Monthly and annual temperature extremes and their changes on the Tibetan Plateau and its surroundings during 1963\u20132015

Jin Ding,Fuxin Zhu,Yongxin Zhang,Lan Cuo

doi:10.1038/s41598-018-30320-0

Abstract

In this study, the spatiotemporal distributions of monthly and annual temperature minima (Tmin) and maxima (Tmax), extreme Tmin and Tmax, the highest (lowest) Tmin (Tmax), frost day (FD), icing day (ID), summer day (SD) and tropical night (TR) at 112 stations and over the ten large river basins on the Tibetan Plateau and its surroundings (TPS) during 1963–2015 are examined. Mann-Kendall test is applied for the trends. The analyses show: the northwest experiences the hottest summer while the central TPS has the coldest winter and most frequent frost and icing days. The northwest (southeast) features the highest (lowest) monthly extreme temperature ranges. The northwest has the most frequent hot summer days, whereas the southeast has the least frequent frost and icing days. The entire TPS displays few tropical nights. Most stations show positive trends for all monthly and annual Tmin and Tmax variables. February displays the most positive trends for both monthly Tmin and Tmax variables while April shows the highest number of stations with decreasing trends in monthly Tmax. The trends of FD and ID are negative, whereas the trends of SU and TR are positive. Over river basins, the trends of monthly Tmin are all positive and statistically significant and the trends of monthly Tmax are all positive except for one negative trend and around 1/3 of the positive trends are statistically significant. Relatively larger increases in monthly Tmin and Tmax are noted for the cold season than the warm. The monthly and annual Tmin variables increase more than Tmax variables.

Highlights

Extreme weather events such as heat waves, floods, droughts or storms have been shown to exhibit an increased frequency in recent decades[1,2,3,4,5,6]
Examining the spatiotemporal distributions of temperature extremes over the river basins in a region constitutes the first step towards understanding the relationship of temperature extremes and water cycle and a finer temporal resolution beyond annual and seasonal scales is needed for the modeling of water resources and ecosystems
Similar to monthly temperature minima (Tmin), the lowest extreme Tmin is found in January (July and August) on the Tibetan Plateau and its surroundings (TPS)

Summary

Introduction

Extreme weather events such as heat waves, floods, droughts or storms have been shown to exhibit an increased frequency in recent decades[1,2,3,4,5,6]. Temperature extremes and using a handful of stations on the TP above certain elevations, systematic investigation based on monthly time series and including the surroundings of the TP has not been carried out as of this writing Temperature extremes and their changes have been shown to influence daily mortality in Spain[32], tendencies of accidents in building facilities and workers’ accidents in Japan[33], injury risk from motor vehicle accidents in Maryland[34], wheat production systems in India[35], and extreme air pollution events in U.S.36. Examining the spatiotemporal distributions of temperature extremes over the river basins in a region constitutes the first step towards understanding the relationship of temperature extremes and water cycle and a finer temporal resolution beyond annual and seasonal scales is needed for the modeling of water resources and ecosystems. Warming happens over the TP in recent decades and the warming rate on the TP exceeds the averages for the Northern Hemisphere and the same latitudinal zone[44]

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Conclusion