scholarly journals Tropical precipitation clusters as islands on a rough water‐vapor topography

2021 ◽  
Author(s):  
Ziwei Li ◽  
Paul A. O’Gorman ◽  
Daniel H. Rothman
Keyword(s):  
Water Vapor ◽  
Tropical Precipitation ◽  
Rough Water

scholarly journals Impact of Convective Organization on the Response of Tropical Precipitation Extremes to Warming

2013 ◽  
Vol 26 (14) ◽  
pp. 5028-5043 ◽  
Author(s):  
Caroline Muller
Keyword(s):  
Water Vapor ◽  
Surface Water ◽  
Precipitation Extremes ◽  
Vertical Shear ◽  
Tropical Precipitation ◽  
Fractional Rate ◽  
Squall Lines ◽  
Rate Of Increase ◽  
Cloud Resolving Model ◽  
Organized Convection

Abstract In this study the response of tropical precipitation extremes to warming in organized convection is examined using a cloud-resolving model. Vertical shear is imposed to organize the convection into squall lines. Earlier studies show that in disorganized convection, the fractional increase of precipitation extremes is similar to that of surface water vapor, which is substantially smaller than the increase in column water vapor. It has been suggested that organized convection could lead to stronger amplifications. Regardless of the strength of the shear, amplifications of precipitation extremes in the cloud-resolving simulations are comparable to those of surface water vapor and are substantially less than increases in column water vapor. The results without shear and with critical shear, for which the squall lines are perpendicular to the shear, are surprisingly similar with a fractional rate of increase of precipitation extremes slightly smaller than that of surface water vapor. Interestingly, the dependence on shear is nonmonotonic, and stronger supercritical shear yields larger rates, close to or slightly larger than surface humidity. A scaling is used to evaluate the thermodynamic and dynamic contributions to precipitation extreme changes. To first order, they are dominated by the thermodynamic component, which has the same magnitude for all shears, close to the change in surface water vapor. The dynamic contribution plays a secondary role and tends to weaken extremes without shear and with critical shear, while it strengthens extremes with supercritical shear. These different dynamic contributions for different shears are due to different responses of convective mass fluxes in individual updrafts to warming.

scholarly journals Mechanisms of Global Warming Impacts on Robustness of Tropical Precipitation Asymmetry

2008 ◽  
Vol 21 (21) ◽  
pp. 5585-5602 ◽  
Author(s):  
Pei-Hua Tan ◽  
Chia Chou ◽  
Jien-Yi Tu
Keyword(s):  
Global Warming ◽  
Water Vapor ◽  
Climate Model ◽  
Hadley Circulation ◽  
The Other ◽  
Multimodel Ensemble ◽  
Model Simulations ◽  
Tropical Precipitation ◽  
Precipitation Anomalies ◽  
Climate Model Simulations

Abstract Hemispherically and temporally asymmetric tropical precipitation responses to global warming are evaluated in 13 different coupled atmosphere–ocean climate model simulations. In the late boreal summer, hemispherical averages of the tropical precipitation anomalies from the multimodel ensemble show a strong positive trend in the Northern Hemisphere and a weak negative trend in the Southern Hemisphere. In the late austral summer, on the other hand, the trends are reversed. This implies that the summer hemisphere becomes wetter and the winter hemisphere becomes a little drier in the tropics. Thus, the seasonal range of tropical precipitation, differences between wet and dry seasons, is increased. Zonal averages of the precipitation anomalies from the multimodel ensemble also reveal a meridional movement, which basically follows the seasonal migration of the main convection zone. Similar asymmetric features can be found in all 13 climate model simulations used in this study. Based on the moisture budget analysis, the vertical moisture advection associated with mean circulation is the main contribution for the robustness of the asymmetric distribution of the tropical precipitation anomalies. Under global warming, tropospheric water vapor increases as the temperature rises and most enhanced water vapor is in the lower troposphere. The ascending motion of the Hadley circulation then transports more water vapor upward, that is, anomalous moisture convergence, and enhances precipitation over the main convection zones. On the other hand, the thermodynamic effect associated with the descending motion of the Hadley circulation, that is, anomalous moisture divergence, reduces the precipitation over the descending regions.

scholarly journals The Tropical Response to Extratropical Thermal Forcing in an Idealized GCM: The Importance of Radiative Feedbacks and Convective Parameterization

