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Measurements, models and drivers of incoming longwave radiation in the Himalaya
Author(s) -
Kok Remco J.,
Steiner Jakob F.,
Litt Maxime,
Wag Patrick,
Koch Inka,
Azam Mohd F.,
Immerzeel Walter W.
Publication year - 2020
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.6249
Subject(s) - longwave , snow , environmental science , elevation (ballistics) , glacier , climatology , snowmelt , atmospheric sciences , outgoing longwave radiation , relative humidity , meteorology , radiation , geology , geography , mathematics , geomorphology , physics , convection , quantum mechanics , geometry
Melting snow and glacier ice in the Himalaya forms an important source of water for people downstream. Incoming longwave radiation (LW in ) is an important energy source for melt, but there are only few measurements of LW in at high elevation. For the modelling of snow and glacier melt, the LW in is therefore often represented by parameterizations that were originally developed for lower elevation environments. With LW in measurements at eight stations in three catchments in the Himalaya, with elevations between 3,980 and 6,352 m.a.s.l., we test existing LW in parameterizations. We find that these parameterizations generally underestimate the LW in , especially in wet (monsoon) conditions, where clouds are abundant and locally formed. We present a new parameterization based only on near‐surface temperature and relative humidity, both of which are easy and inexpensive to measure accurately. The new parameterization performs better than the parameterizations available in literature, in some cases halving the root‐mean‐squared error. The new parameterization is especially improving existing parameterizations in cloudy conditions. We also show that the choice of longwave parameterization strongly affects melt calculations of snow and ice.