Light-absorbing impurities in snow cover across Northern Xinjiang, China

AbstractLight-absorbing impurities (LAIs, e.g. black carbon (BC), organic carbon (OC), mineral dust (MD)) deposited on snow cover reduce albedo and accelerate its melting. Northern Xinjiang (NX) is an arid and semi-arid inland region, where snowmelt leads to frequent floods that have been a serious threat to local ecological security. There is still a lack of quantitative assessments of the effects of LAIs on snowmelt in the region. This study investigates spatial variations of LAIs in snow and its effect on snow albedo, radiative forcing (RF) and snowmelt across NX. Results showed that concentrations of BC, OC (only water-insoluble OC), MD ranged from 32 to 8841 ng g−1, 77 to 8568 ng g−1 and 0.46 to 236 µg g−1, respectively. Weather Research and Forecasting Chemistry model suggested that residential emission was the largest source of BC. Snow, Ice, and Aerosol Radiative modelling showed that the average contribution of BC and MD to snow albedo reduction was 17 and 3%, respectively. RF caused by BC significantly exceeded RF caused by MD. In different scenarios, changes in snow cover duration (SCD) caused by BC and MD decreased by 1.36 ± 0.61 to 6.12 ± 3.38 d. Compared with MD, BC was the main dominant factor in reducing snow albedo and SCD across NX.

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Radiative feedbacks of dust in snow over eastern Asia in CAM4-BAM

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-12683-2018 ◽

2018 ◽

Vol 18 (17) ◽

pp. 12683-12698 ◽

Cited By ~ 6

Author(s):

Xiaoning Xie ◽

Xiaodong Liu ◽

Huizheng Che ◽

Xiaoxun Xie ◽

Xinzhou Li ◽

...

Keyword(s):

Snow Cover ◽

Radiative Forcing ◽

Source Region ◽

Asian Dust ◽

Significant Feature ◽

The Tibetan Plateau ◽

Eastern Asia ◽

Dust Emissions ◽

Snow Albedo ◽

Aerosol Model

Abstract. Dust in snow on the Tibetan Plateau (TP) could reduce the visible snow albedo by changing surface optical properties and removing the snow cover through increased snowmelt, which leads to a significant positive radiative forcing and remarkably alters the regional energy balance and the eastern Asian climate system. This study extends our previous investigation in dust–radiation interactions to investigate the dust-in-snow radiative forcing (SRF) and its feedbacks on the regional climate and the dust cycle over eastern Asia through the use of the Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterizations of the dust size distribution (CAM4-BAM). Our results show that SRF increases the eastern Asian dust emissions significantly by 13.7 % in the spring, countering a 7.6 % decrease in the regional emissions by the dust direct radiative forcing (DRF). SRF also remarkably affects the whole dust cycle, including transport and deposition of dust aerosols over eastern Asia. The simulations indicate an increase in dust emissions of 5.1 %, due to the combined effect of DRF and SRF. Further analysis reveals that these results are mainly due to the regional climatic feedbacks induced by SRF over eastern Asia. By reducing the snow albedo over the TP, the dust in snow mainly warms the TP and influences its thermal effects by increasing the surface sensible and latent heat flux, which in turn increases the aridity and westerly winds over northwestern China and affects the regional dust cycle. Additionally, the dust in snow also accelerates the snow-melting process, reduces the snow cover and then expands the eastern Asian dust source region, which results in increasing the regional dust emissions. Hence, a significant feature of SRF on the TP is the creation of a positive feedback loop that affects the dust cycle over eastern Asia.

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Case study of spatial and temporal variability of snow cover, grain size, albedo and radiative forcing in the Sierra Nevada and Rocky Mountain snowpack derived from imaging spectroscopy

The Cryosphere ◽

10.5194/tc-10-1229-2016 ◽

2016 ◽

Vol 10 (3) ◽

pp. 1229-1244 ◽

Cited By ~ 18

Author(s):

Felix C. Seidel ◽

Karl Rittger ◽

S. McKenzie Skiles ◽

Noah P. Molotch ◽

Thomas H. Painter

Keyword(s):

