Use of Positive Degree-Day Methods for Calculating Snow and Ice Melting and Discharge in Glacierized Basins in the Langtang Valley, Central Nepal

2006 ◽  
pp. 5-14 ◽  
Author(s):  
Rijan B. Kayastha ◽  
Yutaka Ageta ◽  
Koji Fujita
Keyword(s):  
Ice Melting ◽  
Degree Day ◽  
Positive Degree ◽  
Central Nepal ◽  
Snow And Ice ◽  
Langtang Valley

scholarly journals Glacier surface mass balance modeling in the inner tropics using a positive degree-day approach

2016 ◽  
Author(s):  
L. Maisincho ◽  
V. Favier ◽  
P. Wagnon ◽  
V. Jomelli ◽  
R. Basantes Serrano ◽  
...  
Keyword(s):  
Wind Speed ◽  
Mass Balance ◽  
Shortwave Radiation ◽  
Surface Mass Balance ◽  
Glacier Surface ◽  
Surface Mass ◽  
Model Based ◽  
Degree Day ◽  
Positive Degree ◽  
Snow And Ice

Abstract. We present a basic ablation model combining a positive degree-day approach to calculate melting and a simple equation based on wind speed to compute sublimation. The model was calibrated at point scale (4900 m a.s.l.) on Antizana Glacier 15 (0.28 km2; 0°28' S, 78°09' W) with data from March 2002 to August 2003 and validated with data from January to November 2005. Cross validation was performed by interchanging the calibration and validation periods. Optimization of the model based on the calculated surface energy balance allowed degree-day factors to be retrieved for snow and ice, and suggests that melting started when daily air temperature was still below 0 °C, because incoming shortwave radiation was intense around noon and resulted in positive temperatures for a few hours a day. The model was then distributed over the glacier and applied to the 2000–2008 period using meteorological inputs measured on the glacier foreland to assess to what extent this approach is suitable for quantifying glacier surface mass balance in Ecuador. Results showed that a model based on temperature, wind speed, and precipitation is able to reproduce a large part of surface mass-balance variability of Antizana Glacier 15 even though the melting factors for snow and ice may vary with time. The model performed well because temperatures were significantly correlated with albedo and net shortwave radiation. Because this relationship disappeared when strong winds result in mixed air in the surface boundary layer, this model should not be extrapolated to other tropical regions where sublimation increases during a pronounced dry season or where glaciers are located above the mean freezing level.

scholarly journals Modelling of large-scale melt parameters with a regional climate model in south Greenland during the 1991 melt season

2002 ◽  
Vol 35 ◽  
pp. 391-397 ◽  
Author(s):  
Filip Lefebre ◽  
Hubert Gallée ◽  
Jean-Pascal Van Ypersele ◽  
Philippe Huybrechts
Keyword(s):  
Regional Climate Model ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Temperature Deviation ◽  
Degree Day ◽  
Positive Degree ◽  
Snow And Ice

AbstractLarge-scale positive degree-day based melt parameterizations for the Greenland ice sheet are highly sensitive to their parameters (standard temperature deviation, snow and ice degree-day factors). In this paper, these parameters are simulated with a coupled atmosphere–snow regional climate model for southern Greenland during summer 1991, forced at the lateral boundaries with European Centre for Medium-Range Weather Forecasts re-analyses at a high horizontal resolution of 20 km. the calculated (from net ablation, i.e. melt minus refreezing) snow and ice positive degree-day factors vary considerably over the ice sheet. At low elevations, the modelled snow degree-day factor closely approaches the generally accepted value of 3 mm w.e. d–1 ˚C–1.Higher up the ice sheet, large values up to 15 mm w.e. d– 1 ˚C– 1 are simulated. for ice melt, maximum values of 40 mm w.e. d–1 ˚C– 1 are found. the snow and ice positive degree-day factor distributions peak, respectively, at 3 and 8mm w.e. d–1 ˚C–1. Refreezing is of small importance close to the ice-sheet margin. Higher up the ice sheet, refreezing considerably lowers the amount of net ablation. the monthly simulated 2 m air-temperature standard deviation exhibits a strong seasonal cycle, with the highest (3.0–5.0˚C) values in May and June. July shows the lowest temperature fluctuations, due to the melting of the surface.

scholarly journals Eemian Greenland Surface Mass Balance strongly sensitive to SMB model choice

2018 ◽  
Author(s):  
Andreas Plach ◽  
Kerim H. Nisancioglu ◽  
Sébastien Le clec’h ◽  
Andreas Born ◽  
Petra M. Langebroek ◽  
...  
Keyword(s):  
Mass Balance ◽  
Regional Climate ◽  
Greenland Ice Sheet ◽  
Model Complexity ◽  
Surface Mass Balance ◽  
Potential Contribution ◽  
Surface Mass ◽  
Degree Day ◽  
Positive Degree ◽  
Uncertainty Estimates

