Статті в журналах: "Aquaplanet"

1

Yano, Jun-Ichi, and John L. McBride. "An Aquaplanet Monsoon." Journal of the Atmospheric Sciences 55, no. 8 (April 1998): 1373–99. http://dx.doi.org/10.1175/1520-0469(1998)055<1373:aam>2.0.co;2.

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2

Medeiros, Brian, Bjorn Stevens, Isaac M. Held, Ming Zhao, David L. Williamson, Jerry G. Olson, and Christopher S. Bretherton. "Aquaplanets, Climate Sensitivity, and Low Clouds." Journal of Climate 21, no. 19 (October 1, 2008): 4974–91. http://dx.doi.org/10.1175/2008jcli1995.1.

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Abstract Cloud effects have repeatedly been pointed out as the leading source of uncertainty in projections of future climate, yet clouds remain poorly understood and simulated in climate models. Aquaplanets provide a simplified framework for comparing and understanding cloud effects, and how they are partitioned as a function of regime, in large-scale models. This work uses two climate models to demonstrate that aquaplanets can successfully predict a climate model’s sensitivity to an idealized climate change. For both models, aquaplanet climate sensitivity is similar to that of the realistic configuration. Tropical low clouds appear to play a leading role in determining the sensitivity. Regions of large-scale subsidence, which cover much of the tropics, are most directly responsible for the differences between the models. Although cloud effects and climate sensitivity are similar for aquaplanets and realistic configurations, the aquaplanets lack persistent stratocumulus in the tropical atmosphere. This, and an additional analysis of the cloud response in the realistically configured simulations, suggests the representation of shallow (trade wind) cumulus convection, which is ubiquitous in the tropics, is largely responsible for differences in the simulated climate sensitivity of these two models.

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3

Geen, Ruth, F. H. Lambert, and G. K. Vallis. "Regime Change Behavior during Asian Monsoon Onset." Journal of Climate 31, no. 8 (March 27, 2018): 3327–48. http://dx.doi.org/10.1175/jcli-d-17-0118.1.

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Abstract As the ITCZ moves off the equator on an aquaplanet, the Hadley circulation transitions from an equinoctial regime with two near-symmetric, significantly eddy-driven cells to a monsoon-like regime with a strong, thermally direct cross-equatorial cell, intense low-latitude precipitation, and a weak summer hemisphere cell. Dynamical feedbacks appear to accelerate the transition. This study investigates the relevance of this behavior to monsoon onset by using primitive equation model simulations ranging from aquaplanets to more realistic configurations with Earth’s continents and topography. A change in the relationship between ITCZ latitude and overturning strength is identified once the ITCZ moves poleward of approximately 7°. Monsoon onset is associated with off-equatorial ascent in regions of nonnegligible planetary vorticity, and this is found to generate a vortex stretching tendency that reduces upper-level absolute vorticity. In an aquaplanet, this causes a transition to the cross-equatorial, thermally direct regime, intensifying the overturning circulation. Analysis of the zonal momentum budget suggests that a stationary wave, driven by topography and land–sea contrast, can trigger a similar transition in the more realistic model configuration, with the wave extending the ascent region of the Southern Hemisphere Hadley cell northward, and enhanced overturning then developing to the south. These two elements of the circulation resemble the East and South Asian monsoons.

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4

Merlis, Timothy M., and Isaac M. Held. "Aquaplanet Simulations of Tropical Cyclones." Current Climate Change Reports 5, no. 3 (June 8, 2019): 185–95. http://dx.doi.org/10.1007/s40641-019-00133-y.

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5

Zappa, Giuseppe, Valerio Lucarini, and Antonio Navarra. "Baroclinic Stationary Waves in Aquaplanet Models." Journal of the Atmospheric Sciences 68, no. 5 (May 1, 2011): 1023–40. http://dx.doi.org/10.1175/2011jas3573.1.

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Abstract An aquaplanet model is used to study the nature of the highly persistent low-frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, the authors find that a quasi-stationary wave 5 belongs to a wave packet obeying a well-defined dispersion relation with eastward group velocity. The components of the dispersion relation with k ≥ 5 baroclinically convert eddy available potential energy into eddy kinetic energy, whereas those with k < 5 are baroclinically neutral. In agreement with Green’s model of baroclinic instability, wave 5 is weakly unstable, and the inverse energy cascade, which had been previously proposed as a main forcing for this type of wave, only acts as a positive feedback on its predominantly baroclinic energetics. The quasi-stationary wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. It is also found that the Pedlosky bounds on the phase speed of unstable waves provide guidance in explaining the latitudinal structure of the energy conversion, which is shown to be more enhanced where the zonal westerly surface wind is weaker. The wave’s energy is then trapped in the waveguide created by the upper tropospheric jet stream. In agreement with Green’s theory, as the equator-to-pole SST difference is reduced, the stationary marginally stable component shifts toward higher wavenumbers, while wave 5 becomes neutral and westward propagating. Some properties of the aquaplanet quasi-stationary waves are found to be in interesting agreement with a low frequency wave observed by Salby during December–February in the Southern Hemisphere so that this perspective on low frequency variability, apart from its value in terms of basic geophysical fluid dynamics, might be of specific interest for studying the earth’s atmosphere.

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6

Williams, Gareth P., and Kirk Bryan. "Ice Age Winds: An Aquaplanet Model." Journal of Climate 19, no. 9 (May 1, 2006): 1706–15. http://dx.doi.org/10.1175/jcli3766.1.

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Abstract Factors controlling the position and strength of the surface winds during the Last Glacial Maximum (LGM) are examined using a global, multilevel, moist, atmospheric model. The idealized aquaplanet model is bounded below by a prescribed axisymmetric temperature distribution that corresponds to an ocean-covered surface. Various forms of this distribution are used to examine the influence of changes in the surface cooling and baroclinicity rates. The model omits seasonal variations. Increasing the cooling lowers the tropopause and greatly reduces the moist convection in the Tropics, thereby causing a weakening and equatorward contraction of the Hadley cell. Such a cooling also weakens the surface westerlies and shifts the peak westerly stress equatorward. An extra surface baroclinicity in midlatitudes—implicitly associated with an increase in the polar sea ice—also shifts the peak westerly stress equatorward, but strengthens the surface westerlies. Thus, calculations with combined surface cooling and baroclinicity increases, representative of the Last Glacial Maximum, reveal an absence of change in the amplitude of the peak westerly stress but exhibit a substantial equatorward shift in its position, 7° for a 3-K cooling and 11° for a 6-K cooling. The easterlies, however, always increase in strength when the surface westerlies move equatorward. The application of these results to the LGM must take into account the model’s assumption of symmetry between the two hemispheres. Any changes in the climate’s hemispheric asymmetry could also cause comparable latitudinal shifts in the westerlies, probably of opposite sign in the two hemispheres. Published coupled-model simulations for the LGM give an equatorward shift for the peak westerlies in the Northern Hemisphere but give contradictory results for the Southern Hemisphere.

