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An extremely heavy rainfall event lasting from 17 to 22 July 2021 occurred in Henan Province of China, with accumulated precipitation of more than 1000 mm over a 6-day period that exceeded its mean annual precipitation. The present study examines the roles of persistent low-level jets (LLJs) in maintaining the precipitation using surface station observations and reanalysis datasets. The LLJs triggered strong ascending motions and carried moisture mainly from the outflow of Typhoon In-fa (2021). The varying directions of the LLJs well corresponded to the meridional shifts of the rainfall. The precipitation rate reached a maximum during 20–21 July as the LLJs strengthened and expanded vertically into double LLJs, including synoptic-weather-system-related LLJs (SLLJs) at 850–700 hPa and boundary-layer jets (BLJs) at ∼950 hPa. The coupling of the SLLJ and BLJ provided strong mid- and low-level convergence on 20 July, whereas the SLLJ produced mid-level divergence at its entrance that coupled with low-level convergence at the terminus of the BLJ on 21 July. The formation mechanisms of the two types of LLJs are further examined. The SLLJs and the low-pressure vortex (or inverted trough) varied synchronously as a whole and were affected by the southwestward movement of the WPSH in the rainiest period. The persistent large total pressure gradient force at low levels also maintained the strength of low-level geostrophic winds, thus sustaining the BLJs on the synoptic scale. The results based on a Du-Rotunno 1D model show that the Blackadar and Holton mechanisms jointly governed the BLJ dynamics on the diurnal scale.

Multi‐Doppler analyses from the joint Prediction of Rainfall Extremes Campaign in the Pacific 2022 and Taiwan‐Area Heavy rain Observation and Prediction Experiment field campaign are used to examine the relationships between dynamics and rainfall intensity in two Mei‐Yu frontal periods. Statistics from oceanic rainfall over 8 days show a mean increase and a positive shift of the distributions of vertical vorticity, vertical motion, and divergence with increasing rain rate intensity. In regions of higher rain rates, mean ascent maximizes in the upper troposphere, low‐level convergence intensifies over a deeper layer, and upper‐level divergence strengthens. Stratiform rainfall is frequent in light rain rates below 5 mm h−1${\\mathrm{h}}^{-1}$but contributes little to the total rainfall. Heavy convective rain rates between 10 and 50 mm h−1${\\mathrm{h}}^{-1}$are only 6% of the observed raining grid points over the ocean but contribute over 45% of the total volumetric rainfall. The radar analysis indicates that the highest rain accumulations in the oceanic Mei‐Yu precipitation preferentially occur in moderately strong rotating convection.

We investigated the relationship between heavy rainfall events (HREs) and the Pacific Decadal Oscillation (PDO) occurring in Korea over Far East Asia for 40 years (1981–2020). Using K‐means clustering on the low‐level jet, we identified four clusters (C1–C4), with C1 being characterized by weaker synoptic conditions. Out of the four clusters, C1 represented localized extreme HREs compared with the other clusters. Interestingly, only the HRE frequency of C1 was found to have a strong negative correlation with PDO. During the negative‐PDO, sea surface temperature increased above 30°N, which decreased the meridional temperature gradient. This weakened the atmospheric circulation and created thermodynamic instability (i.e., weakened upper jet, increased low‐level temperature, higher atmospheric water capacity), creating a favorable environment for HRE in C1. However, this negative‐PDO environment provided somewhat unfavorable conditions for other clusters (C2–C4), so the PDO impact was insignificant. Plain Language Summary We investigated the relationship between heavy rainfall events (HREs) and the Pacific Decadal Oscillation (PDO) that occurred in Korea over Far East Asia from 1981 to 2020. A high negative correlation with PDO was found for localized heavy precipitation with short duration and heavy precipitation intensity over Korea. The main reason for the different impacts of PDO‐phases is related to the large‐scale environment. During the negative‐PDO‐phase, warm sea surface temperature anomaly above the mid‐latitudes allowed Korea to contain more water vapor, providing favorable conditions for HREs. In addition, during the negative‐PDO‐phase, temperature increases above 30°N weaken the temperature gradient around the South Pacific, creating favorable conditions for the formation of heavy rainfall characterized by localized, short‐lived heavy rainfall events due to the creating thermodynamic conditions. Key Points During Korea's summer, extreme heavy rainfall events show a negative correlation with the Pacific Decadal Oscillation (PDO) During the negative‐PDO, localized extreme precipitation increases over Korea The different effects of PDO in negative and positive could be because of the increasing of sea surface temperature over 30°N

In the light of observed variability in precipitation patterns, there is a growing need for comprehensive data mining of regularly updated rainfall recording databases. Therefore, an analysis of heavy rainfall and hyetographs was conducted using a 30-year high-resolution dataset from 100 rain gauges across Poland, covering 31 646 rainfall events. Distributions of rainfall depths, durations, and intensities were explored, and maxima were compared to global records. Spatial analysis revealed significant variations in the frequency, depths, and durations of extreme rainfall across different regions. Cluster analysis determined model hyetographs for each station. The likelihood of regions belonging to clusters with three to five model hyetographs was assessed using Indicator Kriging. Findings underscore the importance of using local, characteristics rainfalls in hydrodynamic modelling of drainage systems and future rainfall scenarios. These results provide a foundational step towards understanding and monitoring the impacts of climate change on rainfall characteristics, especially extremes, in future decades.

