Aerosols can alter atmospheric stability through radiative forcing, thereby changing mean and daily extreme precipitation on regional scales. However, it is unclear how extreme sub-daily precipitation responds to aerosol radiative effects. In this study, we use the regional climate model (RCM) Consortium for Small-scale Modeling (COSMO) to perform convection-permitting climate simulations at a kilometer-scale (0.04 degrees/similar to 4.4 km) resolution for the period 2001-2010. By evaluating against the observed hourly precipitation-gauge data, the COSMO model with explicit deep convection can effectively reproduce sub-daily and daily extreme precipitation events, as well as diurnal cycles of summer mean precipitation and wet hour frequency. Moreover, aerosol sensitivity simulations are conducted with sulfate and black carbon aerosol perturbations to assess the direct and semi-direct aerosol effects on extreme sub-daily precipitation in the COSMO model. The destabilizing effects associated with decreased sulfate aerosols intensify extreme sub-daily precipitation, while increased sulfate aerosols tend to induce an opposite change. In contrast, the response of extreme sub-daily precipitation to black carbon aerosol perturbations exhibits a nonlinear behavior and potentially relies on geographical location. Overall, the scaling rates of extreme precipitation intensities decrease and approach the Clausius-Clapeyron rate from hourly to daily time scales, and the responses to sulfate and black carbon aerosols vary with precipitation durations. This study improves the understanding of aerosol radiative effects on sub-daily extreme precipitation events in RCMs.

This study quantifies the impacts of climate change on the mine life cycle (development, operation and closure phases) of 30 mines located in the northern regions of Canada. To this end, climate projections based on a five -member transient climate change simulation ensemble, performed using a state-of-the art regional climate model, spanning the 1991-2050 period, corresponding to the Representative Concentration Pathway 8.5 emis-sion scenario are used. A reanalysis-driven simulation for the 1991-2010 period compared against available observations confirm suitability of the model for application in climate change simulations. Assessment of projected changes to mine-relevant climate variables that are important from structural integrity and operation perspectives reveal potential vulnerabilities and opportunities. Active layer thickness increases in the 0.3-2 m range in permafrost regions, coupled with increases in flood probability, as reflected in snow-melt rate increases in the 0.14-6.77% range and increases in the 100-year return levels of daily maximum rainfall in the 5-50% range, suggest potential impacts on the structural integrity of mine infrastructure, such as slope instability and foundation settlement of tailings dams, and supporting infrastructure such as ice/all-season roads. Increases in soil moisture, projected in the 0-11% range, at a few mines, suggest potential impacts on material handling systems, such as increases in the traction factor of the muck-haul and tire rolling resistance, that can lead to low productivity. Projected increases to wind speeds in the 5-10% range for the northernmost regions suggest po-tential impacts on the tailings management facility in terms of increases in tailings resuspension. Overall, this study identified northernmost and northeastern mines to be more vulnerable, with air/soil temperature, pre-cipitation and wind speed being the most influential climate variables. This systematic study, for the first time, has identified potential vulnerabilities of northern Canadian mines, which can inform future high-resolution climate modelling and detailed at-site climate-mine interaction studies that is required for climate-change adaptation related decision-making.

