scholarly journals Midwinter melts in the Canadian prairies: energy balance and hydrological effects

2019 ◽  
Vol 23 (4) ◽  
pp. 1867-1883 ◽  
Author(s):  
Igor Pavlovskii ◽  
Masaki Hayashi ◽  
Daniel Itenfisu
Keyword(s):  
Surface Runoff ◽  
Hydrological Cycle ◽  
Remote Sensing Data ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Net Radiation ◽  
Present Climate ◽  
Canadian Prairies ◽  
Energy Inputs ◽  
Hydrological Effects

Abstract. Snowpack accumulation and depletion are important elements of the hydrological cycle in the Canadian prairies. The surface runoff generated during snowmelt is transformed into streamflow or fills numerous depressions driving the focussed recharge of groundwater in this dry setting. The snowpack in the prairies can undergo several cycles of accumulation and depletion in a winter. The timing of the melt affects the mechanisms of snowpack depletion and their hydrological implications. The effects of midwinter melts were investigated at four instrumented sites in the Canadian prairies. Unlike net radiation-driven snowmelt during spring melt, turbulent sensible heat fluxes were the dominant source of energy inputs for midwinter melt occurring in the period with low solar radiation inputs. Midwinter melt events affect several aspects of hydrological cycle with lower runoff ratios than subsequent spring melt events, due to their role in the timing of the focussed recharge. Remote sensing data have shown that midwinter melt events regularly occur under the present climate throughout the Canadian prairies, indicating applicability of the study findings throughout the region.

scholarly journals Effects of midwinter snowmelt on runoff generation and groundwater recharge in the Canadian prairies

2018 ◽  
Author(s):  
Igor Pavlovskii ◽  
Masaki Hayashi ◽  
Daniel Itenfisu
Keyword(s):  
Surface Runoff ◽  
Hydrological Cycle ◽  
Remote Sensing Data ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Net Radiation ◽  
Present Climate ◽  
Runoff Generation ◽  
Canadian Prairies ◽  
Energy Inputs

Abstract. Snowpack accumulation and depletion are important elements of the hydrological cycle in the prairies. The surface runoff generated during snowmelt is transformed into streamflow or fills numerous depressions driving the focused recharge of groundwater in this dry setting. The snowpack in the prairies can undergo several cycles of accumulation and depletion in a winter. The timing of the melt affects the mechanisms of snowpack depletion and their hydrological implications. The effects of midwinter melt were investigated at three sites in the Canadian prairies. Unlike net radiation-driven snowmelt during spring melt, turbulent sensible heat fluxes were the dominant source of energy inputs for midwinter melt occurring in the period with low solar radiation inputs. Midwinter melt events had lower runoff ratios than subsequent spring melt events and had strong impacts on the timing of the focussed recharge. Remote sensing data have shown that midwinter melt events regularly occur under the present climate throughout the Canadian prairies.

scholarly journals Water tracks intensify surface energy and mass exchange in the Antarctic McMurdo Dry Valleys

2019 ◽  
Vol 13 (8) ◽  
pp. 2203-2219 ◽  
Author(s):  
Tobias Linhardt ◽  
Joseph S. Levy ◽  
Christoph K. Thomas
Keyword(s):  
Climate Change ◽  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Dry Valleys ◽  
Sensible Heat ◽  
Net Radiation ◽  
Taylor Valley ◽  
The Antarctic