Grain Size ◽

Spatial Variability ◽

Snow Cover ◽

Sierra Nevada ◽

Rocky Mountains ◽

Radiative Forcing ◽

Infrared Imaging ◽

Spatial And Temporal Variability ◽

Snow Albedo ◽

The Mean

Abstract. Quantifying the spatial distribution and temporal change in mountain snow cover, microphysical and optical properties is important to improve our understanding of the local energy balance and the related snowmelt and hydrological processes. In this paper, we analyze changes of snow cover, optical-equivalent snow grain size (radius), snow albedo and radiative forcing by light-absorbing impurities in snow and ice (LAISI) with respect to terrain elevation and aspect at multiple dates during the snowmelt period. These snow properties are derived from the NASA/JPL Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data from 2009 in California's Sierra Nevada and from 2011 in Colorado's Rocky Mountains, USA. Our results show a linearly decreasing snow cover during the ablation period in May and June in the Rocky Mountains and a snowfall-driven change in snow cover in the Sierra Nevada between February and May. At the same time, the snow grain size is increasing primarily at higher elevations and north-facing slopes from 200 microns to 800 microns on average. We find that intense snowmelt renders the mean grain size almost invariant with respect to elevation and aspect. Our results confirm the inverse relationship between snow albedo and grain size, as well as between snow albedo and radiative forcing by LAISI. At both study sites, the mean snow albedo value decreases from approximately 0.7 to 0.5 during the ablation period. The mean snow grain size increased from approximately 150 to 650 microns. The mean radiative forcing increases from 20 W m−2 up to 200 W m−2 during the ablation period. The variability of snow albedo and grain size decreases in general with the progression of the ablation period. The spatial variability of the snow albedo and grain size decreases through the melt season while the spatial variability of radiative forcing remains constant.

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How is snow cover in global mountain area changing? Detection of snow cover and snow phenology changes by using MODIS imagery over 2000 - 2018

10.5194/egusphere-egu2020-20482 ◽

2020 ◽

Author(s):

Claudia Notarnicola

Keyword(s):

Snow Cover ◽

Northern Hemisphere ◽

Air Temperature ◽

Lower Latitude ◽

Snow Melt ◽

Snow Cover Area ◽

Mountain Areas ◽

Snow Albedo ◽

Modis Imagery ◽

Snow Cover Duration

Mountain areas have raised a lot of attention in the past years, as they are considered sentinel of climate changes. Quantification of snow cover changes and related phenology in global mountain areas can have multiple implications on water resources, ecosystem services, tourism, and energy production [1]. Up to now, several studies have investigated snow cover changes at continental scale and there are several indications of snow cover decline over the Northern Hemisphere [2, 3], despite no study has analyzed snow behavior specifically in mountain areas at global level. In this context, this study investigates the changes in the main snow cover parameters (snow cover area, snow cover duration, snow onset and snow melt) over global mountain areas from 2000 to 2018.To proper monitor the evolution of snow changes at global mountain areas and interlinkages with meteorological drivers (air temperature, snowfall), automatic procedures were developed based on MODIS imagery in global mountain areas over the period 2000-2018 by exploiting Google Earth Engine where the whole time series of MODIS is available at a global scale. MODIS snow cover products have the highest resolution available, 500 m, and with daily global acquisitions. From MODIS snow cover areas (MOD10v6), snow phenology parameters were derived, namely snow cover duration, snow onset and snow melt. Together with snow cover and phenology changes, snow albedo changes were assessed, especially in relation to snow onset and melt variability.The results of the trend analysis carried with Man-Kendall statistics indicate that around 78% of the global mountain areas present a snow decline. In average, snow cover duration has decreased up to 43 days, and a snow cover area up to 13%. Significant snow cover duration changes can be linked in 58% of the areas to both delayed snow onset, and advanced melt. Few areas show positive changes, mainly during winter time and located in the Northern Hemisphere.Considering the relationship with meteorological parameters and albedo, air temperature is detected as the main driver for snow onset and melt, while a mixed effect of air temperature and precipitation dominates the winter season. Moreover, snowmelt timing is strongly related to significant changes in snow albedo during March and April in the Northern Hemisphere. Regarding snow onset changes, it has been detected a latitude amplification for the dependency con air temperature, indicating that the sensitivity of snow onset on temperature changes is amplified going from higher to lower latitude.&#160;References[1] Barnett, T.P., Adam J.C., Lettenmaier D.P. Potential impact of a warming climate on water availability in snow-dominated regions, Nature 438 (2005).[2] Bormann, K. J., Brown, R. D., Derksen, C., Painter, T. H. Estimating snow-cover trends from space, Nat. Clim. Change&#160;8,&#160;924&#8211;928 (2018).[3] Ye. K. H., & Wu, R. G. Autumn snow cover variability over northern Eurasia and roles of atmospheric circulation. Adv. Atmos. Sci. 34(7), 847&#8211;858 (2017) doi: 10.1007/s00376-017-6287-z.