Dynamical downscaling generally performs poorly on the Tibetan Plateau (TP), due to the region's complex topography and several aspects of model physics, especially convection and land surface processes. This study investigated the effects of the cumulus parameterization scheme (CPS) and land-surface hydrology scheme (LSHS) on TP climate simulation during the wet season using the RegCM4 regional climate model. To address these issues and seek an optimal simulation, we conducted four experiments at a 20 km resolution using various combinations of two CPSs (Grell and MIT-Emanuel), two LSHSs (the default TOPMODEL [TOP], and Variable Infiltration Capacity [VIC]). The simulations in terms of 2-m air temperature, precipitation (including large-scale precipitation [LSP] and convective precipitation [CP]), surface energy-water balance, as well as atmospheric moisture flux transport and vertical motion were compared with surface and satellite-based observations as well as the ERA5 reanalysis dataset for the period 2006-2016. The results revealed that the model using the Grell and TOP schemes better reproduced air temperature but with a warm bias, part of which could be significantly decreased by the MIT scheme. All schemes simulated a reasonable spatial distribution of precipitation, with the best performance in the experiment using the MIT and VIC schemes. Excessive precipitation was produced by the Grell scheme, mainly due to overestimated LSP, while the MIT scheme largely reduced the overestimation, and the simulated contribution of CP to total precipitation was in close agreement with the ERA5 data. The RegCM4 model satisfactorily captured diurnal cycles of precipitation amount and frequency, although there remained some differences in phase and magnitude, which were mainly caused by the CPSs. Relative to the Grell scheme, the MIT scheme yielded a weaker surface heating by reducing net radiation fluxes and the Bowen ratio. Consequently, anomalous moisture flux transport was substantially reduced over the southeastern TP, leading to a decrease in precipitation. The VIC scheme could also help decrease the wet bias by reducing surface heating. Further analysis indicated that the high CP in the MIT simulations could be attributed to destabilization in the low and mid-troposphere, while the VIC scheme tended to inhibit shallow convection, thereby decreasing CP. This study's results also suggest that CPS interacts with LSHS to affect the simulated climate over the TP.

The regional climate model RegCM 4.4 at 50km resolution is used to conduct a sensitivity study over South Asia Coordinated Regional climate Downscaling Experiment domain during the period 1998-2002, in order to investigate the best cumulus convective precipitation scheme, planetary boundary layer (PBL) and land-surface scheme. The inferences obtained from 11 sensitivity experiments include the better performance of community land model version 4.5 (CLM 4.5) over biosphere-atmosphere transfer scheme, Tiedtke as cumulus convective precipitation scheme and University of Washington (UW) as PBL scheme. The simulation with these parameterization schemes well captures the monsoon precipitation pattern over India similar to 7mm/day and North Eastern Region of India (NER) similar to 12mm/day, which are comparable to observations with a significant correlation of R-2>0.93. The observed temperatures are also well simulated by the model. Therefore, RegCM 4.4 with these parameterization schemes is further used to simulate the aerosol fields (aerosol optical depth, AOD and black carbon, BC) and aerosol direct radiative forcing (DRF) for the period 2011-2014 over the same domain with special emphasis on NER. The model captures the seasonality in AOD and BC over the Indian Subcontinent and NER. BC hotspots in the Indo-Gangetic Plain and China are well captured by the model. The observed to simulated BC ratio over Dibrugarh (located in NER) is found to be improved. The model underestimation is significant in the dry season when burning over the region is predominant, which has not been considered by the emission inventories properly. Simulated DRF is found to exhibit seasonality qualitatively as well as a North-South latitudinal gradient.

RegCM4.3, a high-resolution regional climate model, which includes five kinds of aerosols (dust, sea salt, sulfate, black carbon and organic carbon), is employed to simulate the East Asian summer monsoon (EASM) from 1995 to 2010 and the simulation data are used to study the possible impact of natural and anthropogenic aerosols on EASM. The results show that the regional climate model can well simulate the EASM and the spatial and temporal distribution of aerosols. The EASM index is reduced by about 5% by the natural and anthropogenic aerosols and the monsoon onset time is also delayed by about a pentad except for Southeast China. The aerosols heat the middle atmosphere through absorbing solar radiation and the air column expands in Southeast China and its offshore areas. As a result, the geopotential height decreases and a cyclonic circulation anomaly is generated in the lower atmosphere. Northerly wind located in the west of cyclonic circulation weakens the low-level southerly wind in the EASM region. Negative surface radiative forcing due to aerosols causes downward motion and an indirect meridional circulation is formed with the low-level northerly wind and high-level southerly wind anomaly in the north of 25 degrees N in the monsoon area, which weakens the vertical circulation of EASM. The summer precipitation of the monsoon region is significantly reduced, especially in North and Southwest China where the value of moisture flux divergence increases.

