Climate and Dynamics
Evaluation of ERA-40, NCEP-1, and NCEP-2 reanalysis air temperatures with ground-based measurements in China
Article first published online: 8 AUG 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 113, Issue D15, 16 August 2008
How to Cite
2008), Evaluation of ERA-40, NCEP-1, and NCEP-2 reanalysis air temperatures with ground-based measurements in China, J. Geophys. Res., 113, D15115, doi:10.1029/2007JD009549., , , , and (
- Issue published online: 8 AUG 2008
- Article first published online: 8 AUG 2008
- Manuscript Accepted: 17 MAR 2008
- Manuscript Revised: 19 FEB 2008
- Manuscript Received: 29 OCT 2007
- Air temperature;
 We assess the correspondence of reanalysis air temperatures from ERA-40, NCEP-1, and NCEP-2 with homogenized observational data from China for 1958–2001 and 1979–2001. Results indicate that climatologies for annual ERA-40, NCEP-1, and NCEP-2 air temperatures are lower than observations by −0.93°C, −2.78°C, and −2.27°C, respectively. Large negative differences for most of western China primarily contribute to this cool bias. Error analysis indicates that the internal coherence of ERA-40 data is better than NCEP-1 or NCEP-2. Although NCEP-2 air temperatures represent an improvement over NCEP-1, biases of NCEP-1 and NCEP-2 data relative to observations are still much larger than for ERA-40. Areas with positive/negative air temperature differences (dT) between reanalysis and observational data correspond to negative/positive elevation differences (dH). The high correlation coefficients of −0.94, −0.88, and −0.85 between dT and dH for ERA-40, NCEP-1, NCEP-2, and observations, respectively, illustrate that the air temperature differences between reanalysis data and observations are primarily related to elevation differences. Furthermore, a spatial and temporal comparison of trends also indicates that ERA-40 temperature changes correspond most closely to observed trends in China. In general, our comprehensive analysis of the three global reanalysis products indicates that, both on a seasonal and annual basis, ERA-40 temperatures correspond most closely to observations, and biases are due mainly to the elevation differences.