Browsing by Autor "So Kazama"

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ESTIMATION OF GLACIER MELT IN THE TROPICAL ZONGO WITH AN ENHANCED TEMPERATURE-INDEX MODEL
(2013) Pablo Fuchs; Yoshihiro ASAOKA; So Kazama
An enhanced temperature-index model including albedo and shortwave radiation has been applied to the tropical Zongo glacier. The model satisfactorily simulated the daily discharges and their seasonal variations with an efficiency of 0.71 (Nash-Sutcliffe). The energy balance analysis revealed that three factors mainly control melt on this glacier: incoming shortwave radiation, incoming longwave radiation and sensible heat flux. Accordingly, the model differentiates between temperature-dependent and temperature-independent components moving towards a more physically based but still simple model. Modelling was improved with respect to the traditional degree-day method in the wet season characterized by simultaneous accumulation and strong melting while capturing the low melt rates found in the dry season. However the model missed some peaks in discharge due to the underestimation of precipitation at the low elevation meteorological station.
HEAT BALANCE ANALYSIS ON THE GLACIER WITH SUMMERPRECPITATON SEASONALITY AND EFFECT OF SNOW -A CASE STUDY OF ANDEAN TROPICAL GLACIER-
(2013) Yoshihiro ASAOKA; Takeshi Yamazaki; Shunsuke Miyata; So Kazama; Edson Ramírez
The tropical glacier in Andes Mountain has summer precipitation seasonality. A multi-layer snow model was applied to Zongo glacier, Bolivia to evaluate the heat balance on the glacier and the effect of snow on glacier melt. Model simulation at observation point successfully accounted for variations in surface temperature on the glacier in both dry and wet season. Main components of melt heat were shortwave radiation in the dry season and long wave radiation in wet season. Melt flux in mid-wet season was lower than in early-wet season due to continuous snow cover and its high albedo. Moreover, simulation results showed that snow cover on the glacier decline the melt rate in the wet season. This result suggests that mass balance is affected by summer precipitation seasonality and vulnerable to temperature rise.
Modelling melt, runoff, and mass balance of a tropical glacier in the Bolivian Andes using an enhanced temperature-index model
(2016) Pablo Fuchs; Yoshihiro ASAOKA; So Kazama
This paper evaluates the feasibility of applying a coupled melt, runoff, and mass balance model to the tropical Zongo glacier (Cordillera Real, Bolivia) during two hydrological years. Melt rate was estimated using the standard degree-day method (DDM) and an enhanced temperature-index model (ETI). The latter was run with values of parameters obtained for Haut Glacier d’Arolla and a recalibrated parameter set for Zongo glacier. Glacier mass balance was calculated using snowfall inputs and modelled melt and sublimation. Estimated monthly mass balance and discharge were compared with observations from a stake network in the ablation zone and data from a hydrometric station. We concluded that ETI model agrees very well with the reference runoff and mass balance. Net mass balance over the whole glacier was predicted accurately in the ablation zone, but the model overestimated mass balance in the accumulation zone owing to the absence of observations at higher elevations; the equilibrium line altitude and accumulation area ratio were predicted within reasonable limits. The results demonstrate that ETI model is applicable in tropical conditions, provided that the parameters are recalibrated for the climatic settings of this region.