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7

Bhattacharya, Ritthik, Simona Bordoni, Kay Suselj, and João Teixeira. "Parameterization Interactions in Global Aquaplanet Simulations." Journal of Advances in Modeling Earth Systems 10, no. 2 (February 2018): 403–20. http://dx.doi.org/10.1002/2017ms000991.

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8

Shi, Xiaoming, Daehyun Kim, Ángel F. Adames, and Jai Sukhatme. "WISHE‐Moisture Mode in an Aquaplanet Simulation." Journal of Advances in Modeling Earth Systems 10, no. 10 (October 2018): 2393–407. http://dx.doi.org/10.1029/2018ms001441.

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9

Hertwig, Eileen, Frank Lunkeit, and Klaus Fraedrich. "Low-frequency climate variability of an aquaplanet." Theoretical and Applied Climatology 121, no. 3-4 (August 14, 2014): 459–78. http://dx.doi.org/10.1007/s00704-014-1226-8.

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10

Geen, Ruth, F. Hugo Lambert, and Geoffrey K. Vallis. "Processes and Timescales in Onset and Withdrawal of “Aquaplanet Monsoons”." Journal of the Atmospheric Sciences 76, no. 8 (July 12, 2019): 2357–73. http://dx.doi.org/10.1175/jas-d-18-0214.1.

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Abstract Aquaplanets with low-heat-capacity slab-ocean boundary conditions can exhibit rapid changes in the regime of the overturning circulation over the seasonal cycle, which have been connected to the onset of Earth’s monsoons. In spring, as the ITCZ migrates off the equator, it jumps poleward and a sudden transition occurs from an eddy-driven, equinoctial regime with two weak Hadley cells, to a near-angular-momentum-conserving, solstitial regime with a strong, cross-equatorial winter-hemisphere cell. Here, the controls on the transition latitude and rate are explored in idealized moist aquaplanet simulations. It is found that the transition remains rapid relative to the solar forcing when year length and slab-ocean heat capacity are varied, and, at Earth’s rotation rate, always occurs when the ITCZ reaches approximately 7°. This transition latitude is, however, found to scale inversely with rotation rate. Interestingly, the transition rate varies nonmonotonically with rotation, with a maximum at Earth’s rotation rate, suggesting that Earth may be particularly disposed to a fast monsoon onset. The fast transition relates to feedbacks in both the atmosphere and the slab ocean. In particular, an evaporative feedback between the lower-level branch of the overturning circulation and the surface temperature is identified. This accelerates monsoon onset and slows withdrawal. Last, comparing eddy-permitting and axisymmetric experiments shows that, in contrast with results from dry models, in this fully moist model the presence of eddies slows the migration of the ITCZ between hemispheres.

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11

Wang, Lu, Tim Li, and Tomoe Nasuno. "Impact of Rossby and Kelvin Wave Components on MJO Eastward Propagation." Journal of Climate 31, no. 17 (September 2018): 6913–31. http://dx.doi.org/10.1175/jcli-d-17-0749.1.

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There are contrasting views concerning the impact of Rossby wave component of MJO flow on its eastward propagation. One view (called “drag effect”) argues that because Rossby waves propagate westward, a stronger Rossby wave component slows down the eastward propagation. The other view (called “acceleration effect”) argues that a stronger Rossby wave enhances east–west asymmetry of moist static energy (MSE) tendency and thus favors the eastward propagation. This study aims to resolve this issue through diagnosis of both idealized aquaplanet simulations and 26 models from the MJO Task Force/GEWEX Atmospheric System Studies (MJOTF/GASS). In the aquaplanet experiments, three sets of zonally uniform, equatorially symmetric SST distributions are specified. The MJO phase speed is faster in the presence of a narrower SST meridional profile, in which both the Rossby and the Kelvin wave components are stronger and the east–west asymmetry of MSE tendency is larger. A further analysis of the 26 general circulation models reveals that the MJO propagation skill and phase speed are positively correlated to both the Rossby wave and the Kelvin wave strength in the lower free atmosphere (above 800 hPa). Models that have a stronger Rossby and Kelvin wave component tend to simulate realistic and faster eastward propagation. Therefore, both the aquaplanet and the multimodel simulations support the Rossby wave acceleration effect hypothesis.

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12

Rauscher, Sara A., and Todd D. Ringler. "Impact of Variable-Resolution Meshes on Midlatitude Baroclinic Eddies Using CAM-MPAS-A." Monthly Weather Review 142, no. 11 (October 24, 2014): 4256–68. http://dx.doi.org/10.1175/mwr-d-13-00366.1.

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Abstract The effects of a variable-resolution mesh on simulated midlatitude baroclinic eddies in idealized settings are examined. Both aquaplanet and Held–Suarez experiments are performed using the Model for Prediction Across Scales-Atmosphere (MPAS-A) hydrostatic dynamical core implemented within the National Science Foundation–Department of Energy (NSF–DOE) Community Atmosphere Model (CAM-MPAS-A). In the real world, midlatitude eddy activity is organized by orography, land–sea contrasts, and sea surface temperature anomalies. In these zonally symmetric idealized settings, transients should have an equal probability of occurring at any longitude. However, the use of a variable-resolution mesh with a circular high-resolution region centered at 30°N results in a maximum in eddy kinetic energy on the eastern side and downstream of this high-resolution region in both aquaplanet and Held–Suarez CAM-MPAS-A simulations. The presence of a geographically confined maximum in both simulations suggests this response is mainly attributable to CAM-MPAS-A’s ability to resolve eddies via the model dynamics as resolution increases. However, in the aquaplanet simulation, a secondary maximum in eddy kinetic energy is present, which is probably linked to the resolution dependencies of the CAM physics. These mesh responses must be considered when interpreting real-world variable-resolution CAM-MPAS-A simulations, particularly in climate change experiments.

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13

Zarzycki, Colin M., Michael N. Levy, Christiane Jablonowski, James R. Overfelt, Mark A. Taylor, and Paul A. Ullrich. "Aquaplanet Experiments Using CAM’s Variable-Resolution Dynamical Core." Journal of Climate 27, no. 14 (July 10, 2014): 5481–503. http://dx.doi.org/10.1175/jcli-d-14-00004.1.

