Investigation of the abrupt changes in precipitation concentration and the driving forces under the changing environment

The excessive concentration of precipitation in its spatial and temporal distributions could lead to occurrence of flood and drought disasters. Investigating the abrupt changes in precipitation concentration and the driving forces is fundamental for understanding precipitation responses to the changing environment,thus facilitating regional water resources management and early warning of natural disasters. This study investigated the historical changes in precipitation concentration at daily and monthly timescales in the Hanjiang River basin,based on the monthly precipitation concentration index (CIM) and daily precipitation concentration index (CID). The Mann-Kendall trend test and heuristic segmentation algorithm were used to analyze the abrupt changes in precipitation concentration. The potential influences of sunspots and anomalous atmospheric circulation factors on the abrupt changes in precipitation concentration were explored using the cross wavelet analysis technique. Results showed that:① Large values of CIM were found in the northern Hanjiang River basin,while small CIM values were observed in the south part of the study region. As for the CID,large values were found in the east part,with small values observed in the west. CIM has showed an insignificant downward trend,while a significant upward trend of CID was detected at 6 stations;② Mutation points of the CID series were detected at some stations in the basin,while the CIM is shown to be relatively stable,indicating that the CID is more sensitive to the changing environment than the CIM;③ Sunspots and anomalous atmospheric circulation factors have exerted strong influences on the changes in precipitation concentration. Notably,sunspots have exerted the largest influences,as they can indirectly affect precipitation concentration of the Hanjiang River basin through modulating the anomalous atmospheric circulation factors.