Interannual variation and chemical characterization of major water-soluble inorganic ions in snow across Northwest China

From November 2018 to April 2020, 438 snow samples were collected near two field observation sites in Heihe and Altay, Northwest China, and the pH and major water-soluble inorganic ions (Ca2+, SO42−, Na+, NO3−, Cl−, K+, Mg2+, and NH4+) were analyzed. To identify the source of ions, the enrichment factor method, Pearson correlation analysis, and HYSPLIT (Hybrid Single Practical Lagrangian Integrated Trajectory) backward trajectory analysis were employed. The snow was nearly pH neutral, and Ca2+ was the dominant cation present. The anion concentration demonstrated high variability. Affected by geographical location and atmospheric circulation, the concentration of soluble inorganic ions in snow from the Altay region was higher than that in the Heihe region and remote areas at high altitude or high latitude. Compared with 2018/2019, ion concentrations in snow increased in 2019/2020, especially in the Altay region. Moreover, the temporal trend of ion concentrations was stable, indicating that the source and migration path of ions had strong consistency. Our study suggested that terrestrial sources are the main driving factors for the ions observed in snow samples from Northwest China, and some ions are also the result of anthropogenic sources (NH4+, SO42−, and NO3−), marine sources (Cl− and Na+), and salt mine dust (Cl−, Na+, SO42−, and K+)

Contribution of recycled moisture to local precipitation in the inland Heihe River Basin

Recycled moisture contributed by continental evaporation and transpiration plays an important role in regulating the hydrological processes and atmospheric humidity budget in arid inland river basins. However, knowledge of moisture recycling within many large inland basins and the factors that control moisture recycling is generally lacking. Based on a three-component isotopic mixing model, we assessed the characteristics of moisture recycling in China’s semi-arid Heihe River Basin. During the active growing season, almost half of the precipitation in the upper reaches was provided by local moisture recycling, and the main contribution came from transpiration. In the middle reaches, almost half of the precipitation in the artificial oasis and the desert-oasis ecotone was also provided by local moisture recycling, and the transpiration fraction (fTr) and evaporation fraction (fEv) of the artificial oasis differed from those of the desert-oasis ecotone. In the lower reaches, less than 25% of the precipitation was provided by local moisture recycling. Mean fTr values were relatively low in the Gobi (15.0%) in the middle reaches and in the riparian forest at Ejina (25.6%) in the lower reaches. The positive correlations between fTr and both precipitation and relative humidity suggest that higher precipitation and relative humidity promote transpiration fraction, whereas higher vapor pressure deficit reduces transpiration fraction. The positive correlation between fEv and temperature and vapor pressure deficit, and the negative correlation between fEv and relative humidity indicate that higher temperature and vapor pressure deficit promotes evaporation fraction, whereas higher relative humidity reduces the evaporation fraction. Our results show that contributions of recycled moisture (especially transpiration) to local precipitation play an important role in regional water resource redistribution in the arid and semi-arid region of northwestern China

A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium

To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400

Pollen analysis and paleoecology from the Bortala River National Wetland Park, located in the Wenquan County, Xinjiang Province, Northwest China

Grasslands cover 41.7% of China's land surface and distribute mainly in NW China. To project future change of grassland fires, it is essential to explore paleofire dynamics. However, comparatively little is known about the patterns and driving forces of grassland fires in NW China due to the scarcity of paleorecords. Here, we present Holocene sedimentary records of grassland fire and vegetation in westerly-dominated Xinjiang (NW China) to examine fire-fuel-climate interactions. We find that grassland fire-regime is fuel-limited, consistent with other grasslands worldwide. We reveal that burning increased throughout the Holocene, due to increasing moisture, grass cover, fuel load and temperature of spring fire season. The Holocene pattern of burning coincides with several other records nearby and a global-scale grassland fire record. Our results are different from monsoonal China where fuel load is not a constraining factor and more (less) fires occurred during colder/drier (warmer/moister) periods in the Holocene

An evaluation framework for industrial ecology based on the symbiosis theory-Taking the π-shaped Curve Area in the Yellow River of China as an example

This paper defined regional industrial ecology (IE) to include four connotations: sustainable social-economic-ecological development, the high-quality transformation of the industrial system (IS) and the ecological system (ES), and harmonious symbiosis between IS and ES. Regarding the composition of the symbiotic system, this paper proposed that the IE evaluation be carried out from three aspects: the sustainability of the symbiotic environment, the high-quality development of the symbiont, and the symbiotic pattern between the symbiotic units. Then, the maturity index determined by the symbiont and symbiotic mode and the orderliness index determined by the symbiont and symbiotic environment were measured to determine the IE level from the perspectives of the system’s function and structure. Besides, this paper adopted Geodetector and Oprobit model to identify the influencing factors of IE. Taking the π-shaped Curve Area of the Yellow River as the study area, this paper found that the IE systems’ structural orderliness of capital cities and resource-based cities was low, while the orderliness level of non-resource-based cities was high. The IE systems’ functional maturity level in the northwest Area was better than that of the southeast. The IE level was high in Inner Mongolia while low in Shanxi and Ningxia. Scientific innovation, economic development, openness degree, ecological pressure, industrial structure, urbanization level, and government influence have different influences on the IE systems’ orderliness and maturity levels. The findings of this paper provided a basis for realizing IE and promoting the high-quality transformation of the whole basin

Terrain Effects on Regional Precipitation in a Warm Season over Qinling-Daba Mountains in Central China

The terrain effects of Qinling–Daba Mountains on reginal precipitation during a warm season were investigated in a two-month day-to-day experiment using the Weather Research and Forecasting (WRF) model. According to the results from the terrain sensitivity experiment with lowered mountains, Qinling–Daba Mountains have been found to have an obvious effect on both the spatial-temporal distribution and diurnal cycle of reginal precipitation from July to August in 2019, where the Qinling Mountains mainly enhanced the precipitation around 34° N, and the Daba Mountains mainly enhanced it around 32° N at the time period of early morning and midnight. Horizontal distribution of water vapor and convective available potential energy (CAPE), as well as cross section of vertical velocity of wind and potential temperature has been studied to examine the key mechanisms for these two mountains’ effect. The existence of Qinling Mountains intercepted transportation of water vapor from South to North in the lower troposphere to across 34° N and caused an obvious enhancement of CAPE in the neighborhood, while the Daba Mountains intercepted the northward water vapor transportation to across 32° N and caused an enhanced CAPE nearby. The time period of the influence is in a good accordance with the diurnal cycle. In the cross-section, the existence of Qinling Mountains and Daba Mountains are found to stimulate the upward motion and unstable environment effectively at around 34° N and 32° N, separately. As a result, the existence of the two mountains lead to a favorable environment in water vapor, thermodynamic, and dynamic conditions for this warm season precipitation