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Abstract A variable-resolution option has been added within the spectral element (SE) dynamical core of the U.S. Department of Energy (DOE)–NCAR Community Atmosphere Model (CAM). CAM-SE allows for static refinement via conforming quadrilateral meshes on the cubed sphere. This paper investigates the effect of mesh refinement in a climate model by running variable-resolution (var-res) simulations on an aquaplanet. The variable-resolution grid is a 2° (~222 km) grid with a refined patch of 0.25° (~28 km) resolution centered at the equator. Climatology statistics from these simulations are compared to globally uniform runs of 2° and 0.25°. A significant resolution dependence exists when using the CAM version 4 (CAM4) subgrid physical parameterization package across scales. Global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution, resulting in drastically different climates between the uniform grid runs and a physics-induced grid imprinting in the var-res simulation. Using CAM version 5 (CAM5) physics significantly improves cloud scaling at different grid resolutions. Additional precipitation at the equator in the high-resolution mesh results in collocated zonally anomalous divergence in both var-res simulations, although this feature is much weaker in CAM5 than CAM4. The equilibrium solution at each grid spacing within the var-res simulations captures the majority of the resolution signal of the corresponding globally uniform grids. The var-res simulation exhibits good performance with respect to wave propagation, including equatorial regions where waves pass through grid transitions. In addition, the increased frequency of high-precipitation events in the refined 0.25° area within the var-res simulations matches that observed in the global 0.25° simulations.

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14

Brunetti, M., J. Kasparian, and C. Vérard. "Co-existing climate attractors in a coupled aquaplanet." Climate Dynamics 53, no. 9-10 (August 9, 2019): 6293–308. http://dx.doi.org/10.1007/s00382-019-04926-7.

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15

Barpanda, Pragallva, and Tiffany A. Shaw. "Surface Fluxes Modulate the Seasonality of Zonal-Mean Storm Tracks." Journal of the Atmospheric Sciences 77, no. 2 (November 25, 2019): 753–79. http://dx.doi.org/10.1175/jas-d-19-0139.1.

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Abstract The observed zonal-mean extratropical storm tracks exhibit distinct hemispheric seasonality. Previously, the moist static energy (MSE) framework was used diagnostically to show that shortwave absorption (insolation) dominates seasonality but surface heat fluxes damp seasonality in the Southern Hemisphere (SH) and amplify it in the Northern Hemisphere (NH). Here we establish the causal role of surface fluxes (ocean energy storage) by varying the mixed layer depth d in zonally symmetric 1) slab-ocean aquaplanet simulations with zero ocean energy transport and 2) energy balance model (EBM) simulations. Using a scaling analysis we define a critical mixed layer depth dc and hypothesize 1) large mixed layer depths (d > dc) produce surface heat fluxes that are out of phase with shortwave absorption resulting in small storm track seasonality and 2) small mixed layer depths (d < dc) produce surface heat fluxes that are in phase with shortwave absorption resulting in large storm track seasonality. The aquaplanet simulations confirm the large mixed layer depth hypothesis and yield a useful idealization of the SH storm track. However, the small mixed layer depth hypothesis fails to account for the large contribution of the Ferrel cell and atmospheric storage. The small mixed layer limit does not yield a useful idealization of the NH storm track because the seasonality of the Ferrel cell contribution is opposite to the stationary eddy contribution in the NH. Varying the mixed layer depth in an EBM qualitatively supports the aquaplanet results.

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16

Merlis, Timothy M. "Does Humidity’s Seasonal Cycle Affect the Annual-Mean Tropical Precipitation Response to Sulfate Aerosol Forcing?" Journal of Climate 29, no. 4 (February 10, 2016): 1451–60. http://dx.doi.org/10.1175/jcli-d-15-0388.1.

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Abstract Sulfate aerosol radiative forcing alters the distribution of tropical precipitation in climate model simulations. The annual-mean tropical precipitation change is typically described as arising from an annual-mean change in the mean atmospheric circulation. However, the seasonality of the climatology of tropical humidity may modulate the annual-mean precipitation response. Here, the role of seasonality of tropical humidity is assessed using reanalysis and idealized atmospheric general circulation model (GCM) simulations perturbed by sulfate aerosol radiative forcing. When coupled to an aquaplanet slab ocean with low thermal inertia, the seasonal cycle in GCM simulations of the “continental” regime is large and the annual-mean precipitation change depends on both the seasonally varying perturbation mean meridional circulation and the seasonally varying climatological specific humidity. When coupled to an aquaplanet slab ocean with a higher thermal inertia, the seasonal cycle in GCM simulations of the “oceanic” regime is smaller and the annual-mean precipitation change can be approximated by considering the perturbation convergence of the water vapor flux of the annual-mean perturbation mean meridional circulation and the annual-mean climatological specific humidity. The results of the aquaplanet simulations taken together with the magnitude of the seasonality of humidity in an atmospheric reanalysis suggest that the simplest forms of energetic arguments for the tropical precipitation response to perturbations in the atmospheric energy budget, which neglect an explicit role for the seasonality of the radiative forcing and the climatological specific humidity, are not quantitatively accurate for Earth’s tropical land regions.

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17

Thompson, David W. J., Paulo Ceppi, and Ying Li. "A Robust Constraint on the Temperature and Height of the Extratropical Tropopause." Journal of Climate 32, no. 2 (December 18, 2018): 273–87. http://dx.doi.org/10.1175/jcli-d-18-0339.1.

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Abstract In a recent study, the authors hypothesize that the Clausius–Clapeyron relation provides a strong constraint on the temperature of the extratropical tropopause and hence the depth of mixing by extratropical eddies. The hypothesis is a generalization of the fixed-anvil temperature hypothesis to the global atmospheric circulation. It posits that the depth of robust mixing by extratropical eddies is limited by radiative cooling by water vapor—and hence saturation vapor pressures—in areas of sinking motion. The hypothesis implies that 1) radiative cooling by water vapor constrains the vertical structure and amplitude of extratropical dynamics and 2) the extratropical tropopause should remain at roughly the same temperature and lift under global warming. Here the authors test the hypothesis in numerical simulations run on an aquaplanet general circulation model (GCM) and a coupled atmosphere–ocean GCM (AOGCM). The extratropical cloud-top height, wave driving, and lapse-rate tropopause all shift upward but remain at roughly the same temperature when the aquaplanet GCM is forced by uniform surface warming of +4 K and when the AOGCM is forced by RCP8.5 scenario emissions. “Locking” simulations run on the aquaplanet GCM further reveal that 1) holding the water vapor concentrations input into the radiation code fixed while increasing surface temperatures strongly constrains the rise in the extratropical tropopause, whereas 2) increasing the water vapor concentrations input into the radiation code while holding surface temperatures fixed leads to robust rises in the extratropical tropopause. Together, the results suggest that roughly invariant extratropical tropopause temperatures constitutes an additional “robust response” of the climate system to global warming.

