Differences in Variations of Long-lived and Short-lived Summer Heat Waves during 1981–2020 over Eastern China and their Corresponding Large-Scale Circulation Anomalies

Using daily maximum temperature (T_max) data from 516 observation stations in eastern China from 1981 to 2020, this study employed a relative threshold method to define short- and long-lived HWs by considering regional climate differences to investigate the spatial characteristics and evolution of large-scale circulation during summer HWs. The results demonstrated spatial disparities in the frequency distribution of HWs of different durations and differences in the magnitude of duration and intensity between short- and long-lived HWs. Empirical Orthogonal Function analysis revealed three dominant spatial modes for both short- and long-lived HWs. The first mode showed that short-lived HWs occur prominently in both northern and southern regions, whereas long-lived HWs mainly occur in the northern region. The second mode was characterised by a meridional dipole pattern in both cases. The third mode exhibited a quadrupole pattern for short-lived HWs and a tripole pattern for long-lived HWs. Differences in the centre locations of anomalies in the 500-hPa geopotential height and 850-hPa wind fields significantly influenced the temperature and precipitation anomaly distribution of typical HWs by affecting the warm column in the lower troposphere, cloud distribution, and moisture transport. Moreover, the atmospheric circulation evolution processes of typical HWs associated with the different modes of long- and short-lived HWs were linked to distinct teleconnection patterns. During the three modes of long-lived (short-lived) HWs, there was stronger (weaker) wave flux activity with multiple (single) propagation paths. Stronger westward Atlantic wave train activity at 300 hPa triggered the synergistic action of meridional and zonal wave fluxes, favouring the strengthening and maintenance of positive anomalies at a geopotential height of 500 hPa. This may have contributed to the formation of long-lived HWs. These findings provide valuable insights to enhance our understanding and prediction of summer HWs.