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The Nanjing University of Information Science and Technology Earth System Model version 3 (NESM v3) has been developed, aiming to provide a numerical modeling platform for cross-disciplinary Earth system studies, project future Earth climate and environment changes, and conduct subseasonal-to-seasonal prediction. While the previous model version NESM v1 simulates the internal modes of climate variability well, it has no vegetation dynamics and suffers considerable radiative energy imbalance at the top of the atmosphere and surface, resulting in large biases in the global mean surface air temperature, which limits its utility to simulate past and project future climate changes. The NESM v3 has upgraded atmospheric and land surface model components and improved physical parameterization and conservation of coupling variables. Here we describe the new version's basic features and how the major improvements were made. We demonstrate the v3 model's fidelity and suitability to address global climate variability and change issues. The 500-year preindustrial (PI) experiment shows negligible trends in the net heat flux at the top of atmosphere and the Earth surface. Consistently, the simulated global mean surface air temperature, land surface temperature, and sea surface temperature (SST) are all in a quasi-equilibrium state. The conservation of global water is demonstrated by the stable evolution of the global mean precipitation, sea surface salinity (SSS), and sea water salinity. The sea ice extents (SIEs), as a major indication of highlatitude climate, also maintain a balanced state. The simulated spatial patterns of the energy states, SST, precipitation, and SSS fields are realistic, but the model suffers from a cold bias in the North Atlantic, a warm bias in the Southern Ocean, and associated deficient Antarctic sea ice area, as well as a delicate sign of the double ITCZ syndrome. The estimated radiative forcing of quadrupling carbon dioxide is about 7.24Wm-2, yielding a climate sensitivity feedback parameter of -0:98Wm-2 K-1, and the equilibrium climate sensitivity is 3.69 K. The transient climate response from the 1%yr-1 CO2 (1pctCO2) increase experiment is 2.16 K. The model's performance on internal modes and responses to external forcing during the historical period will be documented in an accompanying paper. [ABSTRACT FROM AUTHOR]

Associations between tropospheric ozone (O3) and climate variations have been extensively investigated worldwide. However, given the lack of historical O3 monitoring data, the knowledge gaps regarding the influences of climate variations on long-term O3 trends in China remain. The present study used a unique tropospheric O3 dataset from the summer of 1999 to 2017 simulated by an atmospheric chemistry model to explore the linkage between summer O3 and a dominant atmospheric circulation system – the Western Pacific Subtropical High Pressure (WPSH) on an interannual basis in China. During this period, both WPSH strength and O3 concentrations in eastern and central China illustrated a growing trend. An EOF analysis was conducted to examine significant summer O3 characteristics and patterns and their potential connections with the WPSH. We show that the WPSH determines interannual fluctuations of summer O3, whereas O3 precursor emissions contribute primarily to the O3 long-term trend. Special efforts were made to discern the associations of O3 variations in major urban agglomerations of China and the WPSH. The results reveal that the WPSH plays a more vital role in O3 perturbation in the eastern seaboard regions and inland China, but leads to lower O3 levels in the Pearl River Delta (PRD) region. Precursor emissions made more significant contributions up to 60 % to increasing O3 trends in the inland urban agglomerations than coastal regions in eastern and southern China. The strongest contribution of meteorological conditions associated with the WPSH to summer ozone concentration occurred in the Yangtze River Delta (YRD), accounting for over 9 % to ozone perturbations from 1999 to 2017. Overall, we find that the effect of the WPSH on regional O3 depends on the spatial proximity to the WPSH. We attributed the effects of the WPSH on O3 interannual variations to the changes in air temperature, precipitation, and winds associated with the WPSH's intensity and positions. [ABSTRACT FROM AUTHOR]

Lakes are sensitive indicators of climate change. There are thousands of lakes on the Tibetan Plateau (TP), and more than 1200 of them have an area larger than 1 km 2 ; they respond quickly to climate change, but few observation data of lakes are available. Therefore, the thermal condition of the plateau lakes under the background of climate warming remains poorly understood. In this study, the China regional surface meteorological feature dataset developed by the Institute of Tibetan Plateau Research, Chinese Academy of Sciences (ITPCAS), MODIS lake surface temperature (LST) data and buoy observation data were used to evaluate the performance of lake model FLake, extended by simple parameterizations of the salinity effect, for brackish lake and to reveal the response of thermal conditions, radiation and heat balance of Qinghai Lake to the recent climate change. The results demonstrated that the FLake has good ability in capturing the seasonal variations in the lake surface temperature and the internal thermal structure of Qinghai Lake. The simulated lake surface temperature showed an increasing trend from 1979 to 2012, positively correlated with the air temperature and the downward longwave radiation while negatively correlated with the wind speed and downward shortwave radiation. The simulated internal thermodynamic structure revealed that Qinghai Lake is a dimictic lake with two overturn periods occurring in late spring and late autumn. The surface and mean water temperatures of the lake significantly increased from 1979 to 2012, while the bottom temperatures showed no significant trend, even decreasing slightly from 1989 to 2012. The warming was the strongest in winter for both the lake surface and air temperature. With the warming of the climate, the later ice-on and earlier ice-off trend was simulated in the lake, significantly influencing the interannual and seasonal variability in radiation and heat flux. The annual average net shortwave radiation and latent heat flux (LH) both increase obviously while the net longwave radiation and sensible heat flux (SH) decrease slightly. Earlier ice-off leads to more energy absorption mainly in the form of shortwave radiation during the thawing period, and later ice-on leads to more energy release in the form of longwave radiation, SH and LH during the ice formation period. Meanwhile, the lake–air temperature difference increased in both periods due to shortening ice duration. [ABSTRACT FROM AUTHOR]

