Persistent Precipitation Research Articles

Enlarging Difference Between Persistent Extreme Precipitation and Fixed‐Time Extremes in China

Abstract Extreme precipitation occurs persistently in nature and has caused a series of social, environmental, and ecological problems. However, most analyses of extreme precipitation are conducted at fixed‐time intervals, which may lead to misconceptions of the spatial‐temporal changes and causes, hindering scientific understanding and engineering prevention. In this study, we quantified the differences between persistent and fixed‐time extreme precipitation in China using historical observations from over 2,400 meteorological stations between 1960 and 2019 and future simulations from 10 global climate models during 2021–2100 under three scenarios (SSP126, SSP370, and SSP585). The national average annual‐maximum persistent precipitation (Rx1event) was 2.5 times greater than extremes for fixed‐time precipitation (Rx1day) historically, and 2.8 times higher in the future period. Although Rx1day increased faster than Rx1event in the historical period, it is projected to grow more slowly than Rx1event in all three future scenarios. Both Rx1day and Rx1event exhibit Hook structures responding to temperature. The Peak temperatures of Hook structures are expected to rise by 2–6°C with projected future climate change, causing the precipitation‐temperature response curve to shift to the high‐value direction, thereby increasing the magnitude of Rx1day by 5%–12% and Rx1event by 22%–29%. Our research enlightens disaster preventers and researchers to pay more attention to persistent extreme precipitation, especially in areas where it differs significantly from the fixed‐time scale.

Differences in the effects of 10-30-day oscillations on persistent precipitation across diverse Meiyu climate regions in China

Abstract The Meiyu season is marked by persistent precipitation, often leading to floods and landslides. Due to significant spatial variability, the China National Climate Center has defined three Meiyu monitoring zones: south of Yangtze River (SYR), Yangtze River valley (YRV), and Yangtze-Huaihe valley (YHV). Analyzing the differences of persistent precipitation event (PPE) across these regions is crucial for accurately understanding precipitation patterns and effectively predicting natural disasters. This study employs ground-based observations, ERA5 reanalysis data and RegCM5.0 to examine PPE characteristics and its physical processes concerning sub-seasonal oscillation in these three Meiyu climate regions, aiming to reveal how oscillation affects the PPEs. The observations indicate PPEs last about 4-5 days on average in all three regions, while the dominant sub-seasonal scales demonstrate a period of 10-30 days. However, notable disparities exist in the fundamental mechanisms influencing PPEs, and the trajectories of oscillations also differ. In SYR, PPEs are mainly influenced by mid-high latitude oscillations, whereas in YRV and YHV, they are influenced by both mid-high and low latitudes. Numerical simulation, consistent with observed results, which further elucidates the relative significance of 10-30-day oscillations at different latitudes on PPEs across three regions. The PPEs of SYR are primarily influenced by mid-high latitude oscillations. The response of PPE in YRV to 10-30-day oscillations is consistent across mid-high and low latitudes, with a slightly stronger effect at mid-high latitudes, while in YHV, low-latitude oscillations are the primary influence. The aforementioned results can provide a fundamental basis of precursor signals for predicting Meiyu precipitation.

Extremely persistent precipitation events during April–June 2022 in the southern China: projected changes at different global warming levels and associated physical processes

Extremely persistent precipitation events during April–June 2022 in the southern China: projected changes at different global warming levels and associated physical processes

Rainbelt Properties of Persistent Heavy Precipitation over the Yangtze River Basin and Associated Three-Dimensional Circulations

