Guangheng Ni

Tsinghua University | TH · Department of Hydraulic Engineering

Weather radars commonly suffer from the data-missing problem that limits their data quality and applications. Traditional methods for the completion of weather radar missing data, which are based on radar physics and statistics, have shown defects in various aspects. Several deep learning (DL) models have been designed and applied to weather radar...

Deep learning (DL) models have demonstrated exceptional performance in hydrological modeling; however, they are limited by their inability to output untrained hydrological variables and lack of interpretability compared to process-based hydrological models. We propose a hybrid approach that combines the conceptual EXP-Hydro model with embedded neur...

For urban flood simulation, Digital Elevation Model (DEM) provides essential topographic information for understanding and predicting the flow process. Although advanced techniques such as Light Detection and Ranging (LiDAR) can acquire surface elevation information at a rather high resolution, there is still a gap between detailed measurement data...

Weather radar plays an important role in accurate weather monitoring and modern weather forecasting, as it can provide timely and refined weather forecasts for the public and for decision makers. Deep learning has been applied in radar nowcasting tasks and has exhibited a better performance than traditional radar echo extrapolation methods. However...

Irrigated agriculture plays a crucial role in the local economic and social development of the Tarim Basin, but its sustainability is threatened by water scarcity due to the arid environment. In this study, we investigate the impact of irrigation on the atmospheric hydrological cycle in the region using the Weather Research and Forecast (WRF) model...

Long short-term memory (LSTM) networks have demonstrated their excellent capability in processing long-length temporal dynamics and have proven to be effective in precipitation-runoff modeling. However, the current LSTM hydrological models lack the incorporation of multi-task learning and spatial information, which limits their ability to make full...

Previous projections show consistent increases in river flows of Asian Water Towers under future climate change. Here we find non-monotonic changes in river flows for seven major rivers originating from the Tibetan Plateau at the warming levels of 1.5 °C, 2.0 °C, and 3.0 °C based on an observation-constrained hydrological model. The annual mean str...

The WRF-lake, as a one-dimensional (1D) lake model popularly used for coupling with the Weather Research and Forecasting (WRF) system and modeling lake–atmosphere interactions, does not consider the heat exchange caused by inflow–outflow, which is an important characteristic of large reservoirs and can affect the energy budget and reservoir–atmosph...

Plain Language Summary Western Europe experienced catastrophic extreme rainfall and flooding during mid‐July 2021 with >200 fatalities, making it one of the deadliest floods in European history. Based on high‐resolution weather simulations, we show urbanization plays an important role in enhancing rainfall and flood hazards for this storm over the...

Hillslope-based distributed hydrological model has become an essential tool to simulate hydrological processes in mountainous areas, while how to properly delineate hillslope with key factors still remains to be answered. In this study, we propose a conceptually simple and computationally efficient method, the hillslope-asymmetry-elevation-band-asp...

Microtopography on the building roof will direct the rainfall from roofs to the ground through the downspouts, and transform the rainfall spatial distribution from plane to points. However, the issues on whether and how the building-induced rainfall redistribution (BIRR) influences hydrologic responses are still less understood despite the numerous...

Considering the future rapid economic development and large population growth, Xiong’an New Area (known as a lake-marsh wetland) has been undergoing rapid urbanization especially under the background of the Xiong’an New Area Project, which has caused considerable regional climate changes in local area and has proven to be a research focus for study...

The accessibility of high-resolution surface data enables fine distributed modeling for urban flooding. However, the surface routing processes between non-homogeneous landcover components remain in most grid units, due to the high spatial heterogeneity of urban surface. Limited by the great difficulty in the acquisition, sub-grid routing informatio...

本书是在我国城市化进程快速发展的背景下，针对城市水资源严重短缺、水污染情势严峻、水旱灾害频繁等问题，有针对性地选择、调研了20个城市(其中国内城市8个，国外城市12个)，总结各国城市化过程中在水安全保障方面的经验与教训，梳理了世界各国、特别是发达国家的大城市在水安全保障方面的发展历程，重点介绍国内外大都市的基本概况、自然条件、供需保障、节水与生态环境治理、洪涝灾害防治、地下水保护与修复、水文化和城市水智慧管理等方面的经验，为我国未来城市水安全保障建设提供一些经验。

The Water-Food-Energy nexus helps to clarify the development challenges and necessary trade-offs in transboundary river basins. Due to the intensive reservoir development in the Lancang-Mekong River Basin for hydropower production, concerns from stakeholders highlight three major trade-offs. These trade-offs occur between hydropower and irrigation...