A regional climate model (RegCM4.3.4) coupled with an aerosol-snow/ice feedback module was used to simulate the deposition of anthropogenic light-absorbing impurities in snow/ice and the potential radiative feedback of black carbon (BC) on temperature and snow cover over the Tibetan Plateau (TP) in 1990-2009. Two experiments driven by ERA-interim reanalysis were performed, i.e., with and without aerosol-snow/ice feedback. Results indicated that the total deposition BC and organic matter (OM) in snow/ice in the monsoon season (May-September) were much more than non-monsoon season (the remainder of the year). The great BC and OM deposition were simulated along the margin of the TP in the non-monsoon season, and the higher deposition values also occurred in the western TP than the other regions during the monsoon period. BC-in-snow/ice decreased surface albedo and caused positive surface radiative forcing (SRF) (3.0-4.5 W m(-2)) over the western TP in the monsoon season. The maximum SRF (5-6 W m(-2)) simulated in the Himalayas and southeastern TP in the non-monsoon season. The surface temperature increased by 0.1-1.5 degrees C and snow water equivalent decreased by 5-25 mm over the TP, which showed similar spatial distributions with the variations of SRF in each season. This study provided a useful tool to investigate the mechanisms involved in the effect of aerosols on climate change and the water cycle in the cryospheric environment of the TP.

Mineral aerosols scatter and absorb incident solar radiation in the atmosphere, and play an important role in the regional climate of High Mountain Asia (the domain includes the Himalayas, Tibetan Plateau, Pamir, Hindu-kush, Karakorum and Tienshan Mountains). Dust deposition on snow/ice can also change the surface albedo, resulting in perturbations in the surface radiation balance. However, most studies that have made quantitative assessments of the climatic effect of mineral aerosols over the High Mountain Asia region did not consider the impact of dust on snow/ice at the surface. In this study, a regional climate model coupled with an aerosol-snow/ice feedback module was used to investigate the emission, distribution, and deposition of dust and the climatic effects of aerosols over High Mountain Asia. Two sets of simulations driven by a reanalysis boundary condition were performed, i.e., with and without dust-climate feedback. Results indicated that the model captured the spatial and temporal features of the climatology and aerosol optical depth (ADD). High dust emission fluxes were simulated in the interior of the Tibetan Plateau (TP) and the Yarlung Tsangpo Valley in March-April-May (MAM), with a decreasing trend during 1990-2009. Dry deposition was controlled by the topography, and its spatial and seasonal features agreed well with the dust emission fluxes. The maximum wet deposition occurred in the western (southern and central) TP in MAM (JJA). A positive surface radiative forcing was induced by dust, including aerosol-snow/ice feedback, resulting in 2-m temperature increases of 0.1-0.5 degrees C over the western TP and Kunlun Mountains in MAM. Mineral dust also caused a decrease of 5-25 mm in the snow water equivalent (SWE) over the western TP, Himalayas, and Pamir Mountains in DJF and MAM. The long-term regional mean radiative forcing via dust deposition on snow showed an rising trend during 1990-2009, which suggested the contribution of aerosols surface radiative effects induced by snow darkening was increased since 1990. (C) 2016 Elsevier B.V. All rights reserved.

