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Urban flooding is a global water disaster resulting from the expansion of urban impervious surfaces and the strengthening of extreme precipitation events, especially in China. Nonetheless, few studies have focused on the spatial distributions of urban flooding characteristics and their variations in the context of climate change. In this study, eight critical metrics (i.e., maximum flooding volume, total overloaded manholes with different flooding volumes or durations, total flooding volume, mean and maximum flooding durations, maximum inundation area, and depth) are adopted to characterize the urban flood events. The impacts of climate change on these metrics are assessed for two periods, the 2030s (2020–2049) and 2070s (2060–2089), and compared with those in the baseline period (1976–2005). The Future Science City Park in Beijing, China, is selected as our study area. The results show that all four flood events are well simulated, with both efficiency coefficients and correlation coefficients being over 0.8. The number of overloaded manholes and the total flooding volume are projected to increase 19.3%–44.8% and 171%–716% under 20‐year rainfall events due to climate change in the two future periods. The spatial distribution of overloaded manholes with different increased flooding volumes is projected to expand to almost the whole area from the region with lowland and limited drainage capacity. Furthermore, the maximum inundation area and depth are projected to increase obviously. This study will be helpful for designing and improving the drainage system, controlling urban flooding, and adapting to climate change. Key Points: Flood events related to volume, duration, and inundation metrics are well simulated by integrated SWMM and NewFlood model with a GA algorithmFlooding volume and duration, inundation area, and depth are projected to increase in the futureThe overloaded manholes are projected to expand to the whole area except the region with low impact development applications [ABSTRACT FROM AUTHOR]

Highlights • Anomaly correlation exhibits persistent patterns at the global scale. • Anomaly correlation tends to be similarly high, or low, across initialization times. • Anomaly correlation tends to improve with initialization time. Abstract Global climate models (GCMs) produce informative seasonal forecasts of global precipitation months ahead of the occurrence for hydrological forecasting. Meanwhile, the skill of GCM forecasts varies by location and initialization time. In this paper, we investigate the anomaly correlation, which indicates the correspondence between forecasts and observations, for 10 sets of global precipitation forecasts in the North American Multi-Model Ensemble (NMME) project. We propose to use principal component analysis to characterize the variation of anomaly correlation. We identify the existence of spatial and temporal patterns at the global scale. The spatial pattern reveals that high (low) anomaly correlation at one initialization time coincides with high (low) anomaly correlation at other initialization times. In other words, for a grid cell, the anomaly correlation at different initialization times tends to be similarly high, or low. It is observed that some of the regions where grid cells are with overall high anomaly correlation tend to exhibit tele-connections with global climate drivers. On the other hand, the temporal pattern suggests that the anomaly correlation tends to improve with initialization time. This pattern is attributable to data assimilation that bases forecasts at a later initialization time on more global observations and simulations. Generally, the two patterns are effective and explain 50% to 70% of the variation of anomaly correlation for the 10 sets of NMME forecasts. The projections of anomaly correlation vectors onto the two patterns help illustrate where and when the NMME precipitation forecasts are skillful. [ABSTRACT FROM AUTHOR]

