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In this paper, we evaluate a 48‐member multiphysics ensemble using the Weather Research and Forecasting (WRF) model for the JJA extreme precipitation and temperature in 2003 over the CORDEX‐EA‐II domain. The simulated precipitation and temperature are reasonable in the subregions controlled by a large‐scale circulation, yet the biases for both precipitation and temperature are evident over the subregions where the effects of mesoscale processes are important. The performance of various combinations of WRF physical schemes for simulating the JJA precipitation is dependent on the region. Meanwhile, the cumulus and microphysical schemes have substantial influences on the simulation of precipitation, and the land surface models and cumulus schemes play crucial roles in the surface temperature. Our analysis shows that the combination of Noah for the land surface process, Lin for the microphysics, G3D for the cumulus parameterization, and CAM for the radiation scheme can provide the most reliable reproduction of both precipitation and temperature extremes over China. Ensemble analysis shows that the simulated climate extremes are usually accompanied by a large ensemble spread, implying sensitivities to the model physical processes in some subregions. The simulated wind fields at low‐to‐middle atmospheric levels display responses to the options of the land surface models and cumulus schemes. The essential impact of the land–atmospheric interaction on simulating the extremes can be largely attributed to the active convective processes. WRF has difficulties in reproducing the observed temporal evolution of the rainfall process, which consists of continuous large rainfall episodes in the observation data set during the simulation period. [ABSTRACT FROM AUTHOR]

It is important to understand the hydroclimate history of water‐deficient regions, such as the Alxa desert of northwest China. However, there are few high‐resolution proxy records for the hydroclimate changes over the past centuries in the Alxa desert. Fortunately, there are many tree‐ring hydroclimate reconstructions from the nearby mountains. However, the hydroclimate correlations between the Alxa desert and adjacent mountains are unclear. Here, we collected high‐quality data from 43 meteorological stations in northwest China (1960–2017). We found increasing mean temperatures in the study area, both on seasonal and annual timescales. We also found that while relative humidity had mostly decreased in the Mt. Qilian and Alxa desert, precipitation and the standardized precipitation evapotranspiration index (SPEI) increased mostly. In the Mt. Helan and Hasi ranges, relative humidity, precipitation, and SPEI all showed decreasing trends. Empirical orthogonal function analysis indicated that precipitation, relative humidity, and SPEI in the Mt. Qilian were similar to the corresponding conditions in the central and western Alxa desert. Hydroclimate conditions in the Mt. Helan and Hasi ranges were correlated with data from the eastern desert. Tree‐ring records of precipitation and SPEI from the mountains were used to validate the hydroclimate correlations during the instrumental period. We found strong similarities between hydroclimatic changes in the Mt. Qilian and those in the central and western Alxa desert, on both annual and decadal timescales, from 1877 to 2006. Tree‐ring width chronologies from mountainous areas were shown to faithfully represent the hydroclimatic history of the desert area. Plain Language Summary: Northwestern China has faced serious ecological challenges over the past five decades, including intensified desertification and declining lake levels. Understanding the regional hydroclimate history is necessary to manage water resources in this water‐deficient region. However, there are few climate proxies for these desert areas. In contrast, high‐resolution tree‐ring climate proxies have been studied intensively in the nearby mountains. This study attempts to find reliable correlations between mountain and desert hydroclimate. We found increasing mean temperatures over the entire study area. We also found that precipitation, relative humidity, and drought index data from the western and central desert were strongly correlated with data from Mt. Qilian, while data from the eastern desert were correlated with those from the Helan and Hasi mountain ranges. When relative humidity decreased mostly in the Mt. Qilian, precipitation and SPEI mostly increased; in the Mt. Helan and Hasi areas, relative humidity, precipitation and SPEI mostly decreased. Tree‐ring records from the mountains were compared to validate these correlations. Significant correlations were found between the precipitation reconstructions from the central desert and Mt. Qilian from 1877 to 2006. We also used tree‐ring width chronologies to show that they could represent the hydroclimatic history of the Alxa desert. Key Points: Precipitation and SPEI indicate wetter trends in Mt. Qilian but drier trends in Mt. Helan and Hasi ranges from 1960 to 2017Precipitation, relative humidity, and SPEI in western and central (eastern) Alxa desert resemble conditions in Mt. Qilian (Helan and Hasi)Tree‐ring proxies from nearby mountains can faithfully represent the hydroclimate history of the Alxa desert [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) play vital roles in plant growth and development. Yet how climate regimes and soil fertility influence plant N and P stoichiometry is not well understood, especially in the belowground plant parts. Here we investigated plant aboveground and belowground N and P concentrations ([N] and [P]) and their stoichiometry in three dominant genera along a 2200 km long climatic gradient in northern China. Results showed that temperature explained more variation of [N] and [P] in C4 plants, whereas precipitation exerted a stronger influence on [N] and [P] in C3 plants. Both plant aboveground and belowground [N] and [P] increased with decreasing precipitation, and increasing temperatures yet were negatively correlated with soil [N] and [P]. Plant N:P ratios were unrelated with all climate and soil variables. Plant aboveground and belowground [N] followed an allometric scaling relationship, but the allocation of [P] was isometric. These results imply that internal processes stabilize plant N:P ratios and hence tissue N:P ratios may not be an effective parameter for predicting plant nutrient limitation. Our results also imply that past positive relationships between plant and nutrient stocks may be challenged under changing climatic conditions. While any modeling would need to be able to replicate currently observed relationships, it is conceivable that some relationships, such as those between temperature or rainfall and carbon:nutrient ratios, should be different under changing climatic conditions. [ABSTRACT FROM AUTHOR]