This study explores the controlling factors of the uncertainties and error growth at different spatial and temporal scales in forecasting the high-impact extremely heavy rainfall event that occurred in Zhengzhou, Henan Province China on 19–20 July 2021 with a record-breaking hourly rainfall exceeding 200 mm and a 24-h rainfall exceeding 600 mm. Results show that the strengths of the mid-level low-pressure system, the upper-level divergence, and the low-level jet determine both the amount of the extreme 24-h accumulated and hourly rainfall at 0800 UTC. The forecast uncertainties of the accumulated rainfall are insensitive to the magnitude and the spatial structure of the tiny, unobservable errors in the initial conditions of the ensemble forecasts generated with Global Ensemble Forecast System (GEFS) or sub-grid-scale perturbations, suggesting that the predictability of this event is intrinsically limited. The dominance of upscale rather than upamplitude error growth is demonstrated under the regime of k −5/3 power spectra by revealing the inability of large-scale errors to grow until the amplitude of small-scale errors has increased to an adequate amplitude, and an apparent transfer of the fastest growing scale from smaller to larger scales with a slower growth rate at larger scales. Moist convective activities play a critical role in enhancing the overall error growth rate with a larger error growth rate at smaller scales. In addition, initial perturbations with different structures have different error growth features at larger scales in different variables in a regime transitioning from the k −5/3 to k −3 power law. Error growth with conditional nonlinear optimal perturbation (CNOP) tends to be more upamplitude relative to the GEFS or sub-grid-scale perturbations possibly owing to the inherited error growth feature of CNOP, the inability of convective parameterization scheme to rebuild the k −5/3 power spectra at the mesoscales, and different error growth characteristics in the k −5/3 and k −3 regimes.

The summer rainfall amount over East China is expected to increase along with a strengthening of the East Asian summer monsoon in a warmer climate. However, how the seasonality of precipitation will respond to global warming remains uncertain and is closely related to monsoon circulation. Here, we project future changes in multiple intra-seasonal rainfall characteristics over East China under 1.5 °C, 2 °C, 2.5 °C, and 3 °C of global warming above pre-industrial levels based on coupled model intercomparison project phase 6 multi-model projections. Both the onset and cessation dates over South China are likely to be delayed in a warmer climate, resulting in a later shift of the rainy season. In contrast, advanced cessation dates are projected over Northeast China with high model consensus. As for rainfall characteristics within the rainy season, total rainy season rainfall is expected to increase over the whole East China domain, with remarkable enhancement of heavy rainfall intensity. Further analysis indicates that continuous warming over a 1.5 °C warmer climate is projected to further increase total rainy season rainfall and enhance heavy rainfall intensity, with a magnitude at least twice as large with additional warming of 0.5 to 1.5 °C. Also, changes in cessation dates over South and Northeast China are projected to be enhanced significantly. These results together indicate the vital need to slow down global warming to reduce potential adverse impacts on agricultural and socioeconomic development.

This paper analyzes the multivariate and spatial distribution of heavy precipitation disasters and proposes a method for estimating disaster risk using a joint statistical model. We tested the model with hourly precipitation data from 122 meteorological stations in Shandong from 1990 to 2023. Different marginal distribution functions were used to fit precipitation duration and amount. A Copula joint distribution model established relationships between these variables to analyze heavy precipitation recurrence periods and disaster characteristics. Compared to univariate approaches, the Copula function more reasonably simulates natural disaster occurrence. The joint return period (JRP) estimated by the Copula function reveals that the JRP of 1-hour heavy rainfall is 89% higher than 6-hour rainfall, indicating significantly increased risk from short-term heavy rainfall in Shandong. This method provides a more scientific description of heavy precipitation disaster risk in different scenarios, particularly for short-term events, offering a robust foundation for disaster prevention planning and risk management.

