Typhoon Doksuri (No.2305) caused an extremely rare torrential rainfall over Putian City, Fujian Province. Based on multi-source observational data, including surface meteorological observational data of Fujian Province, radar and satellite data, as well as reanalysis data from ECMWF (European Centre for Medium-Range Weather Forecasts), the stages and intensity characteristics of the extreme rainfall induced by Typhoon Doksuri were analyzed. The main conclusions are as follows: The entire rainfall process was consisted of three seamlessly-linked stages. The first stage was the typhoon eyewall rainstorm, which had the characteristics of intense short-term rainfall and uniform spatial distribution. The second stage was the spiral rainband rainstorm, which was characterized by significant differences in hourly rainfall intensity and distinct rain peaks. The third stage was the monsoon-enhanced rainstorm, with the characteristics of a wide range of heavy rain and a long duration. The heavy rain in Putian caused by Typhoon Doksuri exhibits remarkable extremeness, with specific manifestations as follows: extremely intense heavy rainfall, a wide impact range of extremely heavy rainfall, large cumulative rainfall, high frequency of short-term heavy precipitation, and long duration. Among these, the 24-hour rainfall at Putian Station reached 561.7 mm, breaking the historical record of Fujian Province, and its extreme characteristics are particularly prominent. The continuous maintenance of typhoon warm shear line, low-level southerly jet and monsoon system is an important weather background for the three stages of rainstorm to achieve “seamless connection”. The uplift and contraction of the southerly jet caused by the terrain of Xinghua Plain “surrounded by mountains on three sides and opening to the south” is an important factor for the rainstorm center to be located in the Xinghua Plain to the northeast mountainous area.

In order to strengthen the application of densified automatic station data in rainstorm forecast in the eastern Helan Mountain foothills, based on hourly surface meteorological observations and ERA5 reanalysis data, 17 rainstorm events in this area from 2016 to 2021 were classified into cold-warm air convergence type, warm-sector type, and weak cold air intrusion type, according to the intensity of cold air. The precipitation distribution, circulation characteristics, and the evolution of surface meteorological elements were then comparatively analyzed. The results show that cold-warm air convergence rainstorms are characterized by a deep upper-level trough and an extensive low-level high-humidity zone, but with relatively weak southerly winds and water vapor flux. These storms exhibit a wide precipitation area and high average rainfall, but the precipitation efficiency is lower than that of warm-sector rainstorms. Warm-sector rainstorms have the strongest low-level southerly winds and moisture flux, but the upper-level divergence is the weakest and the high-humidity zone is fragmented. These storms are marked by high precipitation efficiency, strong locality, and extreme intensity. In weak cold air intrusion rainstorms, the low-level warm and moist conditions are better than in the cold-warm air convergence type, and the precipitation and convective intensity which triggered by upper-level cold air are stronger than those of the cold-warm air convergence type. One hour before the onset of precipitation, all three types of rainstorms exhibit temperature drop, pressure rise, and increased wind speed, with temperature changes being the most significant, while dew point temperature varies between cases. In the five hours prior to precipitation, temperature decreased and relative humidity increased, with the most pronounced changes occurring one hour before rainfall onset. After precipitation began, these variables tended to stabilize. However, the timing and magnitude of temperature drops and the rate of relative humidity increase differed among the storm types. Dew point temperature first increased and then decreased, peaking from 1 hour before to 2 hours after rainfall onset. Wind speed variations also differed across storm types. The indicators developed in this study performed best for warm-sector type rainstorms, achieving a TS (threat score) of 48.65%, followed by the cold-warm air convergence type, with the weakest performance in the weak cold air intrusion type. The prediction accuracy of humidity, pressure, and dew point temperature indicators was relatively high (mostly exceeding 50.00%, some over 55.00%), indicating potential for enhancing rainstorm monitoring and early warning. In contrast, indicators based on temperature change (less than 50.00%) and wind speed variation (around 30.00%) showed weaker predictive capability, indicating the need for further optimization.

In order to study the characteristics of typhoon precipitation and typhoon core precipitation in East China and the influence of large-scale circulation on the distribution of typhoon core precipitation, this paper uses the daily precipitation data from the National Meteorological Information Center and reanalysis data from NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research), applies the dynamic synthesis analysis method, compares and analyzes the large-scale circulation characteristics of two types of typhoons (The L-type and the R-type core precipitation typhoons) with different distributions of precipitation during typhoon landing. The results are as follows: (1) Typhoons mainly landed in summer in East China, and the times of typhoon landing and extreme precipitation caused by typhoon had the characteristics of “single-peak mode” in monthly distribution. The precipitation gradually decreased from coastal to inland, from south to north. (2) The precipitation in the typhoon core was asymmetrical, and the heavy precipitation was more likely to occur on the side with the coordination of divergence and convergence field and the better maintenance of ascending motion. (3) The L-type core precipitation typhoon was mainly controlled by warm advection. There were multiple cold advection centers in the west of circulation. Cold and warm advection intersection enhanced the atmospheric convective instability and provided unstable energy for precipitation. R-type core precipitation typhoon was mainly controlled by cold advection after landing. In the northeast of circulation there were warm advections, and the atmospheric stability dropped due to the cold and warm advections interaction. It was beneficial to precipitation on the right side of the path. (4) Strong water vapor convergence existed in the southwest of the L-type core precipitation typhoon, which was conducive to the occurrence of precipitation on the left side of the path. During the landfall of R-type core precipitation typhoon, the water vapor convergence center maintained for a long time in the northeast of the circulation, which was conducive to the occurrence and development of precipitation system on the right side of the path. Divergence and convergence configuration in high and low level, cold and warm advection and water vapor transport were the main factors to affect the precipitation distribution in typhoon core.

