Abstract. Recent studies have shown the cold and arid trans-Himalayan region comprises
significant areas underlain by permafrost. While the information on the
permafrost characteristics of this region started emerging, the governing
energy regime is of particular interest. This paper presents the results of
a surface energy balance (SEB) study carried out in the upper Ganglass
catchment in the Ladakh region of India which feeds directly into the
Indus River. The point-scale SEB is estimated using the 1D mode of the
GEOtop model for the period of 1 September 2015 to 31 August 2017 at 4727 m a.s.l. elevation. The model is evaluated using field-monitored snow depth
variations (accumulation and melting), outgoing long-wave radiation and
near-surface ground temperatures and showed good agreement with the
respective simulated values. For the study period, the SEB characteristics
of the study site show that the net radiation (29.7 W m−2) was the
major component, followed by sensible heat flux (−15.6 W m−2), latent
heat flux (−11.2 W m−2) and ground heat flux (−0.5 W m−2). During
both years, the latent heat flux was highest in summer and lowest in winter,
whereas the sensible heat flux was highest in post-winter and gradually
decreased towards the pre-winter season. During the study period, snow cover
builds up starting around the last week of December, facilitating ground
cooling during almost 3 months (October to December), with sub-zero
temperatures down to −20 ∘C providing a favourable environment
for permafrost. It is observed that the Ladakh region has a very low
relative humidity in the range of 43 % compared to e.g.
∼70 % in the European Alps, resulting in lower incoming
long-wave radiation and strongly negative net long-wave radiation averaging
∼-90 W m−2 compared to −40 W m−2 in the European
Alps. Hence, land surfaces at high elevation in cold and arid regions could be
overall colder than the locations with higher relative humidity, such as the
European Alps. Further, it is found that high incoming short-wave
radiation during summer months in the region may be facilitating enhanced
cooling of wet valley bottom surfaces as a result of stronger evaporation.