Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model

Hawcroft, Matt; Dacre, Helen; Forbes, R. M.; Hodges, Kevin I.; Shaffrey, Len; Stein, Thorwald H. M.

doi:10.1007/s00382-016-3204-6

Cited by 36 publications

(45 citation statements)

References 109 publications

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“…The positive diabatically produced PV tendency at low levels contributes to the northeastward propagation of the low‐level cyclone [ Tamarin and Kaspi , ]. The processes associated with latent heating may be especially important for future projections of climate change [ Hawcroft et al , ], particularly given the observed biases in precipitation intensity produced by some models [ Hawcroft et al , ]. Finally, the total PV tendency (Figure c) shows a dipole that is tilted SW‐NE, consistent with the overall eastward and poleward propagation of the low‐level cyclones.…”

Section: Poleward Motion Of Cyclonesmentioning

confidence: 94%

“…Thus, latent heat release is maximized in the midtroposphere in the northeastern side of the cyclone. Diabatic heating at the middle of the atmosphere can produce a positive low‐level PV tendency and a negative upper level PV tendency [ Davis et al , ; Stoelinga , ; Lackmann , ; Posselt and Martin , ; Hawcroft et al , ]. This occurs because the isentropes above the warming will tend to widen (i.e.,

| \frac{\partial \overset{θ}{true}}{∂p} |

decreases), while the isentropes below the warming will tend to narrow (i.e.,

| \frac{\partial \overset{θ}{true}}{∂p} |

increases).…”

Section: Poleward Motion Of Cyclonesmentioning

confidence: 99%

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The poleward shift of storm tracks under global warming: A Lagrangian perspective

Tamarin-Brodsky

Kaspi

2017

Geophysical Research Letters

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Comprehensive models of climate change projections have shown that the latitudinal band of extratropical storms will likely shift poleward under global warming. Here we study this poleward shift from a Lagrangian storm perspective, through simulations with an idealized general circulation model. By employing a feature tracking technique to identify the storms, we demonstrate that the poleward motion of individual cyclones increases with increasing global mean temperature. A potential vorticity tendency analysis of the cyclone composites highlights two leading mechanisms responsible for enhanced poleward motion: nonlinear horizontal advection and diabatic heating associated with latent heat release. Our results imply that for a 4 K rise in the global mean surface temperature, the mean poleward displacement of cyclones increases by about 0.85° of latitude, and this occurs in addition to a poleward shift of about 0.6° in their mean genesis latitude. Changes in cyclone tracks may have a significant impact on midlatitude climate, especially in localized storm tracks such as the Atlantic and Pacific storm tracks, which may exhibit a more poleward deflected shape.

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Section: Poleward Motion Of Cyclonesmentioning

confidence: 94%

| \frac{\partial \overset{θ}{true}}{∂p} |

decreases), while the isentropes below the warming will tend to narrow (i.e.,

| \frac{\partial \overset{θ}{true}}{∂p} |

increases).…”

Section: Poleward Motion Of Cyclonesmentioning

confidence: 99%

The poleward shift of storm tracks under global warming: A Lagrangian perspective

Tamarin-Brodsky

Kaspi

2017

Geophysical Research Letters

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“…It has previously been shown that climate models of this spatial resolution (100-300 km) have the capacity to reproduce the key structural features of extratropical cyclones (e.g. [30,31]). The CMIP5 dataset also provides sufficient temporal and spatial coverage to allow comprehensive global scale analysis using consistent experiments from multiple models.…”

Section: Methodsmentioning

confidence: 99%

Significantly increased extreme precipitation expected in Europe and North America from extratropical cyclones

Hawcroft

Walsh

Hodges

et al. 2018

Environ. Res. Lett.

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For the Northern Hemisphere extratropics, changes in the mid-latitude storm tracks are key to understanding the impacts of climate warming, but projections of their future location in current climate models are affected by large uncertainty. Here, we show that in spite of this uncertainty in the atmospheric circulation response to warming, by analysing the behaviour of the storms (or extratropical cyclones) themselves, projections of change in the number of the most intensely precipitating extratropical cyclones are substantial and consistent across models. In particular, we show large increases in the frequency of extreme extratropical cyclones (those above the present day 99th percentile of precipitation intensity) by the end of the century. In both Europe and North America, these intensely precipitating extratropical cyclones are projected to more than triple in number by the end of the century unless greenhouse gas emissions are mitigated. Such changes in extratropical cyclone behaviour may have major impacts on society given intensely precipitating extratropical cyclones are responsible for many large-scale flooding events, and associated severe economic losses, in these regions.

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“…We did not find any significant errors in forecast of water vapor or clouds near the tropopause when compared with analyses (not shown) which suggests that the WCB transport in the forecasts is adequate; however, this raises the question of how much we trust the analyses. ECMWF analyses have been shown to have a moist bias in the lower stratosphere (Dyroff et al, 2015) and the ERA-Interim reanalyses have been shown to have insufficient cloud and a low cloud top bias in WCBs (Hawcroft et al, 2016). It is possible that an initial bias in the analyses is maintained through the forecasts leading to an underestimation of the effects of WCBs and long-wave radiation on the tropopause.…”

Section: 1002/2017jd026879mentioning

confidence: 99%

Processes Maintaining Tropopause Sharpness in Numerical Models

et al. 2017

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Recent work has shown that the sharpness of the extratropical tropopause declines with lead time in numerical weather prediction models, indicating an imbalance between processes acting to sharpen and smooth the tropopause. In this study the systematic effects of processes contributing to the tropopause sharpness are investigated using daily initialized forecasts run with the Met Office Unified Model over a three‐month winter period. Artificial tracers, each forced by the potential vorticity tendency due to a different model process, are used to separate the effects of such processes. The advection scheme is shown to result in an exponential decay of tropopause sharpness toward a finite value at short lead times with a time scale of 20–24 h. The systematic effect of nonconservative processes is to sharpen the tropopause, consistent with previous case studies. The decay of tropopause sharpness due to the advection scheme is stronger than the sharpening effect of nonconservative processes leading to a systematic decline in tropopause sharpness with forecast lead time. The systematic forecast errors in tropopause level potential vorticity are comparable to the integrated tendencies of the parametrized physical processes suggesting that the systematic error in tropopause sharpness could be significantly reduced through realistic adjustments to the model parametrization schemes.

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Using satellite and reanalysis data to evaluate the representation of latent heating in extratropical cyclones in a climate model

Cited by 36 publications

References 109 publications

The poleward shift of storm tracks under global warming: A Lagrangian perspective

The poleward shift of storm tracks under global warming: A Lagrangian perspective

Significantly increased extreme precipitation expected in Europe and North America from extratropical cyclones

Processes Maintaining Tropopause Sharpness in Numerical Models

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