Zhongfeng Xu

Chinese Academy of Sciences | CAS · Institute of Atmospheric Physics

The relative impacts of various land–sea distributions (LSDs) and mountains on Asian monsoon extent and intensity are assessed using a series of AGCM simulations. The air–sea coupling effects are not considered in this study. All simulations were integrated with zonal mean SST, globally uniform vegetation, soil color, and, except several simulation...

An improved dynamical downscaling method (IDD) with general circulation model (GCM) bias corrections is developed and assessed over North America. A set of regional climate simulations is performed with the Weather Research and Forecasting Model (WRF) version 3.3 embedded in the National Center for Atmospheric Research's (NCAR's) Community Atmosphe...

Land use and land cover change (LULCC) is primarily characterized as forest conversion to cropland for the development of agriculture. Previous climate modeling studies have demonstrated the LULCC impacts on mean climate and its long-term trends. This study investigates the diurnal and seasonal climatic response to LULCC in monsoon Asia through two...

Vector quantities, e.g., vector winds, play an extremely important role in climate systems. The energy and water exchanges between different regions are strongly dominated by wind, which in turn shapes the regional climate. Thus, how well climate models can simulate vector fields directly affects model performance in reproducing the nature of a reg...

This paper develops a multivariable integrated evaluation (MVIE) method to measure the overall performance of climate model in simulating multiple fields. The general idea of MVIE is to group various scalar fields into a vector field and compare the constructed vector field against the observed one using the vector field evaluation (VFE) diagram. T...

The offshore region of East Asia has a crucial role in recycling precipitation, especially in the current context of a warming climate. This is because the atmospheric feedback from the sea offshore East Asia directly impacts and modifies precipitation patterns by influencing the seasonal cycles of the surface energy and water budgets. We used a re...

The annual precipitation in North China and South China shows a dipole pattern with a clear inter-decadal transition around the late 1970s. However, the relative contribution of internal variability and external forcing to this inter-decadal transition is still unclear. Here, we separate internal variability from the externally forced climate respo...

The Regional Climate Model system version 4 (RegCM4) has been used to dynamically downscale outputs from four different general circulation models (GCM) participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) to the horizontal resolution of 25 km × 25km, in order to study changes in the Southern China hydrological cycle according...

Human activity have caused significant increase in greenhouse gas (GHG) concentration and land use and land cover change (LULCC), which can in turn affect regional and global climate. We investigate the relative contributions of increased GHG concentration and LULCC to the precipitation and surface air temperature (SAT) in Asia through three dynami...

Both reliability and independence of global climate model (GCM) simulation are essential for model selection to generate a reasonable uncertainty range of dynamical downscaling simulations. In this study, we evaluate the performance and interdependency of 37 GCMs from the Coupled Model Intercomparison Project Phase 6 (CMIP6) in terms of seven key l...

Summer mean (June, July, and August) surface 19 air temperature (SSAT) in East Asia during the period from 1958 to 2001 has shown a warming. However, the relative contributions of external forcing (EF) and internal climate variability (ICV) to the SSAT changes over East Asia remain unclear. In this study, a new approach is applied to estimate the c...

In the late 1920’s, a mega-drought in China resulted in widespread crop failure and famine. Sufficient evidence suggests that this drought belonged to a dry period ranging from approximately 1922 to 1932. To understand the characteristics and the cause of this persistent drought period, we combined various data, including observations, tree ring pr...

General circulation model (GCM) biases are one of the important sources of biases and uncertainty in dynamic downscaling–based simulations. The ability of regional climate models to simulate tropical cyclones (TCs) is strongly affected by the ability of GCMs to simulate the large-scale environmental field. Thus, in this work, we employ a recently d...

Dynamical downscaling is an important approach to obtaining fine-scale weather and climate information. However, dynamical downscaling simulations are often degraded by biases in the large-scale forcing itself. We constructed a bias-corrected global dataset based on 18 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the Eu...

Dynamical downscaling is the most widely used physics-based approach to obtaining fine-scale weather and climate information. However, traditional dynamical downscaling approaches are often degraded by biases in the large-scale forcing. To improve the confidence in future projection of regional climate, we used a novel bias-corrected global climate...

Both reliability and independence of global climate model (GCM) simulation are essential for model selection to generate a reasonable uncertainty range of dynamical downscaling simulations. In this study, we evaluate the performance and interdependency of 37 GCMs from the Coupled Model Intercomparison Project Phase 6 (CMIP6) in terms of seven key l...

This study applies three widely used land models (SSiB, CLM, and Noah-MP) coupled in a regional climate model to quantitatively assess their skill in preserving the imposed ± 5 °C anomalies on the initial land surface and subsurface temperature (LST/SUBT) and generating the 2-m air temperature (T2m) anomalies over Tibetan Plateau (TP) during May–Au...

