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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D02101, doi:10.1029/2004JD005230, 2005

Climate change and variability using European Centre for Medium-Range Weather Forecasts reanalysis (ERA-40) temperatures on the Tibetan Plateau

Oliver W. Frauenfeld

National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA


Tingjun Zhang

National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA


Mark C. Serreze

National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA


Abstract

Surface air temperature measurements from meteorological stations on the Tibetan Plateau are compared to 2-m temperatures from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40) to assess the accuracy of this reanalysis product. We focus on ERA-40 grid cells containing at least four stations. The reanalysis temperatures are consistently lower, by as much as 7°C. However, temporal correlations are high, indicating that ERA-40 captures the interannual variability very well. The temperature bias is almost exclusively due to differences between the grid cell and the station elevations. We conclude that the ERA-40 temperatures provide better spatial fields of temperature than is possible with stations in this topographically complex, data-sparse area. Using this spatially and temporally continuous data set, we provide a temperature climatology and assess long-term climate trends. The high elevations of the western plateau are generally 10°C cooler than the eastern plateau. During winter, 2-m temperatures are below 0°C on the entire plateau, with summer values of only 0°C in the west and 10°C in the east. While station records point to a long-term climate warming trend, no trends are observed in ERA-40. This could be due to inadequacies of the reanalysis data, although we see no evidence of anomalous nonclimatic shifts. The significant trends in station data may reflect the extensive land use change and industrialization that has occurred on the Tibetan Plateau. Reanalysis data are less influenced by these local effects.

Received 13 July 2004; accepted 15 November 2004; published 19 January 2005.

Keywords: ERA-40 2-m temperatures; Tibetan Plateau; climate change.

Index Terms: 1620 Global Change: Climate dynamics (0429, 3309); 1803 Hydrology: Anthropogenic effects (4802, 4902); 1809 Hydrology: Desertification; 3322 Atmospheric Processes: Land/atmosphere interactions (1218, 1631, 1843); 3309 Atmospheric Processes: Climatology (1616, 1620, 3305, 4215, 8408).

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Citation: Frauenfeld, O. W., T. Zhang, and M. C. Serreze (2005), Climate change and variability using European Centre for Medium-Range Weather Forecasts reanalysis (ERA-40) temperatures on the Tibetan Plateau, J. Geophys. Res., 110, D02101, doi:10.1029/2004JD005230.