The influence of large-scale atmospheric circulation on the surface energy balance of the King George Island ice cap

2001 ◽  
Vol 21 (1) ◽  
pp. 21-36 ◽  
Author(s):  
Matthias Braun ◽  
Helmut Saurer ◽  
Steffen Vogt ◽  
Jefferson Cardia Simões ◽  
Hermann Goßmann
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Surface Energy Balance ◽  
King George Island ◽  
Ice Cap ◽  
Large Scale Atmospheric Circulation

scholarly journals Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

2013 ◽  
Vol 9 (6) ◽  
pp. 6683-6732
Author(s):  
N. Merz ◽  
A. Born ◽  
C. C. Raible ◽  
H. Fischer ◽  
T. F. Stocker
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Climate Model ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Lapse Rate

Abstract. The influence of a reduced Greenland ice sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation which influences SAT through the lapse rate effect. The resulting lapse rate corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the NH flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHFLX). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHFLX. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHFLX and anomalous cold winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the NEEM ice core site, our model suggests that up to 3.2 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations.

scholarly journals Local climate, circulation and surface-energy balance of an Antarctic blue-ice area

1994 ◽  
Vol 20 ◽  
pp. 160-168 ◽  
Author(s):  
R. Bintanja ◽  
M. R. van den Broeke
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Weddell Sea ◽  
Wave Radiation ◽  
Local Circulation ◽  
Night Time ◽  
Pressure System ◽  
Continental Scale

Results of measurements performed on and around an Antarctic blue-ice field are presented in this paper. The measurements were carried out in a valley of Heimefrontfjella, Dronning Maud Land, during a 2 month field season in the austral summer of 1992–93. A simple model is used to evaluate the surface-energy balance from measured meteorological quantities. The large differences in the surface-energy-balance values between snow and blue ice are mainly caused by differences inalbedo, surface roughness, thermal conductivity and short-wave radiation extinction coefficient. Taking into account uncertainties in the calculations, it appears that the calculated sublimation rates over ice and snow do not differ much.Furthermore, typical circulation patterns are described. The large continental-scale katabatic flow is forced by radiative cooling of the surface (night-time) and the mesoscale horizontal temperature gradient (daytime). The latter penetrates to the surface due to enhanced mixing in an unstable stratified boundary layer. At night, shallow katabatic layers form along local fall lines. On some occasions the large-scale katabatic winds decrease through the presence of a high-pressure system in the weddell Sea and a local circulation can develop inside the valley.

scholarly journals Evaluation of energy balance closure correction methods for multiple eddy-covariance sites in different biomes

2020 ◽  
Author(s):  
Matthias Mauder ◽  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Eddy Covariance ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Energy Transport ◽  
Energy Balance Closure ◽  
Apparent Lack ◽  
Secondary Circulations ◽  
Measurement Height

<p>The apparent lack of surface energy balance closure is one of the most crucial challenges in the measurement of biosphere-atmosphere exchange. In principle, this issue can have a variety of potential reasons, including instrumental errors and errors introduced in the data processing chain. In addition, secondary circulations have been identified as one of the main reasons for a non-closure of the surface energy balance, since the related energy transport cannot be captured by common eddy-covariance tower flux measurements. When present, neglecting this process will result in an underestimation of turbulent fluxes. Secondary circulations can, however, be represented by means of large-eddy simulations, which have been employed to develop a novel semi-empirical model to correct for the missing large-scale flux (De Roo et al. 2018, DOI 10.1371/journal.pone.0209022). In this study, we compare the results of this process-based method with two other previously published bulk-correction methods (Mauder et al. 2013, DOI 10.1016/j.agrformet.2012.09.006; Charuchittipan et al. 2014, DOI 10.1007/s10546-014-9922-6). These three correction methods are applied for multiple sites in different biomes around the world. Independent data of energy fluxes from these sites are used to assess which of these methods leads to the most reliable results, and we discuss the limitations of these corrections methods with respect to meteorological conditions and site characteristics, such as measurement height, the landscape-scale heterogeneity and terrain complexity.</p>

scholarly journals Remote Sensing Based Estimation of Evapo-Transpiration Using Selected Algorithms: The Case of Wonji Shoa Sugar Cane Estate, Ethiopia

