Abstract:

Modeling extreme precipitation processes could provide a pathway for a better understanding of the questions concerning how much precipitation is extreme and how that extreme precipitation responds to warming in the climate change sensitive and ecological fragile zone of China over the coming decades. In this perspective, based on daily precipitation and temperature data from 72 meteorological stations released by the National Meteorological Information Center, the spatial-temporal variation of precipitation is investigated in the Qinling Mountains from 1970 to 2017, which is a critical geographical and climatic boundary between northern subtropical and warm temperate zone in China. Then we applied a framework to identify the dominant pattern of EEP in the study region, and time distribution pattern (TDP) of the event-based extreme precipitation (EEP) could be divided into four types, i.e. early, after, balance-phase and single day EEP, here after referred to as TDP1, TDP2, TDP3 and 1-day EEP. More specifically, the relationship between different EEP and local temperature is investigated through the cross wavelet transform and linear correlation. The result showed that from a long-term climate view, precipitation pattern is relatively stable in the Qinling Mountains in the past 48 years, and the 800 mm isohyetal line is still distributed in the south piedmont of Qinling Mountains. Moreover, precipitation analysis showed an obvious synchronous trend in the sub-region, which could be characterized as non-smooth and non-linear, and after 1997, there is an increasing trend in annual precipitation amount, a declining trend in rainy days, and a continuous increase of extreme precipitation intensity. Spatially, according to percentage of total precipitation amount of EEP, a wide distribution of TDP3 is clearly seen over most regions and 1-day EEP does not prevail, which demonstrates that daily precipitation extremes during an EEP could be mainly distributed at both the first and second half parts of the event duration. In north of Qinling Mountains, the dominant pattern combines TDP3 and TDP2. For south piedmont of Qinling Mountains, it witnesses fewer combinations of EEP. There exists difference between the east and west in Hanjiang River Valley, that is, TDP3 and TDP2 in the west is greater than in the east where the dominance of TDP1 and TDP3 is more prominent. However, based on the percentage of total frequency of EEP, TDP1 is observed in southern and northern Qinling Mountains, and the dominant pattern combines TDP1 and TDP2 in Hanjiang River Valley. Furthermore, in the past 48 years, the influence of local climate change, for the decadal variation of extreme precipitation, was more obvious on the time scale of 8-12 years than of on the time scale of 4-8 years. It is worth mentioning that changes in nearly all indices had a strong correlation to temperature in Hanjiang River Valley, especially TDP2 and 1-day EEP. This is particularly true of high temperature related to more precipitation intensity of single day, which in turn raises the expectation of more intense extreme short-duration rainfall events that could be assessed by the wavelet coherence analysis. Between 1998 and 2012, the phenomenon, 'global warming hiatus', occurred in the Qinling Mountains, which led to the decrease of 1-day EEP, and the increases of TDP1 and TDP3 in the north of Qinling Mountains, as well as the increase of TDP2 over the south piedmont of Qinling Mountains. All the above results are closely linked to lower temperature. The response of TDP3 and TDP2 is stronger than other types in Hanjiang River Valley. It should be noted that these results are helpful to understand the relationship between climate warming and extreme precipitation, but the response of different EEP to anthropogenic forcing and atmospheric oscillation is still complex and not explicitly resolved.

Key words: climate change, event-based extreme precipitation, spatiotemporal analysis, south and north of Qinling Mountains