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18

Rauscher, Sara A., Todd D. Ringler, William C. Skamarock, and Arthur A. Mirin. "Exploring a Global Multiresolution Modeling Approach Using Aquaplanet Simulations*." Journal of Climate 26, no. 8 (April 15, 2013): 2432–52. http://dx.doi.org/10.1175/jcli-d-12-00154.1.

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Abstract Results from aquaplanet experiments performed using the Model for Prediction across Scales (MPAS) hydrostatic dynamical core implemented within the Department of Energy (DOE)–NCAR Community Atmosphere Model (CAM) are presented. MPAS is an unstructured-grid approach to climate system modeling that supports both quasi-uniform and variable-resolution meshing of the sphere based on conforming grids. Using quasi-uniform simulations at resolutions of 30, 60, 120, and 240 km, the authors evaluate the performance of CAM-MPAS via its kinetic energy spectra, general circulation, and precipitation characteristics. By analyzing an additional variable-resolution simulation with grid spacing that varies from 30 km in a spherical, continental-sized equatorial region to 240 km elsewhere, the CAM-MPAS’s potential for use as a regional climate simulation tool is explored. Similar to other quasi-uniform aquaplanet simulations, tropical precipitation increases with resolution, indicating the resolution sensitivity of the physical parameterizations. Comparison with the finite volume (FV) dynamical core suggests a weaker tropical circulation in the CAM-MPAS simulations, which is evident in reduced tropical precipitation and a weaker Hadley circulation. In the variable-resolution simulation, the kinetic energy spectrum within the high-resolution region closely resembles the quasi-uniform 30-km simulation, indicating a robust simulation of the fluid dynamics. As suggested by the quasi-uniform simulations, the CAM4 physics behave differently in the high and low resolution regions. A positive precipitation anomaly occurs on the western edge of the high-resolution region, exciting a Gill-type response; this zonal asymmetry represents the errors incurred in a variable resolution setting. When paired with a multiresolution mesh, the aquaplanet test case offers an exceptional opportunity to examine the response of physical parameterizations to grid resolution.

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19

Lee, Sukyoung, and Steven Feldstein. "Two Types of Wave Breaking in an Aquaplanet GCM." Journal of the Atmospheric Sciences 53, no. 6 (March 1996): 842–57. http://dx.doi.org/10.1175/1520-0469(1996)053<0842:ttowbi>2.0.co;2.

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20

Feldstein, Steven, and Sukyoung Lee. "Mechanisms of Zonal Index Variability in an Aquaplanet GCM." Journal of the Atmospheric Sciences 53, no. 23 (December 1996): 3541–56. http://dx.doi.org/10.1175/1520-0469(1996)053<3541:mozivi>2.0.co;2.

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21

Narinesingh, Veeshan, James F. Booth, Spencer K. Clark, and Yi Ming. "Atmospheric blocking in an aquaplanet and the impact of orography." Weather and Climate Dynamics 1, no. 2 (July 8, 2020): 293–311. http://dx.doi.org/10.5194/wcd-1-293-2020.

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Abstract. Many fundamental questions remain about the roles and effects of stationary forcing on atmospheric blocking. As such, this work utilizes an idealized moist general circulation model (GCM) to investigate atmospheric blocking in terms of dynamics, geographical location, and duration. The model is first configured as an aquaplanet, then orography is added in separate integrations. Block-centered composites of wave activity fluxes and height show that blocks in the aquaplanet undergo a realistic dynamical evolution when compared to reanalysis. Blocks in the aquaplanet are also found to have similar life cycles to blocks in model integrations with orography. These results affirm the usefulness of both zonally symmetric and asymmetric idealized model configurations for studying blocking. Adding orography to the model leads to an increase in blocking. This mirrors what is observed when comparing the Northern Hemisphere (NH) and Southern Hemisphere (SH), where the NH contains more orography and thus more blocking. As the prescribed mountain height increases, so do the magnitude and size of climatological stationary waves, resulting in more blocking overall. Increases in blocking, however, are not spatially uniform. Orography is found to induce regions of enhanced block frequency just upstream of mountains, near high pressure anomalies in the stationary waves, which is poleward of climatological minima in upper-level zonal wind, while block frequency minima and jet maxima occur eastward of the wave trough. This result matches what is observed near the Rocky Mountains. Finally, an analysis of block duration suggests blocks generated near stationary wave maxima last slightly longer than blocks that form far from or without orography. Overall, the results of this work help to explain some of the observed similarities and differences in blocking between the NH and SH and emphasize the importance of general circulation features in setting where blocks most frequently occur.

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22

Harris, Lucas M., Shian-Jiann Lin, and ChiaYing Tu. "High-Resolution Climate Simulations Using GFDL HiRAM with a Stretched Global Grid." Journal of Climate 29, no. 11 (May 31, 2016): 4293–314. http://dx.doi.org/10.1175/jcli-d-15-0389.1.

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Abstract An analytic Schmidt transformation is used to create locally refined global model grids capable of efficient climate simulation with gridcell widths as small as 10 km in the GFDL High-Resolution Atmosphere Model (HiRAM). This method of grid stretching produces a grid that varies very gradually into the region of enhanced resolution without changing the topology of the model grid and does not require radical changes to the solver. AMIP integrations were carried out with two grids stretched to 10-km minimum gridcell width: one centered over East Asia and the western Pacific warm pool, and the other over the continental United States. Robust improvements to orographic precipitation, the diurnal cycle of warm-season continental precipitation, and tropical cyclone maximum intensity were found in the region of enhanced resolution, compared to 25-km uniform-resolution HiRAM. The variations in grid size were not found to create apparent grid artifacts, and in some measures the global-mean climate improved in the stretched-grid simulations. In the enhanced-resolution regions, the number of tropical cyclones was reduced, but the fraction of storms reaching hurricane intensity increased, compared to a uniform-resolution simulation. This behavior was also found in a stretched-grid perpetual-September aquaplanet simulation with 12-km resolution over a part of the tropics. Furthermore, the stretched-grid aquaplanet simulation was also largely free of grid artifacts except for an artificial Walker-type circulation, and simulated an ITCZ in its unrefined region more resembling that of higher-resolution aquaplanet simulations, implying that the unrefined region may also be improved in stretched-grid simulations. The improvements due to stretching are attributable to improved resolution as these stretched-grid simulations were sparingly tuned.