The Regional Climate Model version 4 (RegCM4) has been used to dynamically downscale outputs from four different general circulation models (GCM) participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) to the horizontal resolution of 25 km × 25km, in order to study 2050-to-2099 changes in the Southern China hydrological cycle acc...

Multi-physics ensembles have emerged as a promising approach to hydrological simulations. As multi-physics ensembles are constructed by perturbing the model physics, the ensemble members share a substantial portion of the same physics and hence are not independent of each other. It is unknown whether and to what extent this nonindependence affects...

A crucial step in the application of the Weather Research and Forecasting (WRF) model to regional climate research is the selection of the proper combinations of physical parameterizations. In this study, we examined the performance of various parametrization schemes in the WRF model in terms of precipitation and temperature over the Haihe river ba...

An evaluation of a model's overall performance in simulating multiple fields is fundamental to model intercomparison and development. A multivariable integrated evaluation (MVIE) method was proposed previously based on a vector field evaluation (VFE) diagram, which can provide quantitative and comprehensive evaluation on multiple fields. In this st...

Dynamical downscaling is an important approach to obtaining fine-scale weather and climate information. However, dynamical downscaling simulations are often degraded by biases in the large-scale forcing itself. Here, we construct a set of bias-corrected global dataset based on 18 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6)...

General circulation model (GCM) biases are one of the important sources of biases and uncertainty in dynamic downscaling–based simulations. The ability of regional climate models to simulate tropical cyclones (TCs) is strongly affected by the ability of GCMs to simulate the large-scale environmental field. Thus, in this work, we employ a recently d...

Abstract Specific yield is a key parameter for estimating water table depth in land surface models, which can strongly modulate the interaction between soil moisture and groundwater and further affect the water budget between the land surface and the atmosphere. The error in water table simulation comes mainly from the uncertainty in determining th...

This study applies three widely used land models (SSiB, CLM, and Noah-MP) coupled in a regional climate model to quantitatively assess their skill in preserving the imposed ± 5℃ anomalies on the initial land surface and subsurface temperature (LST/SUBT) and generating the 2-m air temperature (T2m) anomalies over Tibetan Plateau (TP) during May-Augu...

In land surface models, the ability to simulate runoff is a good diagnostic for the hydrological cycle and other surface parameterizations; however, the partitioning of total runoff into surface and subsurface runoff shows considerable uncertainties. The interaction between soil moisture and groundwater plays an important role in simulating the sur...

Hydrological processes are a key component of land surface models and link to the energy budget and carbon cycle. This study assessed the global hydrological processes of the Atmosphere–Vegetation Interaction Model (AVIM) using multiple datasets, including the Global Land Data Assimilation System (GLDAS), the University of New Hampshire and Global...

We develop a novel framework for rigorously evaluating land surface models (LSMs) against observations by recognizing the asymmetry between verification‐ and falsification‐oriented approaches. The former approach cannot completely verify LSMs even though it exhausts every case of consistency between the model predictions and observations, whereas t...

Day-to-day (DTD) temperature variation reflects a rapid weather variability, which significantly affects human health and ecosystems. However, while a few of studies have addressed certain regional variations, no global pattern of rapid temperature variability has yet been investigated. Here, using global daily temperature observation data, we pres...

An evaluation of a model's overall performance in simulating multiple fields is fundamental to model intercomparison and development. A multivariable integrated evaluation (MVIE) method was proposed previously based on a vector field evaluation (VFE) diagram, which can provide quantitative and comprehensive evaluation on multiple fields. In this st...

Multi-physics ensemble simulations have emerged as a promising approach to ensemble hydrological simulations due to the advantages in process understanding and model development. As a multi-physics ensemble is constructed by perturbing the physics of multi-physics models, the ensemble members share a substantial portion of the same physics and henc...

The Tibetan Plateau has experienced substantial warming during the last few decades. As a result, the cryosphere of the Tibetan Plateau, including the snow cover, has shown significant changes. We characterized the changes in snow over the Tibetan Plateau using several snow‐related indices, including snow depth and snow‐covered days based on the ME...

The winter temperature in East Asia from 1958 to 2001 has shown an obvious warming trend superposed with a large amplitude of decadal oscillations. To separate the relative contributions of external forcing and internal variability to the decadal change in winter temperature, we propose a method which combines reanalysis data, global atmosphere‐oce...

Precipitation is one of the major challenges in climate modeling. Among various factors, the large-scale atmospheric circulation plays an important role in modulating regional precipitation through dynamic processes that has been widely discussed in previous studies. However, few efforts have been made to investigate the relationship of model abili...

