Transcript Yang, K. - Third Pole Environment (TPE)

A synthetic report of recent climatic changes
and their impacts on energy and water
budgets over the Tibetan Plateau (TP)
Kun Yang, Jun Qin, Wenjun Tang
Institute of Tibetan Plateau Research (ITP)
Chinese Academy of Sciences
“Third Pole Environment” 3rd Workshop, Iceland, 30 Aug – 1 Sep, 2011
Outline
• Observed climatic changes
• Dependence of temperature and wind speed
trends on elevation
• Solar radiation trend across China and TP
• Thermal response to climatic change
• Hydrological response to climatic change
• Potential collaboration in Glacier studies
Climatology of Precipitation in TP
Wet in SE-TP, Dry in NW-TP
Climate change during 1984-2006
Tibetan Plateau has been experiencing a rapid warming and wetting while
wind speed and sunshine duration are declining in recent decades.
(Yang et al., 2011 climatic change)
Altitudinal dependence of
recent rapid warming over
the Tibetan Plateau
Jun Qin1, Kun Yang1, Shunlin Liang2, Xiaofeng Guo1
1.
2.
Institute of Tibetan Plateau Research, Chinese Academy of
Sciences , China
Department of Geography, University of Maryland, USA
(Qin et al., 2009 Climatic Change)
MODIS warming rate
Validate MODIS observed LST trend
Station warming rate
(Qin et al., 2009 Climatic Change)
Warming rate derived from MODIS data
4800m
?
• increases with the altitude below 4800 m,
• keeps stable above 4800 m,
(Qin et al., 2009 Climatic Change)
• declines above 6200 m
Wind speed trend in China and TP
1960‐1974
1974‐2002
2002‐2009
Surface wind speed variability increases with elevation
Upper-air wind speed changed similarly!
500 hPa
800 hPa
500 hPa
800 hPa
1960‐1974
1974‐2002
2002‐2009
Differential geopotential heights (North, Middle,
South) on 500hPa (from radiosonde)
PGF change well corresponds to wind speed change
Solar radiation trend across China
A number of studies indicate there was a dimming
(solar radiation decreasing) in the world since
1960s, but a transition from dimming to
brightening at the beginning of 1990s. (Wild et al.,
2005 Science)
Similar results were reported for China
(Tang et al., 2011 ACP)
Trends at all CMA stations
from 1961 to 1989
Diming
from 1990 to 2006
No brightening trend
(Tang et al., 2011 ACP)
Regional mean trend
dynamic harmonic regression
Linear fitting
Authors
Number of
Stations
Trend slopes
(W m-2 year-1)
Che et al. (2005)
64
-0.45
Liang et al.
(2005)
42
-0.52
Shi et al. (2008)
72
-0.41
Present -Model
459
-0.23
Present –ANN
71
-0.21
Present- Model
72
-0.21
The magnitude of solar radiation trend was over-estimated
(Tang et al., 2011 ACP)
Is the difference due to station
representativeness?
all radiation stations
all CMA routine stations
Time series of sunshine duration (hour/year) during 1961 ~ 2000.
(Tang et al., 2011 ACP)
How to explain the trend? Due to
pollutants?
