Evaluating microphysics scheme impacts on summer precipitation in Northwestern China using a convection permitting WRF model

A hybrid statistical-dynamical prediction model for summer precipitation in northwestern China based on NCEP CFSv2

Application of deep learning in summer climate prediction over northwestern China based on CWRF model

The precipitation in the Qilian (QMA) and Tienshan (TMA) mountain areas is one of the main sources of subsurface and surface water in northwestern China (NWC). Based on two datasets, CN05.1 and station‐observed daily precipitation, we found that summer precipitation in 1979–2020 exhibited an increasing trend in NWC. The results of rotation empirical orthogonal function (REOF) analysis also separated the increased precipitation patterns in the QMA and TMA from the other REOF modes; the proportion of the precipitation of these areas to the total NWC summer precipitation substantially increased (0.12%⋅year−1 and 0.03%⋅year−1, respectively). According to the moisture budget, the evaporation changes in the QMA and TMA were coherently coupled with precipitation, which suggested the feedback between increasing evaporation and precipitation with the recently warming climate. The precipitation increase was larger than that of evaporation, indicating a net wetting trend in the QMA and TMA. The increase in zonal horizontal and vertical moisture advection terms contributed more to the increased precipitation in the QMA. The increase in meridional moisture advection contributed more to the increased precipitation in the TMA. We concluded comprehensive frameworks of the water vapor transport in climate change in mountain areas in NWC which aimed to contribute to the understanding of arid region hydrology.

Trend of increasing Holocene summer precipitation in arid central Asia: Evidence from an organic carbon isotopic record from the LJW10 loess section in Xinjiang, NW China

Prediction of Summer Precipitation via Machine Learning with Key Climate Variables：A Case Study in Xinjiang, China

Changes in river discharge in typical mountain permafrost catchments, northwestern China

Simulations of the impact of orbital forcing and ocean on the Asian summer monsoon during the Holocene

Spatial characteristics of two dominant shrub populations in the transition zone between oasis and desert in the Heihe River Basin, China

In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annual ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and July. Annual ring and earlywood widths are significantly and positively correlated with total monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that when summer temperatures are higher than the mean summer temperature synchronization and the summer precipitation lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formed when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.

Using daily precipitation data from 25 stations, NCEP/NCAR reanalysis data, and 12 climate indices for boreal summers from 1963 to 2017, we investigate the interdecadal variation and causes of extreme precipitation in northern Xinjiang Province (NXJ), northwestern China. The summer frequency of daily precipitation extremes (DPEs), summer precipitation from DPEs, and contribution of precipitation from DPEs to total summer precipitation have increased significantly since the early 1990s, and this increase in extreme precipitation is more intense at stations in the eastern part of NXJ. Comparing the periods 1963–1988 and 1992–2017, the anomalous circulation over the Mongolian Plateau changed from cyclonic to anti-cyclonic, and the center of the anomalous cyclonic circulation over Central Asia shifted northward from the Iranian Plateau to the Aral Sea. These changes in anomalous circulation pattern induced changes in the paths of water vapor transport and the distribution of moisture convergence, which explain well the interdecadal increase in extreme precipitation and its spatial variability. Further analysis confirms evident impacts of the Indian Ocean basin mode (IOBM) and Scandinavia teleconnection pattern on the development of anomalous circulation related to the interdecadal increase in extreme precipitation. A positive IOBM favors the northward transport of moisture from the northern Indian Ocean to Xinjiang Province and the development of anomalous cyclonic circulation over Central Asia in the middle and upper troposphere. The negative phase of the Scandinavia pattern, which has prevailed since the late 1970s, and the enhanced out of phase connection between the anomalous circulation over Scandinavia Peninsula and the West Siberia during 1992–2017 favors the development of anomalous anti-cyclonic circulation over the Mongolian Plateau.

Precipitation division and climate shift in China were analysed using daily precipitation data from 486 stations for the period 1960–2000. A modified hierarchical clustering method was used to divide China into sub-regions that have a coherent annual cycle, interannual evolutions and long-term trends. A division with 20 grouping areas can well describe the anomalous regional features seasonally, and a division with 40 grouping areas can reach a relatively stable level, theoretically for the annual and summer precipitation in mainland China. Rapid changes or interdecadal transition points of the regional precipitation series are detected by a multiple timescale t-test method. For mean annual precipitation, the interdecadal shift from a low to a high level is found to occur around 1987 in the Xinjiang region and around 1983 in Northeast China. The transition points of increasing summer rainfall in the eastern Tibetan Plateau and the lower Yangtze River are centred closely about 1979. Changes in the double-decadal precipitation are also detected for the two periods of 1961–1980 and 1981–2000. An increasing trend in annual precipitation is mainly found in the lower Yangtze River valley, the Xinjiang region, and Northeast China. Decreasing annual precipitation is mainly situated from the middle Yangtze River to the Yellow River. In summer and winter, the spatial pattern of precipitation anomalies shows two pairs of contrasting shifts with negative departures in North China and southern coastal China, while positive departures are found in the middle and lower Yangtze River valley and Northeast China. This pattern of regional precipitation shift in China is associated with southerly monsoon flow in eastern China and westerly flow in northwestern China.

