Osborn Timothy J, Hulme Mike
Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
Philos Trans A Math Phys Eng Sci. 2002 Jul 15;360(1796):1313-25. doi: 10.1098/rsta.2002.1002.
Daily precipitation in the UK has changed over the period 1961-2000, becoming on average more intense in winter and less intense in summer. Recent increases in total winter precipitation are shown to be mainly due to an increase in the amount of precipitation on wet days, with a smaller contribution in the western UK from a trend towards more wet days. If the wet-day amounts are modelled using a gamma distribution, then positive trends in its scale parameter are found across almost all of the UK, consistent with an increased frequency of heavy winter precipitation. Non-parametric analyses confirm an increase in the contribution of heavy events to winter precipitation totals. Analysis of multi-day sequences of heavy rainfall indicate a corresponding increase in their frequency. Results for summer show almost opposite trends: decreased precipitation totals (driven more equally by fewer wet days and reduced wet-day amounts), decreases in gamma scale parameter (although accompanied by a trend towards a less positively skewed distribution) and decreases in the occurrence of heavy precipitation (whether defined parametrically or non-parametrically). A more sparse network of weather stations with data back to 1901 suggests that the recent winter changes are unusual, while the recent summer changes are not, though the poorer coverage reduces the confidence in these longer-period results.
在1961 - 2000年期间，英国的日降水量发生了变化，冬季平均降水强度增大，夏季平均降水强度减小。研究表明，近期冬季总降水量的增加主要是由于降水日降水量增加所致，而英国西部因降水日数增多的趋势对总降水量增加的贡献较小。如果用伽马分布对降水日降水量进行建模，那么在英国几乎所有地区都发现其尺度参数呈正趋势，这与冬季强降水频率增加相一致。非参数分析证实强降水事件对冬季降水总量的贡献有所增加。对多日暴雨序列的分析表明其频率相应增加。夏季的结果显示出几乎相反的趋势：降水总量减少（降水日数减少和降水日降水量减少的影响程度相当），伽马尺度参数减小（尽管伴随着分布正偏度减小的趋势），强降水事件发生频率降低（无论是参数定义还是非参数定义）。一个数据可追溯到1901年的气象站网络更为稀疏，这表明近期冬季的变化是不寻常的，而近期夏季的变化并非如此，不过覆盖范围较差降低了对这些更长时期结果的可信度。
