Decreasing Spatial Precipitation Unevenness Over Mountainous Areas in Eastern China

Using a 30-year data (1983–2012) from 428 stations, we study summer precipitation differences between urban and rural areas in 5 Chinese climate regions: the Pearl River Delta (PRD), the Middle and Upper reaches of the Yangtze River (MUYR), the Yangtze River Delta (YRD), the North China Plain (NCP), and Northeast China (NEC). By analyzing heavy rain (HR) (24-h precipitation ≥ 100 mm) and light rain (LR) (0.1 mm ≤ 24 h precipitation ≤ 25 mm), we find that urbanization has had inconsistent effects on precipitation. Higher HR occurs over urban areas of the PRD and YRD than rural areas, and lower HR occurs over urban areas of the MUYR, NCP and NEC than rural areas. The urban LR is less than the rural LR in all climate regions. The correlation between precipitation and the convective available potential energy (CAPE) or humidity explains the regional differences in urbanization effects on HR. HR is greatly affected by the CAPE in the PRD and YRD, where the CAPE is high (> 600 J/kg at 14:00 LT), water vapor is abundant (> 45 kg/m2 at 14:00 LT), and the urban heat island increases the urban HR. However, HR is greatly affected by humidity in the MUYR, NCP, and NEC, where the CAPE and water vapor are less (≤ 500 J/kg and ≤ 40 kg/m2 at 14:00 LT) and the urban HR is mainly suppressed by the urban dry island. Our results indicate that urbanization promotes HR in wet climates but suppresses HR in dry climates during summer in central and eastern China.

This study investigates spatiotemporal characteristics of the diurnal cycle (DC) of rainfall over Sarawak in northwest Borneo Island, associated with large-scale intraseasonal disturbances represented by the Madden–Julian oscillation (MJO). This is accomplished using a dense hourly rain gauge network and satellite data. The spatial pattern of the DC is classified into two major groups, coastal and interior regions, based on remarkable differences in rainfall peak times and amplitudes. Amplitudes of the DC and daily rainfall amount increase in active MJO phases at all sites, but the MJO has a stronger effect in the coastal region than the interior region. This modulation of rainfall by the MJO disturbance is largely attributed to rainfall frequency in the interior region, but to both frequency and intensity of rainfall in the coastal region. The low-level westerly wind anomaly enhances convergence, the land–sea breeze, and a midnight rainfall peak in the coastal region during the active MJO phase. Analysis of moisture flux divergence and moist static instability suggests the different dynamics of this modulation of the DC between coastal and interior regions.

Extreme precipitation events have increasingly happened at global and regional scales as the global climate has changed in recent decades. Accurate quantitative precipitation estimation (QPE) plays an important role in the warning of extreme precipitation events. With hourly rain gauge observations as a reference, this study compares the performance of Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) mission (IMERG) and Global Satellite Mapping of Precipitation (GSMaP) quantitative precipitation estimation (QPE) products over Northern China in 2021. The Probability of Detection (POD), Relative Bias (RB), Root-Mean-Squared Error (RMSE), and Fractional Standard Error (FSE) are among the assessment metrics, as are the Probability of Detection (POD), False Alarm Ratio (FAR), and Critical Success Index (CSI). We examined the spatial distribution of cumulative precipitation and the temporal distribution of hourly average precipitation for three severe precipitation occurrences using these assessment metrics. The IMERG products capture strong precipitation centers that are compatible with the gauge observations, especially in extreme precipitation events in areas with relatively flat terrain and low-altitude (≤1000 m). Both IMERG (National Aeronautics and Space Administration, NASA) and GSMaP (Japan Aerospace Exploration Agency, JAXA) satellite-based QPE products have precipitation peaks in advance (2–4 h) and generally underestimate (overestimate) precipitation when the actual precipitation is heavy (light). The satellite-based QPE products generally overestimate the heavy rainfall caused by non-typhoons and underestimate the heavy rainfall caused by typhoons. The GSMaP products may have the capacity to detect short-term rainstorm events. The accuracy of satellite-based QPE products may be influenced by precipitation intensity, sensors, terrain, and other variables. Therefore, in accordance with our recommendations, more ground rainfall stations should be used to collect actual precipitation data in regions with high levels of spatial heterogeneity and complex topography. The data programmers should strengthen the weights computation retrieval technique and fully utilize infrared (IR)-based data. Furthermore, this study is expected to give helpful feedback to the algorithm developers of IMERG and GSMaP products, as well as those researchers into the use of IMERG and GSMaP satellite-based QPE products in applications.