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Case study of spatial and temporal variability of snow cover, grain size, albedo and radiative forcing in the Sierra Nevada and Rocky Mountain snowpack derived from imaging spectroscopy

10.5194/tc-2015-196 ◽

2016 ◽

Author(s):

F. C. Seidel ◽

K. Rittger ◽

S. M. Skiles ◽

T. H. Painter

Keyword(s):

Grain Size ◽

Spatial Variability ◽

Snow Cover ◽

Sierra Nevada ◽

Rocky Mountains ◽

Radiative Forcing ◽

Infrared Imaging ◽

Spatial And Temporal Variability ◽

Snow Albedo ◽

The Mean

Abstract. Quantifying the spatial distribution and temporal change in mountain snow cover, microphysical and optical properties is important to improve our understanding of the local energy balance and the related snowmelt and hydrological processes. In this paper, we analyze changes of snow cover, optical-equivalent snow grain size, snow albedo, and radiative forcing by Light Absorbing Impurities in Snow and Ice (LAISI) with respect to terrain elevation and aspect at multiple dates during the snowmelt period. These snow properties are derived from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data from 2009 of the maritime snowpack in California’s Sierra Nevada and from 2011 of the continental snowpack in Colorado’s Rocky Mountains, USA. Our results show a linearly decreasing snow cover during the ablation season in the Rocky Mountains and a snowfall driven change in snow cover in the Sierra Nevada. At the same time, the snow grain size is increasing primarily at higher elevations and north facing slopes from 200 microns to 800 microns on average. We ﬁnd that intense snowmelt renders the mean grain size almost invariant with respect to elevation and aspect. Our results conﬁrm the inverse relationship between snow albedo and grain size, as well as between snow albedo and radiative forcing by LAISI. At both study sites, the mean snow albedo value decreases from approximately 0.7 to 0.5. The mean snow grain size increased from approximately 150 to 650 microns. The mean radiative forcing increases from 20 W m−2 up to 200 W m−2 during the ablation period. The variability of snow albedo and grain size decreases in general with the progression of the ablation period. The spatial variability of the snow albedo and grain size decreases through the melt season while the spatial variability of radiative forcing remains constant.

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Land-atmosphere interactions in sub-polar and alpine climates in the CORDEX FPS LUCAS models: I. Evaluation of the snow-albedo effect

10.5194/tc-2021-290 ◽

2021 ◽

Author(s):

Anne Sophie Daloz ◽

Clemens Schwingshackl ◽

Priscilla Mooney ◽

Susanna Strada ◽

Diana Rechid ◽

...

Keyword(s):

Snow Cover ◽

Land Surface ◽

Radiative Forcing ◽

Climate Models ◽

Dominant Role ◽

Land Surface Model ◽

Surface Model ◽

Sensitivity Index ◽

Snow Albedo ◽

Albedo Effect

Abstract. In the Northern Hemisphere, the seasonal snow cover plays a major role in the climate system via its effect on surface albedo and fluxes. The parameterization of snow-atmosphere interactions in climate models remains a source of uncertainty and biases in the representation of the local and global climate. Here, we evaluate the ability of an ensemble of regional climate models (RCMs) coupled to different land surface models to simulate the snow albedo effect over Europe, in winter and spring. We use a previously defined index, the Snow Albedo Sensitivity Index (SASI), to quantify the radiative forcing due to the snow albedo effect. By comparing RCM-derived SASI values with SASI calculated from reanalyses and satellite retrievals, we show that an accurate simulation of snow cover is essential for correctly reproducing the observed forcing over mid- and high-latitudes in Europe. The choice of parameterizations with first and foremost the choice of the land surface model but also the convection scheme and the planetary boundary layer, strongly influences the representation of SASI as it affects the ability of climate models to simulate snow cover correctly. The agreement between the datasets differs between the accumulation and ablation periods, with the latter one presenting the greatest challenge for the RCMs. Given the dominant role of land surface processes in the simulation of snow cover during the ablation period, the results suggest that the choice of the land surface model is more critical for the representation of SASI than the atmospheric model during this time period.

