A detailed energy budget analysis of river supercooling and the importance of accurately quantifying net radiation to predict ice formation

Abstract

River supercooling and ice formation is a regular occurrence throughout the winter in northern countries. The resulting frazil ice production can obstruct the flow through intakes along the river, causing major problems for hydropower and water treatment facilities, among others. Therefore, river ice modellers attempt to calculate the river energy budget and predict when supercooling will occur in order to anticipate and mitigate the effects of potential intake blockages. Despite this, very few energy budget studies have taken place during freeze-up, and none have specifically analysed individual supercooling events. To improve our understanding of the freeze-up energy budget detailed measurements of air temperature, relative humidity, barometric pressure, wind speed and direction, short-and longwave radiation, and water temperature were made on the Dauphin River in Manitoba. During the river freeze-up period of late October to early November 2019, a total of six supercooling events were recorded. Analysis of the energy budget throughout the supercooling period revealed that the most significant heat source was net shortwave radiation, reaching up to 298 W/m 2 , while the most significant heat loss was net longwave radiation, accounting for losses of up to 135 W/m 2. Longwave radiation was also the most significant heat flux overall during the individual supercooling events, accounting for up to 84% of the total heat flux irrespective of flux direction, highlighting the importance of properly quantifying this flux during energy budget calculations. Five different sensible (Q h) and latent (Q e) heat flux calculations were also compared, using the bulk aerodynamic method as the baseline. It was found that the Priestley and Taylor method most-closely matched the bulk aerodynamic method on a daily timescale with an average offset of 8.5 W/m 2 for Q h and 10.1 W/m 2 for Q e , while a Daltontype equation provided by Webb and Zhang was the most similar on a sub-daily timescale with average offsets of 20.0 and 14.7 W/m 2 for Q h and Q e , respectively.

Advances in Frazil Ice Evolution Mechanisms and Numerical Modelling in Rivers and Channels in Cold Regions

“…Water temperature measurement is a crucial component of field observations and model studies in the winter because it has a significant impact on the evolution of the river ice [54][55][56][57][58][59][60][61][62][63][64][65]. Researchers gather water temperature data during ice field observations and laboratory experiments using a significant quantity of high-accuracy temperature sensors to determine the water temperature change process and analyze the influencing factors as the basis of the analysis of the evolution of frazil ice.…”

Freeze-Up Ice Jam Formation in the River Bend, a Case Study on the Inner Mongolia Reach of Yellow River

“…The date of the ice run in the winter of 2015 was on 28 November, with decreasing temperature and increasing upstream ice production, the initial freeze-up date was on 2 December, and the freeze-up date along the entire length of the Shensifenzi bend in 2015 was on 17 December. Ice formation process is characterized by heat flux, radiation, and friction with the bed and banks [21]. In this analysis supercooling event is going to be contemplated.…”

“…In the outer bank, the dynamic ice cover forms from the disordered ice particles, while the static and smooth ice cover forms in the inner bank, due to the lower velocity. With the continuous heat exchange between the water surface and the atmosphere, the ice jamming formed at the outlet of the bend, and Ice formation process is characterized by heat flux, radiation, and friction with the bed and banks [21]. In this analysis supercooling event is going to be contemplated.…”

A New Approach for Assessing Heat Balance State along a Water Transfer Channel during Winter Periods

“…The degree of supercooling of the observed river was given. McFarlane et al [15] compared five different methods for calculating sensible heat flux and latent heat flux based on air temperature, During an ice-covered flow condition, the characteristics of river hydraulics have been dramatically changed compared to that under an open flow condition. An ice cover adds an extra boundary to the flow, which leads to considerable changes in the velocity profile, flow rate, bed shear stress distribution, and water temperature [6].…”

“…The degree of supercooling of the observed river was given. McFarlane et al [15] compared five different methods for calculating sensible heat flux and latent heat flux based on air temperature, relative humidity, air pressure, wind speed and wind direction, short-wave and long-wave radiation for the Dauphin River in Manitoba. By calculating the heat balance of the river, the supercooling phenomenon of the river was predicted.…”