Sea-breeze dynamics and convection initiation: the influence of convective parameterization in weather and climate model biases

Cathryn E Birch, Malcolm J Roberts, Luis Garcia-Carreras, Duncan Ackerley, Michael J Reeder, Adrian P Lock, Reinhard Schiemann

Research output: Contribution to journalArticleResearchpeer-review

Abstract

There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land-sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.
Original languageEnglish
Pages (from-to)8093-8108
Number of pages16
JournalJournal of Climate
Volume28
Issue number20
DOIs
Publication statusPublished - 2015

Keywords

  • Atm/Ocean Structure/Phenomena
  • Convective parameterization
  • Diurnal effects
  • General circulation models
  • Geographic location/entity
  • Maritime Continent
  • Models and modeling
  • Precipitation
  • Sea breezes
  • Variability

Cite this

Birch, Cathryn E ; Roberts, Malcolm J ; Garcia-Carreras, Luis ; Ackerley, Duncan ; Reeder, Michael J ; Lock, Adrian P ; Schiemann, Reinhard. / Sea-breeze dynamics and convection initiation: the influence of convective parameterization in weather and climate model biases. In: Journal of Climate. 2015 ; Vol. 28, No. 20. pp. 8093-8108.
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abstract = "There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land-sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.",
keywords = "Atm/Ocean Structure/Phenomena, Convective parameterization, Diurnal effects, General circulation models, Geographic location/entity, Maritime Continent, Models and modeling, Precipitation, Sea breezes, Variability",
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Sea-breeze dynamics and convection initiation: the influence of convective parameterization in weather and climate model biases. / Birch, Cathryn E; Roberts, Malcolm J; Garcia-Carreras, Luis; Ackerley, Duncan; Reeder, Michael J; Lock, Adrian P; Schiemann, Reinhard.

In: Journal of Climate, Vol. 28, No. 20, 2015, p. 8093-8108.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Sea-breeze dynamics and convection initiation: the influence of convective parameterization in weather and climate model biases

AU - Birch, Cathryn E

AU - Roberts, Malcolm J

AU - Garcia-Carreras, Luis

AU - Ackerley, Duncan

AU - Reeder, Michael J

AU - Lock, Adrian P

AU - Schiemann, Reinhard

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AB - There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land-sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.

KW - Atm/Ocean Structure/Phenomena

KW - Convective parameterization

KW - Diurnal effects

KW - General circulation models

KW - Geographic location/entity

KW - Maritime Continent

KW - Models and modeling

KW - Precipitation

KW - Sea breezes

KW - Variability

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DO - 10.1175/JCLI-D-14-00850.1

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SP - 8093

EP - 8108

JO - Journal of Climate

JF - Journal of Climate

SN - 0894-8755

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