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Homogenization of Chinese daily surface air temperatures :An update for CHHT1.0

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: liqx@cma.gov.cn ).

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Homogenization of Chinese daily surface air temperatures :An update for CHHT1.0

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  1. 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: liqx@cma.gov.cn) 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. PMT-with Ref/ daily Ref Test in daily/monthly/ annual scales 1/3 Recent changes CHHT1.0(Dec, 2006) Adj daily seires User needs Mean temperature changes Climate extreme changes

  2. 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: liqx@cma.gov.cn) 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. PMT-with Ref/ daily Ref Test in daily/monthly/ annual scales 2/3 Recent changes CHHT1.0(Dec, 2006) Adj daily seires User needs Mean temperature changes Climate extreme changes

  3. 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: liqx@cma.gov.cn) 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 non-climatic changes. Station relocation was found to be the main cause for non-climatic changes, followed by station automation. PMT-with Ref/ daily Ref Test in daily/monthly/ annual scales 3/3 Recent changes CHHT1.0(Dec, 2006) Adj daily seires User needs Mean temperature changes Climate extreme changes

  4. Release of the China Homogenized Historical Temperature (CHHT1.0) (1951-2001)

  5. Chinese Surface Air Temperature series over 50 years/ 100 years and its uncertainties (Li and Li, 2007)

  6. Stations numbers for Automatic observation starts during 2000-2010 Statistics for Stations relocations from 1951-2010 All the 2400+ stations National reference/Standard stations

  7. 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.

  8. Daily series Objective method Daily series Monthly and annual 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

  9. Temporal change of the discontinuities 最低气温 平均气温

  10. Probability density function of all QM-adjustments applied to daily Tmax and Tmin time series as necessary (a-b), and of the QM-adjustments to daily Tmax and Tmin due to relocation (c-d) and automation (e-f)

  11. Annual mean DTR (Tmax - Tmin) 49%stations significant decrease trends

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