Brown carbon (BrC) has been recognized as an important light-absorbing carbonaceous aerosol, yet understanding of its influence on regional climate and air quality has been lacking, mainly due to the ignorance of regional coupled meteorology-chemistry models. Besides, assumptions about its emissions in previous explorations might cause large uncertainties in estimates. Here, we implemented a BrC module into the WRF-Chem model that considers source-dependent absorption and avoids uncertainties caused by assumptions about emission intensities. To our best knowledge, we made the first effort to consider BrC in a regional coupled model. We then applied the developed model to explore the impacts of BrC absorption on radiative forcing, regional climate, and air quality in East Asia. We found notable increases in aerosol absorption optical depth (AAOD) in areas with high OC concentrations. The most intense forcing of BrC absorption occurs in autumn over Southeast Asia, and values could reach around 4 W m(-2). The intensified atmospheric absorption modified surface energy balance, resulting in subsequent declines in surface temperature, heat flux, boundary layer height, and turbulence exchanging rates. These changes in meteorological variables additionally modified near-surface dispersion and photochemical conditions, leading to changes of PM2.5 and O-3 concentrations. These findings indicate that BrC could exert important influence in specific regions and time periods. A more in-depth understanding could be achieved later with the developed model.

We use a spatially distributed and physically based energy and mass balance model to derive the ostrem curve, which expresses the supraglacial debris-related relative melt alteration versus the debris thickness, for the Djankuat Glacier, Caucasus, Russian Federation. The model is driven by meteorological data from two on-glacier weather stations and ERA-5 Land reanalysis data. A direct pixel-by-pixel comparison of the melt rates obtained from both a clean ice and debris-covered ice mass balance model results in the quantification of debris-related relative melt-modification ratios, capturing the degree of melt enhancement or suppression as a function of the debris thickness. The main results show that the distinct surface features and different surface temperature/moisture and near-surface wind regimes that persist over debris-covered ice significantly alter the pattern of the energy and mass fluxes when compared to clean ice. Consequently, a maximum relative melt enhancement of 1.36 is modeled on the glacier for thin/patchy debris with a thickness of 0.03 m. However, insulating effects suppress sub-debris melt under debris layers thicker than a critical debris thickness of 0.09 m. Sensitivity experiments show that especially within-debris properties, such as the thermal conductivity and the vertical debris porosity gradient, highly impact the magnitude of the sub-debris melt rates. Our results also highlight the scale-dependency as well as the dynamic nature of the debris thickness-melt relationship for changing climatic conditions, which may have significant implications for the climate change response of debris-covered glaciers. The presence of rocks, boulders and sediments on top of glacier ice can highly modify the behavior of mountain glaciers. As such, compared to a clean ice surface, a debris-covered ice surface is subject to a modified melting regime. In our study, we quantify this melt-modification effect for the Djankuat Glacier, a well-studied glacier situated in the Caucasus. The results are expressed by a so-called ostrem curve that quantifies the debris-related melt-modification effect and compares it to the corresponding debris thickness. Here, we present the first attempt to construct such a glacier-specific ostrem curve through sophisticated 2D glacier-wide energy and mass balance modeling. Our results show that the energy and mass balance at the glacier surface are greatly modified due to the debris, resulting in different melting regimes over both surface types. Hence, ice melt is enhanced for thin and patchy debris layers, whereas melt is increasingly suppressed for thick and continuous debris layers due to an insulating effect. The degree of melt modification and the shape of the ostrem curve are found to depend on the debris properties, the spatio-temporal distribution of the debris, and the local climatic conditions. Quantifying such melt-modification effects is important to more accurately understand and assess the behavior of (partly) debris-covered glaciers under a future warming climate. We use a spatially distributed and physically based energy and mass balance model to derive the ostrem curve for the Djankuat Glacier The sub-debris melt rates are especially sensitive to within-debris properties, such as the thermal conductivity, the debris porosity and its gradient The relative melt suppression of the debris cover is modeled to increase in a warming climate, regardless of the changes in debris thickness

