160
and inner ranges have the most highly glaciated areas outside the Polar Regions
(Owen et al. 2002; Dyurgerov and Meier 2005). With increasing temperature and
shifting of winter period at many places in Himalaya, liquid precipitation is on
increase in some regions of Himalaya during winter months (Negi et al. 2018a).
Though most of the data available from the region is from low altitudes except some
from a few high altitude observatories, maintained by Snow and Avalanche Study
Establishment, yet the findings are alarming and demand immediate attention to
the region.
There has been rise in temperature as well as decline in snowfall amount over
high Himalayan altitudes, which has been reported by many studies (Dimri and
Dash 2012; Bhutiyani et al. 2007; Bhutiyani et al. 2010; Gusain et al. 2014; Gusain
et al. 2015; Shekhar et al. 2010). This change has been attributed to rising concentration of greenhouse gases (Schneider 1990) and decreased cloud cover etc.
(Shekhar et al. 2010). The cryosphere responds to rising temperature and declining
snowfall mainly in the form of retreating glaciers (Bolch et al. 2012; Azam et al.
2014a, b; Vijay and Braun 2016). This response though spatially heterogeneous
with significant retreat of glaciers reported at certain locations (Gardelle et al. 2012;
Kääb et al. 2012), is largely stable.
It has been conclusively brought out by many workers (Negi et al. 2018a; Shekhar
et al. 2010, 2017) that there has been increase in winter temperature and liquid precipitation in North-West Himalaya. A hiatus for a decade has also been inferred
from the MODIS derived albedo, which shows insignificant increasing trend in
albedo from 2001 onward (Negi HS et al. 2017). This has been attributed to decrease
in winter average air temperature over NW-Himalaya. In a study by Negi et al.
(2018b, in press), the authors have drawn the following conclusions from the winter
surface data collected from the inner regions of Himalaya.
(i) Overall warming trends in mean and maximum temperature of North Western
Himalaya NWH (1991–2015) and Central Himalaya CH (2001–2012) have
been observed. Unlike observed worldwide, the data of both NWH and CH
reflect higher rate of warming in maximum temperature than minimum temperature. Consequently, there has been an increase in Diurnal Temperature
Range (DTR) over both NWH and CH.
(ii) Regionally, long term (~30 years) warming trends have been observed in all
zones of NWH except in the minimum temperature over Lower Himalaya
(LH), which shows cooling trends. The rate of warming (mean temperature) is
found to be highest in Great Himalaya (GH) than Karakoram Himalaya (KH)
and LH, which partly explains the higher rate of glacier melt in regions of GH
than KH.
(iii) Short term trends (2000–2015) depict cooling in maximum temperature of LH
and GH, which though unexplained, may have some links with rising concentration of aerosols in atmosphere in recent decades as reported in some study
(Krishnan and Ramanathan 2002).
(iv) Long term warming trends over LH, GH and CH has manifested in retreating
of glaciers lying in these areas. Though KH also reports warming but this marA. Ganju and H. S. Negi
and inner ranges have the most highly glaciated areas outside the Polar Regions
(Owen et al. 2002; Dyurgerov and Meier 2005). With increasing temperature and
shifting of winter period at many places in Himalaya, liquid precipitation is on
increase in some regions of Himalaya during winter months (Negi et al. 2018a).
Though most of the data available from the region is from low altitudes except some
from a few high altitude observatories, maintained by Snow and Avalanche Study
Establishment, yet the findings are alarming and demand immediate attention to
the region.
There has been rise in temperature as well as decline in snowfall amount over
high Himalayan altitudes, which has been reported by many studies (Dimri and
Dash 2012; Bhutiyani et al. 2007; Bhutiyani et al. 2010; Gusain et al. 2014; Gusain
et al. 2015; Shekhar et al. 2010). This change has been attributed to rising concentration of greenhouse gases (Schneider 1990) and decreased cloud cover etc.
(Shekhar et al. 2010). The cryosphere responds to rising temperature and declining
snowfall mainly in the form of retreating glaciers (Bolch et al. 2012; Azam et al.
2014a, b; Vijay and Braun 2016). This response though spatially heterogeneous
with significant retreat of glaciers reported at certain locations (Gardelle et al. 2012;
Kääb et al. 2012), is largely stable.
It has been conclusively brought out by many workers (Negi et al. 2018a; Shekhar
et al. 2010, 2017) that there has been increase in winter temperature and liquid precipitation in North-West Himalaya. A hiatus for a decade has also been inferred
from the MODIS derived albedo, which shows insignificant increasing trend in
albedo from 2001 onward (Negi HS et al. 2017). This has been attributed to decrease
in winter average air temperature over NW-Himalaya. In a study by Negi et al.
(2018b, in press), the authors have drawn the following conclusions from the winter
surface data collected from the inner regions of Himalaya.
(i) Overall warming trends in mean and maximum temperature of North Western
Himalaya NWH (1991–2015) and Central Himalaya CH (2001–2012) have
been observed. Unlike observed worldwide, the data of both NWH and CH
reflect higher rate of warming in maximum temperature than minimum temperature. Consequently, there has been an increase in Diurnal Temperature
Range (DTR) over both NWH and CH.
(ii) Regionally, long term (~30 years) warming trends have been observed in all
zones of NWH except in the minimum temperature over Lower Himalaya
(LH), which shows cooling trends. The rate of warming (mean temperature) is
found to be highest in Great Himalaya (GH) than Karakoram Himalaya (KH)
and LH, which partly explains the higher rate of glacier melt in regions of GH
than KH.
(iii) Short term trends (2000–2015) depict cooling in maximum temperature of LH
and GH, which though unexplained, may have some links with rising concentration of aerosols in atmosphere in recent decades as reported in some study
(Krishnan and Ramanathan 2002).
(iv) Long term warming trends over LH, GH and CH has manifested in retreating
of glaciers lying in these areas. Though KH also reports warming but this marA. Ganju and H. S. Negi