantic–European polar vortex intensity, the area of the Indian Ocean warm pool, and the location and area of the subtropical high are the dominant internal variations affecting the patterns.
The propagation of joints and fissures, included by the frost heaving pressure arising from the water-ice phase transition is considered as frost wedging. This process is widely observed and plays a ...crucial role in weathering of jointed hard rocks in cold regions. Despite some fundamental results achieved in former experimental studies, a unified theoretical model is still absent, hindering a thorough understanding of this process. To further explore the mechanism of frost wedging during the freezing process, this paper firstly carries out a frost heave test on a rock block bearing a single open fissure. The results indicate that the evolution of frost heaving pressure in the fissure can be divided into four stages: sealing of the open fissure by ice wedge, ice wedge slipping, crack propagation, as well as stabilization of the ice-filled fissure. Based on the laboratory test results, a unified model for the frost heaving pressure in a single open fissure is established, which comprehensively takes into account the mechanical interaction between ice, water and rock. The model is validated by the test result, and it can reasonably describe the formation of the sealing conditions and the process of crack propagation. Fracture of the ice-rock interface near the free surface increases the likelihood of ice wedge slip, while frost wedging mainly damages geological bodies during crack propagation.
•A novel design ASHP equipped with heaters installed before (B-AEH) the evaporator for frost prevention is proposed first.•The orthogonal experiment design was deployed to aid the selection of design ...parameters and the analysis of the results.•The performance of the novel design increased COP up to 17.94% and decreased input power 25.63% under frosting conditions.•It was demonstrated that the novel system can prevent the evaporator from frosting formation under frosting conditions.
In this study, a novel technology of frost prevention and retardation for air source heat pump (ASHP), which reduces thermal discomfort, is introduced. It utilizes auxiliary electric heaters (AEH) on tubes before (B-AEH) and (or) after (A-AEH) the outdoor evaporator to retard frost formation or prevent frost from accumulating on the outdoor heat exchanger. This enables the supply of hot air into the interior space without interruption. This new method differs from the common high pressure hot gas bypass defrosting (HGBD) methods and the reverse cycle defrosting (RCD), both of which could result in significant temperature fluctuations and thermal discomfort. The orthogonal experiment design (OED) was applied in this study to evaluate the performance of the air source heat pump (ASHP) with different magnitudes of AEH power under a range of ambient frosting conditions. The L25(56) orthogonal array was selected for the experiment and data were analyzed by means of the analysis of range (ANORA) and the analysis of variance (ANOVA). The optimum parameter combination affecting the performance of the ASHP was determined and the most significant parameters were identified. It was demonstrated that the proposed ASHP design is effective for frost prevention and retardation in real applications.
•A macro-micro synergistic frost inhibited surface was prepared.•Millimeter-scale structure enhances the superhydrophobicity and frost resistance ability.•Growth rate of frost crystals is determined ...by the amount of space available for water vapor contact.•A well-designed edge structure can delay the superhydrophobic frost edge effect.•Gradually melting frost in removal process has a special upward movement.
Frost suppression ability and edge effect are crucial for the frost formation on engineering surfaces. However, certain fundamental aspects remain ambiguous, particularly in the context of superhydrophobic surfaces featuring millimeter-scale structures.. In this study, condensation, frosting, and defrosting experiments were conducted on superhydrophobic surfaces with multiple millimeter-scale geometries. The results indicate that condensate droplets tend to grow on the top of right-angled, semi-circular protrusions, and conical structures. In the course of frost formation, superhydrophobic surfaces with millimeter-scale structures exhibit certain anti-frost properties when compared to the non-structured superhydrophobic surface. Condensation state of droplets can be maintained for a long time on the bottom area of the grooves, creating a frost-free zone. By observing the growth of frost crystals in various regions of the millimeter structure, it has been revealed that the manipulation of water vapor contact spaces can lead to the design of anti-frost surfaces with adjustable rates of frost crystal growth. Frost formation process on superhydrophobic surfaces can generate the so-called "edge effect" and is influenced by the edge structure. Frost crystals tend to form first on conical edges due to their sharp structural features. The average height of frost crystals on 90° edges, obtuse edges, and semicircular edges is significantly lower than that on conical edges, with the reductions of 31.8 %, 28.4 %, and 14.3 %, respectively. During the defrosting process, two spontaneous methods were observed to remove the frost layer: a "hand-in-hand" manner lifting off the groove and an "airfoil retraction" contraction on the protruding structures. Regardless of the structure shape, defrosting water floats on top and falls off, allowing for rapid drying of the surface and groove. This work has broadened the understanding of frost formation and defrosting on millimeter-structured superhydrophobic surfaces, and holds potential for applications in anti-frost engineering.