Biomass burning (BB) greatly impacts the Maritime Continent through various mechanisms including agricultural burning, land clearing and natural response to drought. The dynamic characteristics of BB in terms of its spatiotemporal distribution, seasonality, transport mechanism, and aerosol properties have prompted numerous research efforts including field campaigns, in -situ measurements, remote sensing, and modelling. Although the differing perspectives of these studies have offered insights on understanding the regional BB issues, it is challenging to compare and resolve the wider picture because of the diversity of approaches. Human -induced global warming has certainly caused multiple observed changes in the regional meteorological characteristics. In this study, we review BB events in the Maritime Continent from 2012 to 2021, focusing on the meteorological influence and knowledge evolution in cloud -aerosol -radiation (CAR). Unlike other reviews, our review examines the occurrence of BB events using synergistic application of ground -based measurement, global reanalysis model and satellite product, which allows us to examine the anomalies for comparison with other studies and identify the unique features of the event. We identified four dominant modes of variability responsible for the occurrence of large-scale BB in the Maritime Continent: (1) El Nin similar to o Southern Oscillations (ENSO), (2) extreme positiveIndian Ocean Dipole (pIOD), (3) tropical cyclone (TC) activity, and (4) Madden -Julian Oscillations (MJO). We reconcile the past CAR studies and summarize their findings based on the four key CAR mechanisms: (1) instantanous radiative forcing from aerosol -radiation interactions, IRFari (2) and its subsequent adjustments, SAari, (3) instantanous radiative forcing from aerosol -cloud interactions, IRFaci, and (4) and its subsequent adjustments, SAaci. We urge future CAR studies in the Maritime Continent should focus on accurate characterization of the composition of biomass burning plume which is a mixture of peatland, agricultural burning and anthropogenic sources.

Humidity is a basic and crucial meteorological indicator commonly measured in several forms, including specific humidity, relative humidity, and absolute humidity. These different forms can be inter-derived based on the saturation vapor pressure (SVP). In past decades, dozens of formulae have been developed to calculate the SVP with respect to, and in equilibrium with, liquid water and solid ice surfaces, but many prior studies use a single function for all temperature ranges, without considering the distinction between over the liquid water and ice surfaces. These different approaches can result in humidity estimates that may impact our understanding of surface-subsurface thermal-hydrological dynamics in cold regions. In this study, we compared the relative humidity (RH) downloaded and calculated from four data sources in Alaska based on five commonly used SVP formulas. These RHs, along with other meteorological indicators, were then used to drive physics-rich land surface models at a permafrost-affected site. We found that higher values of RH (up to 40 %) were obtained if the SVP was calculated with the over-ice formulation when air temperatures were below freezing, which could lead to a 30 % maximum difference in snow depths. The choice of whether to separately calculate the SVP over an ice surface in winter also produced a significant range (up to 0.2 m) in simulated annual maximum thaw depths. The sensitivity of seasonal thaw depth to the formulation of SVP increases with the rainfall rate and the height of above-ground ponded water, while it diminishes with warmer air temperatures. These results show that RH variations based on the calculation of SVP with or without over-ice calculation meaningfully impact physicallybased predictions of snow depth, sublimation, soil temperature, and active layer thickness. Under particular conditions, when severe flooding (inundation) and cool air temperatures are present, care should be taken to evaluate how humidity data is estimated for land surface and earth system modeling

We measured black carbon (BC) with a seven-wavelength aethalometer (AE-31) at the Nam Co Lake (NCL), the hinterland of the Tibetan Plateau (TP) from May 2015 to April 2016. The daily average concentration of BC was 145 +/- 85 ng m(-3), increasing by 50% since 2006. The seasonal variation of BC shows higher concentrations in spring and summer and lower concentrations in autumn and winter, dominated by the adjacent sources and meteorological conditions. The diurnal variation of BC showed that its concentrations peaked at 9:00-16:00 (UTC + 8), significantly related to local human activities (e.g., animal-manure burning and nearby traffic due to the tourism industry). The concentration-weighted trajectory (CWT) analysis showed that the long-distance transport of BC from South Asia could also be a potential contributor to BC at the NCL, as well as the biomass burning by the surrounding residents. The analyses of the absorption coefficient and absorption angstrom ngstrom exponent show the consistency of sourcing the BC at the NCL. We suggest here that urgent measures should be taken to protect the atmospheric environment at the NCL, considering the fast-increasing concentrations of BC as an indicator of fuel combustion.