The winter haze is a growing problem in North China, but the causes are not well understood. The chemistry version of theWeather Research and Forecasting model (WRF-Chem) was applied in North China to examine how PM2.5 concentrations change in response to changes in emissions (sulfur dioxide (SO2), black carbon (BC), organic carbon (OC), ammonia (NH3), and nitrogen oxides (NOx)), as well as meteorology (temperature, relative humidity (RH), and wind speeds) changes in winter. From 1960 to 2010, the dramatic changes in emissions lead to +260% increases in sulfate, +320% increases in nitrate, +300% increases in ammonium, +160% increases in BC, and +50% increases in OC. The responses of PM2.5 to individual emission species indicate that the simultaneous increases in SO2, NH3, and NOx emissions dominated the increases in PM2.5 concentrations. PM2.5 shows more notable increases in response to changes in SO2 and NH3 as compared to increases in response to changes in NOx emissions. In addition, OC also accounts for a large fraction in PM2.5 changes. These results provide some implications for haze pollution control. The responses of PM2.5 concentrations to temperature increases are dominated by changes in wind fields and mixing heights. PM2.5 shows relatively smaller changes in response to temperature increases and RH decreases compared to changes in response to changes in wind speed and aerosol feedbacks. From 1960 to 2010, aerosol feedbacks have been significantly enhanced due to higher aerosol loadings. The discussions in this study indicate that dramatic changes in emissions are the main cause of increasing haze events in North China, and long-term trends in atmospheric circulations may be another important cause since PM2.5 is shown to be substantially affected by wind speed and aerosol feedbacks. More studies are necessary to get a better understanding of the aerosol-circulation interactions. [ABSTRACT FROM AUTHOR]

With global climate changes intensifying, the hydrological response to climate changes has attracted more attention. It is beneficial not only for hydrology and ecology but also for water resource planning and management to understand the impact of climate change on runoff. In addition, there are large spatial variations in climate type and geographic characteristics across China. To gain a better understanding of the spatial variation of the response of runoff to changes in climatic factors and to detect the dominant climatic factors driving changes in annual runoff, we chose the climate elasticity method proposed by Yang and Yang (2011). It is shown that, in most catchments of China, increasing air temperature and relative humidity have negative impacts on runoff, while declining net radiation and wind speed have positive impacts on runoff, which slow the overall decline in runoff. The dominant climatic factors driving annual runoff are precipitation in most parts of China, net radiation mainly in some catchments of southern China, air temperature and wind speed mainly in some catchments in northern China. [ABSTRACT FROM AUTHOR]

The near-surface soil freeze/thaw status is an important indicator of climate change. Using data from 636 meteorological stations across China, we investigated the changes in the first date, the last date, the duration, and the number of days of the near-surface soil freeze over the period 1956-2006. The results reveal that the first date of the near-surface soil freeze was delayed by about 5 days, or at a rate of 0.10±0.03 day yr-1, and the last date was advanced by about 7 days, or at a rate of 0.15±0.02 day yr-1. The duration of the near-surface soil freeze decreased by about 12 days or at a rate of 0.25±0.04 day yr-1, while the actual number of the near-surface soil freeze days decreased by about 10 days or at a rate of 0.20±0.03 day yr-1. The rates of changes in the near-surface soil freeze/thaw status increased dramatically from the early 1990s through the end of the study period. Regionally, the changes in western China were greater than those in eastern China. Changes in the near-surface soil freeze/thaw status were primarily controlled by changes in air temperature, but urbanization may also play an important role. [ABSTRACT FROM AUTHOR]

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 reduces annual runoff for a given total precipitation. Within the Budyko framework, we develop an equation to quantify the relationship between snow ratio and annual runoff from a water-energy balance viewpoint. Based on the proposed equation, attribution of runoff change during the past several decades and possible runoff change induced by projected snow ratio change using climate experiment outputs archived in the Coupled Model Intercomparison Project Phase 5 (CMIP5) are analyzed. Results indicate that annual runoff in northwestern mountainous and northern high-latitude areas are sensitive to snow ratio change. The proposed model is applicable to other catchments easily and quantitatively for analyzing the effects of possible change in snow ratio on available water resources and evaluating the vulnerability of catchments to climate change. [ABSTRACT FROM AUTHOR]