Hourly or 3-hourly precipitation data from Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) and Tropical Rainfall Measuring Mission (TRMM) 3B42 satellite products and rain gauge records are used to characterize East Asian summer monsoon rainfall, including spatial patterns in June–August (JJA) mean precipitation amount, frequency, and intensity, as well as the diurnal and semidiurnal cycles. The results show that the satellite products are comparable to rain gauge data in revealing the spatial patterns of JJA precipitation amount, frequency, and intensity, with pattern correlation coefficients for five subregions ranging from 0.66 to 0.94. The pattern correlation of rainfall amount is higher than that of frequency and intensity. Relative to PERSIANN, the TRMM product has a better resemblance with rain gauge observations in terms of both the pattern correlation and root-mean-square error. The satellite products overestimate rainfall frequency but underestimate its intensity. The diurnal (24 h) harmonic dominates subdaily variations of precipitation over most of eastern China. A late-afternoon maximum over southeastern and northeastern China and a near-midnight maximum over the eastern periphery of the Tibetan Plateau are seen in the rain gauge data. The diurnal phases of precipitation frequency and intensity are similar to those of rainfall amount in most regions, except for the middle Yangtze River valley. Both frequency and intensity contribute to the diurnal variation of rainfall amount over most of eastern China. The contribution of frequency to the diurnal cycle of rainfall amount is generally overestimated in both satellite products. Both satellite products capture well the nocturnal peak over the eastern periphery of the Tibetan Plateau and the late-afternoon peak in southern and northeastern China. Rain gauge data over the region between the Yangtze and Yellow Rivers show two peaks, with one in the early morning and the other later in the afternoon. The satellite products only capture the major late-afternoon peak.

The rapid development of urbanization has changed landscape patterns and biological habitats severely and, therefore, affected biodiversity. In this study, we selected 75 townships in Lishui, a mountainous area in eastern China, to conduct bird surveys for two years. We analyzed the birds' composition characters in townships with different levels of development in order to identify the effects on bird diversity of the urban development level, land cover pattern, landscape pattern, and other factors. In total, 296 bird species from 18 orders and 67 families were recorded between December 2019 and January 2021. A total of 166 species of birds belonged to Passeriformes (56.08%). The seventy-five townships were divided into three grades by K-means cluster analysis. The average number of bird species, richness index, and diversity index were higher in G-H (highest urban development level) compared with the other grades. At the township level, landscape diversity and landscape fragmentation were the key factors that positively affected the bird species number, diversity index, and richness index. Landscape diversity had a greater effect than landscape fragmentation, particularly on the Shannon-Weiner diversity index. The diversity and heterogeneity of urban landscapes could be improved by constructing biological habitats in future urban development planning to maintain and increase biodiversity. The results obtained in this study provide a theoretical basis for urban planning in mountainous areas, and a reference for policymakers to formulate biodiversity conservation strategies, construct reasonable biodiversity patterns, and solve practical biodiversity conservation problems.

Based on the hourly precipitation data of 34 meteorological stations in Chongqing in the summers (June to August) from 1996 to 2015, the spatial distribution and daily variation of precipitation amount (PA), precipitation intensity (PI), precipitation frequency (PF), and precipitation extremes in Chongqing are analyzed. The results show that, from the perspective of spatial distribution, the precipitation amount (PA) in Chongqing presents a distribution pattern of more around and less in the middle; the area with high precipitation intensity (PI) is mainly located in the northeast of Chongqing; the large value centers of precipitation frequency (PF) are located in the south and west of Chongqing and near Chengkou. On the spatial distribution of hourly precipitation, the precipitation in most areas of Chongqing is mainly concentrated at night [0200–0900 BT (1800–0100 UTC)], and the rain belt spreads from west to east with the passage of time. On the whole, interannual evolution characteristics of summer precipitation amount, precipitation intensity, and precipitation frequency in Chongqing are basically the same, showing a fluctuation characteristic without obvious trend, but there are some peaks and valleys. From the perspective of diurnal cycle, a larger peak of PA in Chongqing appears near 0300 BT (1900 UTC), another lower peak around 1200 BT (0400 UTC), a larger peak of PI around 0300 BT (1900 UTC), another smaller peak around 1500 BT (0700 UTC), and only one peak of PF around 0700 BT (2300 UTC). The extreme precipitation of different duration in summer in Chongqing is closely related to the topographic characteristics and weather system, the extreme centers of each diachronic precipitation are mainly located near Shapingba, Kaizhou, Youyang, and Shizhu, and the time evolution characteristics of the extreme precipitation are not obvious, but the trend of the extreme precipitation accumulated in 1 h, 3 h, 6 h, or 12 h is basically the same.

