Academic literature on the topic 'Aquaplanet'

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.

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.

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.

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.

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.

The coupling between stratosphere and troposphere (ST) has been studied extensively using simple circulation models. It is known that the ozone-rich stratosphere interact with the troposphere through both radiative and dynamical processes. However, many of the models used in these studies only assume a slab ocean with a fixed sea surface temperature (SST) profile. To investigate the role of the ocean in the stratosphere-troposphere coupling, a fully coupled atmosphere-ocean model, FORTE (Fast Ocean Rapid Troposphere Experiment) is used in this study. In this project the Earth is modelled as a perfect sphere with its surface covered with water. In the first set of our experiments we introduce a perturbation to the stratosphere by increasing ozone concentration by a factor of five. In the second experiment we repeat the ozone perturbation experiment with a fixed SST profile such that the atmosphere-ocean coupling is shut off. Our results demonstrate that by including a dynamical ocean, the strength of the jet streams is less sensitive to stratospheric ozone perturbations whereas the extent of their latitudinal displacements is greater. Both of these are found to be a consequence of SST anomalies induced by ocean dynamics. On the other hand, our results show that in the presence of an interactive ocean, there is a general increase in tropospheric air temperature except for polar regions, while lacking the banded anomaly pattern observed in our fixed SST experiment and other ST coupling studies.

As the atmosphere warms under climate change, it will hold more moisture. Latent heat released as water vapour condenses provides an important contribution to the atmospheric heat budget, affecting stability and providing complex feedbacks. Consequently, theories for the general circulation of the atmosphere proposed based on dry dynamics may not apply in moist simulations. In order to understand the possible changes to the Earth's atmospheric circulation as the climate warms, a deeper understanding of these feedbacks is required. Changes to the atmospheric thermal structure and circulation as humidity is increased have been explored in an intermediate complexity general circulation model. To provide a reference climate more comparable with that of previous studies, and of the real world, a simple parameterisation of shortwave and longwave radiative transfer has been developed, which compares favourably with existing simple radiation schemes. Experiments have then been performed with fixed optical depths in which the moisture content of the model is varied. In the zonal mean, increasing moisture content results in an increase in static stability throughout the atmosphere. Consequent changes to the Hadley cell, zonal jets, and storm track have been analysed using simple theories, and by comparison with an experiment in which the sea surface temperature in the tropics is increased. This reveals that the majority of the effects of increased moisture content on the circulation are generated by low latitude warming. The simulations further reveal stronger midlatitude poleward transport of moist static energy as saturation vapour pressure is increased, and an unexpected increase in sensible heat transport in the cold sector of storms. A mechanism for the latter is proposed related to the environmental static stability against which the system develops. The experiments also suggest changes to the rate of conversion of available potential energy to eddy kinetic energy as moisture content increases.