Abstract In this study, we objectively identified rain belts of persistent precipitation processes over the Yangtze River basin during 1961–2021 based on an improved rotating calipers algorithm. Considering the accumulated precipitation volume as the flood-inducing indicator, persistent heavy precipitation events were identified and categorized into three types—along, north, and south of the Yangtze River—by applying k-means clustering for spatial similarity. Results showed that events along and in the south of Yangtze are more persistent and more flood inducing than events in the north of Yangtze. Composite analysis revealed the relevant three-dimensional stable circulation patterns and indicated that the location of their rain belts is determined by circulation configurations. For events along the Yangtze, an eastward-propagating wave train facilitates a single-blocking high and deepens the East Asian trough. A southeastward-positioned South Asian high (SAH) and intensified westerly jet support a strong divergence in the Yangtze River basin at 200 hPa. The western Pacific subtropical high (WPSH) stretches southwestward with a strong low-level jet, inducing warm and humid air to converge with cold air along the Yangtze. For events in the south of the Yangtze, a relatively southeastward wave train maintains under double-blocking highs. The northeast sector of the SAH, the westerly jet, WPSH, and low-level jet are located more to the south. Last, events in the north of the Yangtze are associated with the development of a blocking high and a dominant belt of low pressure to the south. The unfavorable circulation pattern inhibits cold air invasion, resulting in relatively weaker precipitation with shorter duration. Significance Statement Considering the location, spatial coverage, and intensity of persistent precipitation processes in the Yangtze River basin, this study objectively classified rain belts of persistent heavy precipitation (PHP) events, investigated the corresponding stable circulation patterns, and constructed three-dimensional conceptual models for three types of PHP events. This study may help to better understand the formation mechanisms of PHP events and serve as a reference for improving the forecasting of such events operationally.

The diurnal variation characteristics of warm season precipitation in Chongqing from 2011 to 2021

Hourly precipitation data during the warm season (May to September) of 2011–2021 in Chongqing were used to analyze the diurnal variation characteristics. Results reveal a pronounced “night rain” phenomenon, with primary peaks from midnight to early morning and secondary peaks in late afternoon. These peaks and early-night troughs are generally consistent across annual and monthly changes, oscillating every 2–3 years, alternating between trough and peak years. Peak periods are May to June and September, while July to August are trough periods. Precipitation amount (PA), frequency (PF), and intensity (PI) peak phase generally delayed from west to east and south to north. Mountainous topography tends to moderate fluctuations in diurnal precipitation. Central and western regions mainly affected by synoptic systems, PA is mainly contributed by PF, and eastern regions influenced by terrain, PA is mainly contributed by PI. East-west propagation of precipitation is more prominent than north-south, with abnormally high in western, south of northeastern and Daba mountain area. Short-duration precipitation events occur approximately twice as frequently as persistent ones, yet persistent precipitation events dominate warm-season rainfall contributions, accounting for over 80% in most regions. Early-morning persistent rainfall prevails in western Chongqing, while afternoon short-duration precipitation events dominate both south of northeastern Chongqing and the Daba Mountains, corresponding precisely to the primary and secondary peaks of the diurnal variation curve. All persistent events exhibit strong asymmetry: the time from onset to peak rainfall is significantly shorter than the duration from peak to cessation. Mountainous terrain delays the peak timing of persistent rainfall, prolonging the pre-peak phase.

Local climate zone framework: seasonal dynamics of surface urban heat island and its influencing factors in three Chinese urban agglomerations

ABSTRACT The Local Climate Zone (LCZ) framework offers a standardized and widely applicable approach that facilitates detailed investigations of Surface Urban Heat Islands (SUHI) within cities. Based on the LCZ framework, this study selected three urban agglomerations with distinct climate backgrounds: the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), the Liaozhongnan urban agglomeration (LZS), and the Ningxia Yellow River urban agglomeration (NXY). Using a geographically weighted regression model, Moderate Resolution Imaging Spectroradiometer land surface temperature data were downscaled to a resolution of 100 meters. The study used the extreme gradient boosting model and the Shapley Additive Explanations (SHAP) method to analyze the single-factor effects and their interaction effects influencing seasonal SUHI. The results revealed that significant seasonal variations in SUHI exist within the same LCZ type in the three urban agglomerations with different climate backgrounds. In the GBA urban agglomeration, persistent precipitation effectively mitigates the SUHI effect within built-up LCZ types (LCZ 1 to LCZ 10) during summer, resulting in average SUHI intensities that are 0.341 K and 0.132 K lower than in autumn and winter, respectively. Overall, natural factors play a dominant role in influencing SUHI in all four seasons, with latitude and distance from the sea factors being the most crucial factors in all seasons and all three urban agglomerations. However, water bodies smaller than 0.004 km2 fail to provide sufficient cooling effects to significantly alleviate SUHI. Moreover, apart from the proportion of water bodies, the absolute SHAP values of interactions among natural factors are significantly higher than those among human factors or between human and natural factors. This study enhances the refined understanding of the seasonal variations in SUHI within different LCZ types and their crucial influencing factors.

More persistent precipitation regimes induce soil degradation

More persistent precipitation regimes induce soil degradation

The Month-to-Year Precursory and Synchronous Inherent Connections between Global Oceanic Modes and Extreme Precipitation over China

The multiscale variability in summer extreme persistent precipitation (SEPP) in China from 1961 to 2020 was investigated via three extreme precipitation indices: consecutive wet days, total precipitation amount, and daily precipitation intensity. The relationships between precursory and concurrent global oceanic modes and SEPP were identified via a generalized linear model (GLM). The influence of oceanic modes on SEPP was finally investigated via numerical simulations. The results revealed that the climatological SEPP (⩾14 days) mainly appears across the Tibetan Plateau, Yunnan–Guizhou Plateau, and South China coast. The first EOF mode for all three indices showed strong signals over the Yangtze River. Further analysis via the GLM suggested that the positive phases of the tropical North Atlantic (TNA) in autumn, ENSO in winter, the Indian Ocean Basin (IOB) in spring, and the western North Pacific (WNP) in summer emerged as the most effective precursory factors of SEPP, which could serve as preceding signals for future predictions, contributing 30.2%, 36.4%, 38.0%, and 55.6%, respectively, to the GLM. Sensitivity experiments revealed that SST forcing in all four seasons contributes to SEPP over China, whereas the winter and summer SST warming over the Pacific and Indian Ocean (IO) contributes the most. Diagnosis of the hydrological cycle suggested that water vapor advection predominantly originates from the western Pacific and IO in summer, driven by the strengthened subtropical high and Asian summer monsoon (ASM). The enhanced vertical water vapor transport is attributed to stronger upward motion across all four seasons. These findings are helpful for better understanding SEPP variabilities and their prediction under SST warming.

Turning Up the Heat: More Persistent Precipitation Regimes Weaken the Micro-Climate Buffering Capacity of Forage Grasses During a Hot Summer.

Developing climate-proof forage grasslands does not only require developing plant communities that are soil drought resistant, but also adept at buffering elevated atmospheric temperatures to minimize heat stress for plant and soil. Previous studies indicate that the emerging trend towards rainfall regimes with longer dry and wet spells negatively affects forage grass performance (i.e., greater physiological plant stress and yield loss) in Western Europe. We conducted a 120-day open-air experiment testing whether a hot summer (+3°C for the first 60 days) exacerbates the negative effects of increased persistence in precipitation regimes (PR) (3 vs. 30 days consecutive wet/dry) on the performance of four distinct forage varieties (Dactylis glomerata, Festuca arundinacea, Lolium perenne (tetraploid) and Lolium perenne (diploid)) across two soils differing in management history (permanent vs. temporary grasslands). Our results indicate that climate warming indeed worsens negative effects of more persistent PR on forage grass productivity and physiological plant stress by inducing more extreme soil drought and elevated micro-climatic temperatures, but permanent grassland soils with elevated organic carbon can buffer yields. Moreover, higher yielding varieties are more proficient at buffering soil surface and canopy temperatures and maintaining plant greenness and stomatal opening under water shortage and elevated temperatures (Dactylis and Festuca) were impacted less than those which could not (both Lolium cultivars). These results indicate that not only differences in resource-extraction traits but also the ability of a species to buffer its surrounding microclimatic conditions shapes its response to future climate change. Given the indirect positive effects such temperature-buffering traits may have on soil functioning (e.g., reduced soil respiration during heat waves limiting carbon loss), we argue that managers should also incorporate such traits when developing climate-proof forage grasslands.

Influence on the Ecological Environment of the Groundwater Level Changes Based on Deep Learning

In recent years, frequent floods caused by heavy rainfall and persistent precipitation have greatly affected changes in groundwater levels. This has not only caused huge economic losses and human casualties, but also had a significant impact on the ecological environment. The aim of this study is to explore the effectiveness of the new method based on Long Short-Term Memory networks (LSTM) and its optimization model in groundwater level prediction compared with the traditional method, to evaluate the prediction accuracy of the different models, and to identify the main factors affecting the changes in groundwater level. Taking Chaoyang City in Liaoning Province as an example, four assessment indicators, R2, MAE, RMSE, and MAPE, were used. The results of this study show that the optimized LSTM model outperforms both the traditional method and the underlying LSTM model in all assessment metrics, with the GWO-LSTM model performing the best. It was also found that high water-table anomalies are mainly caused by heavy rainfall or heavy storms. Changes in the water table can negatively affect the ecological environment such as vegetation growth, soil salinization, and geological hazards. The accurate prediction of groundwater levels is of significant scientific importance for the development of sustainable cities and communities, as well as the good health and well-being of human beings.

