Cyclonic and anticyclonic contributions to atmospheric energetics

Scientific Reports
| (2021) 11:13202 | 
https://doi.org/10.1038/s41598-021-92548-7
www.nature.com/scientificreports/
Thus, the net CK to the background westerlies from anticyclonic eddies is slightly larger especially in the upper 
troposphere (Supplementary Figs. S10a–b). The cyclonic CP is much stronger especially over the western North 
Pacific (Supplementary Figs. S9c–d), where cyclonic development is promoted along a prominent oceanic frontal 
zone that acts to reinforce the near-surface baroclinicity in addition to abundant moisture supply from the warm 
Kuroshio Extension
23
. The differences between the cyclonic and anticyclonic CP are found mainly in the lower 
and mid-troposphere (Supplementary Figs. S10c–d). The anticyclonic CP is concentrated in the upper tropo-
sphere and actually it is comparable to the cyclonic CP when integrated only in the mid- and upper troposphere 
(Supplementary Fig. S11). These energetic features are overall consistent with the results in Fig. 
3
.
Discussion
In this study, the conventional Eulerian statistics and Lorenz energy cycle are decomposed into the contributions 
from cyclonic and anticyclonic vortices based on the separate identification of these two types of vortices. This 
gives new insights for understanding of storm track dynamics and eddy-mean flow interaction, especially the 
distinct roles of cyclonic and anticyclonic vortices in maintaining the mean westerlies, in addition to the atmos-
pheric energetics. The novel approach used here allows us to expand the knowledge about storm tracks obtained 
thus far based solely on either the Eulerian statistics or Lagrangian tracking. The latter has been applied almost 
exclusively to near-surface cyclones, but our approach suggests that roles of anticyclones should not be over-
looked. Moreover, our approach allows separating the atmospheric energetics into their cyclonic and anticyclonic 
contributions, pointing to the important role of anticyclones in the overall energy budget and energy conversion.
Our new method can lead to identification of distinct roles, if any, of cyclonic and anticyclonic eddies in caus-
ing the counterintuitive observed midwinter suppression of the North Pacific storm track activity
14
,
15
. Likewise, 
dynamics of the annular modes over the Northern and Southern Hemispheres
28
, the baroclinic annular mode
29
, 
and blocking highs
30
–
32
 can also be addressed through our new unified approach between the Lagrangian and 
Eulerian perspectives. The same will be the case for output of climate models, including future climate projec-
tions and large ensemble simulations, in which changes in positions and activity of storm tracks have been 
intensively studied
33
–
36
.
Previous studies have examined the observed trend
37
and future change
38
–
40
 in atmospheric energetics based 
on the Lorenz energy cycle. These studies helped understand climate change from an energetic point of view, 
into which the present study can give a new insight. Furthermore, the separation of cyclonic and anticyclonic 
contributions to the atmospheric energy cycle can be useful for the validation of the climate model simulations, 
providing us with a more phenomenological way to interpret and constituting another constraint for the models. 
Recently, the effect of global warming on wind power generation, which ultimately determines the amount of 
wind energy that can be extracted for power generation
41
, has been investigated in the framework of atmospheric 
energetics
42
. Our new approach has the potential to delineate separate roles of cyclones and anticyclones in the 
origin of near-surface wind energy.