2009 ◽  
Vol 66 (9) ◽  
pp. 2812-2827 ◽  
Author(s):  
Sarah M. Kang ◽  
Dargan M. W. Frierson ◽  
Isaac M. Held
Keyword(s):  
Water Vapor ◽  
Energy Transport ◽  
Convection Scheme ◽  
Thermal Forcing ◽  
Low Level ◽  
Tropical Precipitation ◽  
Idealized Model ◽  
Flux Change ◽  
Precipitation Response ◽  
Atmospheric Energy Transport

Abstract The response of tropical precipitation to extratropical thermal forcing is reexamined using an idealized moist atmospheric GCM that has no water vapor or cloud feedbacks, simplifying the analysis while retaining the aquaplanet configuration coupled to a slab ocean from the authors’ previous study. As in earlier studies, tropical precipitation in response to high-latitude forcing is skewed toward the warmed hemisphere. Comparisons with a comprehensive GCM in an identical aquaplanet, mixed-layer framework reveal that the tropical responses tend to be much larger in the comprehensive GCM as a result of positive cloud and water vapor feedbacks that amplify the imposed extratropical thermal forcing. The magnitude of the tropical precipitation response in the idealized model is sensitive to convection scheme parameters. This sensitivity as well as the tropical precipitation response can be understood from a simple theory with two ingredients: the changes in poleward energy fluxes are predicted using a one-dimensional energy balance model and a measure of the “total gross moist stability” [Δm, which is defined as the total (mean plus eddy) atmospheric energy transport per unit mass transport] of the model tropics converts the energy flux change into a mass flux and a moisture flux change. The idealized model produces a low level of compensation of about 25% between the imposed oceanic flux and the resulting response in the atmospheric energy transport in the tropics regardless of the convection scheme parameter. Because Geophysical Fluid Dynamics Laboratory Atmospheric Model 2 (AM2) with prescribed clouds and water vapor exhibits a similarly low level of compensation, it is argued that roughly 25% of the compensation is dynamically controlled through eddy energy fluxes. The sensitivity of the tropical response to the convection scheme in the idealized model results from different values of Δm: smaller Δm leads to larger tropical precipitation changes for the same response in the energy transport.

scholarly journals Radiative feedbacks on land surface change and associated tropical precipitation shifts

2021 ◽  
pp. 1-63
Author(s):  
Marysa M. Laguë ◽  
Abigail L. S. Swann ◽  
William R. Boos
Keyword(s):  
Water Vapor ◽  
Surface Energy ◽  
Energy Budget ◽  
Negative Feedback ◽  
Land Surface ◽  
Cloud Cover ◽  
Evaporative Resistance ◽  
Near Surface ◽  
Atmospheric Energy ◽  
Tropical Precipitation

AbstractChanges in land surface albedo and land surface evaporation modulate the atmospheric energy budget by changing temperatures, water vapor, clouds, snow and ice cover, and the partitioning of surface energy fluxes. Here idealized perturbations to land surface properties are imposed in a global model to understand how such forcings drive shifts in zonal mean atmospheric energy transport and zonal mean tropical precipitation. For a uniform decrease in global land albedo, the albedo forcing and a positive water vapor feedback contribute roughly equally to increased energy absorption at the top of the atmosphere (TOA), while radiative changes due to the temperature and cloud cover response provide a negative feedback and energy loss at TOA. Decreasing land albedo causes a northwards shift in the zonal mean intertropical convergence zone (ITCZ). The combined effects on ITCZ location of all atmospheric feedbacks roughly cancel for the albedo forcing; the total ITCZ shift is comparable to that predicted for the albedo forcing alone. For an imposed increase in evaporative resistance that reduces land evaporation, low cloud cover decreases in the northern mid-latitudes and more energy is absorbed at TOA there; longwave loss due to warming provides a negative feedback on the TOA energy balance and ITCZ shift. Imposed changes in land albedo and evaporative resistance modulate fundamentally different aspects of the surface energy budget. However, the pattern of TOA radiation changes due to the water vapor and air temperature responses are highly correlated for these two forcings because both forcings lead to near-surface warming.

scholarly journals Southward Intertropical Convergence Zone Shifts and Implications for an Atmospheric Bipolar Seesaw

2013 ◽  
Vol 26 (12) ◽  
pp. 4121-4137 ◽  
Author(s):  
Ivana Cvijanovic ◽  
Peter L. Langen ◽  
Eigil Kaas ◽  
Peter D. Ditlevsen
Keyword(s):  
Water Vapor ◽  
High Latitude ◽  
Intertropical Convergence Zone ◽  
Hadley Cell ◽  
Convergence Zone ◽  
Two Phase ◽  
High Northern Latitude ◽  
Tropical Precipitation ◽  
The Tropics ◽  
Southern High Latitude