Urban catchments are characterized by a wide variety of complex juxtapositions and surface compositions that are linked to multiple overland flow paths. Their extremely high spatial heterogeneity leads to great sensitivity of hydrologic simulation to the scale variation of calculation units. Although extensive efforts have been made for investigati...

This study presents a novel tool, ThSSim, for simulation of thermal stratification (ThS) in reservoirs. ThSSim is a simple and flexible reduced-order model-based the basis function (RMBF) that combines CE-QUAL-W2 (W2) and proper orthogonal decomposition (POD). In a case study, it was used to simulate water temperature in the Karkheh Reservoir (KR),...

In the context of climate change and urban expansion, cities are increasingly vulnerable to floods for increased frequency of rainfall extremes. Timely and accurate flooding prediction is crucial to reduce the losses of life and property. Despite its crucial role in urban hydrologic modelling, storm network, as a key component of urban drainage sys...

Raindrop size distribution (DSD) information is fundamental in understanding the precipitation microphysics and quantitative precipitation estimation, especially in complex terrain or urban environments which are known for complicated rainfall mechanism and high spatial and temporal variability. In this study, the DSD characteristics of rainy seaso...

水库水温对河流水生态环境以及局地气候有重要影响。未来气候变化背景下，水库水温的响应受到国内外关注。本文以气候模式WRF中的湖泊模型为基础，对未来气候态下（RCP2.6、RCP8.5）糯扎渡水库水温变化趋势进行模拟。研究发现，不同未来气候态下，糯扎渡水库水温均呈现上升趋势，且表层水温比深层水温对气候变化的响应更显著。本世纪末水库表层水温上升幅度在4 °C以内，深层水温上升0.8 °C左右。

In this study, we examine the impacts of urbanization and open water surface on heavy convective rainfall based on numerical modeling experiments using the Weather Research and Forecasting (WRF) model. We focus on a severe storm event over the emerging Xiong’an city in northern China. The storm event consists of two episodes, and features intense m...

To simulate the soil water movement process of deformable soils, a modified Richards model considering soil deformation (RMSD) was established. In the model, new parameters were introduced, including deformable soil porosity, deformable soil saturated hydraulic conductivity and unsaturated hydraulic conductivity of expansive soils, which varied wit...

Urban-induced thermal stress can threaten human health, especially during heat waves (HWs). The growth of cities further exacerbates this effect. Here, weather research and forecasting (WRF) with an urban canopy model (UCM) is used to assess the effects of megacities and their growth on the thermal regime of proximal cities during heat waves. Analy...

Large lakes and reservoirs play important roles in modulating regional hydrological cycles and climate; however, their representations in coupled models remain uncertain. The existing lake module in the Weather Research and Forecasting (WRF) system (hereafter WRF-Lake), although widely used, did not accurately predict temperature profiles in deep l...

Raindrop size distribution (DSD) information is fundamental in understanding the precipitation microphysics and quantitative precipitation estimation, especially in complex terrain or urban environment which is known for its complicated rainfall mechanism and high spatial and temporal variability. In this study, the DSD characteristics of rainy sea...

With the past rapid economic development and large population growth, Jing-Jin-Ji District has been undergoing rapid urbanization, which has caused considerable regional weather changes in local regions. In this paper, we used the Weather Research and Forecasting (WRF) model to quantitatively analyze the effects of past urbanization and potential f...

This editorial introduces the latest research advances in the special issue on catchment management and reservoir operations. River catchments and reservoirs play a central role in water security, community wellbeing and social-economic prosperity, but their operators and managers are under increasing pressures to meet the challenges from populatio...

In this study, a combined field experiment and numerical modeling approach is used to examine the water temperature of the lower Lancang influenced by its main tributary the Buyuan River. Water temperature has been observed at three mainstream hydrological stations: Mohan on Buyuan, and Yunjinghong and Guanlei (located downstream to Buyuan confluen...

The construction of gates in watercourses could change the original hydrological and hydrodynamic processes of drainage basins, eventually having a widespread cumulative influence on river habitat and fish resources. In this study, the hydrodynamic force in the Yongjiang River basin, China, was calculated using the MIKE FLOOD model, including water...

