Variation of High and Low Level Circulation of Meiyu in Jiangsu Province in Recent 30 Years

Abstract

By using the NCEP/NCAR re-analysis data from 1990 to 2019 and the daily precipitation data of CN05.1 gridded observation dataset, the high and low level circulation characteristics and their influence on the onset and precipitation of Meiyu in Jiangsu Province in recent 30 years are studied. Comparing Meiyu in the 2010s with that in the 1990s, it is found that during the 2010s Meiyu was characterized by a late arrival and less precipitation. There were obviously earlier Meiyu years in the 1990s, while no extremely early Meiyu year existed in the 2010s, which was mainly caused by the late northward jump of the upper jet and the ridge line of the western Pacific subtropical high (WPSH hereinafter) in the 2010s. Compared with the 1990s, the 2010s witnessed an eastward position of the South Asia high and a westward position of the subtropical westerly jet during the Meiyu period, which are not conducive to precipitation in the Yangtze-Huaihe region. At the same time, the cold air flowing southward to the Yangtze-Huaihe region was hindered in the 2010s due to the change of blocking in the middle troposphere. In the 2010s, the water vapor transport and the vertical transportation weakened, resulting in the decrease of precipitation in the Yangtze-Huaihe region.

Changes of extreme precipitation in the middle and lower reaches of the Yangtze River and their correlation with atmospheric circulation

“…In this study, the daily precipitation indices were derived from the CN05 dataset, which spans from 1979 to 2015 and was provided by the National Climate Center of China with a horizontal resolution of 0.25 °×0.25 ° (Shang et al, 2020). The dataset is generated by applying the thin-disk spline function method (ANUSPLIN) and the angular distance weight method (ADW) and has been widely used for climate assessments in China (Hu and Wang, 2021;Li et al, 2022).…”

Spatial-temporal variations of extreme precipitation indices and their linkage with atmospheric circulation in the middle and lower reaches of the Yangtze River

“…The precipitation in the region is highly affected by the location of WPSH as WPSH controls the precipitation belt position along the edge of the subtropical high. Meanwhile, there exhibits a high level of correlation between PRCPTOT and WPSH area (R =0.49, P<0.01), WPSH intensity (R =0.47, P<0.01), both are statistically significant, indicating that R25mm and PRCPTOT will increase significantly with the increase of WPSH area and intensity (Hu and Wang, 2021;Tian et al, 2022). There is a significant correlation (P<0.01) between the SCSHI and PRCPTOT (r=0.59, P<0.01) and R95 (r=0.46, P<0.01) (Nazari-Sharabian and Karakouzian, 2020; Zeng et al, 2019).…”

“…Among relative indices, R95 and R99 have similar spatial distribution which show a continuous upward trend in most areas. In the intensity indices, PRECPTOT has the same spatial distribution with R25mm, while SDII shows a slight upward trend in most regions except Yichang province.The spatial distribution of the trends of RX1day and RX5day is relatively complex, showing a declining trend in the lower reaches of Dongting Lake and the Han River (Hu and Wang, 2021), and an insignificant upward trend in most areas of Poyang Lake, Taihu, and lower reaches of the Yangtze River. The extreme precipitation indices in the Poyang Lake region are not only quantitatively large, but also present a rapid growth trend.…”

“…In the study, daily precipitation indices were derived from the CN05 dataset during 1979-2015 provided by the National Climate Center of China with a horizontal resolution of 0.25°×0.25° (Shang et al, 2020), which has been widely used in climate assessment in China (Hu and Wang, 2021;Li et al, 2022). The gridded dataset is generated by applying the thin-disk spline function method (ANUSPLIN) and the angular distance weight method (ADW) to the daily observation data of more than 2400 national meteorological stations.…”

Bores Observed During the Warm Season of 2015–2019 Over the Southern North China Plain

“…At this time of year, the Mei‐yu front begins to dominate the synoptic pattern over the region creating more favorable conditions for MCSs and thus for bores. The Mei‐yu front is also often associated with a LLJ (e.g., Du et al., 2014; Hu & Wang, 2021) that would favor the maintenance of bores generated by convection. Another interesting phenomenon is that undular bores tend to occur in June while non‐undular bores in August with the changing of the synoptically periods.…”