Observations show that metropolitan areas throughout China, which are experiencing rapid urbanization, may have enhanced extreme precipitation. However, the underlying urban‐induced mechanism is poorly understood, particularly for entire characteristics of extreme precipitation. Focusing on the Beijing metropolitan area, we investigate regional patterns of extreme precipitation characterized by magnitude, frequency, duration, and timing metrics according to daily observations from 1975 to 2015 at 20 weather stations. Urbanization effects are explored by physical metrics of urbanization, including area, complexity, fragmentation, and dominance deduced from five periods of land use maps. Results show that the magnitudes and frequencies of extreme precipitation have decreased over time, the consecutive precipitation days have been extended, and the Julian date of maximum precipitation has been delayed. Temporal trends at ~40% of weather stations are significant. According to precipitation metrics and geographical features, three representative regions are identified: the central urban region, the windward slope of topographic area, and the mountainous region. Compared with the metrics in mountainous region, the magnitudes of windward slope and central urban region are 24.3–60.6% and 5.9–47.3% greater, respectively; the frequencies are increased by 1.17 and 1.10 days, respectively; and the average date of maximum precipitation values are delayed by 7.0 and 4.0 days, respectively. The magnitudes and frequencies are enhanced by expansion of urban area, complexity, fragmentation, dominance, and heat islands. The durations are positive for urban area and dominance but negative for urban complexity, fragmentation, and heat islands. Furthermore, the effects in central urban region are more significant due to high urbanization rates. Key Points: Extreme precipitation metrics in central urban region and windward slope of topographic area are greater than those in mountainous regionMagnitude and frequency of extreme precipitation are enhanced by expansions of urban area, irregularity, patch, dominance, and heat islandsDuration of extreme precipitation is positive for the urban area and dominance but negative for irregularity, patch, and heat islands [ABSTRACT FROM AUTHOR]

The terrestrial water storage anomalies (TWSAs) in the Tarim River Basin (TRB) were investigated and the related factors of water variations in the mountain areas were analyzed based on Gravity Recovery and Climate Experiment (GRACE) data, in situ river discharge, and precipitation during the period of 2002–2015. The results showed that three obvious flood events in 2005, 2006, and 2010 resulted in significant water surplus, although TWSA decreased in the TRB during 2002–2015. However, while the significant water deficits in 2004, 2009, and 2011 were associated with obvious negative river discharge anomalies at the hydrological stations, the significant water deficits were not well consistent with the negative anomalies of precipitation. While the river discharge behaved with low correlations with TWSA, linear relationships between TWSA and climate indices were insignificant in the TRB from 2002 to 2015. The closest relationship was found between TWSA and Pacific Decadal Oscillation (PDO), with correlations of -0.56 and 0.58 during January 2010–December 2015 and during January 2006–December 2009, respectively. Meanwhile, the correlation coefficient between TWSA and El Niño-Southern Oscillation (ENSO) index in the period of April 2002–December 2005 was -0.25, which reached the significant level (p<0.05). [ABSTRACT FROM AUTHOR]

A 9-year manipulative experiment with nitrogen (N) and water addition, simulating increasing N deposition and changing precipitation regime, was conducted to investigate the bioavailability of trace elements, iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in soil, and their uptake by plants under the two environmental change factors in a semi-arid grassland of Inner Mongolia. We measured concentrations of trace elements in soil and in foliage of five common herbaceous species including 3 forbs and 2 grasses. In addition, bioaccumulation factors (BAF, the ratio of the chemical concentration in the organism and the chemical concentration in the growth substrate) and foliar Fe:Mn ratio in each plant was calculated. Our results showed that soil available Fe, Mn and Cu concentrations increased under N addition and were negatively correlated with both soil pH and cation exchange capacity. Water addition partly counteracted the positive effects of N addition on available trace element concentrations in the soil. Foliar Mn, Cu and Zn concentrations increased but Fe concentration decreased with N addition, resulting in foliar elemental imbalances among Fe and other selected trace elements. Water addition alleviated the effect of N addition. Forbs are more likely to suffer from Mn toxicity and Fe deficiency than grass species, indicating more sensitivity to changing elemental bioavailability in soil. Our results suggested that soil acidification due to N deposition may accelerate trace element cycling and lead to elemental imbalance in soil-plant systems of semi-arid grasslands and these impacts of N deposition on semi-arid grasslands were affected by water addition. These findings indicate an important role for soil trace elements in maintaining ecosystem functions associated with atmospheric N deposition and changing precipitation regimes in the future. [ABSTRACT FROM AUTHOR]