The length of record (LOR) method is an evaluation method that provides quantitative advice for the amount of computational data required for use of the indicators of hydrological alteration (IHA). The use of multi-index hydrological indicators to reflect river hydrological–ecological characteristics is the essence of the IHA method, while the LOR...

Large lakes and reservoirs play important roles in modulating regional hydrological cycles and climate; however, their representations in coupled models remain uncertain. The existing lake module in the Weather Research and Forecasting (WRF) system (hereafter WRF-Lake), although widely used, did not accurately predict temperature profiles in deep l...

Rainfall exhibits substantial variability, and its temporal resolution considerably affects simulation of hydrological processes. This study aims to investigate the effect of the temporal resolution of rainfall (TRR) on urban flood modeling and to explore how high TRR is required. A routing-enhanced detailed urban stormwater (REDUS) model, which ha...

When the urban heat island (UHI) effect coincides with a heat wave (HW), thermal stress in cities is exacerbated. Understanding the surface energy balance (SEB) responses to HWs is critical for improving predictions of the synergies between UHIs and HWs. This study evaluates observed SEB characteristics in four cities (Beijing, Łódź, London and Swi...

To understand the impacts of urbanization on moist convection, we explore how an idealized circular urban island affects the diurnal cycle and spatial distribution of rainfall over urban and surrounding rural areas at the diurnal equilibrium state using large-eddy simulations (LES) performed with the Weather Research and Forecasting (WRF) model. Co...

Atmospheric rivers (ARs), filamentary patterns of strong water vapour fluxes, play a prominent role in global poleward moisture transport and have profound impacts on extreme rainfalls (ERs). Previous AR research has mainly focused on the mid-latitude regions, whereas the characteristics of ARs in low latitudes and their relationship with local ERs...

This study investigates spatial characteristics of annual and decadal precipitation in the Huaihe River basin. Daily precipitation data, obtained from meteorological gauges, are analyzed for a 51-year period, from 1961 to 2011. Precipitation is analyzed in grids (5 km²) with respect to temporal variability. The spatial distribution and intensity of...

Anthropogenic heat is an important component of the urban energy budgets that can affect land surface and atmospheric boundary layer processes. Representation of anthropogenic heat in numerical climate modeling systems is, therefore, important when simulating urban meteorology and climate, and has the potential to improve weather forecasts, climate...

Accurate high-resolution estimates of precipitation are vital to improving the understanding of basin-scale hydrology in mountainous areas. The traditional interpolation methods or satellite-based remote sensing products are known to have limitations in capturing the spatial variability of precipitation in mountainous areas. In this study, we devel...

X-band-radar-based quantitative precipitation estimation (QPE) system is increasingly gaining interest thanks to its strength in providing high spatial resolution rainfall information for urban hydrological applications. However, prior to such applications, a variety of errors associated with X-band radars are mandatory to be corrected. In general,...

Accurate high-resolution estimates of precipitation are vital to improve the understanding on basin-scale hydrology in mountainous areas. The traditional interpolation methods or satellite-based remote sensing products are known to have limitations in capturing spatial variability of precipitation in mountainous areas. In this study, we develop a f...

The aimof this study is to evaluate the accuracy of daily rainfall estimates based on the GPMlevel-3 final product derived from the IMERG algorithm (abbreviated as IMERG) andTRMM3B42, version 7 (abbreviated as 3B42), in the upper Mekong River basin, a mountainous region in southwestern China. High-density rain gauges provide exceptional resources f...

Understanding the impacts of land-use and land-cover change such as urbanization is essential in many disciplines. This study investigates the impacts of urban-rural contrasts in terms of momentum roughness length (z0) and aerodynamic surface temperature (TSK) on dry planetary boundary layers (PBLs) using large-eddy simulations (LES) with the Weath...

This study developed a correction approach to improve the rainfall field estimation by TRMM rainfall product in a sparsely-gauged mountainous basin. First, Thiessen polygons were generated to define the measurement domain of each raingauge. Second, the rainfall of TRMM pixels in each Thiessen polygon were corrected using a benchmark method based on...

As the climate warms, heat waves (HW) are projected to be more intense and to last longer, with serious implications for public health. Urban residents face higher health risks because urban heat islands (UHIs) exacerbate HW conditions. One strategy to mitigate negative impacts of urban thermal stress is the installation of green roofs (GRs) given...