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23

Stevenson, David S. "Phytoclimatic mapping of exoplanets." International Journal of Astrobiology 19, no. 1 (July 19, 2019): 68–77. http://dx.doi.org/10.1017/s1473550419000181.

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AbstractThe concept of exoplanetary habitability is evolving. The driving force is a desire to define the biological potential of planets and identify which can host complex and possibly intelligent life. To assess this in a meaningful manner, climate models need to be applied to realistic surfaces. However, the vast majority of climate models are developed using generic aquaplanet, or swamp planet, scenarios that provide uniform, surface frictional coefficients. However, aside from planets with largely uniform oceans, these models are not obviously useful when it comes to understanding the impact of climate on biodiversity. Here, we show that contrary to expectation, the aquaplanet models can be directly applied to planets with a variety of land areas, with little need for modification. Using this premise, this paper provides a simple mathematical framework that may be applied to more complex planetary surfaces and identifies the majority of the climate-model components that are needed to accurately determine the biological potential of habitable exoplanets. As a proof-of-concept, an available climate model for Proxima b is used to determine its biological potential, given a suitable atmosphere.

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24

NASUNO, Tomoe. "Equatorial Mean Zonal Wind in a Global Nonhydrostatic Aquaplanet Experiment." Journal of the Meteorological Society of Japan 86A (2008): 219–36. http://dx.doi.org/10.2151/jmsj.86a.219.

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25

Das, Surajit, Debasis Sengupta, A. Chakraborty, Jai Sukhatme, and Raghu Murtugudde. "Low-frequency intraseasonal variability in a zonally symmetric aquaplanet model." Meteorology and Atmospheric Physics 128, no. 6 (April 7, 2016): 697–713. http://dx.doi.org/10.1007/s00703-016-0448-y.

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26

Bodas‐Salcedo, A. "Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet." Geophysical Research Letters 45, no. 8 (April 20, 2018): 3635–43. http://dx.doi.org/10.1002/2018gl077217.

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27

Martini, Matus N., William I. Gustafson, Travis A. O'Brien, and Po-Lun Ma. "Evaluation of tropical channel refinement using MPAS-A aquaplanet simulations." Journal of Advances in Modeling Earth Systems 7, no. 3 (September 2015): 1351–67. http://dx.doi.org/10.1002/2015ms000470.

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28

Grabowski, Wojciech W. "Large-scale organization of moist convection in idealized aquaplanet simulations." International Journal for Numerical Methods in Fluids 39, no. 9 (2002): 843–53. http://dx.doi.org/10.1002/fld.332.

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29

Privé, Nikki C., and R. Alan Plumb. "Monsoon Dynamics with Interactive Forcing. Part I: Axisymmetric Studies." Journal of the Atmospheric Sciences 64, no. 5 (May 1, 2007): 1417–30. http://dx.doi.org/10.1175/jas3916.1.

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Abstract The applicability of axisymmetric theory of angular momentum conserving circulations to the large-scale steady monsoon is studied in a general circulation model with idealized representations of continental geometry and simple physics. Results from an aquaplanet setup with localized subtropical forcing are compared with a continental case. It is found that the meridional circulation that develops is close to angular momentum conserving for cross-equatorial circulation cells, both in the aquaplanet and in the continental cases. The equator proves to be a substantial barrier to boundary layer meridional flow; flow into the summer hemisphere from the winter hemisphere tends to occur in the free troposphere rather than in the boundary layer. A theory is proposed to explain the location of the monsoon; assuming quasiequilibrium, the poleward boundary of the monsoon circulation is collocated with the maximum in subcloud moist static energy, with the monsoon rains occurring near and slightly equatorward of this maximum. The model results support this theory of monsoon location, and it is found that the subcloud moist static energy distribution is determined by a balance between surface forcing and advection by the large-scale flow.

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30

Khairoutdinov, Marat F., and Kerry Emanuel. "Intraseasonal Variability in a Cloud-Permitting Near-Global Equatorial Aquaplanet Model." Journal of the Atmospheric Sciences 75, no. 12 (December 1, 2018): 4337–55. http://dx.doi.org/10.1175/jas-d-18-0152.1.

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Abstract Recent studies have suggested that the Madden–Julian oscillation is a result of an instability driven mainly by cloud–radiation feedbacks, similar in character to self-aggregation of convection in nonrotating, cloud-permitting simulations of radiative–convective equilibrium (RCE). Here we bolster that inference by simulating radiative–convective equilibrium states on a rotating sphere with constant sea surface temperature, using the cloud-permitting System for Atmospheric Modeling (SAM) with 20-km grid spacing and extending to walls at 46° latitude in each hemisphere. Mechanism-denial experiments reveal that cloud–radiation interaction is the quintessential driving mechanism of the simulated MJO-like disturbances, but wind-induced surface heat exchange (WISHE) feedbacks are the primary driver of its eastward propagation. WISHE may also explain the faster Kelvin-like modes in the simulations. These conclusions are supported by a linear stability analysis of RCE states on an equatorial beta plane.

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31

Lu, Jian, Gang Chen, L. Ruby Leung, D. Alex Burrows, Qing Yang, Koichi Sakaguchi, and Samson Hagos. "Toward the Dynamical Convergence on the Jet Stream in Aquaplanet AGCMs." Journal of Climate 28, no. 17 (September 1, 2015): 6763–82. http://dx.doi.org/10.1175/jcli-d-14-00761.1.

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Abstract Systematic sensitivity of the jet position and intensity to horizontal model resolution is identified in several aquaplanet AGCMs, with the coarser resolution producing a more equatorward eddy-driven jet and a stronger upper-tropospheric jet intensity. As the resolution of the models increases to 50 km or finer, the jet position and intensity show signs of convergence within each model group. The mechanism for this convergence behavior is investigated using a hybrid Eulerian–Lagrangian finite-amplitude wave activity budget developed for the upper-tropospheric absolute vorticity. The results suggest that the poleward shift of the eddy-driven jet with higher resolution can be attributed to the smaller effective diffusivity of the model in the midlatitudes that allows more wave activity to survive the dissipation and to reach the subtropical critical latitude for wave breaking. The enhanced subtropical wave breaking and associated irreversible vorticity mixing act to maintain a more poleward peak of the vorticity gradient, and thus a more poleward jet. Being overdissipative, the coarse-resolution AGCMs misrepresent the nuanced nonlinear aspect of the midlatitude eddy–mean flow interaction, giving rise to the equatorward bias of the eddy-driven jet. In accordance with the asymptotic behavior of effective diffusivity of Batchelor turbulence in the large Peclet number limit, the upper-tropospheric effective diffusivity of the aquaplanet AGCMs displays signs of convergence in the midlatitude toward a value of approximately 107 m2 s−1 for the ∇2 diffusion. This provides a dynamical underpinning for the convergence of the jet stream observed in these AGCMs at high resolution.

