After the building of the Three Gorges Dam (TGD), the water level abruptly rose from 66 to 135 m in June 2003, and the land use characteristics changed significantly throughout the TGD region. More and more people are concerned with the effect of the TGD reservoir on climate. In this paper, the decadal variation of precipitation in the vicinity of the TGD was analysed using daily data from 27 rain gauges from 1960 to 2005. The empirical orthogonal function (EOF) analysis of annual precipitation anomalies indicates a clear difference in spatial distribution, with an opposite signal for the change in precipitation in the northern and southern areas of the Yangtze River, i.e. precipitation increases in the northern area are accompanied with decreases in the southern area and vice versa. The similar dipole pattern of precipitation variation around the TGD also occurred before the TGD, for example, in the period from 1977 to 1984. Therefore, it has not been shown with reasonable significance that the similar dipole pattern of precipitation variation around the TGD has been affected by the TGD. Copyright © 2009 Royal Meteorological Society

Air temperature and precipitation are two important meteorological factors affecting the earth’s energy exchange and hydrological process. High quality temperature and precipitation forcing datasets are of great significance to agro-meteorology and disaster monitoring. In this study, the accuracy of air temperature and precipitation of the fifth generation of atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5) and High-Resolution China Meteorological Administration Land Data Assimilation System (HRCLDAS) datasets are compared and evaluated from multiple spatial–temporal perspectives based on the ground meteorological station observations over major land areas of China in 2018. Concurrently, the applicability to the monitoring of high temperatures and rainstorms is also distinguished. The results show that (1) although both forcing datasets can capture the broad features of spatial distribution and seasonal variation in air temperature and precipitation, HRCLDAS shows more detailed features, especially in areas with complex underlying surfaces; (2) compared with the ground observations, it can be found that the air temperature and precipitation of HRCLDAS perform better than ERA5. The root-mean-square error (RMSE) of mean air temperature are 1.3 °C for HRCLDAS and 2.3 °C for ERA5, and the RMSE of precipitation are 2.4 mm for HRCLDAS and 5.4 mm for ERA5; (3) in the monitoring of important weather processes, the two forcing datasets can well reproduce the high temperature, rainstorm and heavy rainstorm events from June to August in 2018. HRCLDAS is more accurate in the area and magnitude of high temperature and rainstorm due to its high spatial and temporal resolution. The evaluation results can help researchers to understand the superiority and drawbacks of these two forcing datasets and select datasets reasonably in the study of climate change, agro-meteorological modeling, extreme weather research, hydrological processes and sustainable development.

Mangrove ecosystems can be both significant sources and sinks of greenhouse gases. The restoration of mangrove forests is increasingly used as a natural climate solution tool to mitigate climate change. However, the estimates of carbon exchanges remain unclear, especially from restored mangroves. In this study, we observed the temporal variations in carbon dioxide (CO₂) and methane (CH₄) fluxes and their biophysical controls for 4 years, based on a closed-path eddy covariance (EC) system. The measurements were conducted in a mangrove wetland park with 14-year-old restored mangroves surrounded by open waters in Guangdong Province, China. The EC measurements showed that the mangrove ecosystem acted as a CO₂ source with a net CO₂ ecosystem exchange (NEE) of 305 g C m⁻² from January 2019 to May 2020 by the 5-m tower measurement. After the tower was adjusted to 10 m, the mangrove showed a CO₂ sink with an NEE of −345 g C m⁻² from June 2020 to December 2022. The change in tower height influenced the interpretation of interannual trends on NEE. There were no significant interannual trends in the gross primary productivity (GPP) and the ecosystem respiration (Re) values. The change from CO₂ source to sink may be attributed to the decrease in land surface proportion by the tower replacement, which reduces the proportion of the mangrove canopy respiration and, therefore, captures lower CO₂ fluxes from open waters. The restored mangroves indicated strong CH₄ sources of 23.2–26.3 g C m⁻² a⁻¹. According to the random forest analysis, the land surface proportion, radiation, and relative humidity were the three most important predictors of NEE, while the CH₄ flux was most sensitive to air temperature. Compared to the natural and long-term restored mangroves, this 14-year-old restored mangrove had not yet achieved a maximum carbon sequestration capability. Our study highlights the need for the careful design of long-term observations from restored mangroves and proposes future needs in the context of carbon neutrality.

This report is a summary of China’s climate, as well as major weather and climate events, during 2019. In 2019, the mean temperature in China was 10.34°C, which was 0.79°C above normal (1981–2010 average), and the annual rainfall was 645.5 mm, which was 2.5% above normal. There was increased typhoon genesis but decreased and weaker landfalls. Rainstorms occurred frequently with relatively limited damage. The number of high-temperature days was more than normal, with significant regional features. Obvious regional and periodic droughts resulted in slight impacts and losses. Severe convective weather events were relatively less and brought about limited economic losses. Low-temperature freezing and snow disasters were obviously light. Northern China experienced fewer dust storms in spring. Finally, the areas of affected crops, the numbers of deaths and missing people, and direct economic losses were all significantly less than average over the past 10 years. GRAPHICAL ABSTRACT