Permafrost carbon could produce a positive climate feedback. Until now, the ecosystem carbon budgets in the permafrost regions remain uncertain. Moreover, the frequently used models have some limitations especially regarding to the freeze-thaw process. Herein, we improved the IBIS model by incorporating an unfrozen water scheme and by specifying the parameters to estimate the present and future carbon budget of different land cover types (desert steppe, steppe, meadow, and wet meadow) in the permafrost regions. Incorporating an unfrozen water scheme reduced the mean errors in the soil temperature and soil water content by 25.2%, and the specifying leaf area parameters reduced the errors in the net primary productivity (NPP) by 79.9%. Further, the simulation results showed that steppes are carbon sources (39.16 gC/m(2)/a) and the meadows are carbon sinks (-63.42 gC/m(2)/a ). Under the climate warming scenarios of RCP 2.6, RCP 6.0, and RCP 8.5, the desert steppe and alpine steppe would assimilated more carbon, while the meadow and wet meadow were projected to shift from carbon sinks to carbon sources in 2071-2100, implying that the land cover type plays an important role in simulating the source/sink effects of permafrost ecosystem carbon in the IBIS model. The results highlight the importance of unfrozen water to the soil hydrothermal regime and specific leaf area for the growth of alpine vegetation, and present new insights on the difference of the responses of various permafrost ecosystems to climate warming.

The Black carbon (BC) and Brown carbon (BrC) concentration has been measured over Srinagar (Garhwal) in central Himalayas during October 2020 to September 2021 periods. The average BC mass was 2.59 +/- 1.96 mu g m- 3 and its absorption coefficients were abundant at shorter wavelength. BC seasonal variation exhibited a significant variability, with highest during winter (4.54 +/- 2.64 mu g m- 3) followed by pre-monsoon (2.69 +/- 2.04 mu g m- 3) and post-monsoon (1.93 +/- 0.91 mu g m- 3) while lowest was observed in the monsoon (1.05 +/- 0.54 mu g m- 3). Relatively high contribution of total spectral light absorption coefficient (Abs lambda) was observed (75.94 Mm-1) at 370 nm than longer wavelength (16.86 Mm-1) at 950 nm. The BrC contribution was higher at 370 nm (32.50 Mm-1) to the total babs (lambda), while at higher wavelengths it has extensively decreased (2.54 Mm-1 at 660 nm). Seasonally, the absorption coefficient of BC and BrC was greater in winter (83.99 and 68.37 Mm-1) while lowest in monsoon (19.38 and 9.27 Mm-1), respectively. The babs BrC/babs (t) ratio revealed higher contribution of BrC in winters. The secondary brown carbon (BrCsec) and primary brown carbon (BrCpri) contributed 43.16 % and 56.88 % towards the total BrC Abs (lambda) at 370 nm with higher in winter and lowest in monsoon, respectively. BrCsec and BrCprim has shown higher contribution in evening (18.00-20.00 h) and in morning (09.00-11.00 h) hours. The average radiative forcing (RF) of BC was 36.11 +/- 6.99 Wm-2, 2.19 +/- 1.22 Wm-2 and -33.92 +/- 5.96 Wm-2 at the atmosphere (ATM), Top of the Atmosphere (TOA), and at the Surface (SUR), respectively.

Decline in snow mass threatens the regional economy that critically depends on meltwater. However, the economic scale of snow mass loss is hardly understood, and its role in the vulnerability of future economic development is unclear. We investigate the current reserves of snow cover and the value of its loss. The result showed that the total annual snow mass in western China declines at a rate of 3.3 x 10(9) Pg per decade (p < 0.05), which accounts for approximately 0.46% of the mean of annual snow mass (7.2 x 10(11) Pg). Snow mass loss over the past 40 years in western China turns into an average loss value of CN0.1 billion (in the present value) every year ($1 = CN7). If the trend continues at the current rate, the accumulated loss value would rise to CN63 billion by 2040. Furthermore, subject to the combinations of RCPs and SSPs scenario, the future economic value of snow mass loss in western China appears to accelerate driven by both declining snowmelt resources and socioeconomic development demand. RCP26-SSP1 is the pathway among all to have the least economic cost in replacing the snowmelt loss, and the cost would be quadrupled in RCP80-SSP3 scenario by 2100. At a basin scale, the declining snow mass would turn the regional economy to be more vulnerable except Junggar and Ili endorheic basin. The Ertis river and Qaidam endorheic basins display to be most vulnerable. It highlights that the snowvalue can be economically important in the regions ofwest China and should be considered more properly in water resources management. (C) 2020 The Author(s). Published by Elsevier B.V.