Abstract. The hydrologic cycle in the Antarctic McMurdo Dry Valleys (MDV) is mainly controlled by surface energy balance. Water tracks are channel-shaped high-moisture zones in the active layer of permafrost soils and are important solute and water pathways in the MDV. We evaluated the hypothesis that water tracks alter the surface energy balance in this dry, cold, and ice-sheet-free environment during summer warming and may therefore be an increasingly important hydrologic feature in the MDV in the face of landscape response to climate change. The surface energy balance was measured for one water track and two off-track reference locations in Taylor Valley over 26 d of the Antarctic summer of 2012–2013. Turbulent atmospheric fluxes of sensible heat and evaporation were observed using the eddy-covariance method in combination with flux footprint modeling, which was the first application of this technique in the MDV. Soil heat fluxes were analyzed by measuring the heat storage change in the thawed layer and approximating soil heat flux at ice table depth by surface energy balance residuals. For both water track and reference locations over 50 % of net radiation was transferred to sensible heat exchange, about 30 % to melting of the seasonally thawed layer, and the remainder to evaporation. The net energy flux in the thawed layer was zero. For the water track location, evaporation was increased by a factor of 3.0 relative to the reference locations, ground heat fluxes by 1.4, and net radiation by 1.1, while sensible heat fluxes were reduced down to 0.7. Expecting a positive snow and ground ice melt response to climate change in the MDV, we entertained a realistic climate change response scenario in which a doubling of the land cover fraction of water tracks increases the evaporation from soil surfaces in lower Taylor Valley in summer by 6 % to 0.36 mm d−1. Possible climate change pathways leading to this change in landscape are discussed. Considering our results, an expansion of water track area would make new soil habitats accessible, alter soil habitat suitability, and possibly increase biological activity in the MDV. In summary, we show that the surface energy balance of water tracks distinctly differs from that of the dominant dry soils in polar deserts. With an expected increase in area covered by water tracks, our findings have implications for hydrology and soil ecosystems across terrestrial Antarctica.

scholarly journals Technical note: An experimental set-up to measure latent and sensible heat fluxes from (artificial) plant leaves

2017 ◽  
Vol 21 (7) ◽  
pp. 3377-3400 ◽  
Author(s):  
Stanislaus J. Schymanski ◽  
Daniel Breitenstein ◽  
Dani Or
Keyword(s):  
Energy Balance ◽  
Water Vapour ◽  
Energy Exchange ◽  
Hydrological Cycle ◽  
Leaf Temperature ◽  
Heat Fluxes ◽  
Coupled Processes ◽  
Balance Model ◽  
Sensible Heat ◽  
Set Up

Abstract. Leaf transpiration and energy exchange are coupled processes that operate at small scales yet exert a significant influence on the terrestrial hydrological cycle and climate. Surprisingly, experimental capabilities required to quantify the energy–transpiration coupling at the leaf scale are lacking, challenging our ability to test basic questions of importance for resolving large-scale processes. The present study describes an experimental set-up for the simultaneous observation of transpiration rates and all leaf energy balance components under controlled conditions, using an insulated closed loop miniature wind tunnel and artificial leaves with pre-defined and constant diffusive conductance for water vapour. A range of tests documents the above capabilities of the experimental set-up and points to potential improvements. The tests reveal a conceptual flaw in the assumption that leaf temperature can be characterized by a single value, suggesting that even for thin, planar leaves, a temperature gradient between the irradiated and shaded or transpiring and non-transpiring leaf side can lead to bias when using observed leaf temperatures and fluxes to deduce effective conductances to sensible heat or water vapour transfer. However, comparison of experimental results with an explicit leaf energy balance model revealed only minor effects on simulated leaf energy exchange rates by the neglect of cross-sectional leaf temperature gradients, lending experimental support to our current understanding of leaf gas and energy exchange processes.

scholarly journals Soil Moisture–Atmosphere Interactions during the 2003 European Summer Heat Wave

2007 ◽  
Vol 20 (20) ◽  
pp. 5081-5099 ◽  
Author(s):  
E. M. Fischer ◽  
S. I. Seneviratne ◽  
P. L. Vidale ◽  
D. Lüthi ◽  
C. Schär
Keyword(s):  
Soil Moisture ◽  
Heat Wave ◽  
Regional Climate ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Net Radiation ◽  
Temperature Anomalies ◽  
Continental Scale ◽  
Summer Heat

