---
_id: '9129'
abstract:
- lang: eng
  text: We investigate the role of a warm sea surface temperature (SST) anomaly (hot
    spot of typically 3 to 5 K) on the aggregation of convection using cloud-resolving
    simulations in a nonrotating framework. It is well known that SST gradients can
    spatially organize convection. Even with uniform SST, the spontaneous self-aggregation
    of convection is possible above a critical SST (here 295 K), arising mainly from
    radiative feedbacks. We investigate how a circular hot spot helps organize convection,
    and how self-aggregation feedbacks modulate this organization. The hot spot significantly
    accelerates aggregation, particularly for warmer/larger hot spots, and extends
    the range of SSTs for which aggregation occurs; however, at cold SST (290 K) the
    aggregated cluster disaggregates if we remove the hot spot. A large convective
    instability over the hot spot leads to stronger convection and generates a large-scale
    circulation which forces the subsidence drying outside the hot spot. Indeed, convection
    over the hot spot brings the atmosphere toward a warmer temperature. The warmer
    temperatures are imprinted over the whole domain by gravity waves and subsidence
    warming. The initial transient warming and concomitant subsidence drying suppress
    convection outside the hot spot, thus driving the aggregation. The hot-spot-induced
    large-scale circulation can enforce the aggregation even without radiative feedbacks
    for hot spots sufficiently large/warm. The strength of the large-scale circulation,
    which defines the speed of aggregation, is a function of the hot spot fractional
    area. At equilibrium, once the aggregation is well established, the moist convective
    region with upward midtropospheric motion, centered over the hot spot, has an
    area surprisingly independent of the hot spot size.
article_processing_charge: No
article_type: original
author:
- first_name: Sara
  full_name: Shamekh, Sara
  last_name: Shamekh
- first_name: Caroline J
  full_name: Muller, Caroline J
  id: f978ccb0-3f7f-11eb-b193-b0e2bd13182b
  last_name: Muller
  orcid: 0000-0001-5836-5350
- first_name: Jean-Philippe
  full_name: Duvel, Jean-Philippe
  last_name: Duvel
- first_name: Fabio
  full_name: D’Andrea, Fabio
  last_name: D’Andrea
citation:
  ama: Shamekh S, Muller CJ, Duvel J-P, D’Andrea F. How do ocean warm anomalies favor
    the aggregation of deep convective clouds? <i>Journal of the Atmospheric Sciences</i>.
    2020;77(11):3733-3745. doi:<a href="https://doi.org/10.1175/jas-d-18-0369.1">10.1175/jas-d-18-0369.1</a>
  apa: Shamekh, S., Muller, C. J., Duvel, J.-P., &#38; D’Andrea, F. (2020). How do
    ocean warm anomalies favor the aggregation of deep convective clouds? <i>Journal
    of the Atmospheric Sciences</i>. American Meteorological Society. <a href="https://doi.org/10.1175/jas-d-18-0369.1">https://doi.org/10.1175/jas-d-18-0369.1</a>
  chicago: Shamekh, Sara, Caroline J Muller, Jean-Philippe Duvel, and Fabio D’Andrea.
    “How Do Ocean Warm Anomalies Favor the Aggregation of Deep Convective Clouds?”
    <i>Journal of the Atmospheric Sciences</i>. American Meteorological Society, 2020.
    <a href="https://doi.org/10.1175/jas-d-18-0369.1">https://doi.org/10.1175/jas-d-18-0369.1</a>.
  ieee: S. Shamekh, C. J. Muller, J.-P. Duvel, and F. D’Andrea, “How do ocean warm
    anomalies favor the aggregation of deep convective clouds?,” <i>Journal of the
    Atmospheric Sciences</i>, vol. 77, no. 11. American Meteorological Society, pp.
    3733–3745, 2020.
  ista: Shamekh S, Muller CJ, Duvel J-P, D’Andrea F. 2020. How do ocean warm anomalies
    favor the aggregation of deep convective clouds? Journal of the Atmospheric Sciences.
    77(11), 3733–3745.
  mla: Shamekh, Sara, et al. “How Do Ocean Warm Anomalies Favor the Aggregation of
    Deep Convective Clouds?” <i>Journal of the Atmospheric Sciences</i>, vol. 77,
    no. 11, American Meteorological Society, 2020, pp. 3733–45, doi:<a href="https://doi.org/10.1175/jas-d-18-0369.1">10.1175/jas-d-18-0369.1</a>.
  short: S. Shamekh, C.J. Muller, J.-P. Duvel, F. D’Andrea, Journal of the Atmospheric
    Sciences 77 (2020) 3733–3745.
date_created: 2021-02-15T14:07:30Z
date_published: 2020-11-01T00:00:00Z
date_updated: 2022-01-24T12:30:26Z
day: '01'
doi: 10.1175/jas-d-18-0369.1
extern: '1'
intvolume: '        77'
issue: '11'
keyword:
- Atmospheric Science
language:
- iso: eng
month: '11'
oa_version: None
page: 3733-3745
publication: Journal of the Atmospheric Sciences
publication_identifier:
  issn:
  - 0022-4928
  - 1520-0469
publication_status: published
publisher: American Meteorological Society
quality_controlled: '1'
status: public
title: How do ocean warm anomalies favor the aggregation of deep convective clouds?
type: journal_article
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
volume: 77
year: '2020'
...
