Numerical simulations of sea and land breezes at high latitudes

Abstract

Few investigations of sea land breezes (SB/LB) at high latitudes have been reported in the meteorological literature. However, internal reports at some Norwegian institutions, summarised recently by Grønås and Sandvik, show that SB/LBs, in combination with terrain-driven circulations, are frequent along the coast of Norway and Spitsbergen. In this paper, numerical simulations of SB/LBs for latitudes between 50° and 80°N have been made for spring and summer with a mesoscale non-hydrostatic model in order to study the characteristics of high latitude SB/LBs. The results show that in spring, the latitudinal variation of the extent and strength of the SB is large, and no SB seems to develop north of 70°N. The LB is active at all latitudes and increases in strength and duration with increasing latitudes. In summer it is found that the character of the SB changes from a classical SB at 50°N to a monsoon kind of a SB at the highest latitudes with small diurnal variations. The northward decrease in the extent and strength of the SB is small. The results are found to be in accord with observations. The high latitude SB in summer is further studied by simulations on a circular island at 78°N. A relatively strong SB develops which persists during the night with a stronger circulation the next day. In this way, what we have called a monsoon low SB establishes over the island. The influence of an snow/ice cover and mountains has been investigated. It is indicated from both simulations and observations that monsoon lows might be present at peninsulas and islands at latitudes down to at least 60°N.