Three methods were used to distinguish the characteristics of changes in climate variability and normalized difference vegetation index (NDVI) during the period from 1982 to 2000 in China. Great changes in climate variability and an increased trend in NDVI were observed. The changes in precipitation variability were greater than the changes in temperature variability in each month, which is attributed to changes in the monsoon system in East Asia. The abrupt changes in climate and NDVI were more significant in 1983 than in the other years due to the impacts of El Niño/Southern Oscillation (ENSO). Using these results, the influences of changes in climate variability on vegetation were studied in the whole nation, and eight regions were defined according to the vegetation division map of China. The results show that abrupt climate changes at a small scale cannot cause abrupt NDVI changes directly. At a nationwide level, over a longer time scale the persistence of above/below average temperature determines the changes in NDVI; at a shorter time scale, changes in the magnitude of precipitation influence NDVI significantly. Such regional climate variability affects vegetation in different ways owing to the diversity of vegetation types, climatic conditions and topography of the land. [ABSTRACT FROM AUTHOR]

The hydrological response to climate change in the Tarim River Basin was investigated by analysing the hydrological, temperature and precipitation data of the past 50 years. The long-term trend of the hydrological time-series, including air temperature, precipitation, and streamflow, was examined by using both parametric and non-parametric techniques and the plausible association between streamflow and climate change by the method of grey correlation analysis. The results show that the study area became warmer in the last few decades. The air temperature experienced a significant monotonic increase by 5%; the precipitation showed a significant decrease in the 1970s and then a major increase in the 1980s and 1990s, with average annual precipitation up by 6-8 mm per decade. A step change occurred in both temperature and precipitation around 1986, with mean temperature and precipitation increasing from 67°C and 146 mm before 1986 to 7.3°C and 180 mm respectively after 1986. The temperature has risen by nearly 1 °C over the past 50 years, possibly resulting from the impact of global climate change. Streamflows in the Aksu River and the Yarkant River have shown a significant (P < 0.05) tendency of increase. This is particularly the case for the Aksu River. The coefficients of streamflow increase in the Aksu and Yarkant Rivers are 0.41 and 0.13 respectively. The results of grey correlation analysis show that in the Aksu River, which is located in the northwest of the basin, the impact of precipitation on streamflow is much greater than that of temperature. However, in the Hotan River, which is located in the southwest of the basin, the impact of temperature on streamflow is much greater than that of precipitation. This is likely to be related to the geographic distribution of the headstreams of the rivers. [ABSTRACT FROM AUTHOR]