The southern slope of the Tianshan Mountains features complex terrain and an arid climate, yet paradoxically experiences frequent extreme precipitation events (EPEs), which pose significant challenges for weather forecasting. This study investigates an EPE that occurred from 20 to 21 August 2019 using multi-source data to examine circulation patterns, mesoscale characteristics, moisture dynamics, and energy-instability mechanisms. The results reveal distinct spatiotemporal variability in precipitation, prompting a two-stage analytical framework: stage 1 (western plains), dominated by localized convective cells, and stage 2 (northeastern mountains), characterized by orographically enhanced precipitation clusters. The event was associated with a “two ridges and one trough” circulation pattern at 500 hPa and a dual-core structure of the South Asian high at 200 hPa. Dynamic forcing stemmed from cyclonic convergence, vertical wind shear, low-level convergence lines, water vapor (WV) transport, and jet-induced upper-level divergence. A stronger vorticity, divergence, and vertical velocity in stage 1 resulted in more intense precipitation. The thermodynamic analysis showed enhanced low-level cold advection in the plains before the event. Sounding data revealed increases in precipitable water and convective available potential energy (CAPE) in both stages. WV tracing showed vertical differences in moisture sources: at 3000 m, ~70% originated from Central Asia via the Caspian and Black Seas; at 5000 m, source and path differences emerged between stages. In stage 1, specific humidity along each vapor track was higher than in stage 2 during the EPE, with a 12 h pre-event enhancement. Both stages featured rapid convective cloud growth, with decreases in total black body temperature (TBB) associated with precipitation intensification. During stage 1, the EPE center aligned with a large TBB gradient at the edge of a cold cloud zone, where vigorous convection occurred. In contrast to typical northern events, which are linked to colder cloud tops and vigorous convection, the afternoon EPE in stage 2 formed near cloud edges with lesser negative TBB values. These findings advance the understanding of multi-scale extreme precipitation mechanisms in arid mountains, aiding improved forecasting in complex terrains.

Recent studies on changes in precipitation intensity encompassing North America have found evidence for an increase in the relative amount of precipitation contributed by heavy and extreme rainfall events in the last 80 years. Within this context, the purpose of this paper is to verify whether such a signal can also be detected in northern Italy, where daily precipitation data are available from the beginning of the 19th century. The analysis is performed by applying the non-parametric Mann–Kendall test to mean anomaly series obtained through averaging the anomalies of some precipitation intensity statistics over five stations: Genoa (1833–1998), Milan (1858–1998), Mantova (1868–1997), Bologna (1879–1998) and Ferrara (1879–1996). It provides evidence that in northern Italy, the number of rainy days has a stronger and more significant negative trend than the corresponding precipitation amount, both on a yearly basis and in all of the seasons. As a consequence, precipitation intensity has a positive trend. The increase in precipitation intensity causes a significant positive trend in the proportion of total precipitation contributed by heavy precipitation events (i.e. daily precipitation >25 mm and daily precipitation >50 mm). The trend is mainly caused by the last 60–80 years, and is particularly evident in the periods of 1930–1945 and 1975–1995. The increase in precipitation intensity is connected to a modification of the distribution of daily precipitation values in a year, with trends that grow from the lower to the upper percentiles, and up to 4 mm/100 years for the 95th percentile. Copyright © 2000 Royal Meteorological Society

As the atmosphere warms, precipitation events are becoming less frequent but more intense. A three-year experiment in Kruger National Park, South Africa, found that fewer, more intense precipitation events encouraged woody plant encroachment. To test whether or not these treatment responses persisted over time, here, we report results from all five years of that experiment. Grass growth, woody plant growth, total fine root number and area and hydrologic tracer uptake by grasses and woody plants were measured in six treated plots (8 m by 8 m) and six control plots. Treatment effects on soil moisture were measured continuously in one treated and one control plot. During the fourth year, increased precipitation intensity treatments continued to decrease water flux in surface soils (0–10 cm), increase water flux in deeper soils (20+ cm), decrease grass growth and increase woody plant growth. Greater root numbers at 20–40 cm and greater woody plant uptake of a hydrological tracer from 45–60 cm suggested that woody plants increased growth by increasing root number and activity (but not root area) in deeper soils. During the fifth year, natural precipitation events were large and intense so treatments had little effect on precipitation intensity or plant available water. Consistent with this effective treatment removal, there was no difference in grass or woody growth rates between control and treated plots, although woody plant biomass remained higher in treated than control plots due to treatment effects in the previous four years. Across the five years of this experiment, we found that 1) small increases in precipitation intensity can result in large increases in deep (20–130 cm) soil water availability, 2) plant growth responses to precipitation intensity are rapid and disappear quickly, and 3) because woody plants accumulate biomass, occasional increases in precipitation intensity can result in long-term increases in woody plant biomass (i.e., shrub encroachment). While results are likely to be site-specific, they provide experimental evidence of large ecohydrological responses to small changes in precipitation intensity.

