Climatic features of summertime baroclinic wave packets over Eurasia and the associated possible impacts on precipitation in southern China

Abstract

Climatic features of baroclinic Rossby wave packets at 300 hPa in summers of 1979–2016 over Eurasia are investigated using the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis and daily precipitation observations in China. It is found that the waves with zonal wave‐numbers 5–7 are dominant in Northern Hemisphere. The meridional width (zonal length) of wave packets is up to 50°lat, 130°lon. The wave packets get stronger and incline a little northwestward from 850 up to 300 hPa. Most of strong wave packets are observed around the Alps, the Black Sea and the Caspian Sea, and they propagate eastward, or northeastward, or southeastward. Their zonal and meridional propagation velocities reach about 32 and 7 m/s, respectively. Interannual variations of June–July precipitation in different sub‐regions of southern China are significantly affected by the baroclinic wave packet activities in different regions of Eurasia. These results have important implications for in‐depth understanding wave behaviors and their climate impacts on southern China.

Regional‐Scale Heavy Precipitation Over Fujian‐Jiangxi Region in the Late Spring‐Early Summer of 2006 and Its Connection With Baroclinic Wave Packets in the Upper Troposphere

“…Besides of our previous studies (e.g., S. Sun et al, 2021;Ye, Guan, & Jin, 2019), it is also found that waves with zonal wave-number 5-7 may modify monsoon by triggering monsoon breaks during summer season (Rao et al, 2022). Thereby, the wave-number k is selected to be within the range of 5-7 and the central wave-number is set to 6; which is the same as in our former researches (e.g., S. Sun et al, 2021;Ye, Guan, & Jin, 2019). That is, those waves with zonal wavelength of about 51-72 longitudes are used for wave packets analysis.…”

“…Chen et al, 2022;H. Li & Fan, 2022;Wolf & Wirth, 2017;Ye, Guan, & Jin, 2019) proposed that the T-N flux (Takaya & Nakamura, 2001) can better capture complicated features of individual wave packet than the traditional wave activity flux, and can yield more clear dynamic features of wave packets.…”

Summer Regional Daily‐Precipitation Extreme Events in Huang‐Huai Rivers Region of China and Their Relationships With Rossby Wave Packet Activities

“…Although, the main wave numbers of baroclinic waves in the upper troposphere in middle latitudes are different in different years, the waves with wavenumbers between 5 and 7 are usually the main components of the significant disturbance in meridional winds in the upper troposphere (300 hPa) (Chang & Yu, 1999; Kao & Wendell, 1970; Wirth et al., 2018; Ye et al., 2019). In the present work, Hilbert transformation is used for envelope analyses (Zimin et al., 2003).…”

Rossby wave packets in the upper troposphere and their associations with climatological summertime daily precipitation in MLRYR of China

“…Theoretically, for waves with zonal wavelength larger than the meridional wavelength, the zonal component of group velocity may be zero in a slow varying basic flow (Hoskins et al ., 1983). Of course, except for the wave packet intensity gets a little stronger from −3d to 0d (Figure 3a‐d), the behaviors of the wave packets in the filtered 40‐year mean summer daily climatology look quite different from those in some particular years (Ye et al ., 2019a), especially years such as 1998 and 2003 when the severe flood events occurred in MLRYR (Mei and Guan, 2008, 2009; Ye et al ., 2019b). In those years, the wave packets at 300 hPa migrate very quickly from regions near the Caspian Sea eastward/southeastward to East China.…”

“…Previous studies have indicated that precipitation in MLRYR is closely related to wave packet activities in the upper troposphere (Shi et al ., 2009; Ye et al ., 2019a); each individual precipitation event is affected by the wave packet activities (Li et al ., 2018; Ye et al ., 2019a, 2019b). All the above studies (e.g., Mei and Guan, 2008, 2009; Ye et al ., 2019a, 2019b) suggest that the wave packets are observed in the upper troposphere in particular years. However, in reality, a time‐varying quantity can be separated into the multi‐year mean climatology and the departures from this mean climatology.…”