Characterizing extreme drought and wetness in Guangdong,China using global navigation satellite system and precipitation data

As global temperature rises,the frequency of extreme climate events,e.g.,severe droughts and floods,has increased significantly and caused severe damage over the past years.To this regard,precipitation efficiency,a crucial meteorological parameter,could provide valuable insights for a better understanding of the patterns and characteristics of these extreme events.In this study,taking Guangdong province as an exemplary region,we first obtained long-term and high-resolution historical records of precipitation efficiency by integrating the observations from a dense network of Global Navigation Satellite System(GNSS)stations with precipitation data,and then characterized the extreme drought and wetness through climate indices.We found a distinct seasonal trend in precipitation efficiency in Guangdong,with annual fluctuations ranging from 10 to 25%.Notably,precipitation efficiency is higher in proximity to the Pearl River Delta Plain and gradually decreases towards the east and west.The occurrence of anomalous peaks and valleys in precipitation efficiency generally corresponds to dry and wet conditions,respectively.A total of 9 extreme wet events and 6 dry events occurred from January 2007 to May 2022,with durations from 3 to 6 months.Our results also demonstrated that both wet and dry frequencies exhibit an increasing trend with the expansion of the time scale,and the frequency of extreme events near the Pearl River Delta Plain surpasses that of other regions.Furthermore,the propagation time from meteorological anomalies to agricultural and hydrological anomalies is about 3 months.The periodic characteristics of meteorological anomalies are identified as the primary driver for other anomalous periodic patterns.Our work unveils the long-term dynamic behavior of precipitation efficiency,as well as the characteristics of extreme drought and wetness events in the regions characterized by intricate land–atmosphere interactions.

Ionospheric disturbance analysis of the January 15,2022 Tonga eruption based on GPS data

Hunga Tonga-Hunga Ha’apai climactic eruption on January 15,2022,released enormous energy that affected the ionosphere over the Pacific Rim.We analyzed ionospheric disturbance following volcanic eruptions using near-field(<1000 km),regional(1000–5000 km),and far-field(5000–12000 km) global positioning system(GPS) observations.The results indicate that the near-field ionospheric perturbation that occurred 8–15 min after the cataclysmic eruption was mainly derived from the shock wave(~1000 m/s) generated by the blast,while the low-frequency branch with long-distance propagation characteristics over the regional and the far-field was mainly associated with atmospheric Lamb waves(~330 m/s).Moreover,the amplitude of disturbance and background total electron content(TEC) are related proportionally.The intensity of the volcanic eruption and the background ionospheric conditions determine the magnitude of ionospheric responses.TEC perturbations were invisible on the reference days.Furthermore,the source location and onset time were calculated using the ray tracing technique,which confirms that the Tonga event triggered the ionospheric anomaly beyond the crater.Finally,the change in the frequency of the perturbations coincided with the arrival of the initial tsunami,implying the generation of a meteotsunami.