Publication Date:
2024-04-25
Description:
〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Recent observations and modeling increasingly reveal the key role of cold pools in organizing the convective cloud field. Several methods for detecting cold pools in simulations exist, but are usually based on buoyancy fields and fall short of reliably identifying the active gust front. The current cold pool (CP) detection and tracking algorithm (CoolDeTA), aims to identify cold pools and follow them in time, thereby distinguishing their active gust fronts and the “offspring” rain cells generated nearby. To accomplish these tasks, CoolDeTA utilizes a combination of thermodynamic and dynamical variables and examines the spatial and temporal relationships between cold pools and rain events. We demonstrate that CoolDeTA can reconstruct CP family trees. Using CoolDeTA we can contrast radiative convective equilibrium (RCE) and diurnal cycle CP dynamics, as well as cases with vertical wind shear and without. We show that the results obtained are consistent with a conceptual model where CP triggering of children rain cells follows a simple birth rate, proportional to a CP's gust front length. The proportionality factor depends on the ambient atmospheric stability and is lower for RCE, in line with marginal stability as traditionally ascribed to the moist adiabat. In the diurnal case, where ambient stability is lower, the birth rate thus becomes substantially higher, in line with periodic insolation forcing—resulting in essentially run‐away mesoscale excitations generated by a single parent rain cell and its CP.〈/p〉
Description:
Plain Language Summary: Cold pools are cooled air masses below thunderstorm clouds, produced when rain evaporates underneath such clouds. Cold pools are important, as they produce strong gusts and have been associated with clumping of rain cells, whereby heavy rainfall over relatively small areas could be generated—with implications for flooding. The current work describes a method that helps identify such cold pools in computer simulation data. In contrast to earlier methods, we here show that the interaction between a CP and its surroundings can be reconstructed by the method. We show that this identification works under a range of contexts, such as when horizontal wind is applied in the simulations or when the surface temperature is not constant—as might often be the case over a land surface. The identification reveals interesting dynamical effects, such as that in some cases, cold pools can kick‐start a form of chain reaction, by which “rain cell children” of it give rise to additional cold pools that again produce children, and so forth. The dynamics revealed is in line with expectations of widespread, so‐called mesoscale convective systems over land, whereas over an ocean surface the dynamics is much less explosive.〈/p〉
Description:
Key Points:
〈list list-type="bullet"〉
〈list-item〉
〈p xml:lang="en"〉Our CoolDeTA algorithm reliably detects and tracks cold pools and their causal chains〈/p〉〈/list-item〉
〈list-item〉
〈p xml:lang="en"〉We propose a simple conceptual model which reproduces the cascade‐like mesoscale cold pool dynamics identified by CoolDeTA〈/p〉〈/list-item〉
〈list-item〉
〈p xml:lang="en"〉CoolDeTA opens for new studies into the dynamics of convective self‐organization through cold pools〈/p〉〈/list-item〉
〈/list〉
〈/p〉
Description:
Villum Fonden
http://dx.doi.org/10.13039/100008398
Description:
European Research Council
http://dx.doi.org/10.13039/501100000781
Description:
Novo Nordisk Foundation Interdisciplinary Synergy Program
Description:
Scientific Steering Committee
Description:
https://doi.org/10.5281/zenodo.6513224
Description:
https://github.com/Shakiro7/coldPool-detection-and-tracking
Description:
https://doi.org/10.5281/zenodo.10115957
Description:
https://doi.org/10.7717/peerj.453
Keywords:
ddc:551.6
;
cold pools
;
detection
;
tracking
;
cloud resolving simulation
;
convective organization
Language:
English
Type:
doc-type:article
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