Differentiated influences of anomalous subtropical high on extreme persistent precipitation and heatwave events in the Yangtze River Valley

Abstract In the summers of 2020 and 2022, the Western Pacific Subtropical High (WPSH) intensified extremely and extended westward. However, in summer 2020, the Yangtze River Valley (YRV) witnessed record‐breaking floods, while in 2022, an unprecedented and prolonged heatwave occurred. Distinctly, these two extreme events were caused by different effects of the WPSH: one is enhancement of the transportation of water vapor and the other is adiabatic heating caused by the descending airflow. In June–July 2020, the stable extension of the WPSH ridge line to South China directed a southwesterly airflow along its northwest flank, leading to sustained precipitation in the YRV. Additionally, the midlatitude circulation pattern featured two troughs and two ridges. Such a circulation configuration, combined with the strong and westward WPSH, enabled the continuous southward intrusion of cold air and northward transport of warm moist air, converging over the YRV, and thus influenced extreme persistent precipitation. In contrast, the WPSH covered the YRV almost entirely during summer 2022. Under this influence, the clear‐sky condition and descending airflow through adiabatic warming directly resulted in the heatwave. In addition, local land–atmosphere feedback was crucial in its development and persistence. The soil moisture deficit induced by high temperatures increased the sensible heat flux between the soil and atmosphere upward, further enhanced the surface air temperature and strengthened the heat dry condition.

Weakened Subtropical Westerlies and Their Deflection by the Tibetan Plateau Contribute to Drying Southeastern China in Early Spring

Abstract An obvious long‐term drying trend in recent early springs (February–March–April) is observed over southeastern China (SEC). Here, we attribute this drying to the weakened subtropical westerlies and deflected by the Tibetan Plateau (TP). Climatologically, the low‐level southwesterlies at the southeastern margin of the TP, a branch of the upstream subtropical westerly jet deflected by the TP terrain, bring water vapor to SEC and the southerlies move upward over SEC mainly through isentropic gliding mechanism, inducing persistent precipitation in early spring. However, the subtropical westerlies weakened significantly in recent decades due potentially to the decreased Eurasian snow cover. Consequently, an easterly trend appears along the southern margin of the TP with anomalous northeasterlies over SEC. These northeasterlies suppress both moisture supply and upward motions over SEC, and reduce regional early spring precipitation. Our results highlight the interaction between the TP terrain and the weakened subtropical westerlies that leads to the drying SEC.

Spatiotemporal patterns in persistent precipitation extremes of the Chinese mainland (1961–2022) and association with the dynamic factors

Spatiotemporal patterns in persistent precipitation extremes of the Chinese mainland (1961–2022) and association with the dynamic factors

The impact of monsoon on the landfalling tropical cyclone persistent precipitation in South China

Interactions between landfalling tropical cyclones (TCs) and monsoons in South China significantly influence precipitation duration, leading to severe disasters. Previous studies have primarily been individual cases, lacking systematic large-scale statistical analysis of the monsoon and landfalling tropical cyclone persistent precipitation (LTCPP) relationship. This study quantitatively investigated the relationship between monsoonal wind intensity before TCs landfall and post-landfall persistent precipitation induced by TCs in South China, employing the ERA5 reanalysis data and the best track data of 147 TCs from 1979 to 2018. The LTCPP was characterized by the frequency of persistent precipitation events during 0–72 h after TC landfall within a 500 km radius from the TC center. TCs were subdivided into weak and strong LTCPP groups based on the category-specific median of Frequency of 24 h Landfalling Tropical Cyclone Persistent Precipitation (FLTCPP24): 2705 h for TS, 6007 h for STS, and 6419 h for TY. A South China Tropical Cyclone Precipitation Monsoon Index (SCTCPM) was proposed to quantify monsoonal wind intensity derived from zonal winds at 850 hPa over two regions located in the Indian Ocean and Northwestern Pacific Ocean, within 5 d before TC landfall. The results reveal that SCTCPM < 9 m s−1 yields a 72% probability of weak LTCPP occurrence, which increases to 77% when SCTCPM < 6 m s−1. Conversely, SCTCPM > 18 m s−1 corresponds to an 80% probability of strong LTCPP. SCTCPM is an effective indicator for monsoonal wind that impacts LTCPP. Enhanced monsoonal winds, quantified by higher SCTCPM, result in post-landfall changes in horizontal wind speed, moisture transport, convective activity and upward motion, ultimately increasing LTCPP. This study deepens our understanding of the monsoon-TC relationship, emphasizing the crucial role of monsoonal wind in LTCPP in South China and offering valuable insights for disaster preparedness and risk mitigation.

