the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Jul 2025
Surface Radiation Trends at North Slope of Alaska Influenced by Large-Scale Circulation and Atmospheric Rivers
Abstract. Arctic amplification manifests as a pervasive warming trend emerging over the past century in near-surface air temperature throughout the Arctic that is double the globally averaged temperature increase throughout most of the year. It results from complex processes involving oceanic, atmospheric and terrestrial components which require detailed study to discern roles of the fundamental processes involved to improve predictions of the Arctic environment. We report on signals that are beginning to emerge, on a timescale predicted by recent satellite remote sensing studies, from the unique 25-year record of detailed surface-based radiometer measurements obtained by the US Department of Energy Atmospheric Radiation Measurement (ARM) Facility North Slope of Alaska (NSA) site at Utqiaġvik, Alaska. Statistically significant warming trends are found at the site in the boreal fall, while a decrease in net radiation occurs in late summer. This decrease is driven primarily by the decrease in shortwave radiation resulting from increasing cloud liquid water path as observed by the microwave radiometer. Analysis of prevailing meteorological regimes linking NSA with the Arctic Ocean and subarctic latitudes, and atmospheric rivers, suggests that specific changing circulation patterns are the primary driver for these trends.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(3927 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2025-2768', Anonymous Referee #1, 31 Jul 2025
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RC2: 'Comment on egusphere-2025-2768', Anonymous Referee #2, 06 Aug 2025
This study analyzed the quality-controlled 25-year surface-based observations at DOE North Slope of Alaska site, and showed statistically significant trends in the surface radiative fluxes on semi-monthly intervals. This study also investigated the role of large-scale circulation pattern, including atmospheric rivers and clustered meteorological regimes, in affecting these observed trends. This study provides valuable insights into directly measured surface radiative fluxes and PWV and LWP retrievals from surface-based observations, their dynamics and related atmospheric mechanisms. Overall, the manuscript is technically solid and well-written. Some parts are unclear and can benefit from additional details, but should be manageable with minor revisions. Please find specific comments below.
Specific comments:
- Line 20: “… suggests that specific changing circulation patterns are the primary driver for these trends.” Does this statement apply only to Jul Late or also other intervals?
- Line 79-81: This sentence is overpacked, please consider split it into two or more. For example, it can be confusing as one may wonder are all the variables first averaged over diurnal then semi-monthly? Or semi-monthly averages are only used for time series analysis? Also, you may want to mention the “Early” and “Late” for the semi-monthly intervals here to enhance clarity.
- Line 127-129: Table 1, how did you determine that the cluster count (i.e., number of meteorological regimes) should be four? Were there any considerations per wind directions or adjacent oceans etc.? If so, please specify.
- Line 200: “these quantities are expected to have larger uncertainty than the radiative fluxes…” Do you have rough estimates of the uncertainty value?
- Line 245: Table 4 caption “Shown for each net radiative flux component” is this a typo? I thought Table 4 shows PWV and LWP trends.
- Line 250-251: Just a suggestion, you probably also want to cite the Guan and Waliser paper on AR detection https://doi.org/10.1002/2015JD024257
- Line 258-259: “nearly all lose statistical significance when we omit the AR days” I’m curious about how much sample size would the omitted AR days take away. It seems from Fig. 6a that AR occurrence days for July and Aug can be around 100-200 per interval over the whole 25-year period. So, on average, it would be ~ 40% of the semi-monthly intervals in July and August, right?
- Line 260-261: “other summertime intervals”, according to Table 3, only JUL Early, JUL Late, AUG Early, and AUG Late have statistically significant trends, while June intervals have no statistically significant trends. Do the summertime intervals here refer to July and August intervals? If so, please specify.
- Line 260-261: “whose radiative flux trends largely remain significant when we omit the AR days (Table 4)” Do you meant to refer to Table 5 here?
- Line 348-349: Very nice and clear explanations, except appears a bit late. I would strongly suggest adding the explanations near Line 256-261 when you mentioned “omitting the AR days”. It would help with manuscript clarity and physical interpretations.
Citation: https://doi.org/10.5194/egusphere-2025-2768-RC2 -
AC1: 'Comment on egusphere-2025-2768', Dan Lubin, 26 Aug 2025
We thank both referees for their positive appraisal of our manuscript and for their insightful and helpful comments and suggestions for improvement. All of the referees' suggestions will be incorporated into the revision, which we plan to complete by 30 September 2025.
Citation: https://doi.org/10.5194/egusphere-2025-2768-AC1
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-2768', Anonymous Referee #1, 31 Jul 2025
This study analyzes trends in a 25-year record of surface-based radiometer measurements at the North Slope of Alaska. The authors find a statistically significant trend decreasing trend in cooling in summer, which they attribute to increases in cloud liquid water path driven by atmospheric river activity. This cooling trend seems to contribute to a relatively small positive summer trend that is not statistically significant in the summer.
The study is interesting and contributes to the understanding of Arctic amplification locally at the North Slope of Alaska using surface observations. The authors perform a detailed statistical analysis of the datasets and acknowledge important limitations in the datasets they use. I have a few comments for the authors to consider below before considering this manuscript for publication in ACP.