Carbonaceous aerosols including black carbon and organic carbon over the Third Pole regions are simulated using a regional climate model (RegCM4.3) coupled with a chemistry-aerosol module. Results show that the model can simulate well the climatology of the Third Pole region in monsoon and non-monsoon seasons, but the model shows a cold bias and an overestimation of precipitation over the Himalayas and the northern Tibetan Plateau. The model also performs reasonably well in terms of aerosol optical depth and near surface aerosol concentration when compared with satellite datasets and in situ observations. BC wet deposition in monsoon seasons is more (less) than that in non-monsoon seasons in the southern (northwestern) parts of the Third Pole region. Westerly winds prevail throughout the year and transport carbonaceous particles from central Asia to the northern Tibetan Plateau. In the monsoon period, aerosols can cross the Himalayas and can be transported to high altitudes by the southwesterly winds over South Asia. Dry deposition shows a topography-controlled distribution, with low fluxes within and high fluxes outside of the Tibetan Plateau. Mixed carbonaceous aerosols produce positive shortwave radiative forcing in the atmosphere and negative forcing at the surface. Shortwave forcing is with less magnitude over the Third Pole region. Longwave radiation forcing is negative over the Pamir Plateau and positive over the Tibetan Plateau during monsoon season. In non-monsoon season, longwave radiative forcing is negative in the Himalayas and southern parts of the Tibetan Plateau. Aerosols increase surface air temperatures by 0.1-0.5 A degrees C over the Tibetan Plateau and decrease temperatures in South Asia during the monsoon season. In the non-monsoon period, temperatures decrease by 0.1-0.5 A degrees C over the southern Tibetan Plateau. Spatial changes in temperature are consistent with the distribution of longwave radiative forcing, which indicates that aerosols' longwave radiative forcing probably plays an important role in the climatic impact of aerosols over the Third Pole region.

This study examines the mass distributions and direct and semi-direct effects of different Anthropogenic Aerosols (AAs) [i.e. sulphate, Black Carbon (BC), Organic Carbon (OC) and all together (SBO)] over South Africa using the 12 year runs of the Regional Climate Model (RegCM4). The maximum burden and Surface Radiative Forcing (SRF) values are found over AA source regions: up to 9mg m(-2) [-12W m(-2)] for sulphate and 12.1mg m(-2) [-14W m(-2)] for SBO during austral summer, as well as, up to 0.85mg m(-2) [-2W m(-2)] for BC and 2.2mg m(-2) [-0.68W m(-2)] for OC during austral winter. Contrary to sulphate, both BC and OC aerosols reduce incoming solar radiation reaching the ground via enhancing shortwave radiative heating in the atmosphere. The climatic feedback caused by AAs resulted in changes in background aerosol concentrations. As a result of this and other processes of the climate system, the climatic effects of AAs were also found in remote areas away from the main AA loading zones. However, in terms of statistical significance, the climatic influences of AAs are more prominent in the vicinity of their source regions. The overall feedback of the climate system to the radiative effects of AAs resulted in both positive and negative changes to the Net Atmospheric radiative Heating Rate (NAHR). Areas that experience a reduction in NAHR exhibited an increase in Cloud Cover (CC). During the NAHR enhancement, CC over arid areas decreased; while CC over the wet/semi-wet regions increased. The changes in Surface Temperature (ST) and sensible heat flux are more closely correlated with the CC change than SRF of AAs. Furthermore, decreases or increases in ST, respectively, lead to reductions or enhancements in boundary layer height and the vice versa in surface pressure. Overall, the results suggest that the feedback of cloud fields has a far-reaching role in moderating other climatic anomalies.

The different spatial distributions of aerosol-induced direct radiative forcing and climatic effects in a weak (2003) and a strong (2006) East Asian summer monsoon (EASM) circulation were simulated using a high-resolution regional climate model (RegCM3). Results showed that the atmospheric circulations of summer monsoon have direct relations with transport of aerosols and their climatic effects. Both the top-of-the-atmosphere (TOA) and the surface-negative radiative forcing of aerosols were stronger in weak EASM circulations. The main difference in aerosol-induced negative forcing in two summers varied between 2 and 14 W m(-2) from the Sichuan Basin to North China, where a maximum in aerosol-induced negative forcing was also noticed in the EASM-dominated areas. The spatial difference in the simulated aerosol optical depth (AOD) in two summers generally showed the similar pictures. Surface cooling effects induced by aerosols were spatially more uniform in weak EASM circulations and cooler by about 1-4.5 degrees C. A preliminary analysis here indicated that a weaker low-level wind speed not conducive to the transport and diffusion of aerosols could make more contributions to the differences in the two circulations.