Possible Urban Bias in gridded climate temperature data over the Japan area

Abstract

Long-term trends of gridded land surface temperature data over Japan, provided by the Climatic Research Unit (CRU) at the University of East Anglia, NASA Goddard Institute for Space Studies (GISS), and the Japan Meteorological Agency (JMA) were compared with those at surface observation stations that are used for the JMA's climate monitoring. It was found that the CRU data (CRUTEM3v) for 1901 to 2008 have an anomalous trend of about 0.04°C/decade relatively to the surface stations, except over the Nansei Islands. The trend of the GISS temperature data (the Tsurf250 file) also has some positive departure until 1960. These facts indicate the possibility of urban bias in these gridded data over the Mainland Japan area. © 2010, the Meteorological Society of Japan.