Climatological features and trends of extreme precipitation during 1979–2012 in Beijing, China

In this study, three kinds of hourly precipitation series with the spatial\udresolution of 0.1° are used to analyze the climatological features and\udtrends of extreme precipitation during the period of 1979–2012 in Beijing,\udChina. The results show that: (1) the spatial distribution of median annual\udprecipitation, with a range from 500 to 825 mm, is similar to that of\udlocal topography, which increases from the northwest to the southeast.\udTaking the urban area as a centre, the inter-annual precipitation in the\udBeijing area displays an outward decreasing tendency at the maximum rate of\ud125 mm per decade (125 mm × 10 a⁻¹); (2) extreme precipitation amount,\udwhich accounts for 40–48% of total precipitation amount, has a\udsimilar spatial distribution to average annual precipitation; (3) the\udspatial distribution of extreme precipitation days and threshold estimated\udas the upper 95 percentile are significantly different from that of extreme\udprecipitation, with maximum values concentrated on the urban area and the\udeastern mountain area, and minimum values in northwest; (4) extreme\udprecipitation days (Ex_pd95) show an opposite distribution to\udextreme precipitation threshold (Ex_pv95), indicating that\udareas with greater precipitation threshold may has less precipitation days,\udand vice versa; (5) an apparent spatiotemporal decreasing tendency is\uddetected in extreme precipitation amount. The downward tendencies are also\udfound in extreme precipitation threshold. Unlike Ex_pv95, in\udmost of the study area, Ex_pd95 is virtually unchanged; (6) downward\udtrends of extreme precipitation is slightly smaller than that of\udannual precipitation, and the reducing amplitude of north-eastern areas are\udmuch higher than the areas in the southwest