Analyses of black carbon (BC) data from three different environments in India -Delhi megacity, Srinagar metropolitan and Gulmarg hill station, showed that Delhi had the highest annual average BC concentration (12.3 +/- 10.2 mu g m- 3), followed by Srinagar (4.3 +/- 5 mu g m-3) and Gulmarg (2.4 +/- 2 mu g m-3). The inflow of aerosols from the neighboring agricultural regions, notably during Winter, causes Delhi to have the highest seasonal average BC (16.8 mu g m- 3). Srinagar had the highest average seasonal BC during autumn (6.3 mu g m- 3) due to the burning of horticulture residue and hardwood for charcoal making and residential heating. At Gulmarg, on the other hand, the winter season's high BC (2.2 mu g m- 3) is due to the increased emissions from the tourist traffic, snowmobile/ATVs and wood burning for residential heating. BC concentrations in Delhi and Srinagar were roughly in line with their population size. However, compared to sites with the similar population, BC at Gul-marg was roughly twice higher than the other sites. There was a higher contribution to BC from fossil fuels than biomass burning at all three sites, which indicates that cars are the primary source of BC. Overall, values of BC aerosol optical properties in Delhi are much higher than those in Srinagar and Gulmarg. During the cold season, continental air masses transport BC from the neighboring areas to Delhi and westerlies enhance the local BC loading at Srinagar and Gulmarg. The predominant presence of absorbing aerosols, particularly BC, during late autumn and winter at all three sites leads to an increase in aerosol optical depth (AOD), a reduction in single scattering albedo (SSA) and an increase in asymmetry parameter (AP). As a result, there is a significant increase in the radiative forcing of the atmosphere (RFATM), with the highest values observed in January in Delhi (+71.5 W m-2) and Srinagar (+56.05 W m-2), and in November at Gulmarg (+18.5 W m-2). These findings suggest that small rural towns that are affected by seasonal emissions, low planetary boundary layers, and frequent tem-perature inversions, can contribute to a substantial amount of radiative forcing. This study provides a larger perspective on increasing BC in Delhi, and urban-rural fringe areas in the Indian Himalayas, which is crucial for identifying what actions must be taken to control BC emissions to reduce impacts on cryosphere, human health and other sectors.

Climate changes significantly impact the hydrological cycle. Precipitation is one of the most important atmospheric inputs to the terrestrial hydrologic system, and its variability considerably influences environmental and socioeconomic development. Atmospheric warming intensifies the hydrological cycle, increasing both atmospheric water vapor concentration and global precipitation. The relationship between heavy precipitation and temperature has been extensively investigated in literature. However, the relationship in different percentile ranges has not been thoroughly analyzed. Moreover, a percentilebased regression provides a simple but effective framework for investigation into other factors (precipitation type) affecting this relationship. Herein, a comprehensive investigation is presented on the temperature dependence of daily precipitation in various percentile ranges over the Qinghai-Tibet Plateau. The results show that 1) most stations exhibit a peaklike scaling structure, while the northeast part and south margin of the plateau exhibit monotonic positive and negative scaling structures, respectively. The scaling structure is associated with the precipitation type, and 2) the positive and negative scaling rates exhibit similar spatial patterns, with stronger (weaker) sensitivity in the south (north) part of the plateau. The overall increase rate of daily precipitation with temperature is scaled by Clausius-Clapeyron relationship. 3) The higher percentile of daily precipitation shows a larger positive scaling rate than the lower percentile. 4) The peak-point temperature is closely related to the local temperature, and the regional peak-point temperature is roughly around 10 degrees C.