Abstract In this study, southward intertropical convergence zone (ITCZ) shifts are investigated in three different scenarios: Northern Hemispheric cooling, Southern Hemispheric warming, and a bipolar seesaw-like forcing that combines the latter two. The experiments demonstrate the mutual effects that northern- and southern-high-latitude forcings exert on tropical precipitation, suggesting a time-scale-dependent dominance of northern versus southern forcings. In accordance with this, two-phase tropical precipitation shifts are suggested, involving a fast component dominated by the high-northern-latitude forcing and a slower component due to the southern-high-latitude forcing. The results may thus be useful for the future understanding and interpretation of high-resolution tropical paleoprecipitation proxies and their relation to high-latitude records (e.g., ice core data). The experiments also show that Southern Ocean warming has a global impact, affecting both the tropics and northern extratropics, as seen in a southward ITCZ shift and mid- and high-latitude North Atlantic surface temperature and wind changes. In terms of dynamical considerations, the tropical circulation response to high-latitude forcing is found to be nonlinear: the atmospheric heat transport and Hadley cell anomalies differ significantly (in magnitude) when comparing the warming and cooling experiments. These are related to different interhemispheric temperature gradients that are altered mainly by nonlinearities in water vapor response. Decomposition of the top-of-the-atmosphere flux response into atmospheric feedback effects shows the dominance of water vapor and cloud feedbacks in the tropics, with the longwave cloud feedback effect governing the overall cloud response.

Response of Tropical Precipitation to Global Warming

2011 ◽  
Vol 68 (1) ◽  
pp. 123-138 ◽  
Author(s):  
David M. Romps
Keyword(s):  
Global Warming ◽  
Water Vapor ◽  
High Resolution ◽  
General Circulation ◽  
Co2 Concentration ◽  
General Circulation Models ◽  
Tropical Convection ◽  
Precipitation Extremes ◽  
Tropical Precipitation ◽  
Effective Water

Abstract Using high-resolution cloud-resolving simulations with different CO2 concentrations, local precipitation fluxes are found to obey Clausius–Clapeyron (CC) scaling. Previous studies of the effect of CO2 concentration on precipitation extremes have used general circulation models, which are poor platforms for studying tropical convection because convection is parameterized. In idealized cloud-resolving simulations, it is possible to identify not only the changes in local precipitation fluxes, but also the factors responsible for those changes. There are many properties of convection that can change as the atmosphere warms, each of which could produce deviations from CC scaling. These properties include the effective water-vapor gradient, cloud pressure depth, and cloud velocity. A simple theory is developed that predicts the changes in these properties consistent with CC scaling. Convection in the cloud-resolving simulations is found to change as predicted by this theory, leading to an ∼20% increase in local precipitation fluxes when the CO2 concentration is doubled. Overall, an increase in CO2 leads to more vigorous convection, composed of clouds that are wider, taller, and faster.

scholarly journals A model for the relationship between tropical precipitation and column water vapor

2009 ◽  
Vol 36 (16) ◽  
Author(s):  
Caroline J. Muller ◽  
Larissa E. Back ◽  
Paul A. O'Gorman ◽  
Kerry A. Emanuel
Keyword(s):  
Water Vapor ◽  
Tropical Precipitation ◽  
The Relationship

New Design for a Differentially Pumped Hydration Chamber for a Siemens IA

1971 ◽  
Vol 29 ◽  
pp. 44-45
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Electron Diffraction ◽  
Water Vapor Pressure ◽  
Biological Materials ◽  
Thin Membrane ◽  
Reliable System ◽  
System A ◽  
Water Films ◽  
Aperture Opening

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

Hydration Chamber for Jeolco 200 Kv Microscope

1970 ◽  
Vol 28 ◽  
pp. 542-543
Author(s):  
V. R. Matricardi ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscope ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Room Temperature ◽  
List Type ◽  
Type Number ◽  
Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

Warm and freeze-fracture of cotton seed radicles

1987 ◽  
Vol 45 ◽  
pp. 984-985
Author(s):  
E. L. Vigil ◽  
E. F. Erbe
Keyword(s):  
Thin Film ◽  
Water Vapor ◽  
Fracture Surface ◽  
Membrane Structure ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Longitudinal Axis ◽  
Fracture Plane ◽  
Cotton Seeds ◽  
Condensed Water

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.

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