Changes in snowfall not only alter the temporal distribution of intra-annual runoff, but also the available annual water resources. The characteristics and temporal trend of snowfall were evaluated during the past five decades in China. Based on daily observations from 743 national meteorological stations for the period 1956-2010, an empirical rela...

Mulched drip irrigation has gradually replaced flood irrigation and is now widely used in Xinjiang. This study explores the effects of the irrigation methods on the soil salt dynamics and the crop growth using experiments conducted from 2011 to 2012 in a cotton field with mulched drip and flood irrigation systems. The 6 900 samples was observed. Th...

This study investigated impacts of urban forms on the future thermal environment over Beijing, the capital city of China. Beijing is experiencing remarkable urban expansion and is planned to undergo the transformation of urban forms from single-centric (compact-city) to poly-centric city (dispersed-city). Impacts of urban forms on the future therma...

Soil water dynamics has been a new research field in hydrology and water resources since the 1980s. Research progresses in soil water dynamics achieved in the past decades greatly promoted the advances of sciences and technologies in the fields of irrigation and drainage, hydrology and water resources in China. Based on the soil water dynamics, the...

Using the hourly precipitation observations from 118 gauge stations and a weather radar in the Greater Beijing Region (GBR) during 2008-2012, we investigate the spatiotemporal characteristics of precipitation and discuss the appropriate observational approach for capturing variability of precipitation over this region. In general, the south central...

Soil salinity trend is affected by both salt accumulation and leaching during the growth and non-growth periods. To explore the long-term salinization trend of farmland under mulched drip irrigation, the experiments were conducted from 2008 to 2013 in a cotton field in Xinjiang province, northwestern China. More than 15 000 soil samples were collec...

The hydrological partitioning is not only governed by the relative magnitude of precipitation and potential evapotranspiration (PET), but also by their seasonal distribution. Based on the daily observations from 743 national meteorological stations during 1956 to 2010, the FAO-Penman equation was employed to calculate daily PET. To construct the se...

Oceanic evaporation via the East Asian Monsoon (EAM) has been regarded as the major source of precipitation over China, but a recent study estimated that terrestrial evaporation might contribute up to 80% of the precipitation in the country. To explain the contradiction, this study presents a comprehensive analysis of the contribution of oceanic an...

A warmer climate may lead to less precipitation falling as snow in cold seasons. Such a switch in the state of precipitation not only alters temporal distribution of intra-annual runoff but also tends to yield less total annual runoff. Long-term water balance for 282 catchments across China is investigated, showing that a decreasing snow ratio redu...

Urban modification of rainfall over Beijing metropolitan region has been extensively examined. A review on previous studies is presented focusing on the main approaches and conclusions and the exsiting key issuess. The approaches fall into two categories, i.e., observation-based approach and model-based approach. Their ultimate objective is to sepa...

Warmer climate may lead to less winter precipitation falling as snow. Such a switch in the state of precipitation not only alters temporal distribution of intra-annual runoff, but tends to yield less total annual runoff. Long-term water balance for 282 catchments across China is investigated, showing that decreasing snow ratio reduces annual runoff...

Green roofs (GRs), as compared to conventional roofs, can retain a considerable amount of water in the soil layer and hence have been used in many urban areas to mitigate urban flooding. However, a simple yet physical model for describing the rainfall (P)-runoff (R) relationship over GRs is still lacking. In this study, a physically-based P–R relat...

This paper presents a simplified dynamic method based on the definition of field capacity. Two soil hydraulic characteristics models, the Brooks-Corey (BC) model and the van Genuchten (vG) model, and four soil data groups were used in this study. The relative drainage rate, which is a unique parameter and independent of the soil type in the simplif...

In this study, the performance of an irrigation-integrated green roof (GR) system is analyzed through numerical simulations using the vertically-resolved Princeton ROof Model (PROM). The simulations are driven by a 63-day series of summertime meteorological forcing measured at a GR site in Beijing, China. Due to the importance of the medium layer d...

The efficient planning and design of water networks, as well as the management and strategies of existing water supply systems, require accurate short-term water demand forecasts. In this study, a statistical model for the estimation of daily urban water consumption was developed. The model was applied to analyse and forecast the daily water consum...