My only major comment is that the authors have not attempted to quantify the role of natural variability in their analysis. I would have expected to see either a principal component analysis or some time series filtering to attempt to disentangle these effects.
Other comments:
- The authors have also not considered aerosol effects that can influence local microphysical effects. A recent paper by Stauffer et al. (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025GL114815) find that aerosol influences are important for explaining local cloud effects, including the liquid water path of clouds.
- Can the authors clarify during what season atmospheric rivers peak in their dataset? Do they actually peak in the late summer where they find the largest LWP increases or are they only finding a larger SW cooling signal because sunlight is stronger during those months (removing the surface albedo effects during early summer causing statistical insignificance that they mentioned)?
- The Abstract mentions statistically significant warming trends in the fall as well, but the focus of the manuscript was on the late summer effect due to liquid water path increases. Can the authors elaborate in the manuscript on the whether same mechanism of increasing LWP also applies to the fall months? Figure 4 seems to suggest so, at least for some of the months.
Citation: https://doi.org/10.5194/egusphere-2025-2768-RC1 -
RC2: 'Comment on egusphere-2025-2768', Anonymous Referee #2, 06 Aug 2025
This study analyzed the quality-controlled 25-year surface-based observations at DOE North Slope of Alaska site, and showed statistically significant trends in the surface radiative fluxes on semi-monthly intervals. This study also investigated the role of large-scale circulation pattern, including atmospheric rivers and clustered meteorological regimes, in affecting these observed trends. This study provides valuable insights into directly measured surface radiative fluxes and PWV and LWP retrievals from surface-based observations, their dynamics and related atmospheric mechanisms. Overall, the manuscript is technically solid and well-written. Some parts are unclear and can benefit from additional details, but should be manageable with minor revisions. Please find specific comments below.
Specific comments:
- Line 20: “… suggests that specific changing circulation patterns are the primary driver for these trends.” Does this statement apply only to Jul Late or also other intervals?
- Line 79-81: This sentence is overpacked, please consider split it into two or more. For example, it can be confusing as one may wonder are all the variables first averaged over diurnal then semi-monthly? Or semi-monthly averages are only used for time series analysis? Also, you may want to mention the “Early” and “Late” for the semi-monthly intervals here to enhance clarity.
- Line 127-129: Table 1, how did you determine that the cluster count (i.e., number of meteorological regimes) should be four? Were there any considerations per wind directions or adjacent oceans etc.? If so, please specify.
- Line 200: “these quantities are expected to have larger uncertainty than the radiative fluxes…” Do you have rough estimates of the uncertainty value?
- Line 245: Table 4 caption “Shown for each net radiative flux component” is this a typo? I thought Table 4 shows PWV and LWP trends.
- Line 250-251: Just a suggestion, you probably also want to cite the Guan and Waliser paper on AR detection https://doi.org/10.1002/2015JD024257
- Line 258-259: “nearly all lose statistical significance when we omit the AR days” I’m curious about how much sample size would the omitted AR days take away. It seems from Fig. 6a that AR occurrence days for July and Aug can be around 100-200 per interval over the whole 25-year period. So, on average, it would be ~ 40% of the semi-monthly intervals in July and August, right?
- Line 260-261: “other summertime intervals”, according to Table 3, only JUL Early, JUL Late, AUG Early, and AUG Late have statistically significant trends, while June intervals have no statistically significant trends. Do the summertime intervals here refer to July and August intervals? If so, please specify.
- Line 260-261: “whose radiative flux trends largely remain significant when we omit the AR days (Table 4)” Do you meant to refer to Table 5 here?
- Line 348-349: Very nice and clear explanations, except appears a bit late. I would strongly suggest adding the explanations near Line 256-261 when you mentioned “omitting the AR days”. It would help with manuscript clarity and physical interpretations.
Citation: https://doi.org/10.5194/egusphere-2025-2768-RC2 -
AC1: 'Comment on egusphere-2025-2768', Dan Lubin, 26 Aug 2025
We thank both referees for their positive appraisal of our manuscript and for their insightful and helpful comments and suggestions for improvement. All of the referees' suggestions will be incorporated into the revision, which we plan to complete by 30 September 2025.
Citation: https://doi.org/10.5194/egusphere-2025-2768-AC1
Peer review completion
Journal article(s) based on this preprint
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Dan Lubin
Johannes Mülmenstädt
Andrew Vogelmann
Maria Cadeddu
Damao Zhang
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3927 KB) - Metadata XML
This study analyzes trends in a 25-year record of surface-based radiometer measurements at the North Slope of Alaska. The authors find a statistically significant trend decreasing trend in cooling in summer, which they attribute to increases in cloud liquid water path driven by atmospheric river activity. This cooling trend seems to contribute to a relatively small positive summer trend that is not statistically significant in the summer.
The study is interesting and contributes to the understanding of Arctic amplification locally at the North Slope of Alaska using surface observations. The authors perform a detailed statistical analysis of the datasets and acknowledge important limitations in the datasets they use. I have a few comments for the authors to consider below before considering this manuscript for publication in ACP.
My only major comment is that the authors have not attempted to quantify the role of natural variability in their analysis. I would have expected to see either a principal component analysis or some time series filtering to attempt to disentangle these effects.
Other comments: