the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Measurement of Light absorbing particles in surface snow of central and western Himalayan glaciers: spatial variability, radiative impacts, and potential source regions
- 1State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 73000, China
- 2International Centre for Integrated Mountain Development (ICIMOD), G.P.O. Box 3226, Kathmandu, Nepal
- 3Reading Academy, Nanjing University of Information Sciences and Technology 219 Ningliu Road, Nanjing, Jiangsu, 210044 China
- 4University of Chinese Academy of Sciences, Beijing, China
- 5Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, USA
- 6Research Applications Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA
- 1State Key Laboratory of Cryosphere Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 73000, China
- 2International Centre for Integrated Mountain Development (ICIMOD), G.P.O. Box 3226, Kathmandu, Nepal
- 3Reading Academy, Nanjing University of Information Sciences and Technology 219 Ningliu Road, Nanjing, Jiangsu, 210044 China
- 4University of Chinese Academy of Sciences, Beijing, China
- 5Department of Atmospheric Sciences, Texas A&M University, College Station, TX 77843, USA
- 6Research Applications Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA
Abstract. We collected surface snow samples from three different glaciers: Yala, Thana, and Sachin in the central and western Himalayas to understand the spatial variability and radiative impacts of light-absorbing particles. The Yala and Thana glaciers in Nepal and Bhutan, respectively, were selected to represent the central Himalayas. The Sachin glacier in Pakistan was selected to represent the western Himalayas. The samples were collected during the pre-and post-monsoon seasons of the year 2016. The samples were analysed for black carbon (BC) and water-insoluble organic carbon (OC) through the thermal optical method. The average mass concentrations (BC 2381.39 ng g−1; OC 3896.00 ng g−1; dust 101.05 µg g−1) in the western Himalaya (Sachin glacier) were quite higher compared to the mass concentrations (BC 357.93 ng g−1, OC 903.86 ng g−1, dust 21.95 µg g−1) at the central Himalaya (Yala glacier). The difference in mass concentration may be due to the difference in elevation, snow age, local pollution sources, and difference in meteorological conditions. BC in surface snow was also estimated through WRF-Chem simulations at the three glacier sites during the sampling periods. Simulations reasonably capture the spatial and seasonal patterns of the observed BC in snow but with a relatively smaller magnitude. Absolute snow albedo was estimated through the Snow, Ice, and Aerosol Radiation (SNICAR) model. The absolute snow albedo reduction was ranging between 0.48 % (Thana glacier during September) to 24 % (Sachin glacier during May) due to BC and 0.13 % (Yala glacier during September) to 5 % (Sachin glacier during May) due to dust. The instantaneous radiative forcing due to BC and dust was estimated in the range of 0 to 96.48 W m−2 and 0 to 25 W m−2 respectively. The lowest and highest albedo reduction and radiative forcing were observed in central and western Himalayan glaciers, respectively. The potential source regions of the deposited pollutants were inferred using WRF-Chem tagged-tracer simulations. Selected glaciers in the western Himalayas were mostly affected by long-range transport from the Middle East and Central Asia; however, the central Himalayan glaciers were mainly affected by local and South Asia emissions (from Nepal, India, and China) especially during the pre-monsoon season. Overall, South Asia and West Asia were the main contributing source regions of pollutants.
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Chaman Gul et al.
Status: closed
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RC1: 'Comment on acp-2021-935', Anonymous Referee #1, 09 Mar 2022
General comments on the overall quality of the preprint
The manuscript seems to be closely related to a 2021 EGU presentation (https://meetingorganizer.copernicus.org/EGU21/EGU21-8515.html), and a 2021 paper in Environmental Pollution (https://www.sciencedirect.com/science/article/pii/S0269749121001226?via%3Dihub), by many of the same authors as the submitted manuscript. However, the latter is focused on results from 2017, whereas the present results focus on 2016. Overall, the methodology is sound; in particular, analysis of black carbon and organic carbon in snow is based on Thermal-Optical Analysis, which is widely employed to distinguish organic carbon from elemental carbon in atmospheric aerosols. A novel aspect of the work is the integration of WRF-Chem to compare to observations of impurities in snow.
Specific comments addressing individual scientific questions/issues (section)
- Introduction line 87: I am not sure what “snow shape” is. And I think “snow texture” might mean “snow surface texture”. For both, it would help if the authors clarified the scale of these features: millimeters? meters?