Le syndrome de double zone de convergence intertropicale (ITCZ) est un biais systématique dont souffrent la majorité des modèles de circulation générale (GCM). Les causes de ce comportement problématique ne sont toujours pas élucidées. Le but de la thèse est d'apporter des éléments de réponses à ce sujet et de suggérer des pistes d'amélioration des GCMs. Le travail de thèse a mis en évidence l'importance des rétroactions couplées océan-atmosphère et dynamique-thermodynamique dans la structure de l'ITCZ. Dans un premier temps, les mécanismes à l'origine de l'émergence de régimes de précipitations distincts en réponse à différents forçages en température de surface de la mer (SST) ont été analysés, dans les GCMs atmosphériques ARPEGE-Climat et LMDz, en configuration aquaplanète. La transition du régime double à deux ITCZ vers le régime simple à une seule ITCZ a été plus particulièrement analysée. Dans les deux modèles, cette transition est forcée par la convergence des vents de basses couches associée aux changements de gradients méridiens de température de couche limite. Les rétroactions sèches et humides modulent la transition en favorisant ou en s'opposant au forçage par les SST. Les rétroactions dynamiques sèches sont associées l'advection horizontale d'air froid subtropical. Les rétroactions humides, présentes uniquement dans LMDz, sont associées à la convection et incluent le refroidissement stratosphérique et celui de la couche limite dû aux courants convectifs descendants. Les processus humides sont déterminants pour la structure de l'ITCZ par leur influence sur le profil vertical de chauffage diabatique et sur les rétroactions convection-humidité, deux grandeurs très sensibles au schéma de convection et, en particulier, à l'entraînement latéral convectif. Une analyse de l'influence de l'entraînement latéral convectif sur l'ITCZ est effectuée en utilisant le GCM CNRM-CM5 dans une hiérarchie de modèles (couplé océan-atmosphère, atmosphérique et aquaplanète) et montre que la sensibilité de l'ITCZ à ce paramètre est robuste dans les différentes configurations. L'augmentation de l'entraînement convectif réduit considérablement la double ITCZ. Ce changement de structure de l'ITCZ est associé à un changement de la circulation tropicale résultant de rétroactions entre convection et dynamique de grande échelle. En plus de la dynamique verticale, la SST et les rétroactions couplées sont déterminantes pour la structure de l'ITCZ. Les études de sensibilité à l'entraînement latéral convectif montrent que les rétroactions couplées amplifient le biais de double ITCZ. L'analyse multi-modèle des GCMs CMIP5 montre que les processus thermodynamiques associés à la SST sont en grande partie responsables du problème de double ITCZ dans les simulations couplées
The spurious double intertropical convergence zone (ITCZ) is a systematic bias affecting state-of-the-art coupled general circulation models (GCM); there is still no consensus on its causes. The goal of this thesis is to shed some light on this outstanding problem toward the improvement of climate model performances. This work emphasizes the roles of coupled ocean-atmosphere and dynamics-thermodynamics feedbacks in the ITCZ structure. The first step was to study the response of the atmospheric GCMs ARPEGE-climat and LMDz in aquaplanet configuration, to a range of SST latitudinal distributions. The purpose was to investigate the existence of multiple precipitation regimes, explore their characteristics and untangle the mechanisms at play in regime transition. The transition from the double regime with two ITCZs to the single regime with only one ITCZ at the equator was analyzed. In both models, the transition between these regimes is mainly driven by changes in the low-level convergence that are forced by the atmospheric boundary layer temperature gradients. Model-dependent, dry and moist feedbacks intervene to reinforce or weaken the effect of the temperature forcing. Dry dynamical feedbacks are mainly driven by horizontal advection of cold subtropical air. Moist thermodynamics which are only active in LMDz; they act as negative feedbacks on low-level convergence and are associated with cooling in the stratospheric cold top and in the boundary layer by convective downdrafts. Moist processes play a crucial role in the ITCZ structure through their influence on the vertical profile of convective heating and modulation of moisture-convection feedbacks, two variables that are very sensitive to the convection scheme and, in particular, to lateral convective entrainment. The influence of lateral convective entrainment on the ITCZ structure is analyzed through a hierarchy of model configurations (coupled ocean-atmosphere, atmospheric and aquaplanet) using the CNRM-CM5 GCM. The sensitivity of the ITCZ structure to this parameter is robust across our hierarchy of models. In response to an increased entrainment rate, the realistic simulations exhibit a weakening of the southern side of the double ITCZ over the southeastern Pacific. The change in ITCZ configuration is associated with a more realistic representation of the tropical circulation driven by feedbacks between large-scale dynamics and deep convection. Together with vertical dynamics, SST and associated coupled feedbacks drive the ITCZ location. Sensitivity experiments to lateral entrainment show that ocean-atmosphere feedbacks amplify the double ITCZ bias. A multi-model analysis using CMIP5 GCMs show that the double ITCZ bias has become small in atmosphere-only simulations, and that coupled atmosphere-ocean feedbacks account for a large part of this bias in coupled simulations

