Studies on changes and cause of the minimum air temperature in Songnen Plain of China during 1961–2010

In this study, we took Songnen Plain of China as the study area, collected the observed minimum air temperature, the minimum air temperature reanalysis data (ERA-40), and the minimum land surface temperature from 1961 to 2010, the nighttime land surface temperature (MOD11A2) from 2000 to 2010. Further, with the obtained and processed data, we analyzed the mechanism and impact of land use change on minimum air temperature within the recent 50 years in the Songnen Plain of China using climate tendency rate, Observation Minus Reanalysis (OMR) and spatial analysis methods. The analysis results can be summarized as follows. (1) The areas of agricultural land, built up, unused land, and forest land have increased and the areas of grassland and water have decreased from 1960 to 2010. In particular, the areas of unused land and built up have increased significantly with about 22 times and 9 times respectively compared with their areas in 1960. (2) During 1961–2010, with the land use change in the Songnen Plain, the maximum air temperature and diurnal temperature range trend has decreased, the minimum air temperature trend has increased, and impact of land use change on minimum air temperature trend is greater than maximum air temperature trend. (3) The unused land has the highest minimum air temperature, nighttime land surface temperature, and minimum land surface temperature than any other land uses, and all corresponding temperature is lower in the agricultural land and the lowest in the forestland. (4) The conversion from any other land uses to the unused land will result in the increasing of the temperature and to the agricultural land and forest land will cause the decreasing of the temperature.