Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

波罗的海降水和蒸发的年际、季节和地区变化

本文对波罗的海1981～1994年间的降水和蒸发率进行了分析。基于可获得的天气资料以二维目标分析方法进行插值。得到了网格点的降水率数据。蒸发率通过一个海洋模型计算得到。这一模型将波罗的海处理为13个具有高垂向分辨率的亚流域。海面温度和海冰由计算得到,并根据温度和冰图信息进行了全面校检。在这一模型中,潜热通量由总体公式参数化计算得到。蒸发率通过潜热的计算值得到,而海冰又使蒸发率变小,假定海冰的蒸发可以忽略。从长期来看,降水和蒸发率之间的差异是正值,这说明大气补充淡水到波罗的海中。对于1981～1994年这一段时间来说。来自于大气的淡水总输入量平均为1986m^3/s。这一数值比河流的总径流量小,但同涅瓦河的贡献几乎一样大。因此。大气的淡水输入是波罗的海淡水平衡的重要来源。同虚拟的无冰的波罗的海相比。将冰考虑在内能将研究时段内大气淡水输入量的长期均值提高26%(通过使蒸发降低8%)。波罗的海的降水和蒸发具有较大的年际、季节和地区变化。