Articles | Volume 21, issue 9
Hydrol. Earth Syst. Sci., 21, 4879–4893, 2017
Hydrol. Earth Syst. Sci., 21, 4879–4893, 2017

Cutting-edge case studies 28 Sep 2017

Cutting-edge case studies | 28 Sep 2017

Providing a non-deterministic representation of spatial variability of precipitation in the Everest region

Judith Eeckman1, Pierre Chevallier1, Aaron Boone2, Luc Neppel1, Anneke De Rouw3, Francois Delclaux1, and Devesh Koirala4 Judith Eeckman et al.
  • 1Laboratoire HydroSciences (CNRS, IRD, Université de Montpellier) CC 57 – Université de Montpellier 163, rue Auguste Broussonnet 34090 Montpellier, France
  • 2CNRM UMR 3589, Météo France/CNRS, Toulouse, France
  • 3Institut de Recherche pour le Développement, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris CEDEX 5, France
  • 4Nepal Academy of Science and Technology, G.P.O. box 3323, Khumaltar, Lalitpur, Nepal

Abstract. This paper provides a new representation of the effect of altitude on precipitation that represents spatial and temporal variability in precipitation in the Everest region. Exclusive observation data are used to infer a piecewise linear function for the relation between altitude and precipitation and significant seasonal variations are highlighted. An original ensemble approach is applied to provide non-deterministic water budgets for middle and high-mountain catchments. Physical processes at the soil–atmosphere interface are represented through the Interactions Soil–Biosphere–Atmosphere (ISBA) surface scheme. Uncertainties associated with the model parametrization are limited by the integration of in situ measurements of soils and vegetation properties. Uncertainties associated with the representation of the orographic effect are shown to account for up to 16 % of annual total precipitation. Annual evapotranspiration is shown to represent 26 % ± 1 % of annual total precipitation for the mid-altitude catchment and 34% ± 3 % for the high-altitude catchment. Snowfall contribution is shown to be neglectable for the mid-altitude catchment, and it represents up to 44 % ± 8 % of total precipitation for the high-altitude catchment. These simulations on the local scale enhance current knowledge of the spatial variability in hydroclimatic processes in high- and mid-altitude mountain environments.

Short summary
The central part of the Himalayan Range presents tremendous heterogeneity in terms of topography and climatology, but the representation of hydro-climatic processes for Himalayan catchments is limited due to a lack of knowledge in such poorly instrumented environments. The proposed approach is to characterize the effect of altitude on precipitation by considering ensembles of acceptable altitudinal factors. Ensembles of acceptable values for the components of the water cycle are then provided.