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ADVANCES IN ATMOSPHERIC SCIENCES, VOL. 34, FEBRUARY 2017, 246–257• Original Paper •Multi-scale Cyclone Activity in the Changjiang River–Huaihe River Valleysduring Spring and Its Relationship with Rainfall AnomaliesYujing QIN, Chuhan LU ∗ , and Liping LIKey Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate andEnvironment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science and Technology, Nanjing 210044, China(Received 27 February 2016; revised 3 August 2016; accepted 25 August 2016)ABSTRACTBased on the recognition framework of the outermost closed contours of cyclones, an automated identif i cation algorithmcapable of identifying the multi-scale cyclones that occur during spring in the Changjiang River–Huaihe River valleys (CHV)were developed. We studied the characteristics of the multi-scale cyclone activity that af f ects CHV and its relationship withrainfall during spring since 1979. The results indicated that the automated identif i cation algorithm for cyclones proposed inthis paper could intuitively identify multi-scale cyclones that af f ect CHV. The algorithm allows for ef f ectively describing theshape and coverage area of the closed contours around the periphery of cyclones. We found that, compared to the meso- andsub-synoptic scale cyclone activities, the synoptic-scale cyclone activity showed more intimate correlation with the overallactivity intensity of multi-scale CHV cyclones during spring. However, the frequency of occurrence of sub-synoptic scalecyclones was the highest, and their ef f ect on changes in CHV cyclone activity could not be ignored. Based on the area ofimpact and the depth of the cyclones, the sub-synoptic scale, synoptic scale and comprehensive cyclone intensity indices werefurther def i ned, which showed a positive correlation with rainfall in CHV during spring. Additionally, the comprehensivecyclone intensity index was a good indicator of strong rainfall events.Key words: cyclone activity, multi-scale cyclone, extreme precipitation, CHV areaCitation: Qin, Y. J., C. H. Lu, and L. P. Li, 2017: Multi-scale cyclone activity in the Changjiang River-Huaihe River valleysduring spring and its relationship with rainfall anomalies. Adv. Atmos. Sci., 34(2), 246–257, doi: 10.1007/s00376-016-6042-x.1. IntroductionLower-level synoptic weather systems, such as low vor-tex, trough line, and shear line systems, are direct fac-tors leading to regional rainfall events and severe convec-tive weather. Therefore, many previous works have focusedon developing a method to accurately and ef f i ciently iden-tify and track synoptic-scale cyclones (low vortexes) and toidentify the climatological characteristics of weather systems(Ulbrich et al., 2009).Historically, the earliest origin of the detection of cy-clones can be traced back to the end of the 19th century, whencomputers had not yet been invented (van Bebber, 1891).Scholars at that time used limited weather map data to man-ually identify and analyze the sources, paths, and character-istics of cyclone activity in East Asian regions (Zhang, 1984;Chen and Zhang, 1996). Zhang (1984) revealed that the for-mation of a cyclonic curvature in the air f l ow corresponds∗Corresponding author: Chuhan LUEmail: luchuhan@nuist.edu.cnto the development of cyclones in North China during spring,which leads to rainy weather in most areas of northern China.Wei et al. (2013) used historical weather chart data from theChina Central Meteorological Observatory to study the statis-tics of the climate characteristics of cyclones in ChangjiangRiver–Huaihe River valleys (CHV) over the past 49 years andfound that the frequency of CHV cyclones had a downwardtrend, whereas their intensity of generation had an upwardtrend. With the introduction of computer technology to me-teorology and the release of global reanalysis data, studieson automated Lagrangian identif i cation and characteristic ex-traction methods for cyclones have become a new focus sincethe 1990s (e.g., Murray and Simmonds, 1991; Hodges, 1994;Serreze et al., 1997; Wernli and Schwierz, 2006; Neu et al.,2013).In recent years, new progress has been made in the studyof the climatic characteristics of extratropical cyclones inEast Asia, especially those in northern China. Based on auto-mated identif i cation and tracking methods, Hu et al. (2010)studied the climatic characteristics of the cold vortex overNortheast China and suggested that sustained cold vortex ac-© Institute of Atmospheric Physics / Chinese Academy of Sciences , and Science Press and Springer-Verlag Berlin Heidelberg 2017