Precipitation climatically features over the Huai River Basin, China

Highlights

• Summer precipitation decreases from the coastal area to inland area.

• The precipitation showed obvious decadal variations, especially in summer.

• The range of variation of most regions is above 140 mm.

Abstract

The temporal and spatial characteristics of precipitation in the HRB (Huai River Basin) were studied using the observation data of monthly precipitation provided by the National Climate Center from 1961–2016 and the NCEP/NCAR global monthly reanalysis data. The results showed that: (1) The precipitation was mainly concentrated in summer, accounting for 52% of the total annual precipitation; there was more precipitation in the south, less in the north, and more in the coastal areas, less in the inland in summer; (2) The precipitation showed obvious decadal variations, especially in summer; the range of variation of most regions is above 140 mm; and significant decadal abrupt changes of precipitation from “abnormally less” to “abnormally more” appeared around 1979.

Introduction

The HRB is located at the climatic transitional zone from the south to the north and precipitation in the HRB demonstrates an uneven distribution feature with significant oscillation and large inter-annual variation. The situation that the HR was occupied by the Yellow River for a long time in history have led to frequent flooding and drought disasters in the HRB. Moreover, drought that persists for years or the alternating occurrence of flood and drought (from drought to flood and from flood to drought) in the same year are often observed (Li et al., 2008; Liu and Li, 2014; Ping et al., 2014). These situations can cause great damages to local industry and agriculture and threaten human lives and activities. Therefore, the precipitation, especially the interannual variation of summer precipitation, has become a hot research topic and attracted great attentions.

The spatial distribution and temporal trends are analyzed by many researchers (Wei et al., 2010; He et al., 2015; Shi et al., 2013). Wang and Wang (2002) reported that the HRB experienced a rainy period with abundant summer precipitation before and in the mid-1970s, and then turned into a rainless period with a primary cycle of 2–3 years and a secondary cycle of about 8 years. Lu et al. (2011) found a significant inter-annual variation of precipitation in the HRB but there was no remarkable changing trend for the last 45 years. The extreme precipitation spatiotemporal features were also analyzed (Xia et al., 2012; Du et al., 2013; Liu, 2015). Numerous studies have been conducted with a focus on the anomaly of the Asia Monsoon circulation to investigate the possible reasons for the inter-annual variation of precipitation in the HRB (Ping et al., 2014; Zhang et al., 2015). Anomalies of the Asian Monsoon circulation could result in a northward or southward shift of the circulation system, which eventually leads to droughts or floods in the HBR (Tao et al., 1998). Further, an early (late) onset of the South China Sea summer monsoon can bring in a rainless (rainy) summer and result in droughts (floods) in the Yangtze-Huai River Basin (Huang et al., 2005). By examines the features and dynamical processes of sub-seasonal zonal oscillation of the western Pacific subtropical high (WPSH) during early summer, Ren et al. (2013) and Guan et al. (2018) found that when the western Pacific subtropical high (WPSH) stretches more westward, the above-normal precipitation is observed over the Yangtze–Huaihe River (YHR) basin in China. From the point of view of winter monsoon, Sun and Sun (1995) found that a strong (weak) winter monsoon in the early winter can lead to droughts (floods) in the same year in the HRB. Apart from the monsoon circulation, the anomaly of the sea surface temperature is also considered to be one reason for changes in precipitation in the HRB.

Wang and Wang (2002) reported that there is a positive correlation between summer precipitation in the HRB and sea surface temperature anomalies in the central North Pacific Ocean from August to October of the previous year. Zhou and Xia (2012) studied the Interdecadal change of the connection between winter North Pacific Oscillation and summer precipitation in the Huai River valley and found that their linkage appears to have an apparent interdecadal variation. The close relationship between ENSO and precipitation anomalies in the HRB has been discussed by Xin and Xie (2005); Xuan et al. (2011) and Zhang et al. (2016) and they pointed out that rainfall in the HRB increases in the spring and winter of EI Nino years and decreases in La Nina years. According to the study of Zhao et al. (2006), the HRB often experiences a wet (dry) summer during the development (attenuation) period of EI Nino and/or during the attenuation (development) period of La Nina.

There are many studies about the East Asian summer monsoon and the SSTs (Chen et al., 2014; Hu, 1997; Chang et al., 2000; Wu and Wang, 2002; Hsu and Lin, 2007; Zhou et al., 2008, 2009; Xie et al., 2010; Yuan and Yang, 2012).

Ren et al. (2013, 2015) found that there exist intra-seasonal air-sea interactions between the local sea surface temperature (SST) anomalies and the intra-seasonal zonal oscillation of WPSH and eastward extension of the South Asian High (SAH), and they are important to the persistent heavy rainfall events in the middle-lower reaches of the Yangtze River.

In their previous studies, Wang et al. (2010) applied the fuzzy clustering method to 7 stations selected as the representative stations of the HRB; Zhou and Xia (2012) selected 9 stations to represent the Huai River District; Zhou et al. (2008) analyzed 32 encryption stations by using the encryption observation data from HUBEX (Huai River Basin test); Wei and Zhang (2010) analyzed the annual and interannual oscillations and probability distribution characteristics of summer precipitation at 19 stations in HRB; Xu et al. (2010) selected 18 representative stations in HRB to analyze the low-frequency oscillation characteristics in typical flood and drought years. However, no consensus has been reached so far regarding what stations are representative stations for the HRB, which brings in certain uncertainties in the study of the HRB climatology.

In this study, the representative stations in the HRB were selected through the k-means clustering algorithm. Integrated mathematical statistic methods were employed to study the spatial and temporal distribution of precipitation, which is helpful for discovering the reasons that cause the inter-annual variations in precipitation.

The motivation of this study is to examine spatial and temporal variability of precipitation and its relationship to atmospheric circulation over the Huai River. First, the study area, data and analysis methods used are described in Section 2. We analyze the spatial and temporal distribution of precipitation, atmospheric circulations with the precipitation in Section 3. Concluding remarks are given in Section 4.