EGU2020-4730, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-4730
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Global Near-Surface Wind Speed Trends in Observation and CMIP6 Historical Simulation for 1850–2014

Kaiqiang Deng, Cesar Azorin-Molina, Lorenzo Minola, and Deliang Chen
Kaiqiang Deng et al.
  • Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Sweden (kaiqiang.deng@gu.se)

The changes in near-surface (10-m height) wind speed have direct impacts on human society, such as utilization of wind energy, air pollution dispersion and dust storm frequency, which requires comprehensive assessment and improved understanding. Based on ground-based observations and multiple atmospheric reanalysis datasets, previous research revealed significant negative and positive trends in wind speed over land and oceans, respectively. In this study, we used Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations to investigate the association between global mean wind speed changes and human-induced forcing. It is found that both unforced pre-industrial control run and historical natural forcing experiments failed in reproducing the observed trends in land and ocean wind speeds. However, the CMIP6 historical greenhouse gas forcing successfully simulated the increasing trend in ocean wind speed, while the CMIP6 historical aerosol forcing and experiments with land use changes seemed to have caused a decreasing trend in wind speeds over both land and ocean, suggesting that anthropogenic forcings are crucial drivers for the recent changes in global wind speed. Further attribution studies are needed to better understand wind speed variability under a warming climate.

How to cite: Deng, K., Azorin-Molina, C., Minola, L., and Chen, D.: Global Near-Surface Wind Speed Trends in Observation and CMIP6 Historical Simulation for 1850–2014, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4730, https://doi.org/10.5194/egusphere-egu2020-4730, 2020

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  • CC1: Comment on EGU2020-4730, Linda van Garderen, 05 May 2020

    Thank you very much for this interesting presentation!

    I have a few questions concerning both method and implications of your conclusions.

    First I was wondering if you may have any idea why NCEP is not producing the windspeeds very well and is clearly an outlier among the reanalysis datasets you used. Could this be connected to resolution or do you think something else may be the matter?

    Second, your choise to split land from ocean is insightfull. However, is there a reason why you do not show a general results for the the NH and SH for land and ocean together? I would have helped me  place your results even better.

    Your results on the effect of different forcings on f.i. the Hadley cells is intreging. However, I cannot find the  method on how you changed the forcings. What exactly did you do with the aersosols? Did you take certain type of aerosols out, are the airosols connected to SST altered or just volcanos and input form land?

    Finally I was wondering if you may have any idea on what the trend in stronger SH hadley cells may result into for SH weather. Extreme weather events such as drought in Australia  may be influenced by this trend, do you think?

    Thank you very much!

    Linda

    • AC1: Reply to CC1, Kaiqiang Deng, 05 May 2020

      Hi Linda, 

      Thanks for your interests in this study. For your questions:

      (1) First I was wondering if you may have any idea why NCEP is not producing the windspeeds very well and is clearly an outlier among the reanalysis datasets you used. Could this be connected to resolution or do you think something else may be the matter?

      Answer: We believe that the resolusion of NCEP1 has an impact on the data discrepencies. Compared to other reanalysis data (with a resolusion of 1x1 or higher), the NCEP1 has a larger resolution of 2.5x2.5 and we see that NCEP1 is an obvious outlier in representing the wind speed trends.

      (2) Second, your choise to split land from ocean is insightfull. However, is there a reason why you do not show a general results for the the NH and SH for land and ocean together? I would have helped me  place your results even better.

      Answer: We split land from ocean because the wind speed trends over land and ocean are very different and even opposite. The land wind speed experienced decreasing trends over the past decades, while the ocean wind speed experienced increasing trends. Thus, if we consider the trends over land and ocean together, they may cancel out each other to some extent. In general, ocean wind speed may dominate the trends. That means, if we calculate the wind speed trends over NH and SH (no split of land and ocean), we can always obtain the results that SH wind speed show remarkable upward trends, and the NH show much weaker but still positive trends.

      (3) Your results on the effect of different forcings on f.i. the Hadley cells is intreging. However, I cannot find the  method on how you changed the forcings. What exactly did you do with the aersosols? Did you take certain type of aerosols out, are the airosols connected to SST altered or just volcanos and input form land?

      Answer: We did not run the model experients. The model simulations used in this study are from the CMIP6 output. The model experiments were run from 1850 to 2015 driven by historical all forcing and individual forcings (i.e. greenhouse gases, aerosols, and natural variability (e.g. solar and volcanic eruptions)). The detailed information of the CMIP6 experimental design can be found in Eyring et al. (2016). 

      Reference:
      Eyring, V., B. Sandrine, A. Gerald, and Coauthors, 2016: Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev., 9, 1937–1958. https://doi.org/10.5194/gmd-9-1937-2016.

      (4) Finally I was wondering if you may have any idea on what the trend in stronger SH hadley cells may result into for SH weather. Extreme weather events such as drought in Australia  may be influenced by this trend, do you think?

      Answer: We are indeed interested in the relationships between atmospheric meridional circulation and SH weather extremes. The changes in SH Hadley cell and associated increase in SH wind speed could have potential impacts on weather extremes such as heatwave and drought events over Australia. On the one hand, the intensifed descending branch of the SH Hadley cell may suppress the rainfall over Australia and induce higher air temperatures via adiabatic warming. On the other hand, the strengthening SH surface westerly winds could block the cold air flows from the Antarctica and high latitudes. As a result, hotter and drier surface condition may appear in Australia that favor the occurrences of heatwaves and Droughts. 

      Kaiqiang

      • CC2: Reply to AC1, Linda van Garderen, 05 May 2020

        Thank you very much for your elaborate answers. They clarify a lot.

        It is indeed ineresting to take a look at the effects of the strengthening Hadley Cels on SH extreme weather events.

        Linda