Brown carbon (BrC) are important light-absorbing carbonaceous aerosols in the atmosphere, and it is of great significance to study the climate effects of BrC for regional or global climate change. This paper reviews recent advances in research on the radiative forcing of BrC, its effects on temperature and precipitation, and snow/ice albedo. Recent research suggests that: (1) Climate effects of aerosols can be represented more accurately when including BrC absorption in climate models; the regions with the highest global mean surface BrC concentrations estimated by models are mostly Southeast Asia and South America (biomass burning), East Asia and northeast India (biofuel burning), and Europe and North America (secondary sources); estimates of BrC radiative forcing are quite erratic, with a range of around 0.03-0.57 W m-2. (2) BrC heating lead to tropical expansion and a reduction in deep convective mass fluxes in the upper troposphere; cloud fraction and cloud type have a substantial impact on the heating rate estimates of BrC. The inclusion of BrC in the model results in a clear shift in the cloud fraction, liquid water path, precipitation, and surface flux. BrC heating decreases precipitation on a global scale, particularly in tropical regions with high convective and precipitation intensity, but different in some regions. (3) Uncertain optical properties of BrC, mixing ratio of radiation-absorbing aerosols in snow, snow grain size and snow coverage lead to higher uncertainties and lower confidence in the simulated distribution and radiative forcing of BrC in snow than BC. To reduce the uncertainty of its climate effects, future research should focus on improving model research, creating reliable BrC emission inventories, and taking into account the photobleaching and lense effects of BrC.

Changes in the hydrological regimes of Arctic rivers could affect the thermohaline circulation of the Arctic Ocean. In this study, we analysed spatiotemporal variations in temperature and precipitation in the Ob River Basin regions during 1936-2017 based on data from the Global Precipitation Climatology Center. Changes in discharge and response to climate change were examined based on monthly observed data during the same period. It is indicated the Ob River Basin experienced significant overall rapid warming and wetting (increased precipitation) in the study period, with average rates of 0.20 degrees C (10 year(-1)) and 5.3 mm (10 year(-1)), respectively. The annual spatial variations of temperature and precipitation showed different scales in different regions. The discharge in spring and winter significantly increased at a rate of 384.1 and 173.1 m(3)/s (10 year(-1)), respectively. Hydrograph separation indicated infiltration and supported that deep flow paths increased the contribution of groundwater to base flow. Meanwhile, the variation of the ratio of Q(max)/Q(min) suggested that the basin storage and the mechanism of discharge generation have significantly changed. The hydrological processes were influenced by changes of permafrost in a certain in the Ob River Basin. An increase in the recession coefficient (RC) implies that the permafrost degradation in the basin due to climate warming affected hydrological processes in winter. Permafrost degradation affected the Q(max)/Q(min) more significantly in the warm season than RC due to the enhanced infiltration that converted more surface water into groundwater in the cold season. The impact of precipitation on discharge, including surface flow and base flow, was more significant than temperature at the annual and seasonal scales in the Ob River Basin. The base flow was more obviously influenced by temperature than surface flow. The results of this study are significant for analyses of the basin water budget and freshwater input to the Arctic Ocean.

This study tested the hypothesis that soil organic carbon (SOC) and total nitrogen (TN) spatial distributions show clear relationships with soil properties and vegetation composition as well as climatic conditions. Further, this study aimed to find the corresponding controlling parameters of SOC and TN storage in high-altitude ecosystems. The study was based on soil, vegetation and climate data from 42 soil pits taken from 14 plots. The plots were investigated during the summers of 2009 and 2010 at the northeastern margin of the Qinghai-Tibetan Plateau. Relationships of SOC density with soil moisture, soil texture, biomass and climatic variables were analyzed. Further, storage and vertical patterns of SOC and TN of seven representative vegetation types were estimated. The results show that significant relationships of SOC density with belowground biomass (BGB) and soil moisture (SM) can be observed. BGB and SM may be the dominant factors influencing SOC density in the topsoil of the study area. The average densities of SOC and TN at a depth of 1 m were about 7.72 kg C m(2) and 0.93 kg N m 2. Both SOC and TN densities were concentrated in the topsoil (0-20 cm) and fell exponentially as soil depth increased. Additionally, the four typical vegetation types located in the northwest of the study area were selected to examine the relationship between SOC and environmental factors (temperature and precipitation). The results indicate that SOC density has a negative relationship with temperature and a positive relationship with precipitation diminishing with soil depth. It was concluded that SOC was concentrated in the topsoil, and that SOC density correlates well with BGB. SOC was predominantly influenced by SM, and to a much lower extent by temperature and precipitation. This study provided a new insight in understanding the control of SOC and TN density in the northeastern margin of the Qinghai-Tibetan Plateau.