- I find the description of the snow sampling to be inadequate. On lines 133-134, the manuscript refers the reader to a 2021 paper by Gul et al for details, but that paper describes sampling in a different year (2017), with specific references to dates that obviously can’t apply to the present work, e.g., Before the commencement of snow sampling on May 1, 2017, there was fresh snowfall around the study site. The mean snow thickness of fresh snow was around 15–18 cm and we collected samples from the top 7–10 cm layer. Critical aspects of the sampling protocol employed in this manuscript are therefore unclear to me: were the samples taken in 2016 (this work) also mainly of fresh snowfall? How thick was the fresh snow? At what depths were samples taken? At altitudes above 5000 meters, it will be obvious to some readers that the area lies above the tree line (which is a common source of debris at lower altitudes), but it would be useful to state that; a photograph of the sampling might also be useful.
- I want to commend the authors for their careful analysis of the discrepancy between the magnitude of BC loading in snow as reported here, compared to other regions -- on the order of 100-1000. I have just a few items I would like clarified about this.
- The authors allude to a possible cause of this discrepancy as “strong melting of surface snow and ice in the glacier ablation zone [that] could lead to BC enrichment which causes high BC concentrations (Li et al., 2017)”. But how is that consistent with the description of the samples as “fresh” snow (see my comment #2)? [I know that the authors are aware of these considerations: a recent paper in Earth-Science Reviews co-authored by Kang, states that BC concentrations on an “intensely ablated surface” can be on the order of 1000 ng/g.]
- Use of WRF-Chem runs to explain these numbers is a really great idea, but I feel that characterizing the discrepancy between those results and observations (in the abstract) as “a relatively smaller magnitude” understates it, as does the phrase “almost similar” in line 330. In contrast, looking at Figure 2, the Sachin May results, I’d say the observations are ~5x the WRF-Chem results. Also, and I guess more fundamentally, does the WRM-Chem model incorporate impurity enhancement due to snow ablation?
- I appreciate the discussion of uncertainties in the paragraph beginning on line 297. However, numbers reported elsewhere in the manuscript have unreasonably high precision, in my opinion. For example, in Line 210, the authors report an average concentration of BC at Sachin, during May, to six significant figures. The authors should justify the number of significant figures in values they report, and revise accordingly.
4. Figure 3 does not seem to be referred to in the body of the manuscript.
Technical Corrections
Line 1: Why is “Light” capitalized in the title?
Line 29, Abstract: “were quite higher compared” => “were quite high compared”
Line 68, Introduction: “Mountain glaciers are the most important freshwater resources to the lives of arid and semi-arid regions” => “Mountain glaciers are the most important freshwater resources to the inhabitants of arid and semi-arid regions”
Line 69, Introduction: What is “The great Himalayas”?
Line 78, Introduction: “it is still large uncertainties for” => “large uncertainties remain regarding”
Line 113: I think “mostly covered by firm/snow” is intended to be “mostly covered by firn/snow”.
Line 119: Punctuation issues on this line, and other places in this paragraph, need fixing.
Line 131: I think “few snow samples were also collected” should be “a few snow samples were also collected”.
Line 159: I don’t understand the sentence: “RF-based on measured BC and dust concentration in our samples were estimated using the following equation.” I understand that “RF” means “Radiative Forcing” … but what is “RF-based”? Also, the formatting of the equation on the following line is unconventional.
Line 169: The sentence “To identify the potential source region of pollution for the central and western Himalayan glaciers, the weather research and forecasting (WRF) model coupled with chemistry (WRF-Chem version 3.9.1.1) (Grell et al., 2005) tagged-tracer simulations for the selected sites” seems to be missing a verb.
Line 207: “Possible reasons for the lowest concentration” => “Possible reasons for the lower concentration” (I think).
Line 389: The Gul et al citation does not seem to include the year of publication.
Line 558, Figure 2: I don’t understand the simulation results for Sachin(Oct) – maybe the figure was garbled? Also, the caption doesn’t explain the meaning of the “x” and “+” symbols.
- AC1: 'Response to Reviewer 1 comments', Chaman Gul, 20 Apr 2022
-
RC2: 'Comment on acp-2021-935', Anonymous Referee #2, 12 May 2022
Dear Editor the manuscript can be accepted subject to technical corrections.
- AC2: 'Reply on RC2', Chaman Gul, 16 May 2022
Status: closed
-
RC1: 'Comment on acp-2021-935', Anonymous Referee #1, 09 Mar 2022
General comments on the overall quality of the preprint
The manuscript seems to be closely related to a 2021 EGU presentation (https://meetingorganizer.copernicus.org/EGU21/EGU21-8515.html), and a 2021 paper in Environmental Pollution (https://www.sciencedirect.com/science/article/pii/S0269749121001226?via%3Dihub), by many of the same authors as the submitted manuscript. However, the latter is focused on results from 2017, whereas the present results focus on 2016. Overall, the methodology is sound; in particular, analysis of black carbon and organic carbon in snow is based on Thermal-Optical Analysis, which is widely employed to distinguish organic carbon from elemental carbon in atmospheric aerosols. A novel aspect of the work is the integration of WRF-Chem to compare to observations of impurities in snow.