2017 ◽  
Author(s):  
Mulugeta Genanu ◽  
Tena Alamirew ◽  
Gabriel Senay ◽  
Mekonnen Gebremichael
Keyword(s):  
Remote Sensing ◽  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Wet Season ◽  
Total Crop ◽  
Spatio Temporal ◽  
Water Surplus ◽  
Soil Moisture Variability

Remote sensing datasets are increasingly being used to provide spatially explicit large scale evapotranspiration (ET) estimates. The focus of this study was to estimate and thematically map on a pixel-by-pixel basis, the actual evapotranspiration (ETa) of the Wonji Shoa Sugarcane Estate using the Surface Energy Balance Algorithm for Land (SEBAL), Simplified Surface Energy Balance (SSEB) and Operational Simplified Surface Energy Balance (SSEBop) algorithms. The results obtained revealed that the ranges of the daily ETa estimated on January 25, February 26, September 06 and October 08, 2002 using SEBAL were 0.0 - 6.85, 0.0 – 9.36, 0.0 – 3.61, 0.0 – 6.83 mm/day; using SSEB 0.0 - 6.78, 0.0 – 7.81, 0.0 – 3.65, 0.0 – 6.46 mm/day, and SSEBop were 0.05 - 8.25, 0.0 – 8.82, 0.2 – 4.0, 0.0 – 7.40 mm/day, respectively. The Root Mean Square Error (RMSE) values between SSEB and SEBAL, SSEBop and SEBAL, and SSEB and SSEBop were 0.548, 0.548, and 0.99 for January 25, 2002; 0.739, 0.753, and 0.994 for February 26, 2002;0.847, 0.846, and 0.999 for September 06, 2002; 0.573, 0.573, and 1.00 for October 08, 2002, respectively. The standard deviation of ETa over the sugarcane estate showed high spatio-temporal variability perhaps due to soil moisture variability and surface cover. The three algorithm results showed that well watered sugarcane fields in the mid-season growing stage of the crop had higher ETa values compared with the other dry agricultural fields confirming that they consumptively use more water. Generally during the dry season, ETa is limited to water surplus areas only and in wet season, ETa was high throughout the entire sugarcane estate. The evaporation fraction (ETrF) results also followed the same pattern as the daily ETa over the sugarcane estate. The total crop and irrigation water requirement and effective rainfall estimated using the Cropwat model were 2468.8, 2061.6 and 423.8 mm/yr for January 2001 planted and 2281.9, 1851.0 and 437.8 mm/yr for March 2001 planted sugarcanes, respectively. The mean annual ETa estimated for the whole estate were 107 Mm3, 140 Mm3, and 178 Mm3 using SEBAL, SSEB, and SSEBop, respectively. Even though the algorithms should be validated through field observation, they have potential to be used for effective estimation of ET in the sugarcane estate.

scholarly journals Long-term surface energy balance of the western Greenland ice sheet and the role of large-scale circulation variability

2020 ◽  
Author(s):  
Baojuan Huai ◽  
Michiel R. van den Broeke ◽  
Carleen H. Reijmer
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Climate Variables ◽  
Large Scale Circulation ◽  
Near Surface ◽  
Surface Climate

