scholarly journals Evaluating the impact of climate on snow- and ice-melt dynamics in the Taillon basin, French Pyrénées

1997 ◽  
Vol 43 (145) ◽  
pp. 563-568 ◽  
Author(s):  
David M. Hannah ◽  
Glenn R. McGregor
Keyword(s):  
Large Scale ◽  
Energy Budgets ◽  
Computer Assisted ◽  
Air Masses ◽  
Atmospheric Circulation Patterns ◽  
Ice Melt ◽  
Circulation Types ◽  
The Impact ◽  
Snow And Ice Melt ◽  
Snow And Ice

AbstractThis pilot study adopts a computer-assisted synoptic typing methodology to evaluate the totality of climatic influences on snow- and ice-melt dynamics within a small cirque basin in the French Pyrénées. The synoptic categories identified possess contrasting large-scale atmospheric circulation patterns and surface energy budgets which generate differential ablation responses. Continental air masses yield consistently high melt. Advection of moist maritime air also produces elevated but more variable ablation due to air-mass transitions. The two observed local valley circulation types show melt to be higher under nocturnal katabatic drainage than for anabatic wind flows associated with development of daytime ridge-top cumulus.

scholarly journals Evaluating the impact of climate on snow- and ice-melt dynamics in the Taillon basin, French Pyrénées

1997 ◽  
Vol 43 (145) ◽  
pp. 563-568 ◽  
Author(s):  
David M. Hannah ◽  
Glenn R. McGregor
Keyword(s):  
Large Scale ◽  
Energy Budgets ◽  
Computer Assisted ◽  
Air Masses ◽  
Atmospheric Circulation Patterns ◽  
Ice Melt ◽  
Circulation Types ◽  
The Impact ◽  
Snow And Ice Melt ◽  
Snow And Ice

AbstractThis pilot study adopts a computer-assisted synoptic typing methodology to evaluate the totality of climatic influences on snow- and ice-melt dynamics within a small cirque basin in the French Pyrénées. The synoptic categories identified possess contrasting large-scale atmospheric circulation patterns and surface energy budgets which generate differential ablation responses. Continental air masses yield consistently high melt. Advection of moist maritime air also produces elevated but more variable ablation due to air-mass transitions. The two observed local valley circulation types show melt to be higher under nocturnal katabatic drainage than for anabatic wind flows associated with development of daytime ridge-top cumulus.

scholarly journals Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

2013 ◽  
Vol 13 (12) ◽  
pp. 33491-33521 ◽  
Author(s):  
S. Kaspari ◽  
T. H. Painter ◽  
M. Gysel ◽  
M. Schwikowski
Keyword(s):  
Water Resources ◽  
Black Carbon ◽  
The Other ◽  
Radiative Forcings ◽  
Ice Melt ◽  
Depositional Processes ◽  
The Impact ◽  
The Himalaya ◽  
Snow And Ice Melt ◽  
Snow And Ice

Abstract. Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC concentrations in snow and ice in the Himalaya is of interest because this region borders large BC sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snowpits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal on the southern slope of the Himalaya during spring and fall 2009. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage, and loss of BC particles in the ultrasonic nebulizer. BC and Fe concentrations peak during the winter–spring, and are substantially higher at elevations <6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations <6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass-balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements indicates that BC concentrations in the winter–spring snow/ice horizons are sufficient to reduce albedo by 6–10% relative to clean snow, corresponding to instantaneous radiative forcings of 75–120 W m−2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40–42% relative to clean snow and give instantaneous radiative forcings of 490 to 520 W m−2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3–10 W m−2. While BC contributes to accelerated snow and ice melt, the impact of BC is diminished in the presence of other light absorbing impurities. However, the time span of the BC exposure at the snow surface in the dry winter–spring season is likely a persistent forcing before impurity convergence, but is not addressed by these single measurements. Further observational studies are needed to assess the contribution of BC relative to other absorbing impurities to albedo reductions and snow and ice melt.

scholarly journals Scenario approach for the seasonal forecast of Kharif flows from Upper Indus Basin

2017 ◽  
Author(s):  
Muhammad Fraz Ismail ◽  
Wolfgang Bogacki
Keyword(s):  
Water Availability ◽  
Indus Basin ◽  
Flow Volume ◽  
Seasonal Forecasts ◽  
Important Indicator ◽  
Upper Indus Basin ◽  
Ice Melt ◽  
Degree Day ◽  
Snow And Ice Melt ◽  
Snow And Ice