Abstract The evaluation of the regional climate model is of great importance for model's developments and applications. We assessed the performance of Weather Research and Forecasting (WRF) cloud resolving simulations with various physics options in terms of precipitation and soil moisture over the central Tibetan Plateau (TP) for a 2‐month simulat...

In a recent article, Hu et al. (2019) argued that the commonly used Taylor diagram in climate model evaluation only considered centered statistics, while the absolute error (AE) was not considered. Therefore, they proposed a new index, termed Distance between Indices of Simulation and Observation (DISO), that takes AE, correlation coefficient, and...

Snow cover affects the thermal conditions of the Tibetan Plateau through snow–albedo feedback and snowmelt, which, in turn, modulates the Asian summer monsoon climate. An accurate estimation of the snow condition on the Tibetan Plateau is therefore of great importance in both seasonal forecasts and climate studies. Estimation of snow water equivale...

Drought is the major natural disaster that affects northern China and has regional distinctions in duration, strength, and spatial range. Using five sets of twentieth-century reanalysis data, we investigated a decadal-scale extreme drought recorded in historical documents and tree-ring chronologies during late 1920s to early 1930s. The results indi...

Vector wind plays a crucial role in shaping regional climate through transferring energy and moisture. In this study, we evaluate 37 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and multi-model ensembles (MME) in terms of the climatological mean state, annual cycle, and interannual variability of vector winds in the Asian-Australian...

The traditional dynamical downscaling (TDD) method employs continuous integration of regional climate models (RCM) with the general circulation model (GCM) providing the initial and lateral boundary conditions. Dynamical downscaling simulations are constrained by physical principles and can generate a full set of climate information, providing one...

To investigate the impacts of increased greenhouse gas (GHG) concentrations and land use and land cover change (LULCC) on various components of hydrologic cycle, three sets of numerical experiments were performed using the fully coupled Community Earth System Model (CESM). In the first set of experiments, GHG concentrations were set to preindustria...

The current evaluations of global land data assimilation system (GLDAS) runoff were generally limited to the observation-rich areas. At the global and hemispheric scales, we assessed different runoff components performance of GLDAS (1.0 and 2.1) using the University of New Hampshire and Global Runoff Data Centre (UNH-GRDC) dataset. The results sugg...

Four dynamical downscaling simulations are performed with different combinations of land cover maps and greenhouse gas (GHG) levels using the Weather Research and Forecasting (WRF) model nested in the Community Earth System (CESM) model. A pseudo-global warming downscaling method is used to effectively separate the anthropogenic signals from the in...

Annual precipitation anomalies over eastern China are characterized by a north-south dipole pattern, referred to as the "southern flooding and northern drought" pattern (SF/ND), fluctuating on decadal time scales. Previous research has suggested possible links with oceanic forcing, but the underlying physical mechanisms by which sea surface tempera...

The impacts of land-use and land-cover change (LULCC) on tropospheric temperatures are investigated in this study using the fully coupled Community Earth System Model. Two simulations are performed using potential and current vegetation cover. The results show that LULCC can induce detectable changes in the tropospheric air temperature. Although th...

To improve confidence in regional projections of future climate, a new dynamical downscaling (NDD) approach with both GCM bias corrections and spectral nudging is developed and assessed over North America. GCM biases are corrected by adjusting GCM climatological means and variances based on reanalysis data before the GCM output is used to drive a r...

The role of various mountains in the Asian monsoon system is investigated by AGCM simulations with different mountains. The comparison of the simulation with Asian mountains (MAsia run) with the simulation without mountains (NM run) reveals that the presence of the Asian mountains results in a stronger South Asian summer monsoon (SASM), characteriz...

A number of AGCM simulations were performed by including various land–sea distributions (LSDs), such as meridional LSDs, zonal LSDs, tropical large-scale LSDs, and subcontinental-scale LSDs, to identify their effects on the Asian monsoon. In seven meridional LSD experiments with the continent/ocean located to the north/south of a certain latitude,...

We define a new monsoon index (MV) as the product of relative vorticity and equivalent potential temperature using the long-term NCEP/NCAR reanalysis data. The MV index provides new insights into the intraseasonal and interannual variabilities of the broad-scale tropical Asian summer monsoon (TASM), including the South Asian summer monsoon (SASM) a...

The effects of vegetation and its seasonal variation on energy and the hydrological cycle were ex-amined using a state-of-the-art Community Atmosphere Model (CAM3). Three 15-year numerical experiments were completed: the first with realistic vegetation charac-teristics varying monthly (VEG run), the second without vegetation over land (NOVEG run),...