Depositions of light-absorbing particles (LAPs), such as black carbon (BC) and dust, on the snow surface modulate the snow albedo; therefore, they are considered key factors of snow-atmosphere interaction in the present-day climate system. However, their detailed roles have not yet been fully elucidated, mainly due to the lack of in-situ measurements. Here, we develop a new model chain NHM-Chem-SMAP, which is composed of a detailed regional meteorology-chemistry model and a multilayered physical snowpack model, and evaluate it using LAPs concentrations data measured at Sapporo, Japan during the 2011-2012 winter. NHM-Chem-SMAP successfully reproduces the in-situ measured seasonal variations in the mass concentrations of BC and dust in the surface snowpack. Furthermore, we find that LAPs from domestic and foreign sources played a role in shortening the snow cover duration by 5 and 10 days, respectively, compared to the completely pure snow condition.

Black carbon (BC) mass concentration was measured first-time at a high altitude urban site-Srinagar (1600 m asl), in northwestern Himalaya, India using an Aethalometer during 2013 to study temporal variations (monthly, diurnal and seasonal), meteorological influences, source and its radiative forcing. Diurnal variations with two peaks (at 8-10 h and 20-23 h) and two dips (at 13-17 h and 0-3 h) were observed throughout the year with varying magnitude. November and April showed the highest (13.6 mu g/m(3)) and the lowest (3.4 mu g/m(3)) mean monthly BC concentration respectively. Seasonally, autumn displayed the highest (9.2 mu g/m(3)) and spring the lowest (3.5 mu g/m(3)) mean BC concentration. Annual average BC concentration was quite higher (6 mu g/m(3)) than those reported for other high altitude stations. Wind speed, Minimum temperature and total precipitation showed a clear negative correlation with BC (r = -0.63, -0.51 and -0.55 respectively), while as, the evening relative humidity showed positive correlation (r = 0.56). During autumn, spring and winter seasons, the main source of BC at Srinagar is the biomass burning, while during summer season, equal contribution of BC is from fossil fuel and biomass burning. Back trajectory simulations revealed that, except summer, westerly air masses are the dominant winds, transporting BC from central Asia, west Asia, south Asia, Africa and some parts of Europe to Srinagar adding to its local sources. Clear-sky short wave radiative forcing of atmosphere due to BC was highest (58.2 W m(-2)) during autumn which leads to the increase in lower atmospheric heating rate by 1.6 K/d. The high concentration of BC observed over the high-altitude Himalayan Kashmir region has serious implications for the regional climate, hydrology and cryosphere which needs to be investigated. (C) 2017 Elsevier Ltd. All rights reserved.

Precipitation variability in tropical high mountains is a fundamental yet poorly understood factor influencing local climatic expression and a variety of environmental processes, including glacier behavior and water resources. Precipitation type, diurnality, frequency, and amount influence hydrological runoff, surface albedo, and soil moisture, whereas cloud cover associated with precipitation events reduces solar irradiance at the surface. Considerable uncertainty remains in the multiscale atmospheric processes influencing precipitation patterns and their associated regional variability in the tropical Andesparticularly related to precipitation phase, timing, and vertical structure. Using data from a variety of sourcesincluding new citizen science precipitation stations; new high-elevation comprehensive precipitation monitoring stations at Chacaltaya, Bolivia, and the Quelccaya Ice Cap, Peru; and a vertically pointing Micro Rain Radarthis article synthesizes findings from interdisciplinary research activities in the Cordillera Real of Bolivia and the Cordillera Vilcanota of Peru related to the following two research questions: (1) How do the temporal patterns, moisture source regions, and El Nino-Southern Oscillation relationships with precipitation occurrence vary? (2) What is the vertical structure (e.g., reflectivity, Doppler velocity, melting layer heights) of tropical Andean precipitation and how does it evolve temporally? Results indicate that much of the heavy precipitation occurs at night, is stratiform rather than convective in structure, and is associated with Amazonian moisture influx from the north and northwest. Improving scientific understanding of tropical Andean precipitation is of considerable importance to assessing climate variability and change, glacier behavior, hydrology, agriculture, ecosystems, and paleoclimatic reconstructions.