•A radiation heat transfer model considering self-shadow under the sun is proposed.•A coupled moisture-heat-mechanical model considering solar radiation is developed.•Effects of solar radiation on ...heat and moisture of frozen soil and structural deformation.•Sunny-shady slope effect and damage mechanism of canals under the sun are discussed.•Solar energy can reduce the freezing depth and be used in cold-region engineering.
The sunny-shady slope effect on structures in cold regions is significant due to solar radiation, which threatens structural stability. Solar radiation is rarely considered in modelling frost heave, and its effects on the moisture-heat transfer of frozen soil and structural deformation are unclear. Here, a frost heave model with moisture-heat-mechanical coupling, solar radiation and self-shadowing is presented; its accuracy is verified through comparison with field monitoring data of a canal. Then, the coupling development of the moisture-heat transfer, stress-deformation and differential frost heave progression of differently oriented canals are analyzed. Finally, the effects of solar radiation on the soil frost heave and frost damage mechanism of canals with the sunny-shady slope effect are discussed. The freezing depth is shallower and the water content, deformation, and tensile stress are lower for sunny than for shady slopes. As the canal orientation varies from east-west to north–south, the differences in the freezing characteristics decrease to 0, and the frost damage time of shady slopes is gradually delayed; the opposite occurs for sunny slopes. The developments in structural surface temperature, moisture-heat transfer in frozen soil and structural deformation are consistent with solar radiation and air temperature changes, emphasizing solar radiation’s contribution to structure frost heave. The uneven, asynchronous, asymmetrical frost heave and melting deformation of linings in sunny and shady slopes are the causes of canal damage. This model investigates interactions among solar radiation-diurnal temperature-frozen soil-structures and offers a theoretical basis for using solar energy to reduce frost heave in seasonally frozen regions.
To study the law of water–heat coupling migration and the frost heave deformation characteristics of soil slopes in seasonal areas under groundwater recharge conditions, this paper constructs a ...water–heat–stress coupling model considering moisture migration, ice–water phase change, ice resistance, and frost heave effects based on COMSOL modelling software. Then, numerical simulation results are compared with the experimental results to verify the effectiveness of the multi-field coupling model. The results show that the slope temperature change has an evident lag compared with the ambient temperature change. The shallow soil of slopes changes dramatically under external ambient temperature, while the deep soil gradually tends to the ground temperature under the geothermal influence. The slope temperature distribution rules are basically the same in different groundwater recharge levels. The maximum freezing depth of the slope is deeper at a high groundwater level. When the groundwater level is high, the total moisture content of the slope is larger, and the thawing area may be saturated or oversaturated in the spring thawing period. For unsaturated soil slopes in seasonal freezing for a long time, the total moisture content of slopes tends to increase slightly after each freeze–thaw cycle due to groundwater recharge. The problems of slopes in seasonal frozen areas are manifested by the frost heave of the soil at the top of slopes, which may cause frost heave damage. When the groundwater level is high, the maximum horizontal displacement of the slope surface and the frost heave deformation at the top of slopes increase greatly.
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