Assimilation of the Advanced Geostationary Radiance Imager (AGRI) clear-sky radiance in a regional model is performed. The forecasting effectiveness of the assimilation of two water vapor (WV) channels with conventional observations for the “21·7” Henan extremely heavy rainfall is analyzed and compared with a baseline test that assimilates only conventional observations in this study. The results show that the 24-h cumulative precipitation forecast by the assimilation experiment with the addition of the AGRI exceeds 500 mm, compared to a maximum value of 532.6 mm measured by the national meteorological stations, and that the location of the maximum precipitation is consistent with the observations. The results for the short periods of intense precipitation processes are that the simulation of the location and intensity of the 3-h cumulative precipitation is also relatively accurate. The analysis increment shows that the main difference between the two sets of assimilation experiments is over the ocean due to the additional ocean observations provided by FY-4A, which compensates for the lack of ocean observations. The assimilation of satellite data adjusts the vertical and horizontal wind fields over the ocean by adjusting the atmospheric temperature and humidity, which ultimately results in a narrower and stronger WV transport path to the center of heavy precipitation in Zhengzhou in the lower troposphere. Conversely, the WV convergence and upward motion in the control experiment are more dispersed; therefore, the precipitation centers are also correspondingly more dispersed.

Abstract From June 10 to 13, 2019, continuous heavy rainfall occurred in Longchuan County, Guangdong Province, yielding a cumulative rainfall of nearly 270 mm. The heavy rainfall triggered a large number of landslide disasters and formed three hardest-hit areas. In this paper, Mibei village, Beiling town, Longchuan County, is chosen as the research object; detailed field investigation data, satellite remote sensing images, rainfall monitoring data, and artificial rainfall physical model test results are integrated; the temporal and spatial distribution characteristics of rainfall-induced group-occurring landslides in the study area are obtained; and the rainfall instability mechanism of granite residual soil slopes is explained. Under the influence of continuous heavy rainfall from June 10 to 13, 2019, 327 landslides developed in Mibei village, Beiling town, and these landslides were mainly distributed in low mountainous areas, of which the sections at elevations from 300 ~ 400 m and slopes ranging from 35 ~ 45° were the most susceptible to landslide disasters. Continuous rainfall on June 10 and 11 was the controlling factor leading to these large number of landslides, with numerous landslides occurring from 20:00 on June 11 to 04:00 on June 13. These group-occurring landslides exhibited the characteristics of a considerable rainfall lag. The deformation and failure characteristics of the numerous observed landslides within the study area were highly similar, mainly involving traction sliding failure, and the sliding mass thickness ranged mostly from 1.5 ~ 3 m. The flow pattern characteristics of unconsolidated deposits after landslide instability were significant. According to the deformation and failure characteristics of landslides and the rainfall infiltration pattern, the development of landslides was divided into stages in this paper. Due to the difference between the rainfall intensity and permeability of granite residual soil, the main influence depth of heavy rainfall was limited to the superficial zone of slopes, which is the main reason why the shallow surface zone was damaged by landslides. Under the action of continuous heavy rainfall, a saturated seepage field was established in the shallow surface zone of slopes. Driven by gravitational potential energy, this led to an uneven distribution of the slope saturation zone. Attenuation of the mechanical strength of saturated soil reduced the slope stability, and sliding failure consequently occurred in the shallow surface saturation zone. In regard to excavated slopes, anti-sliding force reduction and free face formation enhanced the slope’s susceptibility to sliding failure under the influence of heavy rainfall, which is also the reason for the large-scale distribution of landslides along the X158 county road.

During July 19–21, 2021, Henan Province in China experienced a historically rare heavy rainfall event, with the maximum hourly rainfall amount appearing in Zhengzhou City, the capital of Henan Province, on 20 July (hereafter “7.20” HRE). In this study, the “7.20” HRE is analyzed based on the observations of 215 ground‐based GNSS stations and 118 national meteorological stations in Henan Province, and ERA5 reanalysis data. By comparing the surface precipitation intensity, water vapor, and atmospheric energy conditions across temporal and spatial scales, it is shown that the area with heavy rainfall near Zhengzhou did not exhibit extreme atmospheric energy values or vertical environmental instability. The environmental conditions in the southeast of Zhengzhou were more conducive to the occurrence and development of precipitation, but there was no obvious precipitation on the ground. The analysis of water vapor consumption rate (Vc) and precipitation flux (F) reveals that a large amount of water vapor was consumed in the southeast of Zhengzhou, resulting in the formation of substantial precipitation above the 600 hPa level. The precipitation was carried to Zhengzhou by the southeast wind, leading to the precipitation content over Zhengzhou and its nearby areas increasing rapidly as altitude decreased from 600 hPa to 1000 hPa. The overlay of precipitation provided by both dynamic transport from the southeast and cloud microphysical production over Zhengzhou was the main cause of the “7.20” HRE under the background of an atypical weak environmental field. In this study, a record‐breaking rainfall is analyzed based on the observation data and reanalysis data. The overlay of precipitation provided by both dynamic delivery from the southeast and cloud microphysical production over Zhengzhou was the main cause of the rainfall under the background of an atypical weak environmental field.