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Radiative feedbacks of dust-in-snow over East Asia in CAM4-BAM

10.5194/acp-2018-350 ◽

2018 ◽

Author(s):

Xiaoning Xie ◽

Xiaodong Liu ◽

Huizheng Che ◽

Xiaoxun Xie ◽

Xinzhou Li ◽

...

Keyword(s):

East Asia ◽

Snow Cover ◽

Radiative Forcing ◽

East Asian ◽

Source Region ◽

Asian Dust ◽

Significant Feature ◽

The Tibetan Plateau ◽

Dust Emissions ◽

Snow Albedo

Abstract. Dust-in-snow on the Tibetan Plateau (TP) could reduce the visible snow albedo by changing surface optical properties and remove the snow cover by increasing snowmelt, which leads to a significant positive radiative forcing and remarkedly alters the regional energy balance and the East Asian climate system. This study extends our previous investigation in dust-radiation interactions to investigate the dust-in-snow radiative forcing (SRF) and its feedbacks on the regional climate and the dust cycle over East Asia by use of the Community Atmosphere Model version 4 with a Bulk Aerosol Model parameterization of the dust size distribution (CAM4-BAM). Our results show that SRF increases the East Asian dust emissions significantly, by 13.7 % in the spring, in contrast to −7.6 % of decreased dust emissions by the dust direct radiative forcing (DRF). SRF also remarkedly enhances the whole dust cycle, including dust transports, dry and wet depositions over East Asia. The simulated results show that the combined effect of DRF and SRF increases the dust emissions by 5.1 %, and enhances the overall dust cycle over this region. Further analysis reveals that these results are mainly due to the regional climatic feedbacks induced by SRF over East Asia. By reducing the snow albedo over the TP, the dust-in-snow mainly warms the TP to enhance its thermal effects by increasing the surface sensible and latent heat flux, and then increases the aridity and westerly winds over Northwest China, in turn enhances the East Asian dust cycle. Additionally, the dust-in-snow also accelerates snow melting, reduces the snow cover, and then expands the East Asian dust source region area, which results in increasing the regional dust emissions. Hence, a significant feature of SRF on the TP can create a positive feedback loop to enhance the dust cycle over East Asia.

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Impact of light-absorbing particles on snow albedo darkening and associated radiative forcing over High Mountain Asia: High resolution WRF-Chem modeling and new satellite observations

10.5194/acp-2018-979 ◽

2018 ◽

Cited By ~ 1

Author(s):

Chandan Sarangi ◽

Yun Qian ◽

Karl Rittger ◽

Kat J. Bormann ◽

Ying Liu ◽

...

Keyword(s):

Grain Size ◽

Snow Cover ◽

Spatial Resolution ◽

Radiative Forcing ◽

High Mountain ◽

Western Himalayas ◽

Snow Albedo ◽

Snow Properties ◽

Realistic Representation ◽

The Impact

Abstract. Light-absorbing particles (LAPs), mainly dust and black carbon, can significantly impact snowmelt and regional water availability over High Mountain Asia (HMA). In this study, for the first time, online aerosol-snow interactions enabled and a fully coupled chemistry Weather Research and Forecasting (WRF-Chem) regional model is used to simulate LAP-induced radiative forcing on snow surfaces in HMA at relatively high spatial resolution (12 km, WRF-HR) than previous studies. Simulated macro- and micro-physical properties of the snowpack and LAP-induced snow darkening are evaluated against new spatially and temporally complete datasets of snow covered area, grain size, and impurities-induced albedo reduction over HMA. A WRF-Chem quasi-global simulation with the same configuration as WRF-HR but a coarser spatial resolution (1 degree, WRF-CR) is also used to illustrate the impact of spatial resolution on simulations of snow properties and aerosol distribution over HMA. Due to a more realistic representation of terrain slopes over HMA, the higher resolution model (WRF-HR) shows significantly better performance in simulating snow area cover, duration of snow cover, snow albedo and snow grain size over HMA, as well as an evidently better atmospheric aerosol loading and mean LAPs concentration in snow. However, the differences in albedo reduction from model and satellite retrievals is large during winter due to associated overestimation in simulated snow fraction. It is noteworthy that Himalayan snow cover have high magnitudes of LAP-induced snow albedo reduction (4–8 %) in summer (both from WRF-HR and satellite estimates), which, induces a snow-mediated radiative forcing of ∼ 30–50 W/m2. As a result, Himalayas (specifically western Himalayas) hold the most vulnerable glaciers and mountain snowpack to the LAP-induced snow darkening effect within HMA. In summary, coarse spatial resolution and absence of snow-aerosol interactions over Himalaya cryosphere will result in significant underestimation of aerosol effect on snow melting and regional hydroclimate.