Droughts are extremely widespread natural disasters, which cause the most severe losses among natural disasters. The comprehensive drought risk in Northwest China (NWC) was evaluated based on the self-calibrating (SC) Palmer Drought Severity Index (PDSI) and copula method. The major conclusions are the following: (1) based on the rotated empirical orthogonal function (REOF), a significant consistency in the spatial distribution of the monthly averaged SC-PDSI was observed in NWC, especially in the subregions Inner Mongolia Plateau (IM), Hexi Corridor (HX), and Qiangtang Plateau (QT); (2) the largest frequency was obtained for slight drought and slight wet conditions, while extreme drought and extreme wet showed the lowest values; (3) with respect to the PDSI-th, the Clayton, Arch12, Arch12, Arch12, Arch12, and Frank played the major roles in the copula weight in the subregions IM, HX, Qinghai River Basin (QH), QT, North Xinjiang (NXJ), and South Xinjiang (SXJ), respectively. In terms of PDSI-pm, Arch12, Clayton, Gaussian, Arch12, Clayton, and Clayton dominated the weights of multi-copula functions in the regions IM, HX, QH, QT, NXJ, and SXJ, respectively; and (4) the frequency and probability of droughts in each area differed. The least drought events occurred in the QT and the most emerged in the HX for SC-PDSI. [ABSTRACT FROM AUTHOR]

Based on the precipitation data from 96 weather stations in Northwest China (NWC) during 1960–2013, the Continuous Wavelet Transform (CWT) and the Mann-Kendall (MK) test were applied to analyze the precipitation spatiotemporal variations at different time scales. The relationships between the original precipitation and different periodic components were investigated. The results indicated that the annual precipitation was significantly increasing (P < 0.01) at the rate of 0.55 mm/a in the NWC. In terms of seasonal precipitation, the summer original precipitation significantly increased (P < 0.05) in the Southern Altay Mountain Basin (SAMB), Qaidam Basin (QB), Qiang Tang Plateau Basin (QTPB), Turpan-Hami Basin (THB), Tarim Desert Basin (TDB), Northern Tianshan Mountain Basin (NTMB) and NWC. For the winter original precipitation, except the Inner Mongolia Inland Rivers Basin and Northern Kunlun Mountain Basin, the significant increases (P < 0.05) were detected in the other sub-basins. In terms of monthly precipitation, significant increases were detected in January in the SAMB, NTMB and NWC, and July in the QB, Headstreams of Tarim River Basin (HTRB) and N. Additionally, most of the increasing and decreasing trends began in the mid-1980s or mid-1990s. Moreover, the periodic components were not always similar to the original data with the significant trends. The dominant scale of the original data from the periodic components was different in spatiotemporal distribution. Meanwhile, the relationship between the precipitation and El Niño-Southern Oscillation (ENSO) was different from period to period and from time scale to time scale. This study will help to develop better management measures to account for climate change and the supply/demand of water. [ABSTRACT FROM AUTHOR]

Atmospheric nitrogen (N) deposition can result in soil acidification and reduce soil acid buffering capacity. However, it remains poorly understood how changes in precipitation regimes with elevated atmospheric N deposition affect soil acidification processes in a water-limited grassland. Here, we conducted a 9-year split-plot experiment with water addition as the main factor and N addition as the second factor. Results showed that soil acid buffering capacity significantly decreased with increased N inputs, mainly due to the decline of soil effective cation exchange capacity (ECEC) and exchangeable basic cations (especially Ca 2+ ), indicating an acceleration of soil acidification status in this steppes. Significant interactive N and water effects were detected on the soil acid buffering capacity. Water addition enhanced the soil ECEC and exchangeable base cations and thus alleviated the decrease of soil acid buffering capacity under N addition. Our findings suggested that precipitation can mitigate the impact of increased N deposition on soil acidification in semi-arid grasslands. This knowledge should be used to improve models predicting soil acidification processes in terrestrial ecosystems under changing environmental conditions. [ABSTRACT FROM AUTHOR]