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Urbanization induces rapid plant environmental modifications, leading to alterations in plant diversity distribution patterns and plant homogenization. However, how plant diversity is distributed along urbanization gradients in regional urban agglomerations and its relationship with environmental factors are not well defined. In three nearby Henan Province Chinese cities—Zhengzhou, Kaifeng, and Zhongmu—along an urbanization gradient, the distribution pattern of plant diversity was quantified. Both native and non-native plants found in urban green spaces were taken into consideration. A total of 176 plant quadrats were selected and separated into three urbanization gradient types using space-constrained hierarchical clustering: urban core, urban suburb, and urban outskirt. Polynomial fitting was used to characterize the spatial distribution patterns of plants along the urbanization gradient, and Pearson correlation and the Mantel test were employed to examine the effects of environmental factors, including longitude, latitude, altitude, distance from the urban center, temperature, and illumination, on plant diversity. A total of 313 vascular plant species, comprising 137 woody species and 176 herbaceous species, were examined. Along the three urbanization gradients, remarkable variations in plant diversity for woody and herbaceous species were observed. The spatial patterns of plant diversity were consistent across cities, whereas woody plants and herbaceous plants displayed the opposite behavior. Distance to the city center and temperature were the most substantial environmental effect factors for the diversity of woody plants, whereas light factors had a major impact on herbaceous plants. These findings show different life-type plants are affected differently by urbanization, and they offer managers and planners a recommendation for increasing urban plant diversity by executing various interventions throughout the urban gradient. [ABSTRACT FROM AUTHOR]

In this study, three typical and most extreme precipitation events in the history of North China are analyzed and compared in terms of accumulated precipitation and synoptical circulation using surface station observations of China and the ERA5 dataset. The three events happened in August 1963 ("63.8" event, hereafter), August 1975 ("75.8" event), and July 2021 ("21.7" event), respectively, mainly in Hebei and Henan Provinces of North China. The results show that the maximum daily and 4-day accumulated precipitation of all three events exceeded 500 mm and 800 mm, with many stations' daily precipitation ranking Top 1. The "63.8" event persisted for the longest time, affected the largest area, and rained the most in 7 days (over 1000 mm). The "75.8" event was characterized by the most extreme daily precipitation and a concentrated area. All three events characterize a normal northward subtropical high that was located in North China and Northeast China. At 500 hPa, the area from South China to the South China Sea was dominated by a uniform pressure field. In the upper levels, there were troughs and divergence anomalies in all three events. In the low levels, there were anomalous low-level jets and the associated water vapor flux anomalies, which were located at different levels and came from different directions. Stable synoptical circulation and persistent jet and water vapor flux anomalies are the key factors in these extreme events. [ABSTRACT FROM AUTHOR]

During mid‐July 2021, an extreme heavy rainfall event (HRE) occurred in Henan Province (hereafter "21.7" HRE), with extreme hourly precipitation of 201.9 mm appearing at Zhengzhou station. Our preliminary analyses of the "21.7" HRE using the observations and ECMWF (European Centre for Medium‐Range Weather Forecasts) ERA5 reanalysis data, reached the following conclusions. Favorable configurations of various synoptic weather systems (e.g., strong upper‐level high‐pressure ridge, intense middle‐level low‐pressure trough) acted as crucial background conditions for the occurrence of the "21.7" HRE. A 21‐h long‐lived mesoscale convective vortex (MCV), mainly located in the middle and lower troposphere west of Zhengzhou city, was a key system that produced the extreme hourly rainfall of 201.9 mm·h−1. The MCV's development/sustainment was dominated by the vertical transport of cyclonic vorticity and tilting, as well as the horizontal import of cyclonic vorticity to the vortex's key region. In contrast, the divergence‐related vertical shrinking was the most detrimental factor. Lagrangian moisture transport analysis showed that moisture for the extreme heavy rainfall in Zhengzhou on July 20 mainly came from levels below 2200 m, driven by airflows on the peripheries of tropical cyclones IN‐FA and CEMPAKA. To enhance the understanding of "21.7" HRE, we suggest more in‐depth investigations in the future. [ABSTRACT FROM AUTHOR]

