Post on 24-Dec-2015
transcript
Climate change impacts on water cycle in the Tibetan Plateau: A review
Kun YangInstitute of Tibetan Plateau Research
Chinese Academy of Sciences
The fifth Third Pole Environment Workshop
Berlin, Germany, 2014/12/8-91
Outline
Climate changes over the Tibetan Plateau
Surface water balance changes
Possible causes of glacier and lake changes
Conclusions
22
Moistening
Dimming
Warming
Stilling
(Yang et al. 2014, GPC)
The Tibetan Plateau has been experiencing a rapid climate change since middle of 1980s: warming, moistening, wind stilling and solar dimming
3
The warming rate changes with elevation (2000-2006), derived from MODIS data
?
(Qin et al., 2009 Clim. Chang.)4
Cooling
Rapid warming
Warming
Spatial pattern of recent warming/cooling (2000-2006), derived from MODIS data
(Yang et al. 2014, GPC)5
Precipitable water vapor increased during 1979-2011
Lu et al. (2014, JC) 6
Precipitable water vapor increased during 1979-2011, and an abrupt increase occurred in 1998
Lu et al. (2014, JC)7
1998
China TP
Lin et al. (2013, JC)
Wind speed decreased since 1970 but slightly recovered since 2002.
8
Solar radiation decreased since the end of 1970s, due to more Deep Cloud Cover (DCC)
Surface observations Satellite observations
(Yang et al. 2012, GRL)9
Outline
Decadal climate changes over the Tibetan
Plateau
Surface water balance changes
Possible causes of glacier and lake changes
Conclusions
1010
How surface water balance responded to climate change?
The number of CMA stations is not sufficient to support water balance analysis at basin-scale by DHM; instead, we
use a land surface model to simulate it11
RainRadForcings
Land surface modeling at each station
Improved LSM for Arid and semi-arid regions:1. Surface flux parameterization for bare soil surfaces2. Aerodynamic model for sparse canopy 3. High-accuracy soil water flow scheme4. Soil freezing and thawing
(Yang et al. 2009, HESS)12
Hydrological cycle response: more runoff in central TP and less runoff in south/east TP
P E
Roff SM
(Yang et al., 2011 Clim Change) 13
Evaporation derived by data fusion of GLDAS simulations and GRACE gravity data shows increasing
trends in both east and west.
Li et al. (2014, JGR)
Qiangtang
Qaidam
Yangtze
Yellow
14
The positive trend in soil moisture also supports northwestern TP got wet (1988-2008, m3m-3 per 10a)
Spring Summer
Autumn Northwestern TP
(Velde et al. 2014, HESS)15
Yang et al. (2014, GPC)
Sensible heat decreased
The evaporation increase is consistent with sensible heat decrease found in recent studies. This may be explained by the response of Bowen ratio to warming
1
- -
s sg a
g a g ag a
g a g as g s a
e eT rh T
T T T TT TB
B T T T Te T - rh e T
Sensible HeatBowen Ratio
Latent Heat
1 4 CaT . 1 8 CgT . 56rh %
16
Outline
Decadal climate changes over the Tibetan
Plateau
Surface water balance changes
Possible causes of glacier and lake changes
Conclusions
1717
Glacier change and its possible causes
Cooling
Rapid warming
Stable or extend
Rapid shrink
Moderate shrink
Warming
Yang et al. (2014, GPC)
18
(Yao et al. 2012, NCC)
Surface warming/cooling spatial pattern also corresponds well to the spatial pattern of glacier changes
(Yao et al. 2012, NCC)
Observed lake changes: expanded in central and northwestern TP and shrank in south TP
( Lei et al, 2014, Climatic Change) 19
Rapid shrink
Rapid warming
Relationship between lake expansion and glacier/lake area ratio in interior TP during 1976-2010
( Lei et al, 2014, Climatic Change) 20
Non-glacier-fed lakes expanded, too. Glacier melt does not dominate lake changes but seems accelerating the expansion.
Lake area change is highly correlated with the accumulation of precipitation anomaly
( Lei et al, 2014, Climatic Change) 21
Water vapor changes correlates with large-scale indices
NHSM circulation intensity:V850-V200
HTC: hemispheric thermal contrast
AMO: Atlantic multi-decadal oscillation
mega-ENSO” index:SST difference between the western Pacific K-shape area and eastern Pacific triangle as
( Lei et al, 2014, Climatic Change) 22
Conclusions• Dry (Central and Western TP) got less dry, and wet
(Southern and Eastern TP) got less wet.
• Evaporation increased overall, which is a response to warming.
• Glacier change may be related to the spatial change of both precipitation and air temperature.
• Lake changes are mainly due to precipitation increasing/decreasing, and glacier melt may have accelerated lake expansion.
• An integrated model is needed to understand the processes of these changes.
23
Simple water balance calculation without glacier and frozen soil explains lake level changes except Nam Co
Lei et al. (2013)
24