Transcript CHHT1.0 - Copernicus.org

Homogenization of Chinese daily surface air temperatures:An
update for CHHT1.0
Li Qingxiang , Xu Wenhui, Xiaolan Wang, and coauthors
(National Meteorological Information Center, CMA, Email: [email protected])
Inhomogenity exits in Chinese observational historic
temperature data series due to stations relocation,
changes of observations, calculation daily mean values,
etc. One should paid careful attention on this when
using the data set, we start to detect and adjust the
discontinuities from about 20 years ago.
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PMT-with Ref/ daily Ref
Test in daily/monthly/ annual
scales
Recent changes
CHHT1.0(Dec, 2006)
Adj daily seires
User needs
Mean temperature changes
Climate extreme changes
Homogenization of Chinese daily surface air temperatures:An
update for CHHT1.0
Li Qingxiang , Xu Wenhui, Xiaolan Wang, and coauthors
(National Meteorological Information Center, CMA, Email: [email protected])
The CHHT1.0 Dataset (1951–2004) consists of
monthly and daily surface observations from all
national stations in mainland China. CHHT 1.0
includes mean, maximum, and minimum temperature
data; assessments of data quality; and gridded
versions of the three temperature variables.
2/3
PMT-with Ref/ daily Ref
Test in daily/monthly/ annual
scales
Recent changes
CHHT1.0(Dec, 2006)
Adj daily seires
User needs
Mean temperature changes
Climate extreme changes
Homogenization of Chinese daily surface air temperatures:An
update for CHHT1.0
Li Qingxiang , Xu Wenhui, Xiaolan Wang, and coauthors
(National Meteorological Information Center, CMA, Email: [email protected])
Using both metadata and the penalized maximum t test
with the first order autocorrelation being accounted for to
detect changepoints, and using the quantile-matching
algorithm to adjust the data time series to diminish nonclimatic changes. Station relocation was found to be the
main cause for non-climatic changes, followed by station
automation.
3/3
PMT-with Ref/ daily Ref
Test in daily/monthly/ annual
scales
Recent changes
CHHT1.0(Dec, 2006)
Adj daily seires
User needs
Mean temperature changes
Climate extreme changes
Release of the China Homogenized Historical Temperature (CHHT1.0) (1951-2001)
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Chinese Surface Air Temperature series over 50 years/ 100 years and its uncertainties
1.5
1
0.5
0
-0.5
(Li and Li, 2007)
-1
-1.5
1900
5
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Statistics for Stations relocations
from 1951-2010
Stations numbers for Automatic
observation starts during 2000-2010
All the
2400+
stations
National
reference/Sta
ndard
stations
700
600
500
400
300
200
100
0
300
250
200
150
100
50
0
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Why update?
• Time duration：CHHT1.0, 1951-2004, now, 1951-2012
• Metadata: more integrated, more density of stations；
• Advances in techniques: annual, monthly to daily.(1 st generation to 2nd
generation) ；
• Raw data updated：2011－2012，CMA’s special project on the basic data,
some missing, questionable data has been made up or corrected;(below)
• Requirement of data users：CHHT1.0 users, climate change researchers.
3.5
120
Tmax
Tmin
100
Tmax
Tmin
3.0
Number of stations
Percentage of erroneous data(%)
4.0
2.5
2.0
1.5
1.0
80
60
40
20
0.5
0.0
0
1950 1960 1970 1980 1990 2000 2010
Year
1950 1960 1970 1980 1990 2000 2010
Daily series
Objective method
Monthly and annual
series
Daily series
Subjective approach
1.Metadata; 2.climate change; 3.comparason with different scales
Integrated
metadata, discontinuities in monthly
and annual series
No metadata, discontinuities in monthly
and annual series
Discontinuities
Temporal change of the discontinuities
最低气温
平均气温
Probability density
function of all QMadjustments
applied to daily
Tmax and Tmin
time series as
necessary (a-b),
and of the QMadjustments to
daily Tmax and
Tmin due to
relocation (c-d)
and automation
(e-f)
49% stations significant
decrease trends
-0.9
-0.6
-0.3
-0.1
0 0.1
0.3
0.6
- -0.6
- -0.3
- -0.1
- 0
0.1
- 0.3
- 0.6
- 0.9
Annual mean DTR (Tmax - Tmin)