Characteristics of convective precipitation over tropical Africa in storm‐resolving global simulations

Becker, Tobias; Bechtold, Peter; Sandu, Irina

doi:10.1002/qj.4185

Cited by 32 publications

(43 citation statements)

References 81 publications

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“…While over 90% of the tropical rainfall was explicitly resolved, the convective parameterization still contributed a small fraction of rainfall in that region. It is possible, although unproven, that the scale‐aware convective parameterization mitigated some issues of global models with entirely resolved deep convection, such as the production of overly intense rainfall extremes or the lack of organized convective systems (e.g., Becker et al., 2021). This issue must be investigated to explore the possibility of using scale‐aware convection parameterizations even when global models move to grid spacings smaller than 10 km (Freitas et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Judt and Rios‐Berrios (2021) further showed that the improved representation of rainfall variability stemmed from explicitly resolving convection because their simulations with sub 10 km cell spacing and a convection parameterization did not show improvements over the simulations with 15 km cell spacing or greater. Not all aspects of tropical rainfall are improved in global models with explicit convection; for instance, resolving convection can produce overly intense rainfall that precludes the formation of mesoscale convective systems (Becker et al., 2021; Stevens et al., 2019).…”

Section: Motivationmentioning

confidence: 99%

“…That hypothesis has been investigated with global storm‐resolving models—that is, models that use grid spacing smaller than 10 km and no convection parameterization (e.g., Becker et al., 2021; Hohenegger et al., 2020; Judt, 2018; Judt et al., 2021; Judt & Rios‐Berrios, 2021; Stevens et al., 2019; Weber et al., 2020; Weber & Mass, 2019; Wedi et al., 2020). For example, Weber et al.…”

Section: Motivationmentioning

confidence: 99%

See 2 more Smart Citations

Differences in Tropical Rainfall in Aquaplanet Simulations With Resolved or Parameterized Deep Convection

Ríos-Berríos

Bryan

Medeiros

et al. 2022

J Adv Model Earth Syst

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Tropical rainfall systems happen across many spatiotemporal scales. On the planetary scale, clouds and rainfall organize along a narrow band known as the intertropical convergence zone (ITCZ). Within the ITCZ, zonally-propagating phenomena-known as convectively coupled equatorial waves-modulate tropical rainfall from days to weeks and from synoptic to planetary scales (Kiladis et al., 2009). Embedded within those waves are groups of organized precipitation systems known as mesoscale convective systems, which have a lifetime of hours to days but which contribute over 50% of the climatological rainfall in the tropics (Nesbitt et al., 2006). While most convective systems are organized into clusters, a large fraction of the total vertical mass flux is accomplished by relatively narrow, weak updrafts (Yuter & Houze, 1995;Zipser & LeMone, 1980). The objective of this paper is to examine how those multiscale processes are represented in global models when deep convection is explicitly resolved or parameterized.

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Section: Discussionmentioning

confidence: 99%

Section: Motivationmentioning

confidence: 99%

Section: Motivationmentioning

confidence: 99%

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Differences in Tropical Rainfall in Aquaplanet Simulations With Resolved or Parameterized Deep Convection

Ríos-Berríos

Bryan

Medeiros

et al. 2022

J Adv Model Earth Syst

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“…The moist physics upgrade also addresses errors in the parametrization of deep convection, especially for the representation of propagating mesoscale convective systems and their diurnal cycle. In particular, insufficient night-time convection over land has been identified as a major shortcoming in IFS forecasts of convective activity (Becker et al, 2021;Forbes et al, 2021).…”

Section: New Moist Physicsmentioning

confidence: 99%

The representation of winds in the lower troposphere in ECMWF forecasts and reanalyses during the EUREC4A field campaign

Savazzi

Nuijens

Sandu

et al. 2022

Preprint

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Abstract. The characterization of systematic forecast errors in lower-tropospheric winds over the ocean is a primary need for reforming models. Winds are among the drivers of convection, thus an accurate representation of winds is essential for better convective parameterizations. We focus on the temporal variability and vertical distribution of lower-tropospheric wind biases in operational medium-range weather forecasts and ERA5 reanalyses produced with the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). Thanks to several sensitivity experiments and an unprecedented wealth of measurements from the 2020 EUREC4A field campaign, we show that the wind bias varies greatly from day to day, resulting in RSME's up to 2.5 m s−1, with a mean wind speed bias up to −1 m s−1 near and above the trade-inversion in the forecasts and up to −0.5 m s−1 in reanalyses. The modeled zonal and meridional wind exhibit a too strong diurnal cycle, leading to a weak wind speed bias everywhere up to 5 km during daytime, turning into a too strong wind speed bias below 2 km at nighttime. The biases are fairly insensitive to the assimilation of sondes and likely related to remote convection and large scale pressure gradients. Convective momentum transport acts to distribute biases throughout the lowest 1.5 km, whereas at higher levels, other unresolved or dynamical tendencies play a role in setting the bias. Below 1 km, modelled friction due to unresolved physical processes appears too strong, but is (partially) compensated by dynamical tendencies, making this a challenging coupled problem.

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“…One approach to improving the representation of convective organization in these schemes could be an explicit inclusion of large‐scale circulations in their closure formulation. One recent study has shown that coupling a convection scheme to the mesoscale dynamics (by including an advective moisture tendency term to the mass flux closure) improved both the organization and propagation of deep convective systems (Becker et al., 2021). Note, however, this approach would only impact the behavior of a 3D but not 1D setup, given that the additional moisture convergence term would not result in any changes in an SCM configuration.…”

Section: Discussionmentioning

confidence: 99%

Can We Use 1D Models to Predict 3D Model Response to Forcing in an Idealized Framework?

Hwong

Sherwood

Fuchs

2022

J Adv Model Earth Syst

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Single‐column models (SCMs) simulations are sometimes used to evaluate model physics and aid parameterization development. However, few studies have systematically compared SCM behavior—where column boundary conditions are specified—with that of corresponding 3D models, where columns interact dynamically. Here we address this by comparing forced responses of an SCM in radiative‐convective equilibrium (RCE) with those of a multi‐column model (MCM) where the model domain is in RCE but individual columns are not, examining what factors affect the models' comparability. We find that convective organization in the MCM depends at least as much on the convection scheme as on other mechanisms known to organize convection (e.g., radiative feedback). Moreover, convective organization emerges as a robust factor affecting SCM–MCM comparability, with more aggregated states in 3D associated with larger behavior deviations from the 1D counterpart. This is found across five convection schemes and applies to simulated mean states, linear responses to small tendency perturbations, and adjustments to doubled‐CO2 forcing. Nevertheless, we find that even when convection is organized, behavior differences between pairs of schemes in the SCM are largely preserved in the MCM. This indicates that when model physics produces accurate behavior in a 1D setup, it will be more likely to do so in a 3D setup. However, our idealized RCE framework implies that these conclusions may not apply to situations with strong large‐scale forcing or encountered over land. Lastly, we demonstrate the practical value of linear responses by showing that they can accurately predict an SCM's tropospheric adjustment to doubled‐CO2 forcing.

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Characteristics of convective precipitation over tropical Africa in storm‐resolving global simulations

Cited by 32 publications

References 81 publications

Differences in Tropical Rainfall in Aquaplanet Simulations With Resolved or Parameterized Deep Convection

Differences in Tropical Rainfall in Aquaplanet Simulations With Resolved or Parameterized Deep Convection

The representation of winds in the lower troposphere in ECMWF forecasts and reanalyses during the EUREC4A field campaign

Can We Use 1D Models to Predict 3D Model Response to Forcing in an Idealized Framework?

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