Implications of aerosol-induced snow darkening on regional hydroclimate over the Himalayas

Mapping Intimacies ◽

10.5194/egusphere-egu21-11972 ◽

2021 ◽

Author(s):

Vijayakumar Sivadasan Nair ◽

Usha Keshav Hasyagar ◽

Surendran Nair Suresh Babu

Keyword(s):

South Asia ◽

Climate Model ◽

Hydrological Cycle ◽

Monsoon Season ◽

Radiation Balance ◽

Western Himalayas ◽

Radiative Effect ◽

Anthropogenic Aerosols ◽

Snow Albedo ◽

Snow Cover Extent

The snow-covered mountains of Himalayas are known to play a crucial role in the hydrology of South Asia and are known as the &#8220;Asian water tower&#8221;. Despite the high elevations, the transport of anthropogenic aerosols from south Asia and desert dust from west Asia plays a significant role in directly and indirectly perturbing the radiation balance and hydrological cycle over the region. Absorbing aerosols like black carbon (BC) and dust deposited on the snow surface reduces the albedo of the Himalayan snow significantly (snow darkening or snow albedo effect). Using a Regional Climate Model (RegCM-4.6.0) coupled with SNow, ICe and Aerosol Radiation (SNICAR) module, the implications of aerosol-induced snow darkening on the regional hydroclimate of the Himalayas are investigated in this study. The aerosols deposited on snow shows a distinct regional heterogeneity. The albedo reduction due to aerosols shows a west to east gradient during pre-monsoon season and this results in the positive radiative effect of about 29 Wm-2, 17 Wm-2 and 5 Wm-2 over western, central and eastern Himalayas respectively. The reduction in the snow albedo also results in the sign reversal of the aerosol direct radiative effect i.e., from warming to cooling at the top of the atmosphere during pre-monsoon season. The excess solar energy trapped at the surface due to snow darkening warms the surface (0.66-1.9 K) and thus decreases the snow cover extent significantly. This results in the reduction of the number of snow-covered days by more than a month over the western Himalayas and about 10 &#8211; 15 days over the central Himalayas. The early snowmelt due to aerosol-induced snow darkening results in the increase of runoff throughout the melting season. Therefore, the present study highlights the heterogeneous response of aerosol induced snow albedo feedbacks over the Himalayan region and its impact on the snowpack and hydrology, which has further implications on the freshwater availability over the region.

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Effective radiative forcing in the aerosol–climate model CAM5.3-MARC-ARG

10.5194/acp-2018-118 ◽

2018 ◽

Cited By ~ 1

Author(s):

Benjamin S. Grandey ◽

Daniel Rothenberg ◽

Alexander Avramov ◽

Qinjian Jin ◽

Hsiang-He Lee ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Regional Distribution ◽

Radiative Effect ◽

Mixing State ◽

Anthropogenic Aerosols ◽

Effective Radiative Forcing ◽

Aerosol Module ◽

Aerosol Emissions ◽

Global Mean

Abstract. We quantify the effective radiative forcing (ERF) of anthropogenic aerosols modelled by the aerosol–climate model CAM5.3-MARC-ARG. CAM5.3-MARC-ARG is a new configuration of the Community Atmosphere Model version 5.3 (CAM5.3) in which the default aerosol module has been replaced by the two-Moment, Multi-Modal, Mixing-state-resolving Aerosol model for Research of Climate (MARC). CAM5.3-MARC-ARG uses the default ARG aerosol activation scheme, consistent with the default configuration of CAM5.3. We compute differences between simulations using year-1850 aerosol emissions and simulations using year-2000 aerosol emissions in order to assess the radiative effects of anthropogenic aerosols. We compare the aerosol column burdens, cloud properties, and radiative effects produced by CAM5.3-MARC-ARG with those produced by the default configuration of CAM5.3, which uses the modal aerosol module with three log-normal modes (MAM3). Compared with MAM3, we find that MARC produces stronger cooling via the direct radiative effect, stronger cooling via the surface albedo radiative effect, and stronger warming via the cloud longwave radiative effect. The global mean cloud shortwave radiative effect is similar between MARC and MAM3, although the regional distributions differ. Overall, MARC produces a global mean net ERF of −1.75 ± 0.04 W m−2, which is stronger than the global mean net ERF of −1.57 ± 0.04 W m−2 produced by MAM3. The regional distribution of ERF also differs between MARC and MAM3, largely due to differences in the regional distribution of the cloud shortwave radiative effect. We conclude that the specific representation of aerosols in global climate models, including aerosol mixing state, has important implications for climate modelling.