Abstract. Understanding the behavior of the Greenland ice sheet in a warmer climate, and particularly its surface mass balance (SMB), is important for assessing Greenland’s potential contribution to future sea level rise. The Eemian interglacial, the most recent warmer-than-present period in Earth’s history approximately 125 000 years ago, provides an analogue for a warm summer climate over Greenland. The Eemian is characterized by a positive Northern Hemisphere summer insolation anomaly, which introduces uncertainties in Eemian SMB when using positive degree day estimates. In this study, we use Eemian global and regional climate simulations in combination with three types of SMB models – a simple positive degree day, an intermediate complexity, and a full surface energy balance model – to evaluate the importance of regional climate and model complexity for estimates of Greenland SMB. We find that all SMB models perform well under the relatively cool pre-industrial and late Eemian. For the relatively warm early Eemian, the differences between SMB models are large which is associated with the representation of insolation in the respective models. For all simulated time slices there is a systematic difference between globally and regionally forced SMB models, due to the different representation of the regional climate over Greenland. We conclude that both the resolution of the simulated climate as well as the method used to estimate the SMB, are important for an accurate simulation of Greenland’s SMB. Whether model resolution or SMB method is most important depends on the climate state and in particular the prevailing insolation pattern. We suggest that future Eemian climate model inter-comparison studies are combined with different SMB models to quantify Eemian SMB uncertainty estimates.

scholarly journals Assessment of current methods of positive degree-day calculation using in situ observations from glaciated regions

2015 ◽  
Vol 61 (226) ◽  
pp. 329-344 ◽  
Author(s):  
L.M. Wake ◽  
S.J. Marshall
Keyword(s):  
Variable Temperature ◽  
Quadratic Function ◽  
Absolute Error ◽  
Common Assumption ◽  
Degree Day ◽  
Monthly Temperature ◽  
Positive Degree ◽  
Hourly Temperature ◽  
Hourly Temperature Data

AbstractThe continued use of the positive degree-day (PDD) method to predict ice-sheet melt is generally favoured over surface energy-balance methods partly due to the computational efficiency of the algorithm and the requirement of only one input variable (temperature). In this paper, we revisit some of the assumptions governing the application of the PDD method. Using hourly temperature data from the GC-Net network we test the assumption that monthly PDD total (PDDM) can be represented by a Gaussian distribution with fixed standard deviation of monthly temperature (σM). The results presented here show that the common assumption of fixed σM does not hold, and that σM may be represented more accurately as a quadratic function of average monthly temperature. For Greenland, the mean absolute error in predicting PDDM using our methodology is 3.9°C d, representing a significant improvement on current methods (7.8°C d, when σM = 4.5°C). Over a range of glaciated settings, our method reproduces PDDM, on average, to within 1.5–8.5°C d, compared to 4.4–15.7°C d when σM = 4.5°C. The improvement arises because we capture the systematic reduction in temperature variance that is observed over melting snow and ice, when surface temperatures cannot warm above 0°C.

scholarly journals High resolution (1 km) positive degree-day modelling of Greenland ice sheet surface mass balance, 1870–2012 using reanalysis data

2016 ◽  
Vol 63 (237) ◽  
pp. 176-193 ◽  
Author(s):  
DAVID J. WILTON ◽  
AMY JOWETT ◽  
EDWARD HANNA ◽  
GRANT R. BIGG ◽  
MICHIEL R. VAN DEN BROEKE ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Models ◽  
Local Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Reanalysis Data ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Degree Day ◽  
Positive Degree

ABSTRACTWe show results from a positive degree-day (PDD) model of Greenland ice sheet (GrIS) surface mass balance (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB: mean 1979–2012 SMB (± standard deviation), in Gt a−1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.

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.

Snow and ice melting properties of self-healing asphalt mixtures with induction heating and microwave heating

2018 ◽  
Vol 129 ◽  
pp. 871-883 ◽  
Author(s):  
Yihan Sun ◽  
Shaopeng Wu ◽  
Quantao Liu ◽  
Jianfu Hu ◽  
Yuan Yuan ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Induction Heating ◽  
Asphalt Mixtures ◽  
Self Healing ◽  
Ice Melting ◽  
Melting Properties ◽  
Snow And Ice

scholarly journals A Short Note on the Tsergo Ri Landslide, Langtang Himal, Nepal

1995 ◽  
Vol 11 ◽  
Author(s):  
J. T. Weidinger ◽  
J. M. Schramm
Keyword(s):  
Large Scale ◽  
Mass Movement ◽  
Short Note ◽  
North Central ◽  
Central Nepal ◽  
Geological Map ◽  
Displacement Deposition ◽  
Langtang Valley

The large-scale mass movement at Tsergo-Ri (Langtang valley) in north-central Nepal was mapped in detail and an engineering geological map was prepared. Five different phases of displacement, deposition and erosion of the landslide are reconstructed. The present morphology of the area is largely the result of the above movement.

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