Abstract The role of land surface–related processes and feedbacks during the record-breaking 2003 European summer heat wave is explored with a regional climate model. All simulations are driven by lateral boundary conditions and sea surface temperatures from the ECMWF operational analysis and 40-yr ECMWF Re-Analysis (ERA-40), thereby prescribing the large-scale circulation. In particular, the contribution of soil moisture anomalies and their interactions with the atmosphere through latent and sensible heat fluxes is investigated. Sensitivity experiments are performed by perturbing spring soil moisture in order to determine its influence on the formation of the heat wave. A multiyear regional climate simulation for 1970–2000 using a fixed model setup is used as the reference period. A large precipitation deficit together with early vegetation green-up and strong positive radiative anomalies in the months preceding the extreme summer event contributed to an early and rapid loss of soil moisture, which exceeded the multiyear average by far. The exceptionally high temperature anomalies, most pronounced in June and August 2003, were initiated by persistent anticyclonic circulation anomalies that enabled a dominance of the local heat balance. In this experiment the hottest phase in early August is realistically simulated despite the absence of an anomaly in total surface net radiation. This indicates an important role of the partitioning of net radiation in latent and sensible heat fluxes, which is to a large extent controlled by soil moisture. The lack of soil moisture strongly reduced latent cooling and thereby amplified the surface temperature anomalies. The evaluation of the experiments with perturbed spring soil moisture shows that this quantity is an important parameter for the evolution of European heat waves. Simulations indicate that without soil moisture anomalies the summer heat anomalies could have been reduced by around 40% in some regions. Moreover, drought conditions are revealed to influence the tropospheric circulation by producing a surface heat low and enhanced ridging in the midtroposphere. This suggests a positive feedback mechanism between soil moisture, continental-scale circulation, and temperature.

scholarly journals Simulation of the radiative effect of haze on the urban hydrological cycle using reanalysis data in Beijing

2019 ◽  
Vol 19 (10) ◽  
pp. 7001-7017 ◽  
Author(s):  
Tom V. Kokkonen ◽  
Sue Grimmond ◽  
Sonja Murto ◽  
Huizhi Liu ◽  
Anu-Maija Sundström ◽  
...  
Keyword(s):  
Water Balance ◽  
Surface Runoff ◽  
Urban Areas ◽  
Hydrological Cycle ◽  
Layer Structure ◽  
Model Performance ◽  
Reanalysis Data ◽  
Heat Fluxes ◽  
Radiative Effect ◽  
Reanalysis Dataset

Abstract. Although increased aerosol concentration modifies local air temperatures and boundary layer structure in urban areas, little is known about its effects on the urban hydrological cycle. Changes in the hydrological cycle modify surface runoff and flooding. Furthermore, as runoff commonly transports pollutants to soil and water, any changes impact urban soil and aquatic environments. To explore the radiative effect of haze on changes in the urban surface water balance in Beijing, different haze levels are modelled using the Surface Urban Energy and Water Balance Scheme (SUEWS), forced by reanalysis data. The pollution levels are classified using aerosol optical depth observations. The secondary aims are to examine the usability of a global reanalysis dataset in a highly polluted environment and the SUEWS model performance. We show that the reanalysis data do not include the attenuating effect of haze on incoming solar radiation and develop a correction method. Using these corrected data, SUEWS simulates measured eddy covariance heat fluxes well. Both surface runoff and drainage increase with severe haze levels, particularly with low precipitation rates: runoff from 0.06 to 0.18 mm d−1 and drainage from 0.43 to 0.62 mm d−1 during fairly clean to extremely polluted conditions, respectively. Considering all precipitation events, runoff rates are higher during extremely polluted conditions than cleaner conditions, but as the cleanest conditions have high precipitation rates, they induce the largest runoff. Thus, the haze radiative effect is unlikely to modify flash flooding likelihood. However, flushing pollutants from surfaces may increase pollutant loads in urban water bodies.

scholarly journals Capability of the variogram to quantify the spatial patterns of surface fluxes and soil moisture simulated by land surface models

2021 ◽  
Vol 45 (2) ◽  
pp. 279-293
Author(s):  
S Garrigues ◽  
A Verhoef ◽  
E Blyth ◽  
A Wright ◽  
B Balan-Sarojini ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Spatial Patterns ◽  
Land Surface ◽  
Heat Fluxes ◽  
Surface Model ◽  
Sensible Heat ◽  
Net Radiation ◽  
Land Surface Models ◽  
Surface Models

