<scp>ITCZ</scp> structure as determined by parameterized versus explicit convection in aquachannel and aquapatch simulations

Nolan, David S.; Tulich, Stefan N.; Blanco, Joaquin

doi:10.1002/2015ms000560

Cited by 25 publications

(33 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is possible that such mechanisms also contribute to the ITCZ differences between aquaplanet CAM4 and CAM5.3, but this analysis is beyond the scope of this study and relegated to future work. Identification and understanding of such model behaviors is vital to accurately interpreting the response and uncertainty of simulated tropical precipitation patterns in current and future climate states [ Voigt and Shaw , ; Nolan et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Sensitivities of the hydrologic cycle to model physics, grid resolution, and ocean type in the aquaplanet Community Atmosphere Model

Benedict

Medeiros

Clement

et al. 2017

J Adv Model Earth Syst

View full text Add to dashboard Cite

Precipitation distributions and extremes play a fundamental role in shaping Earth's climate and yet are poorly represented in many global climate models. Here, a suite of idealized Community Atmosphere Model (CAM) aquaplanet simulations is examined to assess the aquaplanet's ability to reproduce hydroclimate statistics of real‐Earth configurations and to investigate sensitivities of precipitation distributions and extremes to model physics, horizontal grid resolution, and ocean type. Little difference in precipitation statistics is found between aquaplanets using time‐constant sea‐surface temperatures and those implementing a slab ocean model with a 50 m mixed‐layer depth. In contrast, CAM version 5.3 (CAM5.3) produces more time mean, zonally averaged precipitation than CAM version 4 (CAM4), while CAM4 generates significantly larger precipitation variance and frequencies of extremely intense precipitation events. The largest model configuration‐based precipitation sensitivities relate to choice of horizontal grid resolution in the selected range 1–2°. Refining grid resolution has significant physics‐dependent effects on tropical precipitation: for CAM4, time mean zonal mean precipitation increases along the Equator and the intertropical convergence zone (ITCZ) narrows, while for CAM5.3 precipitation decreases along the Equator and the twin branches of the ITCZ shift poleward. Increased grid resolution also reduces light precipitation frequencies and enhances extreme precipitation for both CAM4 and CAM5.3 resulting in better alignment with observational estimates. A discussion of the potential implications these hydrologic cycle sensitivities have on the interpretation of precipitation statistics in future climate projections is also presented.

show abstract

Section: Discussionmentioning

confidence: 99%

Sensitivities of the hydrologic cycle to model physics, grid resolution, and ocean type in the aquaplanet Community Atmosphere Model

Benedict

Medeiros

Clement

et al. 2017

J Adv Model Earth Syst

View full text Add to dashboard Cite

show abstract

“…Vertical profiles of c temperature, d water vapor and e vertical velocities in the radiatively subsiding dry pool, identified by PW 20th percentile, and in the precipitation-induced cold pools, identified by the near-surface (first atmospheric level z ¼ 37 m) temperature T air 20th percentile, and precipitation [ 0 at the end of the simulation. An inset in the first 2 km added to c to indicate the inversion in the dry pool at the top of the subcloud layer Surv Geophys (2017) 38:1283-1305 1285 simulated squall lines help broaden the precipitating intertropical convergence zone poleward (Nolan et al 2016). Precipitatively-generated cold pools also counteract convective self-aggregation through suppression of local convection by divergence of the nearsurface air ( Fig.…”

Section: Introductionmentioning

confidence: 99%

A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment

et al. 2017

View full text Add to dashboard Cite

Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed $ 2 mm h À1 , convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4-5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical 123Surv Geophys (2017) 38:1283-1305 https://doi.org/10.1007/s10712-017-9447-x convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings.

show abstract

“…The ITCZ is a region of frequent moist convection and a computational hierarchy to understand ITCZ sensitivity should include a model with the capability to explicitly simulate deep convection. Limited-domain, fixed-SST, convectionpermitting simulations are becoming increasingly feasible, and novel "aquachannel" configurations have recently been used to study the climatological ITCZ [134]. Performing analogous convection-permitting simulations with a range of SSTs would be a first step towards accounting for the role of explicit atmospheric convection in modulating the ITCZ response to climate change.…”

Section: Path Forwardmentioning

confidence: 99%

Response of the Intertropical Convergence Zone to Climate Change: Location, Width, and Strength

Byrne¹,

Pendergrass²,

Rapp³

et al. 2018

Curr Clim Change Rep

213

193

View full text Add to dashboard Cite

Purpose of Review The intertropical convergence zone (ITCZ) is a planetary-scale band of heavy precipitation close to the equator. Here, we consider the response of the ITCZ structure to climate change using observations, simulations, and theory. We focus on the substantial yet underappreciated projected changes in ITCZ width and strength, and highlight an emerging conceptual framework for understanding these changes. Recent FindingsSatellite observations and reanalysis data show a narrowing and strengthening of precipitation in the ITCZ over recent decades in both the Atlantic and Pacific basins, but little change in ITCZ location. Consistent with observations, coupled climate models predict no robust change in the zonal-mean ITCZ location over the twenty-first century. However, the majority of models project a narrowing of the ITCZ and weakening mean ascent. Interestingly, changes in ITCZ width and strength are strongly anti-correlated across models.Summary The ITCZ has narrowed over recent decades yet its location has remained approximately constant. Climate models project further narrowing and a weakening of the average ascent within the ITCZ as the climate continues to warm. Following intense work over the last ten years, the physical mechanisms controlling the ITCZ location are now well understood. The development of complementary theories for ITCZ width and strength is a current research priority. Outstanding challenges include understanding the ITCZ response to past climate changes and over land versus ocean regions, and better constraining all aspects of the ITCZ structure in model projections.

show abstract

ITCZ structure as determined by parameterized versus explicit convection in aquachannel and aquapatch simulations

Cited by 25 publications

References 59 publications

Sensitivities of the hydrologic cycle to model physics, grid resolution, and ocean type in the aquaplanet Community Atmosphere Model

Sensitivities of the hydrologic cycle to model physics, grid resolution, and ocean type in the aquaplanet Community Atmosphere Model

A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment

Response of the Intertropical Convergence Zone to Climate Change: Location, Width, and Strength

Contact Info

Product

Resources

About