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Influence of biomass burning from South Asia at a high-altitude mountain receptor site in China

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6853-2017 ◽

2017 ◽

Vol 17 (11) ◽

pp. 6853-6864 ◽

Cited By ~ 17

Author(s):

Jing Zheng ◽

Min Hu ◽

Zhuofei Du ◽

Dongjie Shang ◽

Zhaoheng Gong ◽

...

Keyword(s):

Tibetan Plateau ◽

South Asia ◽

Biomass Burning ◽

Monsoon Season ◽

Organic Aerosol ◽

Submicron Particles ◽

The Tibetan Plateau ◽

Anthropogenic Aerosols ◽

Air Masses ◽

Average Mass

Abstract. Highly time-resolved in situ measurements of airborne particles were conducted at Mt. Yulong (3410 m above sea level) on the southeastern edge of the Tibetan Plateau in China from 22 March to 14 April 2015. The detailed chemical composition was measured by a high-resolution time-of-flight aerosol mass spectrometer together with other online instruments. The average mass concentration of the submicron particles (PM1) was 5.7 ± 5.4 µg m−3 during the field campaign, ranging from 0.1 up to 33.3 µg m−3. Organic aerosol (OA) was the dominant component in PM1, with a fraction of 68 %. Three OA factors, i.e., biomass burning organic aerosol (BBOA), biomass-burning-influenced oxygenated organic aerosol (OOA-BB) and oxygenated organic aerosol (OOA), were resolved using positive matrix factorization analysis. The two oxygenated OA factors accounted for 87 % of the total OA mass. Three biomass burning events were identified by examining the enhancement of black carbon concentrations and the f60 (the ratio of the signal at m∕z 60 from the mass spectrum to the total signal of OA). Back trajectories of air masses and satellite fire map data were integrated to identify the biomass burning locations and pollutant transport. The western air masses from South Asia with active biomass burning activities transported large amounts of air pollutants, resulting in elevated organic concentrations up to 4-fold higher than those of the background conditions. This study at Mt. Yulong characterizes the tropospheric background aerosols of the Tibetan Plateau during pre-monsoon season and provides clear evidence that the southeastern edge of the Tibetan Plateau was affected by the transport of anthropogenic aerosols from South Asia.

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Post-Monsoon Season Precipitation Reduction over South Asia: Impacts of Anthropogenic Aerosols and Irrigation

Atmosphere ◽

10.3390/atmos9080311 ◽

2018 ◽

Vol 9 (8) ◽

pp. 311 ◽

Cited By ~ 2

Author(s):

Wei-Ting Chen ◽

Kung-Tzu Huang ◽

Min-Hui Lo ◽

L. LinHo

Keyword(s):