The Intraseasonal Oscillation (ISO) plays an important role to modulate deep convective activity in the tropical region. In this thesis, I aim to understand the role of land and warm oceans in ISO, using a general circulation model. For this, I conduct a series of experiments in the Community Atmosphere Model (CAM) with various idealized and realistic surface boundary conditions to study tropical ISO. To investigate the influence of tropical sea surface temperature (SST) on ISO and convectively coupled equatorial waves in the global atmosphere, I conduct experiments with idealized, zonally symmetric SST profiles having different widths of warm ocean centered at the equator. I use the model in its basic “Aquaplanet” configuration, with the sun at the equator, i.e. perpetual spring equinox forcing; with idealized zonally symmetric SST, the aquaplanet model produces a double Intertropical Convergence Zone (ITCZ) on either side of the equator, and an eastward propagating Madden Julian oscillation (MJO)like mode with variance at intraseasonal (30 to 96 day) periods and zonal wavenumber one. In the experiment with the narrowest meridional width of warm SST, the variance of moist convective activity lies predominantly in equatorially trapped Kelvin wave band. As the width of the warm equatorial SST is increased, the eastward propagating speed of the MJO-like signal decreases; for the broadest SST profile (warm SST covering 20 degrees of latitude), the speed of the model MJO is about 5.5 m s−1, close to the observed speed. This is because the latitudinal extent of warm SST is comparable to the equatorial Rossby radius, and the model produces off equatorial Rossby waves of sufficient strength to interact with the Kelvin wave and slow down the MJO-like mode. The model also generates westward propagating waves with intraseasonal periods and zonal wavenumber 1–3; the structure of these signals, which extend well into the mid-latitudes, projects onto equatorially trapped Rossby waves with meridional mode numbers 1, 3 and 5, associated with convection that is symmetric about the equator. In addition, the model generates 30–80 day westward moving signals with zonal wavenumber 4–7, particularly in the experiment with a narrow region of warm SST. Although these waves are seen in the wavenumber-frequency spectra in the equatorial region, they have the largest amplitude in the middle and high latitudes. Thus, our study shows that wider, meridionally symmetric SST profiles support a strong MJO-like eastward propagation, and even in an aquaplanet setting, westward propagating Rossby waves comprise a large portion of tropical intraseasonal variability. In the observations (ERA-Interim daily reanalysis), the MJO signal lies in the range of zonal wavenumbers 1 to 5. The variance of MJO at higher wavenumbers (2–5) is absent in the aquaplanet model. For this, I design model experiments in order to study how model MJO responds to the introduction of continents in the presence of zonally symmetric SST, and a realistic SST distribution with the Indo-Pacific warm pool and cool SST in the eastern Pacific. As before, the model is in the aquaplanet-like configuration, to eliminate the effects of seasonality. Model results are compared with 21 years (1995–2015) ERA-Interim reanalysis data and analyzed in terms of the moist static energy (MSE) budget to study the growth and propagation of MJO. When I introduce continents with realistic orography and interactive surface temperature, soil moisture, and albedo, the variance of model MJO is reduced due to weaker boundary layer moisture convergence. However,MJO variance extends to higher wavenumbers. With prescribed climatological January SST boundary condition in the presence of continents, the variance of model MJO is enhanced by a factor of 2–3, and it is distributed across zonal wavenumbers 1 to 5, in closer agreement with observations. Thus, I find that the presence of land by itself is not enough to produce realistic MJO in CAM, but realistic SST distribution is also necessary to simulate MJO with improved spacetime characteristics. Both in simulations and ERA-Interim data, column-integrated longwave radiation plays a key role in the growth of MSE anomaly associated with MJO; in general, meridional and vertical advection of MSE both acts to promote eastward movement of MJO. In the model experiments, meridional advection of low-level MSE anomaly is most significant in the vicinity of the ITCZ. This indicates that the physical processes which determine the location of (single or double) ITCZ are linked to MJO dynamics. The westward propagating “quasi-biweekly” oscillation (QBWO) with 10–25 day period is an important intraseasonal mode of the Asian summer monsoon, yet very few model studies focus on this mode. I study QBWO in the northern and southern tropics in the model and compare it with ERA-Interim reanalysis data. The pure aquaplanet model produces a double Intertropical Convergence Zone (ITCZ), winds that are predominantly zonal, and weak quasi-biweekly variance. When continents are introduced in the model with zonally symmetric SST, the northern ITCZ, as well as quasi-biweekly variance between 10◦N to 24◦N are strengthened in the Pacific Ocean, bringing model results closer to observations. In the model with continents, the QBWO signal dwells inside the mean envelope of high atmospheric moisture, or total precipitable water (TPW), in agreement with observations. However, in the presence of zonally symmetric SST, the model fails to simulate sufficiently high precipitable water in the region extending from the north Indian Ocean to East Asia, resulting in very weak QBWO variance. When the model includes continents and realistic (January) SST boundary conditions, the spatial structure of both TPW and QBWO variance becomes more realistic. I study the mechanisms of propagation and maintenance of the quasi-biweekly mode using vorticity budget and moist static energy (MSE) budget analysis. Advection due to the effect is responsible for the northwestward propagation of QBWO vorticity, while the propagation of column MSE anomaly is mainly due to horizontal advection. Surface turbulent heat fluxes and vertical MSE advection are the dominant contributors to the growth and maintenance of column MSE anomaly in observations and model respectively. Surface heat flux makes a significant contribution to the growth of quasi-biweekly MSE anomaly in the presence of land, in association with the enhanced meridional wind, and vortical structures that resemble moist Rossby waves with a wavelength of about 4000 kilometers.

