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Adaptive behavior of marine cellular clouds.

Koren I, Feingold G - Sci Rep (2013)

Bottom Line: Shallow marine clouds appear in two formations - open cells that are weakly reflective and closed cells that are more reflective and hence more effective at cooling the climate system.Lagrangian satellite data analysis reveals that open cells oscillate, forming and disappearing with a periodicity of ~3 hours.These dynamical states are linked to two theoretical solutions of population dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences Weizmann Institute, Rehovot 76100, Israel. ilan.koren@weizmann.ac.il

ABSTRACT
Shallow marine clouds appear in two formations - open cells that are weakly reflective and closed cells that are more reflective and hence more effective at cooling the climate system. Lagrangian satellite data analysis reveals that open cells oscillate, forming and disappearing with a periodicity of ~3 hours. In contrast, closed cells maintain rigid structures for periods of more than 10 hours, suggesting that self-organisation breaks the link between the lifetime and the scale of a convective entity. These dynamical states are linked to two theoretical solutions of population dynamics.

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Time evolution of cellular cloud fields.(A) Three regions of interest are marked on a Meteostat Second Generation (MSG) satellite, SEVIRI image over the South Atlantic on 08-20-11. The horizontal cross-sections on panels B, C, and D show a snapshot (normalised reflectance in the visible) of the fields marked in the 3 boxes on panel A at 08:15 (UTC). The vertical segments follow the evolution of one cross-section in time until sunset (where colours get bluer). (B) Pockets of open cells (yellow box) surrounded by a closed cellular field. The evolution in time shows very little change in the arrangement of the cells. (C) A field of much thicker (~2 km) open cell clouds (red box). Their temporal evolution shows a rearrangement of the cloud field during the course of the day, much like those modeled3. (D) A field of closed cells (green box). The cloud field structure maintains a relatively rigid spatial pattern throughout the day. Note that the colour-scale of the closed field was modified to stretch the dynamic range because of the large cloud coverage.
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f2: Time evolution of cellular cloud fields.(A) Three regions of interest are marked on a Meteostat Second Generation (MSG) satellite, SEVIRI image over the South Atlantic on 08-20-11. The horizontal cross-sections on panels B, C, and D show a snapshot (normalised reflectance in the visible) of the fields marked in the 3 boxes on panel A at 08:15 (UTC). The vertical segments follow the evolution of one cross-section in time until sunset (where colours get bluer). (B) Pockets of open cells (yellow box) surrounded by a closed cellular field. The evolution in time shows very little change in the arrangement of the cells. (C) A field of much thicker (~2 km) open cell clouds (red box). Their temporal evolution shows a rearrangement of the cloud field during the course of the day, much like those modeled3. (D) A field of closed cells (green box). The cloud field structure maintains a relatively rigid spatial pattern throughout the day. Note that the colour-scale of the closed field was modified to stretch the dynamic range because of the large cloud coverage.

Mentions: Analysing the Lagrangian morphological evolution of the cloud fields reveals striking differences between the self-organisation strategies of open and closed cells (Fig. 2). Closed-cell fields maintain their tight spatial structure down to a resolution of a few km over the course of a day. After correcting for horizontal wind advection (as described in the methods part), the organisation of the field is approximately fixed in space. Although areas of the cloud field can be stretched or compressed, the field topology does not experience any spatial rearrangement. The internal organisation of updrafts and downdrafts at scales <10 km is resilient. In contrast, the open cell field is much more flexible. While the average structure of the cloud field can be maintained for a few days18, the internal organisation constantly rearranges, as cloud elements form and dissipate. For all the scenes analysed in this study (~100 individual analyses), the periodicity is on the order of 3 h (see the methods part), similar to rearrangement timescales obtained by fine-scale modeling3.


Adaptive behavior of marine cellular clouds.

Koren I, Feingold G - Sci Rep (2013)

Time evolution of cellular cloud fields.(A) Three regions of interest are marked on a Meteostat Second Generation (MSG) satellite, SEVIRI image over the South Atlantic on 08-20-11. The horizontal cross-sections on panels B, C, and D show a snapshot (normalised reflectance in the visible) of the fields marked in the 3 boxes on panel A at 08:15 (UTC). The vertical segments follow the evolution of one cross-section in time until sunset (where colours get bluer). (B) Pockets of open cells (yellow box) surrounded by a closed cellular field. The evolution in time shows very little change in the arrangement of the cells. (C) A field of much thicker (~2 km) open cell clouds (red box). Their temporal evolution shows a rearrangement of the cloud field during the course of the day, much like those modeled3. (D) A field of closed cells (green box). The cloud field structure maintains a relatively rigid spatial pattern throughout the day. Note that the colour-scale of the closed field was modified to stretch the dynamic range because of the large cloud coverage.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3753593&req=5

f2: Time evolution of cellular cloud fields.(A) Three regions of interest are marked on a Meteostat Second Generation (MSG) satellite, SEVIRI image over the South Atlantic on 08-20-11. The horizontal cross-sections on panels B, C, and D show a snapshot (normalised reflectance in the visible) of the fields marked in the 3 boxes on panel A at 08:15 (UTC). The vertical segments follow the evolution of one cross-section in time until sunset (where colours get bluer). (B) Pockets of open cells (yellow box) surrounded by a closed cellular field. The evolution in time shows very little change in the arrangement of the cells. (C) A field of much thicker (~2 km) open cell clouds (red box). Their temporal evolution shows a rearrangement of the cloud field during the course of the day, much like those modeled3. (D) A field of closed cells (green box). The cloud field structure maintains a relatively rigid spatial pattern throughout the day. Note that the colour-scale of the closed field was modified to stretch the dynamic range because of the large cloud coverage.
Mentions: Analysing the Lagrangian morphological evolution of the cloud fields reveals striking differences between the self-organisation strategies of open and closed cells (Fig. 2). Closed-cell fields maintain their tight spatial structure down to a resolution of a few km over the course of a day. After correcting for horizontal wind advection (as described in the methods part), the organisation of the field is approximately fixed in space. Although areas of the cloud field can be stretched or compressed, the field topology does not experience any spatial rearrangement. The internal organisation of updrafts and downdrafts at scales <10 km is resilient. In contrast, the open cell field is much more flexible. While the average structure of the cloud field can be maintained for a few days18, the internal organisation constantly rearranges, as cloud elements form and dissipate. For all the scenes analysed in this study (~100 individual analyses), the periodicity is on the order of 3 h (see the methods part), similar to rearrangement timescales obtained by fine-scale modeling3.

Bottom Line: Shallow marine clouds appear in two formations - open cells that are weakly reflective and closed cells that are more reflective and hence more effective at cooling the climate system.Lagrangian satellite data analysis reveals that open cells oscillate, forming and disappearing with a periodicity of ~3 hours.These dynamical states are linked to two theoretical solutions of population dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Sciences Weizmann Institute, Rehovot 76100, Israel. ilan.koren@weizmann.ac.il

ABSTRACT
Shallow marine clouds appear in two formations - open cells that are weakly reflective and closed cells that are more reflective and hence more effective at cooling the climate system. Lagrangian satellite data analysis reveals that open cells oscillate, forming and disappearing with a periodicity of ~3 hours. In contrast, closed cells maintain rigid structures for periods of more than 10 hours, suggesting that self-organisation breaks the link between the lifetime and the scale of a convective entity. These dynamical states are linked to two theoretical solutions of population dynamics.

Show MeSH
Related in: MedlinePlus