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32

Ajayamohan, R. S., Boualem Khouider, and Andrew J. Majda. "Simulation of monsoon intraseasonal oscillations in a coarse-resolution aquaplanet GCM." Geophysical Research Letters 41, no. 15 (August 6, 2014): 5662–69. http://dx.doi.org/10.1002/2014gl060662.

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33

Langen, Peter L., and Vladimir A. Alexeev. "Polar amplification as a preferred response in an idealized aquaplanet GCM." Climate Dynamics 29, no. 2-3 (February 9, 2007): 305–17. http://dx.doi.org/10.1007/s00382-006-0221-x.

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34

Maloney, Eric D., and Brandon O. Wolding. "Initiation of an intraseasonal oscillation in an aquaplanet general circulation model." Journal of Advances in Modeling Earth Systems 7, no. 4 (December 2015): 1956–76. http://dx.doi.org/10.1002/2015ms000495.

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35

Bhattacharya, Ritthik, Simona Bordoni, and João Teixeira. "Tropical precipitation extremes: Response to SST-induced warming in aquaplanet simulations." Geophysical Research Letters 44, no. 7 (April 14, 2017): 3374–83. http://dx.doi.org/10.1002/2017gl073121.

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36

Seo, Jeongbin, Sarah M. Kang, and Dargan M. W. Frierson. "Sensitivity of Intertropical Convergence Zone Movement to the Latitudinal Position of Thermal Forcing." Journal of Climate 27, no. 8 (April 10, 2014): 3035–42. http://dx.doi.org/10.1175/jcli-d-13-00691.1.

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Abstract A variety of recent studies have shown that extratropical heating anomalies can be remarkably effective at causing meridional shifts in the intertropical convergence zone (ITCZ). But what latitudinal location of forcing is most effective at shifting the ITCZ? In a series of aquaplanet simulations with the GFDL Atmospheric Model, version 2 (AM2), coupled to a slab mixed layer ocean, it is shown that high-latitude forcing actually causes a larger shift in the ITCZ than when equivalent surface forcing is applied in the tropics. Equivalent simulations are run with an idealized general circulation model (GCM) without cloud and water vapor feedbacks, also coupled to an aquaplanet slab ocean, where the ITCZ response instead becomes weaker the farther the forcing is from the equator, indicating that radiative feedbacks must be important in AM2. In the absence of radiative feedbacks, the tendency for anomalies to decrease in importance the farther away they are from the equator is due to the quasi-diffusive nature of energy transports. Cloud shortwave responses in AM2 act to strengthen the ITCZ response to extratropical forcing, amplifying the response as it propagates toward the equator. These results emphasize the great importance of the extratropics in determining the position of the ITCZ.

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37

Lipat, Bernard R., Aiko Voigt, George Tselioudis, and Lorenzo M. Polvani. "Model Uncertainty in Cloud–Circulation Coupling, and Cloud-Radiative Response to Increasing CO2, Linked to Biases in Climatological Circulation." Journal of Climate 31, no. 24 (December 2018): 10013–20. http://dx.doi.org/10.1175/jcli-d-17-0665.1.

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Recent analyses of global climate models suggest that uncertainty in the coupling between midlatitude clouds and the atmospheric circulation contributes to uncertainty in climate sensitivity. However, the reasons behind model differences in the cloud–circulation coupling have remained unclear. Here, we use a global climate model in an idealized aquaplanet setup to show that the Southern Hemisphere climatological circulation, which in many models is biased equatorward, contributes to the model differences in the cloud–circulation coupling. For the same poleward shift of the Hadley cell (HC) edge, models with narrower climatological HCs exhibit stronger midlatitude cloud-induced shortwave warming than models with wider climatological HCs. This cloud-induced radiative warming results predominantly from a subsidence warming that decreases cloud fraction and is stronger for narrower HCs because of a larger meridional gradient in the vertical velocity. A comparison of our aquaplanet results with comprehensive climate models suggests that about half of the model uncertainty in the midlatitude cloud–circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models. This illustrates how understanding of large-scale dynamics can help reduce uncertainty in clouds and their response to climate change.

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38

O’Gorman, P. A., Z. Li, W. R. Boos, and J. Yuval. "Response of extreme precipitation to uniform surface warming in quasi-global aquaplanet simulations at high resolution." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2195 (March 2021): 20190543. http://dx.doi.org/10.1098/rsta.2019.0543.

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Projections of precipitation extremes in simulations with global climate models are very uncertain in the tropics, in part because of the use of parameterizations of deep convection and model deficiencies in simulating convective organization. Here, we analyse precipitation extremes in high-resolution simulations that are run without a convective parameterization on a quasi-global aquaplanet. The frequency distributions of precipitation rates and precipitation cluster sizes in the tropics of a control simulation are similar to the observed distributions. In response to climate warming, 3 h precipitation extremes increase at rates of up to 9 % K − 1 in the tropics because of a combination of positive thermodynamic and dynamic contributions. The dynamic contribution at different latitudes is connected to the vertical structure of warming using a moist static stability. When the precipitation rates are first averaged to a daily timescale and coarse-grained to a typical global climate-model resolution prior to calculating the precipitation extremes, the response of the precipitation extremes to warming becomes more similar to what was found previously in coarse-resolution aquaplanet studies. However, the simulations studied here do not exhibit the high rates of increase of tropical precipitation extremes found in projections with some global climate models. This article is part of a discussion meeting issue ‘Intensification of short-duration rainfall extremes and implications for flash flood risks’.

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39

Adams, Arthur D., William R. Boos, and Eric T. Wolf. "Aquaplanet Models on Eccentric Orbits: Effects of the Rotation Rate on Observables." Astronomical Journal 157, no. 5 (April 23, 2019): 189. http://dx.doi.org/10.3847/1538-3881/ab107f.

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40

Woolnough, S. J., J. M. Slingo, and B. J. Hoskins. "The Diurnal Cycle of Convection and Atmospheric Tides in an Aquaplanet GCM." Journal of the Atmospheric Sciences 61, no. 21 (November 1, 2004): 2559–73. http://dx.doi.org/10.1175/jas3290.1.

