Climatology Of Arctic Planetary Boundary Layer Height And Surface Energy Balance

The Arctic climate system has undergone a dramatic rapid change since 1990s.Planetary boundary layer (PBL) plays an important role in air-surface interactions,and has great impacts on the evolution of the climate system. We first evaluate the commonly used methods in calculating PBL height, and the bulk Richardson number method proves to be the most suitable one for our study. Then, we test the ERA-Interim reanalysis data in creating the PBL height climatology for the Arctic region. Using the ERA-Interim reanalysis dataset and the bulk Richardson number method, we conduct a climatological analysis of the Arctic PBL heights by generating the Arctic PBL height climatology from 1979 to 2014. The results indicate that, the PBL heights over the sea-surface regions and the land-surface regions exhibit the opposite seasonal variations. For sea-surface regions, the PBL heights are larger in winter and smaller in summer, whereas for land-surface regions, the PBL in summer are higher than those in winter. The PBL heights in the sea-ice covered region have a rather weak seasonal cycle. Large uncertainties of the PBL heights are existed, especially in seasons when PBL are climatologically higher. By diagnosing two contributing factors which influence the seasonal cycles of the PBL heights, we find that the thermal factor makes greater contributions compared with the dynamic factor. By analyzing the surface energy balance terms in the Arctic, we further explain why the PBL heights over different area exhibit different seasonal cycles. We also demonstrated that the surface energy balance terms have good relationship with PBL heights, and the surface latent heat flux could be served as one of the indicators for the Arctic PBL heights.