In this thesis we examine intra-seasonal oscillations (ISO) in the aqua-planet setup of the Community Atmospheric Model (CAM) version 5.1, mainly based on July and January climatological sea surface temperature (SST). We investigate mainly two questions -what should be the SST distribution for the existence of (a) northward moving ISO in summer, and (b) eastward moving MJO-like modes in winter. In the first part of the thesis we discuss the northward propagation. A series of experiments were performed with zonally symmetric and asymmetric SST distributions. The basic lower boundary condition is specified from zonally averaged observed July and January SST. The zonally symmetric July SST experiment produced an inter tropical convergence zone (ITCZ) on both sides of the equator. Poleward movement is not clear, and it is confined to the region between the double ITCZ. In July, the Bay of Bengal (BOB) and West Pacific SST is high compared to the rest of the northern tropics. When we impose a zonally asymmetric SST structure with warm SST spanning about 80 of longitude, the model shows a monsoon-like circulation, and some northward propagating convective events. Analysis of these events shows that two adjacent cells with cyclonic and anticyclonic vorticity are created over the warm SST anomaly and to the west. The propagation occurs due to the convective region drawn north in the convergence zone between these vortices. Zonally propagating Madden-Julian oscillations (MJO) are discussed in the second part of the thesis. All the experiments in this part are based on the zonally symmetric SST. The zonally symmetric January SST configuration gives an MJO-like mode, with zonal wave number 1 and a period of 40-90 days. The SST structure has a nearly meridionally symmetric structure, with local SST maxima on either side of the equator, and a small dip in the equatorial region. If we replace this dip with an SST maximum, the time-scale of MJO becomes significantly smaller (20-40 days). The implication is that an SST maximum in the equatorial region reduces the strength of MJO, and a flat SST profile in the equatorial region is required for more energetic of MJO. This result was tested and found to be valid in a series of further experiments.

In this thesis we examine intra-seasonal oscillations (ISO) in the aqua-planet setup of the Community Atmospheric Model (CAM) version 5.1, mainly based on July and January climatological sea surface temperature (SST). We investigate mainly two questions -what should be the SST distribution for the existence of (a) northward moving ISO in summer, and (b) eastward moving MJO-like modes in winter. In the first part of the thesis we discuss the northward propagation. A series of experiments were performed with zonally symmetric and asymmetric SST distributions. The basic lower boundary condition is specified from zonally averaged observed July and January SST. The zonally symmetric July SST experiment produced an inter tropical convergence zone (ITCZ) on both sides of the equator. Poleward movement is not clear, and it is confined to the region between the double ITCZ. In July, the Bay of Bengal (BOB) and West Pacific SST is high compared to the rest of the northern tropics. When we impose a zonally asymmetric SST structure with warm SST spanning about 80 of longitude, the model shows a monsoon-like circulation, and some northward propagating convective events. Analysis of these events shows that two adjacent cells with cyclonic and anticyclonic vorticity are created over the warm SST anomaly and to the west. The propagation occurs due to the convective region drawn north in the convergence zone between these vortices. Zonally propagating Madden-Julian oscillations (MJO) are discussed in the second part of the thesis. All the experiments in this part are based on the zonally symmetric SST. The zonally symmetric January SST configuration gives an MJO-like mode, with zonal wave number 1 and a period of 40-90 days. The SST structure has a nearly meridionally symmetric structure, with local SST maxima on either side of the equator, and a small dip in the equatorial region. If we replace this dip with an SST maximum, the time-scale of MJO becomes significantly smaller (20-40 days). The implication is that an SST maximum in the equatorial region reduces the strength of MJO, and a flat SST profile in the equatorial region is required for more energetic of MJO. This result was tested and found to be valid in a series of further experiments.