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Abstract The diurnal cycle of tropical convection and its relationship to the atmospheric tides is investigated using an aquaplanet GCM. The diurnal and semidiurnal harmonics of precipitation are both found to contribute significantly to the total diurnal variability of precipitation in the model, which is broadly consistent with observations of the diurnal cycle of convection over the open ocean. The semidiurnal tide is found to be the dominant forcing for the semidiurnal harmonic of precipitation. In contrast the diurnal tide plays only a small role in forcing the diurnal harmonic of precipitation, which is dominated by the variations in shortwave and longwave heating. In both the diurnal and semidiurnal harmonics, the feedback onto the convection by the humidity tendencies due to the convection is found to be important in determining the phase of the harmonics. Further experiments show that the diurnal cycle of precipitation is sensitive to the choice of closure in the convection scheme. While the surface pressure signal of the simulated atmospheric tides in the model agree well with both theory and observations in their magnitude and phase, sensitivity experiments suggest that the role of the stratospheric ozone in forcing the semidiurnal tide is much reduced compared to theoretical predictions. Furthermore, the influence of the cloud radiative effects seems small. It is suggested that the radiative heating profile in the troposphere, associated primarily with the water vapor distribution, is more important than previously thought for driving the semidiurnal tide. However, this result may be sensitive to the vertical resolution and extent of the model.

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41

Nasuno, Tomoe, Hirofumi Tomita, Shinichi Iga, Hiroaki Miura, and Masaki Satoh. "Multiscale Organization of Convection Simulated with Explicit Cloud Processes on an Aquaplanet." Journal of the Atmospheric Sciences 64, no. 6 (June 2007): 1902–21. http://dx.doi.org/10.1175/jas3948.1.

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This study investigated the multiscale organization of tropical convection on an aquaplanet in a model experiment with a horizontal mesh size of 3.5 km (for a 10-day simulation) and 7 km (for a 40-day simulation). The numerical experiment used the nonhydrostatic icosahedral atmospheric model (NICAM) with explicit cloud physics. The simulation realistically reproduced multiscale cloud systems: eastward-propagating super cloud clusters (SCCs) contained westward-propagating cloud clusters (CCs). SCCs (CCs) had zonal sizes of several thousand (hundred) kilometers; typical propagation speed was 17 (10) m s−1. Smaller convective structures such as mesoscale cloud systems (MCs) of O(10 km) and cloud-scale elements (<10 km) were reproduced. A squall-type cluster with high cloud top (z > 16 km) of O(100 km) area was also reproduced. Planetary-scale equatorial waves (with wavelengths of 10 000 and 40 000 km) had a major influence on the eastward propagation of the simulated SCC; destabilization east of the SCC facilitated generation of new CCs at the eastern end of the SCC. Large-scale divergence fields associated with the waves enhanced the growth of deep clouds in the CCs. A case study of a typical SCC showed that the primary mechanism forcing westward propagation varies with the life stages of the CCs or with vertical profiles of zonal wind. Cold pools and synoptic-scale waves both affected CC organization. Cloud-scale elements systematically formed along the edges of cold pools to sustain simulated MCs. The location, movement, and duration of the MCs varied with the large-scale conditions.

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42

Langen, Peter L., Rune Grand Graversen, and Thorsten Mauritsen. "Separation of Contributions from Radiative Feedbacks to Polar Amplification on an Aquaplanet." Journal of Climate 25, no. 8 (April 10, 2012): 3010–24. http://dx.doi.org/10.1175/jcli-d-11-00246.1.

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Abstract When climate is forced by a doubling of CO2, a number of feedback processes are induced, such as changes of water vapor, clouds, and surface albedo. Here the CO2 forcing and concomitant feedbacks are studied individually using a general circulation model coupled to an aquaplanet mixed layer ocean. A technique for fixing the radiative effects of moisture and clouds by reusing these variables from 1 × CO2 and 2 × CO2 equilibrium climates in the model’s radiation code allows for a detailed decomposition of forcings, feedbacks, and responses. The cloud feedback in this model is found to have a weak global average effect and surface albedo feedbacks have been eliminated. As in previous studies, the water vapor feedback is found to approximately double climate sensitivity, but while its radiative effect is strongly amplified at low latitudes, the resulting response displays about the same degree of polar amplification as the full all-feedbacks experiment. In fact, atmospheric energy transports are found to change in a way that yields the same meridional pattern of response as when the water vapor feedback is turned off. The authors conclude that while the water vapor feedback does not in itself lead to polar amplification by increasing the ratio of high- to low-latitude warming, it does double climate sensitivity both at low and high latitudes. A polar amplification induced by other feedbacks in the system, such as the Planck and lapse rate feedbacks here, is thus strengthened in the sense of increasing the difference in high- and low-latitude warming.

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43

Marshall, John, David Ferreira, J.-M. Campin, and Daniel Enderton. "Mean Climate and Variability of the Atmosphere and Ocean on an Aquaplanet." Journal of the Atmospheric Sciences 64, no. 12 (December 1, 2007): 4270–86. http://dx.doi.org/10.1175/2007jas2226.1.

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Abstract Numerical experiments are described that pertain to the climate of a coupled atmosphere–ocean–ice system in the absence of land, driven by modern-day orbital and CO2 forcing. Millennial time-scale simulations yield a mean state in which ice caps reach down to 55° of latitude and both the atmosphere and ocean comprise eastward- and westward-flowing zonal jets, whose structure is set by their respective baroclinic instabilities. Despite the zonality of the ocean, it is remarkably efficient at transporting heat meridionally through the agency of Ekman transport and eddy-driven subduction. Indeed the partition of heat transport between the atmosphere and ocean is much the same as the present climate, with the ocean dominating in the Tropics and the atmosphere in the mid–high latitudes. Variability of the system is dominated by the coupling of annular modes in the atmosphere and ocean. Stochastic variability inherent to the atmospheric jets drives variability in the ocean. Zonal flows in the ocean exhibit decadal variability, which, remarkably, feeds back to the atmosphere, coloring the spectrum of annular variability. A simple stochastic model can capture the essence of the process. Finally, it is briefly reviewed how the aquaplanet can provide information about the processes that set the partition of heat transport and the climate of Earth.

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44

Brayshaw, David James, Brian Hoskins, and Michael Blackburn. "The Storm-Track Response to Idealized SST Perturbations in an Aquaplanet GCM." Journal of the Atmospheric Sciences 65, no. 9 (September 1, 2008): 2842–60. http://dx.doi.org/10.1175/2008jas2657.1.