South Asia ◽

Monsoon Season ◽

North India ◽

Surface Cooling ◽

Anthropogenic Aerosols ◽

Post Monsoon ◽

Climate Simulations ◽

Precipitation Decrease ◽

Post Monsoon Season ◽

Precipitation Reduction

A significant declining trend of post-monsoon season precipitation in South Asia is observed between 2000–2014. Two major anthropogenic climate change drivers, aerosols and irrigation, have been steadily increasing during this period. The impacts of their regional and seasonal forcings on the post-monsoon precipitation reduction is investigated in this study through using idealized global climate simulations. The increased post-monsoon aerosol loadings lead to surface cooling downwind of the source areas by reduced surface shortwave flux. The addition of post-monsoon irrigation induces a stronger temperature decrease mainly around the irrigation hotspots by enhanced evaporation. Precipitation over West and North India is reduced post-monsoon by either aerosol or irrigation, which is mainly contributed by the anomalous subsidence. With concurrent forcings, the surface cooling and precipitation decrease are stronger and more extended spatially than the response to the separate forcing, with nonlinear amplification in surface cooling, but nonlinear damping in precipitation reduction. The anomalous vertical motion accelerates the transition of the regional meridional circulation, and hence the earlier withdrawal of the summer monsoon, which is consistent with the observed signals. The current results highlight the importance of including anthropogenic aerosol and irrigation effects in present and future climate simulations over South Asia.

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Effective radiative forcing in the aerosol–climate model CAM5.3-MARC-ARG

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-15783-2018 ◽

2018 ◽

Vol 18 (21) ◽

pp. 15783-15810 ◽

Cited By ~ 8

Author(s):

Benjamin S. Grandey ◽

Daniel Rothenberg ◽

Alexander Avramov ◽

Qinjian Jin ◽

Hsiang-He Lee ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Regional Distribution ◽

Normal Modes ◽

Radiative Effect ◽

Anthropogenic Aerosols ◽

Cloud Radiative Effect ◽

Log Normal ◽

Aerosol Module ◽

Aerosol Emissions

Abstract. We quantify the effective radiative forcing (ERF) of anthropogenic aerosols modelled by the aerosol–climate model CAM5.3-MARC-ARG. CAM5.3-MARC-ARG is a new configuration of the Community Atmosphere Model version 5.3 (CAM5.3) in which the default aerosol module has been replaced by the two-Moment, Multi-Modal, Mixing-state-resolving Aerosol model for Research of Climate (MARC). CAM5.3-MARC-ARG uses the ARG aerosol-activation scheme, consistent with the default configuration of CAM5.3. We compute differences between simulations using year-1850 aerosol emissions and simulations using year-2000 aerosol emissions in order to assess the radiative effects of anthropogenic aerosols. We compare the aerosol lifetimes, aerosol column burdens, cloud properties, and radiative effects produced by CAM5.3-MARC-ARG with those produced by the default configuration of CAM5.3, which uses the modal aerosol module with three log-normal modes (MAM3), and a configuration using the modal aerosol module with seven log-normal modes (MAM7). Compared with MAM3 and MAM7, we find that MARC produces stronger cooling via the direct radiative effect, the shortwave cloud radiative effect, and the surface albedo radiative effect; similarly, MARC produces stronger warming via the longwave cloud radiative effect. Overall, MARC produces a global mean net ERF of -1.79±0.03 W m−2, which is stronger than the global mean net ERF of -1.57±0.04 W m−2 produced by MAM3 and -1.53±0.04 W m−2 produced by MAM7. The regional distribution of ERF also differs between MARC and MAM3, largely due to differences in the regional distribution of the shortwave cloud radiative effect. We conclude that the specific representation of aerosols in global climate models, including aerosol mixing state, has important implications for climate modelling.

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Climate Effects of Anthropogenic Aerosol Forcing on Tropical Precipitation and Circulations

Journal of Climate ◽

10.1175/jcli-d-18-0641.1 ◽

2019 ◽

Vol 32 (16) ◽

pp. 5275-5287 ◽

Cited By ~ 1

Author(s):

Chia-Chi Wang ◽

Wei-Liang Lee ◽

Chia Chou

Keyword(s):