Despite the importance of the Yellow River to China, climate change for the middle reaches of the Yellow River Basin (YRB) has been investigated far less than for other regions. This work focuses on future changes in mean and extreme climate of the YRB for the near-term (2021-2040), mid-term (2041-2060), and far-term (2081-2100) future, and assesses these with respect to the reference period (1986-2005) using the latest REgional MOdel (REMO) simulations, driven by three global climate models (GCMs) and assuming historical and future [Representative Concentration Pathway (RCP) 2.6 and 8.5] forcing scenarios, over the CORDEX East Asia domain at 0.22 degrees horizontal resolution. The results show that REMO reproduces the historical mean climate state and selected extreme climate indices reasonably well, although some cold and wet biases exist. Increases in mean temperature are strongest for the far-term in winter, with an average increase of 5.6 degrees C under RCP 8.5. As expected, the future temperatures of the warmest day (TXx) and coldest night (TNn) increase and the number of frost days (FD) declines considerably. Changes to mean temperature and FD depend on elevation, which could be explained by the snow-albedo feedback. A substantial increase in precipitation (34%) occurs in winter under RCP 8.5 for the far-term. Interannual variability in precipitation is projected to increase, indicating a future climate with more extreme events compared to that of today. Future daily precipitation intensity and maximum 5-day precipitation would increase and the number of consecutive dry days would decline under RCP 8.5. The results highlight that pronounced warming at high altitudes and more intense rainfall could cause increased future flood risk in the YRB, if a high GHG emission pathway is realized.

Black carbon (BC), primary brown carbon (BrCpri), and secondary brown carbon (BrCsec) are important light-absorbing aerosol. BC and BrC from the surrounding area can reach the Tibetan Plateau (TP) and influence climate change and glacial melting. Here, we presented a study of the light absorption, radiative forcing, and potential source areas of BC and BrC over the northeastern, central, and southwestern TP. The higher light absorption was observed in the northeastern and southwestern sites compared to the central TP site. The major carbonaceous light-absorbing was attributed to BC with the percentages of 65%, 56%, and 82% in Ngari, Qinghai Lake, and Beiluhe, respectively. The heighten contribution of BrCsec to total light absorption indicated the importance of BrCsec in the TP, especially in the northeastern and southwestern areas. The BrCsec radiative forcings relative to BC were much higher than those of BrCpri. The potential BC and BrCpri source distributions were obtained.

We estimated the current (base years) and future (2021-2100) direct radiative forcing ( DRF) of four aerosol components (water-soluble, insoluble, black carbon (BC), and sea-salt) at urban (Yeonsan (Busan) and Gwangjin (Seoul)) and background sites (Aewol and Gosan (Jeju Island)), based on a modeling approach. The analysis for base years was conducted using PM2.5 samples measured at two urban and two background sites (Yeonsan and Gwangjin: 2016, Aewol and Gosan: 2014). The future DRFs were estimated according to changes in relative humidity (RH) of RCP8.5 climate change scenario at the same sites during four different periods (PI: 2021 similar to 2040, PII: 2041 similar to 2060, PIII: 2061 similar to 2080, and PIV: 2081 similar to 2100). In addition, we compared the differences between the DRFs of future (PI similar to PIV) and base years (2016 and 2014). Overall, the water-soluble component was predominant over all other components in terms of the concentrations, optical parameters (e.g., AOD), and DRFs, regardless of sites. For the base years, the monthly patterns of total DRFs for all components and the DRFs for the water-soluble component varied with sites, and months of their highest and lowest DRFs were different depending on sites. This might be due to the combined effect of the monthly patterns of the concentrations and RHs for each site. For the differences between the DRFs of future and base years, the highest future DRFs at Yeonsan and Aewol ranged from -59 to -63 W/m(2) increasing -20 (July in PII) to -28 W/m(2) (August in PIII) compared to the base years and from -73 to -74 W/m(2) increasing -31 (July in PII) to -41 W/m(2) (September in PIV), respectively. These DRFs at Gwangjin and Gosan ranged from -79 to -84 W/m(2) increasing -29 (June in PII and PIII) to -34 W/m(2) (June in PI) and from -58 to -92 W/m(2) increasing -14 (July in PII) to -26 W/m(2) (May in PI), respectively. The high heating rates at Yeonsan (up to 4.4 K/day in November) and Aewol (up to 3.7 K/day in February) of BC component might be caused by its strong radiative absorption.