The thermal and dynamic processes of the convective boundary layer over the Tibetan Plateau (TP) have an important impact on weather and climate of the downstream region and even the entire East Asia region. This paper uses a summer case of 2017 as an example to analyze the applicability of three sets of reanalysis data including ERA-Interim, JRA-55 and MERRA-2 in the study of the boundary layer over the TP, and further uses the constraints of the numerical model physical framework to correct its analysis error. In the summer of 2017, the variation of air temperature and dew point temperature were presented well through the three sets of reanalysis data in the boundary layer over the southeastern TP, while the reproducibility of the horizontal wind field was very poor, and the reanalysis data with better applicability over the TP during the study period was ERA-Interim. The results from the 12 parameterization scheme combinations selected in this paper were compared by the dispersion degree of the horizontal wind field error, improvements of the simulations in clear skies and moderate rain were significant. Therefore, for the simulated critical physical quantity (the horizontal wind field), the combination of Betts-Miller-Janjic, WSM6 and ACM2 scheme was the most locally applicable in the study area. The wind field in the reanalysis data could describe the summer boundary layer development over the TP more closely after adjustment using simulation results. It was proved that the model parameterization scheme could reduce its deviation of seasonal distribution in the plateau area, which had certain guiding significance for subsequent research and application.

Based on the precipitation data from regional automatic  weather stations and conventional meteorological observational stations of Jiangxi Province, FNL reanalysis data and NCEP GDAS data, the characteristics of water vapor during the continuous heavy rainfall process in Jiangxi Province from June 6 to 10, 2019, the influence of atmospheric river (AR) water vapor transportation on the intensity, rain zones and movement of rain bands of heavy rainfall were analyzed. The water budget across four boundaries over heavy rainfall area was also studied and the trajectories of water vapor at different stages were traced by using HYSPLIT model. The results show it was a typical ‘Ω-type’ heavy rain pattern, the continuous confluence of cold and warm air over Jiangxi resulted in this continuous heavy rain. AR(atmospheric river) played a media role in transport of water vapor during the storm. At different stages, AR showed different strength and locations for the transport of water vapor from the south China Sea, the western Pacific and the Bay of Bengal, resulting in different intensity and location of heavy precipitation at various stages. The intensity and duration of the net inflow of water vapor across four boundaries over the heavy precipitation area played a key role in development and maintenance of heavy rainfall. The simulation of HYSPLIT model illustrated that water vapor in the lower layer mainly originated from the south China Sea and the western Pacific, while the water vapor in the middle layer mainly came from the Bay of Bengal. Low-level water vapor flowing into the rainstorm area from different boundaries may be one of the reasons for the different rainfall intensity at different periods.

To explore the mesoscale characteristics of heavy rainfalls triggered by warm shear line with low vortex over the Yangtze-Huaihe region, based on the conventional and intensive observation data, FY-2E satellite cloud images and NCEP/NCAR reanalysis data, two typical rainstorm processes with different types were comparatively analyzed in the Yangtze-Huaihe region. The rainfall with the stable pattern continued for a long time in wide range of the Yangtze-Huaihe region, while that with the eastward moving pattern relatively concentrated for a short time with stronger rainfall intensity. The results are as follows: (1) Two rainstorms were caused by the interaction of upper trough and low-level warm shear line, but the upper trough and low-level warm shear line were stable during the rainfall process with the stable pattern, while the low pressure trough on 500 hPa, low vortex in low layer and surface mesoscale low pressure moved eastward during the rainfall process with the eastward moving pattern, and the convergence was stronger in low and middle layer. (2) The convective organization form for the stable pattern was forward sequential development, and the structure of convection system was relatively loose, while the convective organization form for the eastward moving pattern was backward sequential development, and the organized degree was higher. (3) Two processes occurred in wet environment, and the low-level jet (LLJ) played a key role in transporting water vapor. The rainfalls mainly appeared in wind convergence area in the front of the southwesterly jet axis. The water vapor continuously transported on 850 hPa during the stable moving process, which was beneficial to the heavy rainfall with a wide range. LLJ was relatively strong during the eastward moving process, and the active southeasterly extra LLJ occurred in the late of the rainfall, which was conducive to the local concentrated rainfall. The convergence of the southwest and southeast winds in low level formed obvious mesoscale lifting during two processes, and the uplifting condition for the eastward moving process was better than that for the stable process. The heavy rainfall was mostly occurred nearby surface convergence. So, the surface convergence line played an important role in triggering convective instability, which can afford some indication to the rainfall area of short-term and imminent prediction.