Observation Of Global Significant Warming Over Semiarid Region In Winter

In this paper, the mechanism of regional warming over semiarid region has been taken as our study topic. We analyzed the factors which influence the temperature variability over semi-arid region. The main reasons induced in significant warming over semiarid region are atmospheric circulation, sea surface temperature, the interaction between atmosphere and land, feedback of snow and ice albedo and anthropogenic activity. The results show that the discrepancy of warming extent is large in semiarid region with different location. In order to analyze and discuss the influence of semiarid regional warming, our work was focused on the variability of surface temperature increasing over semiarid region via temperature variability in different semiarid region to explore the inner mechanism of warming. The main conclusions are as follow:1) The global precipitation and temperature of Climate Research Unit with the spatial resolution is 0.5 degree which time period is from 1901 to 2009 have been analyzed and found the global warming has the significant regional character. The main semiarid regions of globe are in the mid-high latitude of Asia, Europe and North America and the contributions of these semiarid regions to global warming are 11.88%,6.09%, and 7.04%.2) The phenomenon of significant warming in cold season has been found. The increasing temperatures are 1.25K,1.14K and 1.06K over semiarid region in mid-high latitude of North hemisphere, North Hemisphere and globe in recent 109 years. The discrepancy of warming in cold season and warm season are obvious, the difference is more distinct in Asia than Europe and North America. It illustrated the warming mechanism is different in North America, Central Asia and Eastern Asia. Our results show that the atmospheric circulation, sea surface temperature, anthropogenic activity and variability of land cover type play different role in climate change; our work is to distinguish the influence of these factors from temperature variability. It is also going to be helpful for our dynamic mechanism work.3) Noah-MP land surface model is one of the advanced land surface models in the world. We studied the influence of land cover on surface temperature via Noah-MP model, especially the feedback between different land cover type and surface temperature and the relationship between land cover type and atmospheric circulation. The land cover type we used in this work is MODIS data. The simulation results show that the change of land cover type can influence the variability of surface temperature and the extent of variability in semiarid region is more obvious than arid region.4) In order to study the feedback of mechanism between temperature and snow in semiarid region, we designed seven sensitive experiments to find out the effect of melting factor, roughness length in land surface model on surface temperature variability. Currently, snow is easily impacted by the aerosol which increased the value of snow melting and decreases the land albedo in further. We proved that the temperature over semiarid region increased rapidly when the snow melting factor becomes larger.