Specific comments addressing individual scientific questions/issues (section)
- Introduction line 87: I am not sure what “snow shape” is. And I think “snow texture” might mean “snow surface texture”. For both, it would help if the authors clarified the scale of these features: millimeters? meters?
- I find the description of the snow sampling to be inadequate. On lines 133-134, the manuscript refers the reader to a 2021 paper by Gul et al for details, but that paper describes sampling in a different year (2017), with specific references to dates that obviously can’t apply to the present work, e.g., Before the commencement of snow sampling on May 1, 2017, there was fresh snowfall around the study site. The mean snow thickness of fresh snow was around 15–18 cm and we collected samples from the top 7–10 cm layer. Critical aspects of the sampling protocol employed in this manuscript are therefore unclear to me: were the samples taken in 2016 (this work) also mainly of fresh snowfall? How thick was the fresh snow? At what depths were samples taken? At altitudes above 5000 meters, it will be obvious to some readers that the area lies above the tree line (which is a common source of debris at lower altitudes), but it would be useful to state that; a photograph of the sampling might also be useful.
- I want to commend the authors for their careful analysis of the discrepancy between the magnitude of BC loading in snow as reported here, compared to other regions -- on the order of 100-1000. I have just a few items I would like clarified about this.
- The authors allude to a possible cause of this discrepancy as “strong melting of surface snow and ice in the glacier ablation zone [that] could lead to BC enrichment which causes high BC concentrations (Li et al., 2017)”. But how is that consistent with the description of the samples as “fresh” snow (see my comment #2)? [I know that the authors are aware of these considerations: a recent paper in Earth-Science Reviews co-authored by Kang, states that BC concentrations on an “intensely ablated surface” can be on the order of 1000 ng/g.]
- Use of WRF-Chem runs to explain these numbers is a really great idea, but I feel that characterizing the discrepancy between those results and observations (in the abstract) as “a relatively smaller magnitude” understates it, as does the phrase “almost similar” in line 330. In contrast, looking at Figure 2, the Sachin May results, I’d say the observations are ~5x the WRF-Chem results. Also, and I guess more fundamentally, does the WRM-Chem model incorporate impurity enhancement due to snow ablation?
- I appreciate the discussion of uncertainties in the paragraph beginning on line 297. However, numbers reported elsewhere in the manuscript have unreasonably high precision, in my opinion. For example, in Line 210, the authors report an average concentration of BC at Sachin, during May, to six significant figures. The authors should justify the number of significant figures in values they report, and revise accordingly.
4. Figure 3 does not seem to be referred to in the body of the manuscript.
Technical Corrections
Line 1: Why is “Light” capitalized in the title?
Line 29, Abstract: “were quite higher compared” => “were quite high compared”
Line 68, Introduction: “Mountain glaciers are the most important freshwater resources to the lives of arid and semi-arid regions” => “Mountain glaciers are the most important freshwater resources to the inhabitants of arid and semi-arid regions”
Line 69, Introduction: What is “The great Himalayas”?
Line 78, Introduction: “it is still large uncertainties for” => “large uncertainties remain regarding”
Line 113: I think “mostly covered by firm/snow” is intended to be “mostly covered by firn/snow”.
Line 119: Punctuation issues on this line, and other places in this paragraph, need fixing.
Line 131: I think “few snow samples were also collected” should be “a few snow samples were also collected”.
Line 159: I don’t understand the sentence: “RF-based on measured BC and dust concentration in our samples were estimated using the following equation.” I understand that “RF” means “Radiative Forcing” … but what is “RF-based”? Also, the formatting of the equation on the following line is unconventional.
Line 169: The sentence “To identify the potential source region of pollution for the central and western Himalayan glaciers, the weather research and forecasting (WRF) model coupled with chemistry (WRF-Chem version 3.9.1.1) (Grell et al., 2005) tagged-tracer simulations for the selected sites” seems to be missing a verb.
Line 207: “Possible reasons for the lowest concentration” => “Possible reasons for the lower concentration” (I think).
Line 389: The Gul et al citation does not seem to include the year of publication.
Line 558, Figure 2: I don’t understand the simulation results for Sachin(Oct) – maybe the figure was garbled? Also, the caption doesn’t explain the meaning of the “x” and “+” symbols.
- AC1: 'Response to Reviewer 1 comments', Chaman Gul, 20 Apr 2022
-
RC2: 'Comment on acp-2021-935', Anonymous Referee #2, 12 May 2022
Dear Editor the manuscript can be accepted subject to technical corrections.
- AC2: 'Reply on RC2', Chaman Gul, 16 May 2022
Chaman Gul et al.
Chaman Gul et al.
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