Ambient Air Quality Department, Czech Hydrometeorological Institute, Prague, Czech Republic; Charles University in Prague, Faculty of Science, Institute for Environmental Studies, Czech Republic.
Institute of Computer Science, Academy of Sciences of the Czech Republic, Prague, Czech Republic; National Institute of Public Health, Prague, Czech Republic.
Sci Total Environ. 2020 Apr 1;711:135018. doi: 10.1016/j.scitotenv.2019.135018. Epub 2019 Nov 6.
Fog is a very important and complex atmospheric phenomenon of the utmost importance for the environment and for human society. For practical reasons, fog occurrence is observed regularly at meteorological stations worldwide. Decreasing trends in fog frequency reported from numerous regions have been often associated with either decreasing pollution or climate change, including increasing temperature and changes in atmospheric circulation. We have examined the data on fog occurrence from twelve Czech sites representing different environments (urban, rural, mountain), geographical areas, and altitudes across the country. For our analysis we used long-term records from the time period of 1961-2018, covering both the ambient air's heavily polluted periods of the 1970s and 1980s and the cleaner period, following the adoption of new, more stringent legislation and effective countermeasures after the 1990s. We applied a generalised additive model (GAM) framework as a flexible, semiparametric regression approach to address nonlinear trend shapes in a formalised and unified way. In particular, we employed a penalised spline approach with cross-validated penalty coefficient estimation. Our study confirmed non-linear behaviour for both year-to-year trends and annual seasonality. Our results showed further that over the analysed, almost sixty-year period, fog occurrence has decreased significantly at all the examined sites, though the pattern of the long-term change differed among individual sites. Moreover, we have found significant seasonality in fog occurrence, though it is different at individual sites. Furthermore, apart from the overall annual fog probability change over the years, at some sites the fog's seasonal profile has also deformed substantially over the long term.
雾是一种非常重要且复杂的大气现象，对环境和人类社会都至关重要。出于实际原因，世界各地的气象站都会定期观测雾的出现情况。许多地区报告的雾频下降趋势通常与污染减少或气候变化有关，包括温度升高和大气环流变化。我们研究了来自 12 个捷克站点的雾出现数据，这些站点代表了不同的环境（城市、农村、山区）、地理位置和全国范围内的海拔高度。对于我们的分析，我们使用了 1961 年至 2018 年期间的长期记录，涵盖了 20 世纪 70 年代和 80 年代空气严重污染时期以及 90 年代以后采用新的、更严格的立法和有效对策之后的清洁时期。我们应用了广义加性模型（GAM）框架作为一种灵活的、半参数回归方法，以正式和统一的方式解决非线性趋势形状。特别是，我们采用了具有交叉验证惩罚系数估计的惩罚样条方法。我们的研究证实了年际趋势和年度季节性的非线性行为。我们的研究结果还表明，在分析的近六十年期间，所有研究站点的雾出现都显著减少，尽管个别站点的长期变化模式有所不同。此外，我们发现雾的出现存在显著的季节性，但在个别站点有所不同。此外，除了多年来雾出现的总体年度概率变化外，在某些站点，雾的季节性特征也在长期内发生了实质性变化。
