Investigation of historical low-temperature events in the warm season in China based on documentary data

Low-temperature events, as an important and disastrous weather process, can cause severe damage to agriculture, transportation, and economic systems. However, low-temperature events occurring during the warm season have received less attention from climatologists compared to the harsh winters, with the exception of the well-known cold summer of the post-Tambora period during 1815-1817, which resulted in terrible famines in southwest China. Documentary data have been widely used to study past climate. Aside from abnormal phenomena like snow, frost, and ice, past low-temperature events occurring in late summer and early autumn, which are key periods of rice growth, also attracted people's attention and have been documented. Through the excavation of the original literature, the presented study reconstructed a chronology of low-temperature events in the warm season over the past hundreds of years and analyzed their temporal-spatial characteristics. We also detected low-temperature events in the past decades in southwest China and discussed the corresponding circulation pattern and potential forcing using the instrumental, reanalysis (ERA5), and paleo-simulation (ModE-Sim) datasets. Volcanic eruptions are one of the most important forcings, and Superposed Epoch Analysis (SEA) results show lower temperatures in the years following eruptions in the North Hemisphere and tropical regions. The large-scale circulation anomaly composition presents as the East-Atlantic (EA) pattern. The impact of Pacific sea surface temperature (SST) is also present in both reanalysis and simulations, which could force an EA pattern by inducing a Rossby wave train. In further work, we will make a comparison between low-temperature events in China and Europe, which are both potentially influenced by the EA pattern and volcanic eruptions.