Up to now, relatively little effort has been dedicated to the quantitative assessment of the differences in spatial patterns of model outputs. In this paper, we employed a variogram-based methodology to quantify the differences in the spatial patterns of root-zone soil moisture, net radiation, and latent and sensible heat fluxes simulated by three land surface models (SURFEX/ISBA, JULES and CHTESSEL) over three European geographic domains – namely, UK, France and Spain. The model output spatial patterns were quantified through two metrics derived from the variogram: i) the variogram sill, which quantifies the degree of spatial variability of the data; and ii) the variogram integral range, which represents the spatial length scale of the data. The higher seasonal variation of the spatial variability of sensible and latent heat fluxes over France and Spain, compared to the UK, is related to a more frequent occurrence of a soil-moisture-limited evapotranspiration regime during summer dry spells in the south of France and Spain. The small differences in spatial variability of net radiation between models indicate that the spatial patterns of net radiation are mostly driven by the climate forcing data set. However, the models exhibit larger differences in latent and sensible heat flux spatial variabilities, which are related to their differences in i) soil and vegetation ancillary datasets and ii) physical process representation. The highest discrepancies in spatial patterns between models are observed for soil moisture, which is mainly related to the type of soil hydraulic function implemented in the models. This work demonstrates the capability of the variogram to enhance our understanding of the spatiotemporal structure of the uncertainties in land surface model outputs. Therefore, we strongly encourage the implementation of the variogram metrics in model intercomparison exercises.

scholarly journals ESTUDO DA RAZÃO DE BOWEN EM UMA ÁREA DE FLORESTA NO SUDOESTE DA AMAZÔNIA

2016 ◽  
Vol 38 ◽  
pp. 504
Author(s):  
Maylla Caroline Rodrigues Soares ◽  
Alberto Dresch Webler
Keyword(s):  
Climate Change ◽  
Water Scarcity ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Climate Interactions ◽  
Pasture Area

The changes mainly occurred in the hydrological cycle are associated with anthropogenic changes. In Brazil are already seen possible changes in the southwestern region that has suffered from water scarcity in their reservoirs. Understanding the Bowen ratio in the Amazon region becomes important to try to understand this ecosystem, since such information connect regional climate change. The latent heat fluxes were analyzed (λE) and sensible heat (H) in REBIO Jaru to determine the reason for Bowen and seek possible climate interactions in humid, wetdry, dry, dry-wet periods in 2009. The results observed in these periods in the Bowen ratio were 0:21; 0:24; 0:30; 0:21, and show that the forest little changes with seasonality during the year unlike the transition of biomes (Amazon - cerrado) and pasture area.

scholarly journals Understanding wind-driven melt of patchy snow cover

2021 ◽  
Author(s):  
Luuk D. van der Valk ◽  
Adriaan J. Teuling ◽  
Luc Girod ◽  
Norbert Pirk ◽  
Robin Stoffer ◽  
...  
Keyword(s):  
Snow Cover ◽  
Large Scale ◽  
Patch Size ◽  
Climate Models ◽  
Leading Edge ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Sensible Heat ◽  
Net Radiation ◽  
Main Challenge

Abstract. The simplified representation of snow processes in most large-scale hydrological and climate models is known to introduce considerable uncertainty in the predictions and projections of water availability. During the critical snowmelt period, the main challenge in snow modeling is that net radiation is spatially highly variable for a patchy snow cover, resulting in large horizontal differences in temperatures and heat fluxes. These differences can drive advection of turbulent heat from the snow free areas to the snow patches, potentially enhancing the melt rates at the leading edge and increasing the variability of subgrid melt rates. To get more insight in these processes, we examine the melt along the upwind and downwind edges of a 50 meter long snow patch in the Finseelvi catchment, Norway, and try to explain the observed behaviour with highly idealized simulations of heat fluxes and air movement over patchy snow. The melt of the snow patch was monitored from 11 June until 15 June 2019 by making use of height maps obtained through the photogrammetric Structure-from-Motion principle. A vertical melt of 23 ± 2.0 cm was observed at the upwind edge over the course of the field campaign, whereas the downwind edge melted only 3 ±  0.4 cm. When comparing this with meteorological measurements, we estimate the turbulent heat fluxes to be responsible for 60 to 80 % of the upwind melt of which a significant part is caused by the latent heat flux. The melt at the downwind edge approximately matches the melt occurring due to net radiation. To better understand the dominant processes, we represented this behaviour in idealized direct numerical simulations, which are based on the measurements on a single snow patch by Harder et al. (2017) and resemble a flat patchy snow cover with typical snow patch sizes of 15, 30 and 60 m. Using these simulations, we found that the reduction of the vertical temperature gradient over the snow patch was the main cause for the reductions in sensible heat over distance from the leading edge, independent of typical snow patch size. Moreover, we observed that the sensible heat fluxes at the leading edge and the decay over distance were independent of snow patch size as well, which resulted in a 15 % and 25 % reduction in average snowmelt for respectively a doubling and quadrupling of typical snow patch size. These findings lay out pathways to include the effect of local-scale heat advection based on the typical snow patch size in large-scale hydrological and climate models to improve snowmelt modelling.