Various aspects of dry and moist atmospheric dynamics are explored through systems of varying complexity, ranging from a 2-D shallow water model to a more complex 3-D general circulation model. First, we examine the response of the nonlinear spherical shallow water equations to tropical vorticity forcing. For a wide range of scenarios we show the emergence of a robust superrotating state. Unlike previous examples, this state of superrotation does not rely on any particular form of dissipation. In fact, even in the absence of any damping we find propagating solutions that have superrotating zonal mean winds. Further, our prescription allows for the construction of arbitrary equatorial zonal wind profiles. In all the cases, rotational eddy fluxes in the equatorial region are responsible for the required eastward acceleration. Arguments based on the nature of potential vorticity (PV) and enstrophy are put forth to shed some light on these results. Next, we introduce moisture and examine the transient response of a spherical moist shallow water system to tropical imbalances. In particular, our focus is on studying the response in the presence of inhomogeneous moist saturation fields. While the initial moist response is similar to the dry reference run, albeit with a reduced equivalent depth, the long-time solution depends quite strikingly on the nature of the saturation field. With a latitudinally varying background saturation, height imbalances adjust to large-scale, low-frequency westward propagating modes. When the background saturation environment is also allowed to vary with longitude, in addition to a westward quadrupole, a distinct moist PV conserving eastward propagating mode (“moist Rossby” wave) emerges at long times. Many of these basic features carry over to the response in the presence of realistic saturation fields, and we catalogue the changing nature of the nonlinear atmospheric responses in the presence of saturation fields that characterize the summer and winter seasons. After this, we proceed to moist steady and statistically stationary solutions that result from continuous forcing and dissipation. The moist analogue of the “Matsuno-Gill” problem yields a response which is comparatively localized in both latitude and longitude. The sensitivity of the moist solutions to various model parameters like strength of latent heating, condensation and evaporation timescales, momentum and radiative damping as well as the background saturation field and mean flows is examined. In the presence of a random large or small-scale forcing, i.e., moist turbulence, the system is seen to support significantly slower large-scale waves along with a smaller scale turbulent field. Also, in contrast to the dry shallow water turbulence, interscale kinetic energy transfer is inhibited and smaller scales are also dominated by rotational modes. Interestingly, unlike the dry momentum forced case, moist solution yields superrotation, which is again tied to tropical eddy fluxes. Further, the effects of varying forcing protocols on kinetic energy spectra, the relative roles of divergent and rotational components as well as the spontaneous aggregation of moisture fields is systematically documented. Finally, we extend our theme of moist versus dry atmospheres to a more complex general circulation model. Specifically, dynamically dry and moist responses to uniform sea-surface temperature are studied in an aquaplanet setting by varying the latent heat of condensation. Despite having no meridional thermal gradients, Hadley and Ferrel cells with magnitude comparable to present-day Earth are observed for relatively moist cases. This tropical circulation, and the secondary Ferrel cell reverses as water vapor becomes dynamically inactive. In all cases, the Hadley cell is thermally indirect and is strongly influenced by eddy fluxes. Further, there is a systematic poleward transport of energy that remains almost invariant for relatively strong coupling of water substance. The emergence of tropical storm-like warm core vortices, associated extreme rainfall events and their sensitivity to moist coupling is examined. Finally, the changing nature of precipitation and tropical intraseasonal variability is documented for varying latent heats. Here, we see a systematic decrease in the dominant time period of the tropical disturbances with weaker dynamical coupling of water vapor. In fact, low-frequency modes such as the Madden Julian Oscillation (MJO) disappear when water vapor becomes dynamically passive in nature.