为了研究多年冻土区地基融沉效应对路面结构应力状态的影响,基于水-热-力耦合作用理论,利用COMSOL有限元软件建立了冻土区连续配筋混凝土路面(CRCP)有限元模型,研究了基层与底基层材料参数、面板厚度与模量、配筋率对CRCP路面结构组合应力的影响,提出了适用于多年冻土区CRCP路面的合理结构形式.结果表明,地基融沉效应对于CRCP路面结构应力影响显著.融沉效应和车辆荷载耦合作用下,板内最大主应力随时间推移逐渐变大.板内最大主应力随面板、基层和底基层的厚度增加而减小,随各层模量的增加而增大,但配筋率的变化对其无影响.考虑融沉效应时,CRCP路面板+水泥稳定碎石+石灰土的路面结构较适宜于多年冻土区,可为多年冻土地区CRCP路面结构设计提供参考.

This study applies the nested-grid version of Goddard Earth Observing System (GEOS) chemical transport model (GEOS-Chem) to examine future changes (2000-2050) in SOA concentration and associated direct radiative forcing (DRF) over China under the Representative Concentration Pathways (RCPs). The projected changes in SOA concentrations over 2010-2050 generally follow future changes in emissions of toluene and xylene. On an annual mean basis, the largest increase in SOA over eastern China is simulated to be 25.1% in 2020 under RCP2.6, 20.4% in 2020 under RCP4.5, 56.3% in 2050 under RCP6.0, and 44.6% in 2030 under RCP8.5. The role of SOA in PM2.5 increases with each decade in 2010-2050 under RCP2.6, RCP4.5, and RCPS.5, with a maximum ratio of concentration of SOA to that of PM2.5 of 16.3% in 2050 under RCP4.5 as averaged over eastern China (20 degrees-45 degrees N, 100 degrees-125 degrees E). Concentrations of SOA are projected to be able to exceed those of sulfate, ammonium, and black carbon (BC) in the future. The future changes in SOA levels over eastern China are simulated to lead to domain-averaged (20 degrees-45 degrees N, 100 degrees-125 degrees E) DRI's of +0.19 W m(-2), +0.12 W m(-2), -0.28 W m(-2), and -0.17 W m(-2) in 2050 relative to 2000 under RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. Model results indicate that future changes in SOA owing to future changes in anthropogenic precursor emissions are important for future air quality planning and climate mitigation measures. (C) 2018 Elsevier B.V. All rights reserved.

The response of the East Asian summer monsoon (EASM) system to reductions in emissions of anthropogenic aerosols and their precursors at the end of the twenty-first century projected by Representative Concentration Pathway 4.5 is studied using an aerosol-climate model with aerosol direct, semi-direct, and indirect effects included. Our results show that the global annual mean aerosol effective radiative forcing at the top of the atmosphere (TOA) is +1.45 W m(-2) from 2000 to 2100. The summer mean net all-sky shortwave fluxes averaged over the East Asian monsoon region (EAMR) at the TOA and surface increased by +3.9 and +4.0 W m(-2), respectively, due to the reductions of aerosols in 2100 relative to 2000. Changes in radiations affect local thermodynamic and dynamic processes and the hydrological cycle. The summer mean surface temperature and pressure averaged over the EAMR are shown to increase by 1.7 K and decreased by 0.3 hPa, respectively, due to the reduced aerosols. The magnitudes of these changes are larger over land than ocean, causing a marked increase in the contrast of land-sea surface temperature and pressure in the EAMR, thus strengthening the EASM. The summer mean southwest and south winds at 850 hPa are enhanced over eastern and southern China and the surrounding oceans, and the East Asian subtropical jet shifted northward due to the decreases of aerosols. These factors also indicate enhanced EASM circulation, which in turn causes a 10 % increase in summer mean precipitation averaged over the EAMR.