Abstract. We present the surface energy balance (SEB) of the west Greenland ice sheet (GrIS), using an energy balance model forced with hourly observations from nine automatic weather stations (AWS) along two transects: the K-transect with seven AWS in the southwest and the T-transect with two AWS in the northwest. Modeled and observed surface temperatures for non-melting conditions agree well, with RMSEs of 1.1–1.6 K, while reasonable agreement is found between modeled and observed 10-day cumulative ice melt. Absorbed shortwave radiation (Snet) is the main energy source for melting (M), followed by the sensible heat flux (Qh). The multi-year average seasonal cycle of SEB components show that Snet and M peak in July at all AWS. The turbulent fluxes of sensible (Qh) and latent heat (Ql) decrease significantly with elevation, and the latter becomes negative at higher elevations, partly offsetting Qh. Average June, July, August (JJA) albedo values are  0.7 for the higher stations. The near-surface climate variables and surface energy fluxes from reanalysis products ERA-interim, ERA5 and the regional climate model RACMO2.3 were compared to the AWS values. The newer ERA5 product only significantly improves on ERA-interim for albedo. The regional model RACMO2.3, which has higher resolution (5.5 km) and a dedicated snow/ice module, unsurprisingly outperforms the re-analyses for (near-) surface climate variables, but the reanalyses are indispensable to detect dependencies of west Greenland climate and melt on large-scale circulation variability. We correlate ERA5 with the AWS data to show a significant positive correlation of western GrIS summer surface temperature and melt with the Greenland Blocking Index (GBI), and weaker and opposite correlations with the North Atlantic Oscillation (NAO). This analysis may further help to explain melting patterns in the western GrIS from the perspective of circulation anomalies.

scholarly journals Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

2014 ◽  
Vol 10 (3) ◽  
pp. 1221-1238 ◽  
Author(s):  
N. Merz ◽  
A. Born ◽  
C. C. Raible ◽  
H. Fischer ◽  
T. F. Stocker
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Large Scale ◽  
Surface Energy Balance ◽  
Climate Model ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Lapse Rate

Abstract. The influence of a reduced Greenland Ice Sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a set of simulations with different GrIS realizations performed with a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation, which influences SAT through the lapse rate effect. The resulting lapse-rate-corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the Northern Hemisphere (NH) flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHF). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHF. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHF, and anomalous low winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the Eemian ice found in the NEEM core, our model suggests that up to 3.1 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations.

scholarly journals Parameter uncertainty, refreezing and surface energy balance modelling at Austfonna ice cap, Svalbard, 2004-08

2013 ◽  
Vol 54 (63) ◽  
pp. 229-240 ◽  
Author(s):  
Torbjørn I. Østby ◽  
Thomas V. Schuler ◽  
Jon Ove Hagen ◽  
Regine Hock ◽  
Carleen H. Reijmer
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Model Performance ◽  
Surface Displacement ◽  
Glacier Mass Balance ◽  
Ice Cap ◽  
Physically Based ◽  
Parameter Values ◽  
Snow And Ice

AbstractWe apply a physically based coupled surface energy balance and snowpack model to a site close to the equilibrium line on Austfonna ice cap, Svalbard, over the 2004-08 melt seasons, to explain contributions to the energy available for melting and to quantify the significance of refreezing. The model is forced using in situ meteorological measurements and precipitation downscaled from ERA-Interim reanalysis. Applying a Monte Carlo approach to determine the tunable parameters of the model, we estimate the uncertainty related to the choice of parameter values. Multiple criteria are evaluated to identify well-performing parameter combinations, evaluating the model performance with respect to longwave outgoing radiation, snow and ice temperatures and surface displacement. On average, over the investigated melt seasons (1 June to 15 September) net radiation and sensible heat contributed 90 ± 2% and 10 ± 2%, respectively, to the mean energy available for melting snow and ice. The energy consumed by subsurface heat exchange reduced runoff by 15±2% in 2004 and 49±3% in 2008. Refreezing of meltwater and rain was estimated to be 0.37 ± 0.04 m w.e. a-1 on average over the five seasons, which represents a considerable reduction of mass loss during summer. Our findings suggest that refreezing potentially exerts a decisive control on glacier mass balance in persistently snow- or firn-covered areas.

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