Background: Emergence and the rising prevalence of extended-spectrum β-lactamases (ESBLs) producing multidrug-resistant Klebsiella spp. is a global concern. Methods: 391 samples were collected from environmental and people in an intensive vegetable cultivation area in eastern China in June 2019. ESBLs-producing Klebsiella spp. were obtained by PCR and strain identification. The resistance genotype and phenotype of the strain were determined by PCR and drug susceptibility test. The number and size of plasmids were determined by pulsed-field gel electrophoresis assays of plasmids. The plasmid of blaCTX-M was determined by DNA imprinting hybridization, and the transferability of plasmid was understood by plasmid conjugation experiment. Whole-genome sequencing analysis (WGS) was used to obtain other antimicrobial resistance genes, virulence factors, mobile elements, and genetic environment. Results: Seventeen ESBL-producing Klebsiella spp. were multi-drug resistant. Sixteen ESBLs-producing Klebsiella spp. carried the blaCTX-M, and the size of the plasmid containing the blaCTX-M anged from ∼33.3 kb to ∼244.4 kb. Thirteen ESBLs-producing Klebsiella spp. carried the blaCTX-M were successfully transferred to the recipient bacterium through plasmid mediation. Single nucleotide polymorphism analysis showed clonal transmission between river water (J4-J8) and river sediment (J9), in river water (J3) and human feces (J12). WGS showed that all blaCTX-M were associated with the mobile element Tn3 and/or IS1380 family. All strains carried virulence factors related to adhesion, colonization, and pathogenicity. Conclusion: This study reminds us that antibiotic-resistant bacteria (ARB) from vegetable cultivation environments can spread to human. It is vital to enhance surveillance of the vegetable cultivation area and high vigilance for the risk of ARB movement from the vegetable plantation environment to humans.

Perfluorinated compounds in soil, surface water, and groundwater from rural areas in eastern China

Fusarium species are common fungal contaminants of maize and a number of them can produce mycotoxin fumonisins. China is one of the largest maize producers in the world. This study investigated the contamination of maize samples from three areas in eastern China by Fusarium and fumonisin-producing fungi as well as their fumonisin-producing potential. A total of 22 Fusarium strains were isolated, 19 of which were able to produce fumonisin. Among the 19 strains, 16 belonged to F. verticillioides, two to F. subglutinans and one to F. proliferatum. The majority (17/19) of the fumonisin-forming strains were high FB(1) producers, which is a potential health risk for the population in these areas. Fusarium contamination in samples from the mideastern area was the most serious (11 Fusarium strains, with nine producing fumonisin, isolated from 24 samples), followed by the northeastern area (nine Fusarium strains, with all nine producing fumonisin, isolated from 21 samples) and the southeastern area (two Fusarium strains, with one producing fumonisin, isolated from 19 samples). Although the overall levels of FBs and contamination by fumonisin-producing fungi in corn samples were not serious, the contaminating Fusarium strains possessed fairly strong toxicogenic ability and potential risk for food safety.