The variation of microbiological characteristics in surface waters during persistent precipitation

The variation of microbiological characteristics in surface waters during persistent precipitation

Spatial spillovers of violent conflict amplify the impacts of climate variability on malaria risk in sub-Saharan Africa

Africa carries a disproportionately high share of the global malaria burden, accounting for 94% of malaria cases and deaths worldwide in 2019. It is also a politically unstable region and the most vulnerable continent to climate change in recent decades. Knowledge about the modifying impacts of violent conflict on climate-malaria relationships remains limited. Here, we quantify the associations between violent conflict, climate variability, and malaria risk in sub-Saharan Africa using health surveys from 128,326 individuals, historical climate data, and 17,429 recorded violent conflicts from 2006 to 2017. We observe that spatial spillovers of violent conflict (SSVCs) have spatially distant effects on malaria risk. Malaria risk induced by SSVCs within 50 to 100 km from the households gradually increases from 0.1% (not significant, P>0.05) to 6.5% (95% CI: 0 to 13.0%). SSVCs significantly promote malaria risk within the average 20.1 to 26.9 °C range. At the 12-mo mean temperature of 22.5 °C, conflict deaths have the largest impact on malaria risk, with an approximately 5.8% increase (95% CI: 1.0 to 11.0%). Additionally, a pronounced association between SSVCs and malaria risk exists in the regions with 9.2 wet days per month. The results reveal that SSVCs increase population exposure to harsh environments, amplifying the effect of warm temperature and persistent precipitation on malaria transmission. Violent conflict therefore poses a substantial barrier to mosquito control and malaria elimination efforts in sub-Saharan Africa. Our findings support effective targeting of treatment programs and vector control activities in conflict-affected regions with a high malaria risk.

Assimilation of the deep learning-corrected global forecast system fields into the regional model for improving medium-range persistent precipitation forecasts

Assimilation of the deep learning-corrected global forecast system fields into the regional model for improving medium-range persistent precipitation forecasts

Can permanent grassland soils with elevated organic carbon buffer negative effects of more persistent precipitation regimes on forage grass performance?

Can permanent grassland soils with elevated organic carbon buffer negative effects of more persistent precipitation regimes on forage grass performance?

Circulation patterns in the middle and upper troposphere and their relationships with summer precipitation in the Jianghuai River Basin

Abstract The upper and lower‐level circulations can be divided into four distinct modes based on ERA5 daily reanalysis data. The impact of these patterns on the summer persistent precipitation (SPP) in the Jianghuai River Basin (JRB) is investigated, with the ‘−SR (Silk Road)/+EAP (East Asia‐Pacific)’ mode identified as the most favourable for triggering SPP. The main manifestations are as follows: (1) From 1981 to 2020, 29.4% (30.7%) of extreme precipitation days (the frequencies of persistent extreme precipitation) are related to the ‘−SR/+EAP’ mode, indicating the importance of the ‘−SR/+EAP’ mode to the SPP in the JRB. (2) The ‘−SR’ pattern accelerates the westerly jet, leading to strong divergence over the JRB. Concurrently, the eastward movement of the South Asia High and westward shift of the Western Pacific subtropical high (WPSH) create conditions favourable for SPP in the JRB. (3) Abundant water vapour, facilitated by strong moisture convergence and upward motion, significantly contributes to SPP in the JRB.

Drought cascade lag time estimation across Africa based on remote sensing of hydrological cycle components

Drought cascade lag time estimation across Africa based on remote sensing of hydrological cycle components