TP is less polluted area, but the decreasing magnitude over TP is even
larger than the average over China (-0.2 Wm-2/a)
(Tang et al., 2011 ACP)
Thermal Response to Climate Change over
the Tibetan Plateau
Method:
combine Surface obs., Satellite and LSM
(Yang et al., 2011 J. Clim)
Westerly
Heat source
Monsoon
Thermal anomaly
Monsoon variability
Atmospheric heating
Rn_toa
Air
Latent heat release
Rn_sfc
Sensible
heat
Surface
Heat source =H + lP + dR
where dR=Rn_toa – Rn_sfc
Spatial distribution of the total heat source
This spatial pattern is contrast to the one presented
in most of previous studies
(Yang et al., 2011 J. Clim)
Heat source trends
H
Rc
TH
H: decrease, the magnitude is ~ 1/2-1/3 of conventional estimate
RC: decrease , the magnitude is ~ 1/2 of conventional estimate
TH: decrease, the magnitude is ~ 1/2 of conventional estimate
(Yang et al., 2011 J. Clim)
Heat source trend over China
50
45
Latitude
40
35
30
25
positive
negative
0 to 5
5 to 10
10 to 15
15 to 20
above 20
20
15
80
90
100
110
Longitude
120
130
Modeled hydrological cycle response to climate change
Runoff anomaly ~ Discharge anomaly
Hydrological cycle response to climate change
P
E
Roff
SM
(Yang et al., 2011 climatic change)
Physical picture of climate change over TP
More warming in North
than in South
Global warming
Weaken upper-air PGF
Reduce wind speed
Less heat transfer
from Plateau
Enhance local
warming
Weaken Bowen-ratio
Less sensible heat
Enhance OLR
More evaporation
Heat source
decrease
Less discharge
from Plateau
Weaken monsoon
Enhance radiative
cooling
Parlang No.4 Glacier
11.7km2 in area
8 km long
Glacier experiments in TP
The first turbulence station on a Tibetan glacier
 eddy-covariance (EC) system
 May 20 to September 9, 2009







(CSAT3; LI-7500) / 10 Hz
Southeast Tibetan Plateau
CNR1 radiometers
Palong-Zangbu No. 4 glacier
HMP45C temp. & R.H. sensor
ablation zone
mass balance stakes (N=9)
(2915N, 9655E) / 4800 m ASL
(05-20)
(06-21)
(08-02)
Diurnal variations of the turbulent fluxes
120
80
40
LE (W m-2)
0
H (W m-2)
-40
-80
-120
0
4
8
12
16
20
24
Turbulent heat fluxes are not so strong
(Guo et al., 2011 BLM)
Parameterizing sensible heat flux (Guo et al., 2011 BLM)
-30
-2
-2
HBA (W m )
-30
-60
(c)
0
Yang et al. (2002)
P1
P2
P3
-30
0
-120
-120
-2
HEC (W m )
-2
Error (W m )
HBA=0.93×HEC-12.4
2
(R =0.90)
2
(R =0.91)
-60
-60
HBA=0.74×HEC-13.4
2
(R =0.85)
-90
P1
P2
P3
-90
HBA=0.56×HEC-12.0
-120
-120
Smeets and
van den Broeke (2008b)
-30
-60
-90
-90
0
-2
Andreas (1987)
P1
P2
P3
HBA (W m )
(a)
(b)
HBA (W m )
0
20
15
10
5
0
-5
-10
-90
-60
0
-60
-30
HEC (W m )
HEC (W m )
MBE
-90
-2
-2
MAD
Andreas (1987)
-30
-120
-120
RMSE
Yang et al. (2002) Smeets and van den
Broeke (2008)
0
Parameterizing latent heat flux (Guo et al., 2011 BLM)
120
Yang et al. (2002)
P1
P2
P3
0
T
T
LEBA=0.81×LEEC-0.95
-30
-30
0
30
T
0
T
-2
T
LEBA=1.00×LEEC-1.11
-30
P1
P2
P3
30
0
T
60
90
120
-60
-60
-2
-30
0
30
T
T
LEBA=1.18×LEEC-1.47
-30
2
(R =0.93)
2
(R =0.92)
LEEC (W m )
Error (W m )
60
Smeets and
van den Broeke (2008b)
T
30
2
(R =0.91)
-60
-60
120
90
T
30
60
(c)
-2
90
-2
60
Andreas (1987)
P1
P2
P3
T
-2
LEBA (W m )
90
(b)
LEBA (W m )
120
LEBA (W m )
(a)
60
90
120
-60
-60
-30
0
30
T
-2
60
90
-2
LEEC (W m )
LEEC (W m )
15
10
MAD
MBE
RMSE
5
0
-5
Andreas (1987)
Yang et al. (2002) Smeets and van den
Broeke (2008)
120
Ablation and energy budget (Yang W et al., 2011 JGR)
5000
Cumulative ablation (mm w.e.)
4000
3000
Accumulated melt
2000
1000
0
5/21
6/4
6/18
7/2
7/16
7/30
8/13
P1
P2
P3
8/27
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
Rn/Total
H/Total
lE/Total
G/Total
Components contributing to melt
Ablation is rapid, and net radiation is the major contributor
A global survey: Rnet/Emelt
Tibet
Others
The ratios for Tibetan glaciers are higher than for other regions
Welcome cooperative work in
 Climatic change
 Glacier melting modeling
 Glacier change
Thank you for your attention!