Spatiotemporal variations in precipitation in Ji‘nan,China

In the past few years, urban areas have experienced frequent extreme climate events and
 disasters due to the effects of climate change and human activities, which have resulted in serious casualties and
 loss of properties. Therefore, it is of great importance to analyze the spatiotemporal variations and
characteristics of precipitation in metropolis areas.In the present work, both Mann-Kendall test and Sen’s
slope estimator were adopted to analyze the spatiotemporal variations and characteristics of precipitation for
different land covers in Ji’nan City based on precipitation data extracted from China Meteorological Forcing
Dataset(CMFD). It has been found that annual mean precipitation was 634.4mm in Ji’nan City from 1979
 2015, while annual precipitation showed significant changes in different years, indicating great interannual
variability of precipitation. But annual precipitation showed an insignificant increasing trend with fluctuations.
Annual precipitation was found to gradually decrease from southwest to northwest in Ji’nan City. This
followed closely the to pographic features, showing extremely in homogeneous spatial distribution
characteristics. Precipitation in Ji’nan City usually concentrated in summer, accounting for more than 60% of
 the annual precipitation. Summer precipitation in northern mountainous area was 494.6mm, with very high
 risk for flash flooding in downtown Ji’nan. Precipitation in wet season showed an increasing trend in plain and
downtown areas, but showed a decreasing tendency in mountainous area in Ji’nan City in the past 37 years, but
with no statistical significance.