Climate Models ◽

Energy Transport ◽

Hydrological Cycle ◽

Order Approximation ◽

Hadley Circulation ◽

Walker Circulation ◽

Radiation Balance ◽

Anthropogenic Aerosols ◽

Anthropogenic Aerosol ◽

Tropical Precipitation

ABSTRACT Aerosols are one of the key factors influencing the hydrological cycle and radiation balance of the climate system. Although most aerosols deposit near their sources, the induced cooling effect is on a global scale and can influence the tropical atmosphere through slow processes, such as air–sea interactions. This study analyzes several simulations of fully coupled atmosphere–ocean climate models under the influence of anthropogenic aerosols, with the concentrations of greenhouse gases kept constant. In the cooling simulations, precipitation is reduced in deep convective areas but increased around the edges of convective areas, which is opposite to the “rich-get-richer” phenomenon in global warming scenarios in the first-order approximation. Tropical convection is intensified with a shallower depth, and tropical circulations are enhanced. The anomalous gross moist stability (M′) mechanism and the upped-ante mechanism can be used to explain the dynamic and thermodynamic processes in the changes in tropical precipitation and convection. There is a northward cross-equatorial energy transport due to the cooler Northern Hemisphere in most of the simulations, together with the southward shift of the intertropical convergence zone (ITCZ) and the enhancement of the Hadley circulation. The enhancement of the Hadley circulation is more consistent between models than the changes of the Walker circulation. The change in the Hadley circulation is not as negligible as in the warming cases in previous studies, which supports the consistency of the ITCZ shift in cooling simulations.

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Explicit representation of subgrid variability in cloud microphysics yields weaker aerosol indirect effect in the ECHAM5-HAM2 climate model

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-703-2015 ◽

2015 ◽

Vol 15 (2) ◽

pp. 703-714 ◽

Cited By ~ 10

Author(s):

J. Tonttila ◽

H. Järvinen ◽

P. Räisänen

Keyword(s):

Indirect Effect ◽

Radiative Forcing ◽

Climate Model ◽

Cloud Microphysics ◽

Radiation Balance ◽

Anthropogenic Aerosols ◽

Aerosol Indirect Effect ◽

Cloud Activation ◽

The Impact ◽

Global Mean

Abstract. The impacts of representing cloud microphysical processes in a stochastic subcolumn framework are investigated, with emphasis on estimating the aerosol indirect effect. It is shown that subgrid treatment of cloud activation and autoconversion of cloud water to rain reduce the impact of anthropogenic aerosols on cloud properties and thus reduce the global mean aerosol indirect effect by 19%, from −1.59 to −1.28 W m−2. This difference is partly related to differences in the model basic state; in particular, the liquid water path (LWP) is smaller and the shortwave cloud radiative forcing weaker when autoconversion is computed separately for each subcolumn. However, when the model is retuned so that the differences in the basic state LWP and radiation balance are largely eliminated, the global-mean aerosol indirect effect is still 14% smaller (i.e. −1.37 W m−2) than for the model version without subgrid treatment of cloud activation and autoconversion. The results show the importance of considering subgrid variability in the treatment of autoconversion. Representation of several processes in a self-consistent subgrid framework is emphasized. This paper provides evidence that omitting subgrid variability in cloud microphysics contributes to the apparently chronic overestimation of the aerosol indirect effect by climate models, as compared to satellite-based estimates.

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Multi-layer distribution of Black Carbon and Inorganic Ions in the Snow-packs of western Himalayas and Snow Albedo Forcing

Atmospheric Environment ◽

10.1016/j.atmosenv.2021.118564 ◽

2021 ◽

pp. 118564

Author(s):

Roseline C. Thakur ◽

B.S. Arun ◽

Mukunda M. Gogoi ◽

Meloth Thamban ◽

Renoj J. Thayyen ◽

...