The effect of different cumulus parameterization schemes (CPSs) on precipitation over China is investigated by using the International Centre for Theoretical Physics (ICTP) Regional Climate Model version 4.3 (RegCM-4.3) coupled with the land surface model BATS1e (Biosphere-Atmosphere Transfer Scheme version 1e). The ERA-interim data are utilized to drive a group of simulations over a 31-yr period from September 1982 to December 2012. Two typically sensitive regions, i.e., the eastern Tibetan Plateau (TP; 29°–38°N, 90°–100°E) and eastern China (EC; 26°–32°N, 110°–120°E), are focused on. The results show that all the CPSs have well reproduced the spatial distribution of annual precipitation in China. The simulation with the Emanuel scheme shows an overall overestimation of precipitation in China, different from the other three CPSs which only overestimate over northern and northwestern China but underestimate over southern China. Seasonally, the Tiedtke scheme shows the smallest overestimation in winter and summer, and the best simulation of the annual variance of precipitation. Interannual variations of precipitation among the four CPSs are generally simulated better in summer than in winter, and better for entire China than in the subregions of TP and EC. The precipitation trend is simulated better over EC than over TP, and better in summer than in winter. An overestimate (underestimate) of the East Asian summer monsoon index (EASMI) exists in the simulations with the Grell and the Emanuel (the Kuo and the Tiedtke) schemes. The smallest EASMI bias in the Tiedtke simulation could explain its small precipitation bias. A negative correlation between the EASMI and summer precipitation over the middle and lower reaches of Yangtze River is found in the Grell and the Emanuel simulations, but was missed by the simulations using the Kuo and the Tiedtke schemes.

Understanding the responses of different plant species to changes in available water sources is critical for accurately modeling and predicting species dynamics. Our study aimed to explore whether there were differences in water-use strategies between the two coexisting shrubs (Reaumuria soongorica and Nitraria sphaerocarpa) in response to different amounts of summer precipitation. We conducted 3 years of field observations at three sites along an aridity gradient from the middle to lower reaches of the Heihe River basin, northwestern China. Stable oxygen composition (δ18O) in plant xylem water, soil water and groundwater were analyzed concurrently with ecophysiological measurements at monthly intervals during the growing seasons. Water source for coexisting R. soongorica and N. sphaerocarpa did not differ at the sites with high precipitation, but significantly differed in more arid locations. The N. sphaerocarpa was more sensitive to summer precipitation than R. soongorica in terms of predawn water potential, stomatal conductance and foliage carbon-isotope discrimination. The plants relying on groundwater maintained consistent water use strategies, but not plants that took up precipitation-derived water. We also found that the difference in water source uptake between the coexisting species was more apparent in more arid locations.

The northwestern corner of China (NWCC) experienced a decadal transition in summer precipitation during 1982–2010, with a significant upward trend in 1982–2000 (P1) but a downward one in 2001–2010 (P2). A spatially unbounded dynamic recycling model is developed to estimate the moisture sources and moisture transport variations based on ERA‐Interim data. The results suggest that more than 88% of NWCC precipitation has external moisture origins in the southwest and northwest terrestrial areas. The increasing precipitation trend during P1 can be explained by the increasing moisture contribution from the southwest and decreasing contribution from the northwest. However, the opposite trends cause the decreasing precipitation trend during P2. In general, the decadal precipitation transition is mainly determined by the variation of short‐distance moisture transport from central Asia, although opposite moisture transport variations exist in the Ural Mountains and Northeast Europe. The variation of the precipitation trend is closely associated with a well‐organized wave train propagation from the North Atlantic to central Asia. During P1, the wave train structure consists of a titled positive phase North Atlantic Oscillation (NAO), an anticyclonic circulation over Europe, and a cyclonic anomaly over central Asia, which promotes the southwest moisture flux to NWCC. But the opposite circulation pattern dominates P2. The energy dispersion due to the breakdown of the NAO determines the phase and strength of the downstream wave anomalies over Eurasia. This suggests that the summer NAO might influence the decadal variation of NWCC precipitation through the decadal modulation of the Eurasia wave train.

According to simulations, permafrost area in the Tienshan Mountains has decreased by about 1.73 × 104 km2 (or 20.91%) from the 1960s to the 2000s, and the freeze state of seasonally frozen ground (SFG) exhibited delaying freeze, advancing thaw, shortening freeze days and shallowing freeze depth. River discharge has changed largely, especially for winter and minimum monthly discharge. The rivers with low catchment permafrost coverage tended to have the highest increasing rates in winter discharge, minimum monthly discharge, winter discharge ratio (proportion of winter discharge contribution to total annual flow) and minimum monthly discharge ratio (proportion of minimum monthly discharge contribution to total annual flow). Gradually increasing correlations of maximum seasonally frozen depth (SFD) with the hydrological variables may indicate that the response of river discharge to frozen ground change is a long-term process. Possibly a result of frozen ground degradation, summer precipitation may strengthen the influences on low flow.