scholarly journals Integrating GIS-Based MCDA Techniques and the SCS-CN Method for Identifying Potential Zones for Rainwater Harvesting in a Semi-Arid Area

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 704
Author(s):  
Hussein Al-Ghobari ◽  
Ahmed Z. Dewidar
Keyword(s):  
Water Conservation ◽  
Surface Runoff ◽  
Rainwater Harvesting ◽  
Global Climate ◽  
Remote Sensing Data ◽  
Curve Number ◽  
Drainage Density ◽  
Promising Alternative ◽  
Thematic Layers ◽  
Scs Cn

An increasing scarcity of water, as well as rapid global climate change, requires more effective water conservation alternatives. One promising alternative is rainwater harvesting (RWH). Nevertheless, the evaluation of RWH potential together with the selection of appropriate sites for RWH structures is significantly difficult for the water managers. This study deals with this difficulty by identifying RWH potential areas and sites for RWH structures utilizing geospatial and multi-criteria decision analysis (MCDA) techniques. The conventional data and remote sensing data were employed to set up needed thematic layers using ArcGIS software. The soil conservation service curve number (SCS-CN) method was used to determine surface runoff, centered on which yearly runoff potential map was produced in the ArcGIS environment. Thematic layers such as drainage density, slope, land use/cover, and runoff were allotted appropriate weights to produced RWH potential areas and zones appropriate for RWH structures maps of the study location. Results analysis revealed that the outcomes of the spatial allocation of yearly surface runoff depth ranging from 83 to 295 mm. Moreover, RWH potential areas results showed that the study areas can be categorized into three RWH potential areas: (a) low suitability, (b) medium suitability, and (c) high suitability. Nearly 40% of the watershed zone falls within medium and high suitability RWH potential areas. It is deduced that the integrated MCDA and geospatial techniques provide a valuable and formidable resource for the strategizing of RWH within the study zones.

A Positive Feedback Process Related to the Rapid Development of an Extratropical Cyclone over the Kuroshio/Kuroshio Extension

2018 ◽  
Vol 146 (2) ◽  
pp. 417-433 ◽  
Author(s):  
Hidetaka Hirata ◽  
Ryuichi Kawamura ◽  
Masaya Kato ◽  
Taro Shinoda
Keyword(s):  
Water Vapor ◽  
Positive Feedback ◽  
Heat Supply ◽  
Rapid Development ◽  
Kuroshio Extension ◽  
Heat Fluxes ◽  
Latent Heating ◽  
Sensible Heat ◽  
Feedback Process ◽  
The Kuroshio

Abstract The active roles of sensible heat supply from the Kuroshio/Kuroshio Extension in the rapid development of an extratropical cyclone, which occurred in the middle of January 2013, were examined by using a regional cloud-resolving model. In this study, a control experiment and three sensitivity experiments without sensible and latent heat fluxes from the warm currents were conducted. When the cyclone intensified, sensible heat fluxes from these currents become prominent around the cold conveyor belt (CCB) in the control run. Comparisons among the four runs revealed that the sensible heat supply facilitates deepening of the cyclone’s central pressure, CCB development, and enhanced latent heating over the bent-back front. The sensible heat supply enhances convectively unstable conditions within the atmospheric boundary layer along the CCB. The increased convective instability is released by the forced ascent associated with frontogenesis around the bent-back front, eventually promoting updraft and resultant latent heating. Additionally, the sensible heating leads to an increase in the water vapor content of the saturated air related to the CCB through an increase in the saturation mixing ratio. This increased water vapor content reinforces the moisture flux convergence at the bent-back front, contributing to the activation of latent heating. Previous research has proposed a positive feedback process between the CCB and latent heating over the bent-back front in terms of moisture supply from warm currents. Considering the above two effects of the sensible heat supply, this study revises the positive feedback process.

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