Atmospheric water vapour content is a key variable that controls the development of deep convective storms and rainfall extremes over the central Andes. Direct measurements of water vapour are challenging; however, recent developments in microwave processing allow the use of phase delays from L-band radar to measure the water vapour content throughout the atmosphere: Global Navigation Satellite System (GNSS)-based integrated water vapour (IWV) monitoring shows promising results to measure vertically integrated water vapour at high temporal resolutions. Previous works also identified convective available potential energy (CAPE) as a key climatic variable for the formation of deep convective storms and rainfall in the central Andes. Our analysis relies on GNSS data from the Argentine Continuous Satellite Monitoring Network, Red Argentina de Monitoreo Satelital Continuo (RAMSAC) network from 1999 to 2013. CAPE is derived from version 2.0 of the ECMWF’s (European Centre for Medium-Range Weather Forecasts) Re-Analysis (ERA-interim) and rainfall from the TRMM (Tropical Rainfall Measuring Mission) product. In this study, we first analyse the rainfall characteristics of two GNSS-IWV stations by comparing their complementary cumulative distribution function (CCDF). Second, we separately derive the relation between rainfall vs. CAPE and GNSS-IWV. Based on our distribution fitting analysis, we observe an exponential relation of rainfall to GNSS-IWV. In contrast, we report a power-law relationship between the daily mean value of rainfall and CAPE at the GNSS-IWV station locations in the eastern central Andes that is close to the theoretical relationship based on parcel theory. Third, we generate a joint regression model through a multivariable regression analysis using CAPE and GNSS-IWV to explain the contribution of both variables in the presence of each other to extreme rainfall during the austral summer season. We found that rainfall can be characterised with a higher statistical significance for higher rainfall quantiles, e.g., the 0.9 quantile based on goodness-of-fit criterion for quantile regression. We observed different contributions of CAPE and GNSS-IWV to rainfall for each station for the 0.9 quantile. Fourth, we identify the temporal relation between extreme rainfall (the 90th, 95th, and 99th percentiles) and both GNSS-IWV and CAPE at 6 h time steps. We observed an increase before the rainfall event and at the time of peak rainfall—both for GNSS-integrated water vapour and CAPE. We show higher values of CAPE and GNSS-IWV for higher rainfall percentiles (99th and 95th percentiles) compared to the 90th percentile at a 6-h temporal scale. Based on our correlation analyses and the dynamics of the time series, we show that both GNSS-IWV and CAPE had comparable magnitudes, and we argue to consider both climatic variables when investigating their effect on rainfall extremes.

In this thesis the sensitivity of a modelled tropical cyclone to sea surface temperature (SST) and Convective Available Potential Energy (CAPE) is investigated. In Chapter 1 previous studies on this topic are discussed and an overview is given of our current knowledge of the effects of latent and sensible heat fluxes from the ocean on tropical cylcones. In Chapter 2 the experiments that make up this study are descibed in some detail. They have been carried out to compare the importance of SST to that of CAPE on tropical cyclone intensity. In order to achieve this, three experiments were designed, a control experiment, an experiment with increased SST and finally an experiment with increased SST, but CAPE equal to that of the control run. The simulations were carried out with the CSIRO Division of Atmospheric Research Limited area model using the Betts Miller cumulus parameterisation scheme. Both the model and this scheme are described in Chapter 3. The tropical cyclone used in this study is Tropical Cyclone Connie, which occurred in the Timor Sea from 15 to 23 January. The track and central pressure of the control simulation are compared with the observations and other simulations of the same storm. The simulation in this study compares very well to the other simulations and given its coarse resolution of 76 x 76 km, produces an acceptable simulation of cyclone Connie, given its coarse resolution of 76 x 76 km. When comparing the three experiments to each other it is found that the storm with increased SST and increased CAPE produces the strongest tropical cyclone. Finally, the sensitivity of the Betts Miller scheme to a model parameter called the relaxation time is discussed briefly. The relaxation time simulates the lag between the large scale forcing and the convective response. It was found that a decrease in relaxation time leads to faster convective adjustment and deeper tropical cyclones. It is concluded in Chapter 5 that SST is not as obviously tied to tropical cyclone intensity as was previously thought. Evaporation from the surface was found to play a very important role, but the importance of CAPE is still unclear. For that reason it will be necessary to perform more simulations with other convective schemes that respond directly to CAPE and are independent of external parameters that have not been verified against observations.

Lightning is a naturally occurring phenomenon with significant socioeconomic and environmental impacts, underlining the need for the application of advanced methods to predict it. This study aims to evaluate the performance of the Weather Research and Forecasting (WRF) model in the prediction of the lightning potential index (LPI), the lightning threat index (LTI), and the product of convective available potential energy (CAPE) and precipitation (CAPE × P). Based on the intensity of convection and the number of lightning flashes, we simulated seven thundercloud events that occurred in Tehran between 2008 and 2013. The simulated LPI, LTI, and CAPE × P values are compared both qualitatively and quantitatively against ground‐based lighting data obtained from the world wide lightning location network (WWLLN). LPI, LTI, and CAPE × P predict the location of lightning with relatively good accuracy, although LPI outperforms LTI and CAPE × P. We also compared the simulated area‐averaged LPI, LTI, and CAPE × P against the number of lightning flashes from the WWLLN data, based on which LPI shows a better performance. Overall, LPI can be used as an effective index for the prediction of lightning. As LPI is based on cloud microphysics and LTI and CAPE × P are thermodynamic‐based methods, a better performance of LPI implies that a method based on the microphysical approach can better predict lightning. The performance of LPI, LTI, and CAPE × P is also sensitive to the horizontal resolution of model simulations, with a considerable improvement in simulations with higher horizontal resolutions.