Abstract. Snow and glacial melt runoff are the major sources of water contribution from the high mountainous terrain of Indus river upstream of the Tarbela reservoir. A reliable forecast of seasonal water availability for the Kharif cropping season (April–September) can pave the way towards the better water management and subsequently boost the agro-economy of Pakistan. The use of degree-day models in conjunction with the satellite based remote sensing data for the forecasting of seasonal snow and ice melt runoff has proved to be a suitable approach for the data scarce regions. In the present research, Snowmelt Runoff Model (SRM) has not only been enhanced by incorporating the “glacier (G)” component but also applied for the forecast of seasonal water availability from the Upper Indus Basin (UIB). Excel based SRM + G takes into account of separate degree-day factors for snow and ice melt processes. The UIB has been divided into Upper and Lower part because of the different climatic conditions in the Tibetan plateau. The application of seasonal scenario based approach proved to be very adequate for long term water availability forecast. The comparison between different models of operational seasonal forecasts for the UIB for the period in consideration show that SRM + G tends to slightly underestimate the flow volume on average by about 2 % with an overall mean absolute error MAE of 9.6 %, while the two other approaches overestimate the Kharif flow volume on average by about 6 %. More important, the standard deviation of SRM + G forecast errors is 5.7 % only, which is an important indicator for the forecasting skill.

Lagrangian analysis of the dynamical and thermodynamic drivers of large-scale Greenland melt events during 1979-2017

2021 ◽  
Author(s):  
Mauro Hermann ◽  
Lukas Papritz ◽  
Heini Wernli
Keyword(s):  
Large Scale ◽  
Heat Waves ◽  
Lower Troposphere ◽  
Greenland Ice Sheet ◽  
Region Of Origin ◽  
Air Masses ◽  
Accumulation Zone ◽  
Warm Anomaly ◽  
Downward Longwave Radiation ◽  
The Impact

&lt;p&gt;We systematically investigate the dynamical and thermodynamic processes that lead to 77 large-scale melt events affecting high-elevation regions of the Greenland Ice Sheet (GrIS) in June-August (JJA) 1979-2017. For that purpose, we compute 8&amp;#8201;day kinematic backward trajectories from the lowermost ~500&amp;#8201;m above the GrIS. The key synoptic feature accompanying the melt events is an upper-tropospheric ridge over Southeast Greenland associated with a surface high-pressure system. This circulation pattern is favorable to induce rapid poleward transport (up to 40&amp;#176; latitude) of warm (~15&amp;#8201;K warmer than climatological air masses arriving on the GrIS) and moist air masses from the lower troposphere to the western GrIS and subsequently to distribute them in the anticyclonic flow over north and east Greenland. During transport to the GrIS, the melt event air masses cool by ~15&amp;#8201;K due to ascent and radiation, which keeps them just above the critical threshold to induce melting.&lt;/p&gt;&lt;p&gt;The thermodynamic analyses reveal that the final warm anomaly of the air masses is primarily owed to anomalous horizontal transport from a climatologically warm region of origin. However, before being transported to the GrIS, i.e., in their region of origin, these air masses were not anomalously warm. Latent heating from condensation of water vapor, occurring as the airstreams are forced to ascend orographically or dynamically, is of secondary importance. These characteristics were particularly pronounced during the most extensive melt event in early July 2012. In this event, importantly, the warm anomaly was not preserved from anomalously warm source regions such as North America experiencing a record heat wave. Considering the impact of moisture on the surface energy balance, we find that radiative effects are closely linked to the air mass trajectories and enhance melt over the entire GrIS accumulation zone due to (i) enhanced downward longwave radiation related to poleward moisture transport and a shift in the cloud phase from ice to liquid primarily west of the ice divide and (ii) increased shortwave radiation in clear-sky regions east of the ice divide.&lt;/p&gt;&lt;p&gt;The temporal evolution, positioning, and intensity of synoptic scale weather systems deserve further attention as they are responsible for strong and partly opposing atmospheric forcing of the GrIS surface mass balance. Also, the mechanisms identified here are in contrast to melt events in the low-elevation high Arctic and to midlatitude heat waves, where the upper-tropospheric ridge is essential to induce adiabatic warming by large-scale subsidence. Given the ongoing increase in the frequency and the melt extent of large-scale melt events, the understanding of upper-tropospheric ridges over the North Atlantic, i.e., also Greenland blocking, and its representation in climate models is crucial in determining future GrIS accumulation zone melt and thus global sea level rise.&amp;#160;&lt;/p&gt;

The variability of the snow and ice melt in alpine rivers in northwestern China

2014 ◽  
Vol 11 (4) ◽  
pp. 884-895 ◽  
Author(s):  
Chang-bin Li ◽  
Jia-guo Qi ◽  
Lin-shan Yang ◽  
Wen-jin Yang ◽  
Gao-feng Zhu ◽  
...  
Keyword(s):  
Northwestern China ◽  
Ice Melt ◽  
Alpine Rivers ◽  
Snow And Ice Melt ◽  
Snow And Ice

scholarly journals Summertime low clouds mediate the impact of the large-scale circulation on Arctic sea ice

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yiyi Huang ◽  
Qinghua Ding ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Ian Baxter
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Climate Models ◽  
Lower Troposphere ◽  
Arctic Sea Ice ◽  
Albedo Feedback ◽  
Ice Melt ◽  
Low Clouds ◽  
Arctic Sea ◽  
The Impact

