EGU2020-21344
https://doi.org/10.5194/egusphere-egu2020-21344
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport

Johanne H. Rydsaa, Rune G. Graversen, and Patrick Stoll
Johanne H. Rydsaa et al.
  • UiT The Arctic University of Norway, Norway

Atmospheric energy transport into the Arctic (>70° N) has been shown to greatly alter the Arctic temperatures and the development of the Arctic weather and climate. Recent research suggests that latent energy transport into the Arctic by large, planetary-scale atmospheric systems cause a stronger and more long-lasting impact on near surface temperatures, than energy transported by smaller, synoptic scale systems. This implies that Rossby waves impact Arctic climate more than synoptic cyclones. Therefore, shifts in circulation patterns driving atmospheric energy transport into the Arctic on different scales have a potential to change Arctic climate.

Here, we show that the annual mean impact of latent energy transport on Arctic temperatures is dominated by the winter season transport. Furthermore, by examining the ERA5 dataset for the years 1979-2018, we find that over the past four decades, there has been a shift in the mean winter season latent energy transport, from smaller, synoptic scale systems (-0.03 PW/decade), towards larger, planetary scale systems (+0.05 PW/decade) which as mentioned, have a larger climatic impact. As a consequence, this shift is estimated to have increased the Arctic temperatures. We find that the trends are driven by an increase in the extreme transport events (here we examine the upper 97.5th percentile). The upper extremes have increased more than the average on the planetary scale, and decreased more on the synoptic scale. The decrease in extreme synoptic scale transport at 70° N has been confirmed in other analyses of high vorticity weather systems. By examining the extreme transport events on seasonal scales, we reveal differences in the temporal distribution of planetary vs. synoptic scale extreme events, and identify areas of the Arctic that receive the strongest impact with respect to increases in near-surface temperatures.

How to cite: Rydsaa, J. H., Graversen, R. G., and Stoll, P.: Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21344, https://doi.org/10.5194/egusphere-egu2020-21344, 2020

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Display material version 1 – uploaded on 05 May 2020
  • CC1: Comment on EGU2020-21344, Tetsu Nakamura, 05 May 2020

    Hi Johanne,

     

    I am very interested in this study, thank you.

     

    In the figure of top-right of second slide, we can see the long-term trends of vQ due to planetary and  synoptic waves cancell out each other. Then, the total effect of vQ on the long-term tendency will be nearly zero?

    • CC2: Reply to CC1, Johanne H. Rydsaa, 05 May 2020

      Hi tetsu, 

      thank you, nice to hear you find it interesting. About the trends, yes, the trends nearly cancel each other out, but the combined effect is a slight (non-significant) increase in winter anomalies. There are also significant, opposite trends in the summer, not shown here. On an annual means, the trends are very weak and non-significant.

      • CC3: Reply to CC2, Johanne H. Rydsaa, 05 May 2020

        Sorry about my spelling, Tetsu (now with a capitalized T, sorry!)

      • CC4: Reply to CC2, Tetsu Nakamura, 05 May 2020

        Thank you, Johanne.

         

        Direct impcats of vQ are nearly cancelled, I see.

         

        Then can we suppose any diffrent impcats of vQ on cloud formation and/or downward radiation between planetary and synoptic, as was discuessed in Tuomas's presentation? 

        • CC5: Reply to CC4, Johanne H. Rydsaa, 06 May 2020

          Hi Tetsu,

          Well, in our findings, and confirming earlier findings by Graversen and Burtu (2016), the effects of LE that is transported into the Arctic by planetary scale systems seem to be associated with a much greater impact on cloud formation, long wave radiation, local greenhouse effect and thus near surface temperatures, than the LE transported by synoptic scale systems. In the composites in our presentation here, as well as regression analysis not shown here, we find that the events defined as planetary motions here seem to on average transport LE deeper into the Arctic, and for longer time durations, as compared to the synoptic systems. As the impact of LE is not uniform across which type of system that transports it (and which areas it reaches and under which conditions), we find that looking at temperature and cloud effects, it is the total transport on each scale that seems important, rather than the sum of LE transported across different sizes and types of systems. And in that way, changes in the magnitude on each scale would be able to affect Arctic temperatures, even while the total LE stayed the same. So I think that the different effects seen in Tuomas' presentation are to be expected, and I think we see similar findings in the results presented here.

          • CC6: Reply to CC5, Tetsu Nakamura, 06 May 2020

            Thank you very much for detail discussions, Johanne.

            Such asymmetry impacts of latent transport due to wave scale is very interesting.

            Thank you again.