---
_id: '9142'
abstract:
- lang: eng
  text: "In models of radiative–convective equilibrium it is known that convection
    can spontaneously aggregate into one single localized moist region if the domain
    is large enough. The large changes in the mean climate state and radiative fluxes
    accompanying this self-aggregation raise questions as to what simulations at lower
    resolutions with parameterized convection, in similar homogeneous geometries,
    should be expected to produce to be considered successful in mimicking a cloud-resolving
    model.\r\nThe authors investigate this self-aggregation in a nonrotating, three-dimensional
    cloud-resolving model on a square domain without large-scale forcing. It is found
    that self-aggregation is sensitive not only to the domain size, but also to the
    horizontal resolution. With horizontally homogeneous initial conditions, convective
    aggregation only occurs on domains larger than about 200km and with resolutions
    coarser than about 2km in the model examined. The system exhibits hysteresis,
    so that with aggregated initial conditions, convection remains aggregated even
    at our finest resolution, 500m, as long as the domain is greater than 200–300km.\r\nThe
    sensitivity of self-aggregation to resolution and domain size in this model is
    due to the sensitivity of the distribution of low clouds to these two parameters.
    Indeed, the mechanism responsible for the aggregation of convection is the dynamical
    response to the longwave radiative cooling from low clouds. Strong longwave cooling
    near cloud top in dry regions forces downward motion, which by continuity generates
    inflow near cloud top and near-surface outflow from dry regions. This circulation
    results in the net export of moist static energy from regions with low moist static
    energy, yielding a positive feedback."
article_processing_charge: No
article_type: original
author:
- first_name: Caroline J
  full_name: Muller, Caroline J
  id: f978ccb0-3f7f-11eb-b193-b0e2bd13182b
  last_name: Muller
  orcid: 0000-0001-5836-5350
- first_name: Isaac M.
  full_name: Held, Isaac M.
  last_name: Held
citation:
  ama: Muller CJ, Held IM. Detailed investigation of the self-aggregation of convection
    in cloud-resolving simulations. <i>Journal of the Atmospheric Sciences</i>. 2012;69(8):2551-2565.
    doi:<a href="https://doi.org/10.1175/jas-d-11-0257.1">10.1175/jas-d-11-0257.1</a>
  apa: Muller, C. J., &#38; Held, I. M. (2012). Detailed investigation of the self-aggregation
    of convection in cloud-resolving simulations. <i>Journal of the Atmospheric Sciences</i>.
    American Meteorological Society. <a href="https://doi.org/10.1175/jas-d-11-0257.1">https://doi.org/10.1175/jas-d-11-0257.1</a>
  chicago: Muller, Caroline J, and Isaac M. Held. “Detailed Investigation of the Self-Aggregation
    of Convection in Cloud-Resolving Simulations.” <i>Journal of the Atmospheric Sciences</i>.
    American Meteorological Society, 2012. <a href="https://doi.org/10.1175/jas-d-11-0257.1">https://doi.org/10.1175/jas-d-11-0257.1</a>.
  ieee: C. J. Muller and I. M. Held, “Detailed investigation of the self-aggregation
    of convection in cloud-resolving simulations,” <i>Journal of the Atmospheric Sciences</i>,
    vol. 69, no. 8. American Meteorological Society, pp. 2551–2565, 2012.
  ista: Muller CJ, Held IM. 2012. Detailed investigation of the self-aggregation of
    convection in cloud-resolving simulations. Journal of the Atmospheric Sciences.
    69(8), 2551–2565.
  mla: Muller, Caroline J., and Isaac M. Held. “Detailed Investigation of the Self-Aggregation
    of Convection in Cloud-Resolving Simulations.” <i>Journal of the Atmospheric Sciences</i>,
    vol. 69, no. 8, American Meteorological Society, 2012, pp. 2551–65, doi:<a href="https://doi.org/10.1175/jas-d-11-0257.1">10.1175/jas-d-11-0257.1</a>.
  short: C.J. Muller, I.M. Held, Journal of the Atmospheric Sciences 69 (2012) 2551–2565.
date_created: 2021-02-15T14:39:03Z
date_published: 2012-08-01T00:00:00Z
date_updated: 2022-01-24T13:49:41Z
day: '01'
doi: 10.1175/jas-d-11-0257.1
extern: '1'
intvolume: '        69'
issue: '8'
keyword:
- Atmospheric Science
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.1175/JAS-D-11-0257.1
month: '08'
oa: 1
oa_version: Published Version
page: 2551-2565
publication: Journal of the Atmospheric Sciences
publication_identifier:
  issn:
  - 0022-4928
  - 1520-0469
publication_status: published
publisher: American Meteorological Society
quality_controlled: '1'
status: public
title: Detailed investigation of the self-aggregation of convection in cloud-resolving
  simulations
type: journal_article
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
volume: 69
year: '2012'
...