AbstractThe rapid Arctic sea ice retreat in the early 21st century is believed to be driven by several dynamic and thermodynamic feedbacks, such as ice-albedo feedback and water vapor feedback. However, the role of clouds in these feedbacks remains unclear since the causality between clouds and these processes is complex. Here, we use NASA CERES satellite products and NCAR CESM model simulations to suggest that summertime low clouds have played an important role in driving sea ice melt by amplifying the adiabatic warming induced by a stronger anticyclonic circulation aloft. The upper-level high pressure regulates low clouds through stronger downward motion and increasing lower troposphere relative humidity. The increased low clouds favor more sea ice melt via emitting stronger longwave radiation. Then decreased surface albedo triggers a positive ice-albedo feedback, which further enhances sea ice melt. Considering the importance of summertime low clouds, accurate simulation of this process is a prerequisite for climate models to produce reliable future projections of Arctic sea ice.

Exploring teachers’ professional development through participation in virtual exchange

ReCALL ◽  
2021 ◽  
pp. 1-16
Author(s):  
Robert O’Dowd ◽  
Melinda Dooly
Keyword(s):  
Professional Development ◽  
Language Learning ◽  
Large Scale ◽  
Teaching Practice ◽  
Language Teachers ◽  
Computer Assisted ◽  
Computer Assisted Language Learning ◽  
Methodological Innovation ◽  
Teachers Professional Development ◽  
The Impact

Abstract Virtual exchange (VE) is an umbrella term used to refer to the engagement of groups of students in sustained online intercultural interaction and collaboration with international partners under the guidance of their teachers. In the computer-assisted language learning literature, telecollaboration and eTandem approaches to VE have been researched extensively. However, this research has principally focused to date on learner gains and the impact on teachers has been much less explored. This paper identifies the impact of VE on foreign language teachers’ practices and their professional development by examining the results of a qualitative study of 31 teacher trainers who engaged their classes in VE projects as part of a large-scale European project. The findings of the study suggest that participation in VE projects provides teachers with valuable experience in continued professional development and methodological innovation. In particular, VE was seen to open up opportunities for teachers to develop new professional partnerships, collaborative academic initiatives, to develop their own online collaboration skills, and also to introduce more innovative approaches in their current teaching practice.

scholarly journals A Lagrangian analysis of the dynamical and thermodynamic drivers of large-scale Greenland melt events during 1979–2017

2020 ◽  
Vol 1 (2) ◽  
pp. 497-518 ◽  
Author(s):  
Mauro Hermann ◽  
Lukas Papritz ◽  
Heini Wernli
Keyword(s):  
Large Scale ◽  
Heat Waves ◽  
Lower Troposphere ◽  
Greenland Ice Sheet ◽  
Region Of Origin ◽  
Air Masses ◽  
Accumulation Zone ◽  
Warm Anomaly ◽  
Downward Longwave Radiation ◽  
The Impact

Abstract. In this study, we systematically investigate the dynamical and thermodynamic processes that lead to 77 large-scale melt events affecting high-elevation regions of the Greenland Ice Sheet (GrIS) in June–August (JJA) 1979–2017. For that purpose, we compute 8 d kinematic backward trajectories from the lowermost ∼500 m above the GrIS during these events. The key synoptic feature accompanying the melt events is an upper-tropospheric ridge southeast of the GrIS associated with a surface high-pressure system. This circulation pattern is favorable to induce rapid poleward transport (up to 40∘ latitude) of warm (∼15 K warmer than climatological air masses arriving on the GrIS) and moist air masses from the lower troposphere to the western GrIS and subsequently to distribute them in the anticyclonic flow over north and east Greenland. During transport to the GrIS, the melt event air masses cool by ∼15 K due to ascent and radiation, which keeps them just above the critical threshold to induce melting. The thermodynamic analyses reveal that the final warm anomaly of the air masses is primarily owed to anomalous horizontal transport from a climatologically warm region of origin. However, before being transported to the GrIS, i.e., in their region of origin, these air masses were not anomalously warm. Latent heating from condensation of water vapor, occurring as the airstreams are forced to ascend orographically or dynamically, is of secondary importance. These characteristics were particularly pronounced during the most extensive melt event in early July 2012, where, importantly, the warm anomaly was not preserved from anomalously warm source regions such as North America experiencing a record heat wave. The mechanisms identified here are in contrast to melt events in the low-elevation high Arctic and to midlatitude heat waves, where adiabatic warming by large-scale subsidence is essential. Considering the impact of moisture on the surface energy balance, we find that radiative effects are closely linked to the air mass trajectories and enhance melt over the entire GrIS accumulation zone due to (i) enhanced downward longwave radiation related to poleward moisture transport and a shift in the cloud phase from ice to liquid primarily west of the ice divide and (ii) increased shortwave radiation in clear-sky regions east of the ice divide. Given the ongoing increase in the frequency and the melt extent of large-scale melt events, the understanding of upper-tropospheric ridges over the North Atlantic, i.e., also Greenland blocking, and its representation in climate models is crucial in determining future GrIS accumulation zone melt and thus global sea level rise.

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