Keyword(s):

Black Carbon ◽

Inorganic Ions ◽

Western Himalayas ◽

Snow Albedo

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South Asia river-flow projections and their implications for water resources

Hydrology and Earth System Sciences ◽

10.5194/hess-19-4783-2015 ◽

2015 ◽

Vol 19 (12) ◽

pp. 4783-4810 ◽

Cited By ~ 6

Author(s):

C. Mathison ◽

A. J. Wiltshire ◽

P. Falloon ◽

A. J. Challinor

Keyword(s):

Water Resources ◽

South Asia ◽

River Flow ◽

Climate Model ◽

Asian Summer Monsoon ◽

Regional Climate ◽

Global Climate Models ◽

Climate Projections ◽

The South ◽

River Flows

Abstract. South Asia is a region with a large and rising population, a high dependence on water intense industries, such as agriculture and a highly variable climate. In recent years, fears over the changing Asian summer monsoon (ASM) and rapidly retreating glaciers together with increasing demands for water resources have caused concern over the reliability of water resources and the potential impact on intensely irrigated crops in this region. Despite these concerns, there is a lack of climate simulations with a high enough resolution to capture the complex orography, and water resource analysis is limited by a lack of observations of the water cycle for the region. In this paper we present the first 25 km resolution regional climate projections of river flow for the South Asia region. Two global climate models (GCMs), which represent the ASM reasonably well are downscaled (1960–2100) using a regional climate model (RCM). In the absence of robust observations, ERA-Interim reanalysis is also downscaled providing a constrained estimate of the water balance for the region for comparison against the GCMs (1990–2006). The RCM river flow is routed using a river-routing model to allow analysis of present-day and future river flows through comparison with available river gauge observations. We examine how useful these simulations are for understanding potential changes in water resources for the South Asia region. In general the downscaled GCMs capture the seasonality of the river flows but overestimate the maximum river flows compared to the observations probably due to a positive rainfall bias and a lack of abstraction in the model. The simulations suggest an increasing trend in annual mean river flows for some of the river gauges in this analysis, in some cases almost doubling by the end of the century. The future maximum river-flow rates still occur during the ASM period, with a magnitude in some cases, greater than the present-day natural variability. Increases in river flow could mean additional water resources for irrigation, the largest usage of water in this region, but has implications in terms of inundation risk. These projected increases could be more than countered by changes in demand due to depleted groundwater, increases in domestic use or expansion of water intense industries. Including missing hydrological processes in the model would make these projections more robust but could also change the sign of the projections.

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Simulation of the isotopic composition of stratospheric water vapour – Part 1: Description and evaluation of the EMAC model

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5537-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5537-5555 ◽

Cited By ~ 8

Author(s):

R. Eichinger ◽

P. Jöckel ◽

S. Brinkop ◽

M. Werner ◽

S. Lossow

Keyword(s):

Isotopic Composition ◽

Water Vapour ◽

General Circulation ◽

Climate Model ◽

Hydrological Cycle ◽

Circulation Model ◽

Isotope Ratios ◽

Physical Fractionation ◽

Water Isotopologues ◽

Stratospheric Water Vapour

Abstract. This modelling study aims at an improved understanding of the processes that determine the water vapour budget in the stratosphere by means of the investigation of water isotope ratios. An additional (and separate from the actual) hydrological cycle has been introduced into the chemistry–climate model EMAC, including the water isotopologues HDO and H218O and their physical fractionation processes. Additionally an explicit computation of the contribution of methane oxidation to H2O and HDO has been incorporated. The model expansions allow detailed analyses of water vapour and its isotope ratio with respect to deuterium throughout the stratosphere and in the transition region to the troposphere. In order to assure the correct representation of the water isotopologues in the model's hydrological cycle, the expanded system has been evaluated in several steps. The physical fractionation effects have been evaluated by comparison of the simulated isotopic composition of precipitation with measurements from a ground-based network (GNIP) and with the results from the isotopologue-enabled general circulation model ECHAM5-wiso. The model's representation of the chemical HDO precursor CH3D in the stratosphere has been confirmed by a comparison with chemical transport models (1-D, CHEM2D) and measurements from radiosonde flights. Finally, the simulated stratospheric HDO and the isotopic composition of water vapour have been evaluated, with respect to retrievals from three different satellite instruments (MIPAS, ACE-FTS, SMR). Discrepancies in stratospheric water vapour isotope ratios between two of the three satellite retrievals can now partly be explained.

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