Revisiting the Relationship between Observed Warming and Surface Pressure in the Tibetan Plateau

The Tibetan Plateau (TP) has an average elevation of over 4000 m and with its surrounding mountains is regarded as Earth’s “third pole.” As a result of its size and height, climate change in the TP has its own unique characteristics that include a proposed positive correlation between the surface temperature and pressure. This study examines the trends and relationships between the surface pressure and temperature in the TP through the examination of monthly mean data from 71 stations during 1961–2013. On annual, seasonal, and monthly time scales, the TP exhibits a statistically significant warming trend that attains a rate of 0.30°C decade−1 for annual means over the period 1961–2013. The most pronounced warming occurs in winter, in agreement with previous studies, with evidence of acceleration in the rate after the mid-1980s and the global warming slowdown period. For the entire period of 1961–2013, the surface pressure in the TP has a positive trend of 0.08 hPa decade−1 on an annual basis, again with the largest trends occurring in winter. However, unlike what occurred with the surface temperature, the trend in surface pressure, in most cases, reversed sign after the mid-1980s. The trend in the geopotential height at 500 hPa from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis is consistent with the observed surface pressure trends. Over the period 1961–2013, there is a seasonal shift in the nature of the relationship between the surface temperature and pressure with a negative correlation during summer and autumn, and a positive correlation during winter. This suggests that the nature of the relationship between these two climate elements reflects the changing nature of the seasonal snow cover (land surface property) and cloud in the region.