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Abstract The tropospheric response to midlatitude SST anomalies has been investigated through a series of aquaplanet simulations using a high-resolution version of the Hadley Centre atmosphere model (HadAM3) under perpetual equinox conditions. Model integrations show that increases in the midlatitude SST gradient generally lead to stronger storm tracks that are shifted slightly poleward, consistent with changes in the lower-tropospheric baroclinicity. The large-scale atmospheric response is, however, highly sensitive to the position of the SST gradient anomaly relative to that of the subtropical jet in the unperturbed atmosphere. In particular, when SST gradients are increased very close to the subtropical jet, then the Hadley cell and subtropical jet is strengthened while the storm track and eddy-driven jet are shifted equatorward. Conversely, if the subtropical SST gradients are reduced and the midlatitude gradients increased, then the storm track shows a strong poleward shift and a well-separated eddy-driven jet is produced. The sign of the SST anomaly is shown to play a secondary role in determining the overall tropospheric response. These findings are used to provide a new and consistent interpretation of some previous GCM studies concerning the atmospheric response to midlatitude SST anomalies.

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45

Horinouchi, Takeshi. "Moist Hadley Circulation: Possible Role of Wave–Convection Coupling in Aquaplanet Experiments." Journal of the Atmospheric Sciences 69, no. 3 (March 1, 2012): 891–907. http://dx.doi.org/10.1175/jas-d-11-0149.1.

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Abstract Aquaplanet simulations for a given sea surface temperature (SST) are conducted to elucidate possible roles of transient variability in the Hadley circulation and the intertropical convergence zone (ITCZ). Their roles are best illustrated with globally uniform SSTs. For such SSTs, an ITCZ and a Hadley circulation that are nearly equatorially symmetric emerge spontaneously. Their strength varies over a wide range from being faint to climatologically significant depending on a tunable parameter of the model’s cumulus parameterization. In some cases asymmetric Hadley circulations formed along with long-lived tropical cyclones. The tunable parameter affects the transient variability of tropical precipitation. In the runs in which well-defined near-symmetric ITCZs formed, tropical precipitation exhibited clear signatures of convectively coupled equatorial waves. The waves can explain the concentration of precipitation to the equatorial region, which induces the Hadley circulation. Also, the meridional structures of simulated ITCZs are consistent with the distribution of convergence/divergence associated with dominant equatorial wave modes. Even when the pole–equator temperature gradient is introduced, the dependence of the strength of the circulation to transient disturbances remains. Therefore, transient variability may have a broader impact on tropical climate and its numerical modeling than has been thought. The reason that a wide variety of circulation is possible when the SST gradient is weak is because the distribution of latent heating can be interactively adjusted while a circulation is formed. Angular momentum budget does not provide an effective thermodynamic constraint, since baroclinic instability redistributes the angular momentum.

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46

Möbis, Benjamin, and Bjorn Stevens. "Factors controlling the position of the Intertropical Convergence Zone on an aquaplanet." Journal of Advances in Modeling Earth Systems 4, no. 4 (April 2012): n/a. http://dx.doi.org/10.1029/2012ms000199.

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47

Feldstein, Steven B. "The Dynamics Associated with Equatorial Atmospheric Angular Momentum in an Aquaplanet GCM." Journal of the Atmospheric Sciences 60, no. 15 (August 2003): 1822–34. http://dx.doi.org/10.1175/1520-0469(2003)060<1822:tdawea>2.0.co;2.

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48

Hsu, Pang-Chi, Tim Li, and Hiroyuki Murakami. "Moisture Asymmetry and MJO Eastward Propagation in an Aquaplanet General Circulation Model*." Journal of Climate 27, no. 23 (December 1, 2014): 8747–60. http://dx.doi.org/10.1175/jcli-d-14-00148.1.

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Abstract The role of zonal moisture asymmetry in the eastward propagation of the Madden–Julian oscillation (MJO) is investigated through a set of aquaplanet atmospheric general circulation model (AGCM) experiments with a zonally symmetric sea surface temperature distribution. In the control experiment, the model produces eastward-propagating MJO-like perturbations with a dominant period of 30–90 days. The model MJO exhibits a clear zonal asymmetry in the lower-tropospheric specific humidity field, with a positive (negative) anomaly appearing to the east (west) of the MJO convection. A diagnosis of the lower-tropospheric moisture budget indicates that the asymmetry primarily arises from vertical moisture advection associated with boundary layer convergence, while horizontal moisture advection has the opposite effect. In a sensitivity experiment, the lower-tropospheric specific humidity field is relaxed toward a zonal-mean basic state derived from the control simulation. In this case, the model’s mean state remains the same, but its intraseasonal mode becomes quasi-stationary. The numerical model experiments clearly demonstrate the importance of the zonal moisture asymmetry in MJO eastward propagation.

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49

Lu, Jian, Koichi Sakaguchi, Qing Yang, L. Ruby Leung, Gang Chen, Chun Zhao, Erik Swenson, and Zhangshuan J. Hou. "Examining the Hydrological Variations in an Aquaplanet World Using Wave Activity Transformation." Journal of Climate 30, no. 7 (April 2017): 2559–76. http://dx.doi.org/10.1175/jcli-d-16-0561.1.

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Building on the recent advent of the concept of finite-amplitude wave activity, a contour-following diagnostics for column water vapor (CWV) is developed and applied to a pair of aquaplanet model simulations to understand and quantify the higher moments in the global hydrological cycle. The Lagrangian nature of the diagnostics leads to a more tractable formalism for the transient, zonally asymmetric component of the hydrological cycle, with a strong linear relation emerging between the wave activity and the wave component of precipitation minus evaporation ([Formula: see text]). The dry-versus-wet disparity in the transient hydrological cycle is measured by [Formula: see text], and it is found to increase at a super-Clausius–Clapeyron rate at the poleward side of the mean storm track in response to a uniform sea surface temperature (SST) warming and the meridional structure of the increase can be largely attributed to the change of the meridional stirring scale of the midlatitude Rossby waves. Further scaling for [Formula: see text] indicates that the rate of the wavy hydrological cycle, measured by the ratio of [Formula: see text] to the CWV wave activity, is subdued almost everywhere in the extratropics, implying an overall weakening of the transient circulation. Extending the CWV wave activity analysis to the transient moist regions helps reveal some unique characteristics of atmospheric rivers in terms of transport function, minimum precipitation efficiency, and maximum hydrological cycle rate, as well as an overall weakening of the hydrological cycle rate in the atmospheric river regions under SST warming.

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50

Woelfle, Matthew D., Christopher S. Bretherton, and Dargan M. W. Frierson. "Time scales of response to antisymmetric surface fluxes in an aquaplanet GCM." Geophysical Research Letters 42, no. 7 (April 11, 2015): 2555–62. http://dx.doi.org/10.1002/2015gl063372.

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