From July 19 to 21, 2021, Henan, a province in northern China (NC), was affected by severe flooding (referred to hereafter as "21·7") caused by a prolonged record-breaking extreme precipitation (EP) event. Understanding the extremes of the large-scale circulation pattern during "21·7" is essential for predicting EP events and preventing future disasters. In this study, daily atmospheric large-scale circulations over NC in the summers from 1979 to 2021 were investigated using the circulation classification method of an obliquely rotated principal component analysis in T-mode (PCT). The geopotential height at 500 hPa and 925 hPa were applied successively in classification. Among the nine summer circulation patterns at 500 hPa were found, the 3 days of "21·7" belonged to the Type 8 pattern, which had the second highest probability of EP days among all patterns. It was characterized by a southeasterly wind toward North China Plain driven by a dipole geopotential height field, with the West Pacific subtropical high (WPSH) extending far north to 30°N and low to the south near NC. Tropical cyclones (TCs) occurred on 72.5% of EP days, in which larger amounts of precipitation and a longer duration of EP days were found along the mountains in NC, as compared with other patterns. The distribution of EP events under this pattern was mainly influenced by the location of the low at 925 hPa in the dipole. The subtype 8−3 circulation, with lows in the east of Taiwan Island, included "21·7" and accounted for 1.6% of all summer days. Typhoon In-fa, together with the WPSH, gave rise to intense column integrated moisture flux convergence (IMFC) via the southeasterly wind to Henan, which occurred continuously during the 3 days of "21·7", resulting in the largest (second largest) mean IMFC among 3 consecutive EP days under type 8 (all types) during the past 43 summers in NC. Further analysis revealed that the large-scale dynamic process could not completely explain the record-breaking EP during "21·7", indicating possible contributions of other dynamic processed related to meso-scale convective storms. [ABSTRACT FROM AUTHOR]

To address the problems of traditional hydrological and hydraulic methods of estimating disasters in urban flood areas, such as small scale, poor timeliness, and difficulty of obtaining data, an inversion method of estimating urban flood disaster area based on remote sensing spectroscopy is proposed. In this paper, the spatial distribution of urban flood disasters is first inverted based on large-scale multidimensional remote sensing spectral orthography. Then, spatial coupling inversion of the remote sensing spectrum-urban economy-flood disaster is performed by simulating the urban economic density through single spectral remote sensing at night. Finally, losses at the urban flood area are estimated. The results show that (1) the heavy rain in Henan Province on 20 July is centered in Zhengzhou, and the spatial distribution of urban flood disasters accords with Zipf's law; (2) the estimated damage to the urban flood area in Henan Province is 132,256 billion yuan, and Zhengzhou has the most serious losses at 43,147 billion yuan, accounting for 32.6% of the entire province's losses. These results are consistent with the official data (accuracy ≥ 90%, R2 ≥ 0.95). This study can provide a new approach for accurately and efficiently estimating urban flood damage at a large scale. [ABSTRACT FROM AUTHOR]

Background and Objectives: The Yellow River is the sixth longest river in the world, and it is considered the mother river of China. Biodiversity conservation in the middle and lower reaches of the Yellow River is an urgent concern due to the impact of topography, sediment deposition, and human activities. Therefore, in this study, we aimed to investigate the diversity of plant communities in wetlands along the middle and lower reaches of the Yellow River from the perspectives of the natural environment and human disturbance. Materials and Methods: In this study, 830 plots were set up in seven nature reserves in the middle and lower reaches of the Yellow River to investigate wetland plant diversity. The distribution characteristics of plant diversity and the effects of environmental and human activities on plant diversity were analyzed. Results: (1) A total of 184 plant species belonging to 52 families and 135 genera were found in the seven nature reserves. Network analysis showed that the connectance index was 0.3018. (2) Betadisper analysis followed by ANOVA revealed differences in the community composition of the wetland plants (F = 21.123, p < 0.001) in the different nature reserves. (3) Analysis of variation partitioning indicated that the effects of pure environmental factors (elevation, precipitation, evaporation, and temperature) on the beta diversity of the wetland plants in the nature reserves was the strongest (15.45% and 17.08%, respectively), followed by the effects of pure human disturbance factors (population density, industrial output value, and agricultural output value) (15.13% and 16.71%, respectively). Conclusions: Variations occurred in the assemblage characteristics of the wetland plants in the different Yellow River wetland nature reserves. The wetland species exhibited strong associations with the reserves in the Yellow River wetland in Henan Province. Elevation, longitude, precipitation, and evaporation were important factors that affected the diversity of wetland plants in the middle and lower reaches of the Yellow River in China. The findings provide insights into plant biodiversity conservation in riverine wetlands. [ABSTRACT FROM AUTHOR]