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Impact of light-absorbing particles on snow albedo darkening and associated radiative forcing over high-mountain Asia: high-resolution WRF-Chem modeling and new satellite observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7105-2019 ◽

2019 ◽

Vol 19 (10) ◽

pp. 7105-7128 ◽

Cited By ~ 9

Author(s):

Chandan Sarangi ◽

Yun Qian ◽

Karl Rittger ◽

Kathryn J. Bormann ◽

Ying Liu ◽

...

Keyword(s):

Grain Size ◽

Snow Cover ◽

Spatial Resolution ◽

Radiative Forcing ◽

High Mountain ◽

Western Himalayas ◽

Snow Albedo ◽

Microphysical Properties ◽

Snow Properties ◽

The Impact

Abstract. Light-absorbing particles (LAPs), mainly dust and black carbon, can significantly impact snowmelt and regional water availability over high-mountain Asia (HMA). In this study, for the first time, online aerosol–snow interactions are enabled and a fully coupled chemistry Weather Research and Forecasting (WRF-Chem) regional model is used to simulate LAP-induced radiative forcing on snow surfaces in HMA at relatively high spatial resolution (12 km, WRF-HR) compared with previous studies. Simulated macro- and microphysical properties of the snowpack and LAP-induced snow darkening are evaluated against new spatially and temporally complete datasets of snow-covered area, grain size, and impurity-induced albedo reduction over HMA. A WRF-Chem quasi-global simulation with the same configuration as WRF-HR but a coarser spatial resolution (1∘, WRF-CR) is also used to illustrate the impact of spatial resolution on simulations of snow properties and aerosol distribution over HMA. Due to a more realistic representation of terrain slopes over HMA, the higher-resolution model (WRF-HR) shows significantly better performance in simulating snow area cover, duration of snow cover, snow albedo and snow grain size over HMA, as well as an evidently better atmospheric aerosol loading and mean LAP concentration in snow. However, the differences in albedo reduction from model and satellite retrievals is large during winter due to associated overestimation in simulated snow fraction. It is noteworthy that Himalayan snow cover has high magnitudes of LAP-induced snow albedo reduction (4 %–8 %) in pre-monsoon seasons (both from WRF-HR and satellite estimates), which induces a snow-mediated radiative forcing of ∼30–50 W m−2. As a result, the Himalayas (specifically the western Himalayas) hold the most vulnerable glaciers and mountain snowpack to the LAP-induced snow darkening effect within HMA. In summary, coarse spatial resolution and absence of snow–aerosol interactions over the Himalayan cryosphere will result in significant underestimation of aerosol effects on snow melting and regional hydroclimate.

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Analyses of Continuous Snow Cover Duration and Its First and Last Days Using Weibull Distribution Method.

Journal of Agricultural Meteorology ◽

10.2480/agrmet.54.63 ◽

1998 ◽

Vol 54 (1) ◽

pp. 63-69 ◽

Cited By ~ 4

Author(s):

Kazushige YAMADA ◽

Tomoyoshi HIROTA ◽

Ryuichi SHIROOKA

Keyword(s):

Weibull Distribution ◽

Snow Cover ◽

Distribution Method ◽

Snow Cover Duration

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Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-15-0126.1 ◽

2016 ◽

Vol 73 (4) ◽

pp. 1507-1527 ◽

Cited By ~ 18

Author(s):

Jason M. Keeler ◽

Brian F. Jewett ◽

Robert M. Rauber ◽

Greg M. McFarquhar ◽

Roy M. Rasmussen ◽

...

Keyword(s):

Vertical Velocity ◽

Radiative Forcing ◽

Initial Conditions ◽

Vertical Wind Shear ◽

Weather Research And Forecasting ◽

Velocity Spectrum ◽

Latent Heating ◽

Heating Rates ◽

Winter Storms ◽

Radiation Parameterizations

Abstract This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.

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