scholarly journals Radiative Effects of Clouds and Water Vapor on an Axisymmetric Monsoon

2020 ◽  
Vol 33 (20) ◽  
pp. 8789-8811 ◽  
Author(s):  
Michael P. Byrne ◽  
Laure Zanna
Keyword(s):  
Climate Change ◽  
Water Vapor ◽  
Monsoon Circulation ◽  
Radiative Effects ◽  
Surface Cooling ◽  
Radiative Processes ◽  
Cloud Radiative Effects ◽  
Cloud Effect ◽  
New Perspective ◽  
The Tropics

AbstractMonsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling an axisymmetric monsoon and its response to climate change are investigated using aquaplanet simulations. The influences of clouds, water vapor, and CO2 on the axisymmetric monsoon are decomposed using the radiation-locking technique. Seasonal variations in clouds and water vapor strongly modulate the axisymmetric monsoon, reducing net precipitation by approximately half. Warming and moistening of the axisymmetric monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect also expedites onset of the axisymmetric monsoon by approximately two weeks, whereas longwave cloud and water vapor effects delay onset. A conceptual model relates the timing of monsoon onset to the efficiency of surface cooling. In climate change simulations CO2 forcing and the water vapor feedback have similar influences on the axisymmetric monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the monsoon circulation response. A new perspective for understanding how cloud radiative effects shape the monsoon circulation response to climate change is introduced. The radiation-locking simulations and analyses advance understanding of how radiative processes influence an axisymmetric monsoon, and establish a framework for interpreting monsoon–radiation coupling in observations, in state-of-the-art models, and in different climate states.

Radiative effects of clouds and water vapor on the monsoon

2020 ◽  
Author(s):  
Michael Byrne ◽  
Laure Zanna
Keyword(s):  
Climate Change ◽  
Water Vapor ◽  
Monsoon Onset ◽  
Monsoon Circulation ◽  
Radiative Effects ◽  
Surface Cooling ◽  
Radiative Processes ◽  
Cloud Effect ◽  
The Tropics ◽  
Emergent Constraint

<p>Monsoons are summertime circulations shaping climates and societies across the tropics and subtropics. Here the radiative effects controlling the climatological monsoon and its response to climate change are investigated using idealized simulations. The influences of clouds, water vapor and CO<sub>2</sub> on the monsoon are decomposed using the radiation-locking technique. Seasonal cloud and water vapor radiative effects strongly modulate the climatological monsoon, reducing net monsoon precipitation by approximately half. Warming and moistening of the monsoon by seasonal longwave cloud and water vapor effects are counteracted by a strong shortwave cloud effect. The shortwave cloud effect expedites monsoon onset by approximately 10 days, whereas longwave cloud and water vapor effects delay onset. A simple theory for monsoon onset relates monsoon onset to the efficiency of surface cooling. In climate change simulations the water vapor feedback and CO<sub>2</sub> forcing have similar influences on the monsoon, warming the surface and moistening the region. In contrast, clouds have a negligible effect on surface temperature yet dominate the response of the monsoon circulation to climate change. The radiation-locking simulations and analyses advance understanding of how and why radiative processes influence the monsoon, and establish a new framework for interpreting monsoon--radiation coupling in observations, in state-of-the-art models and in different climate states. Moreover, sensitivities of the monsoon to the longwave cloud feedback are found to be similar over the seasonal cycle and under CO<sub>2</sub> forcing, suggesting a potential emergent constraint for monsoons in a changing climate.</p>

scholarly journals Thermodynamic Control on the Poleward Shift of the Extratropical Jet in Climate Change Simulations: The Role of Rising High Clouds and Their Radiative Effects

2019 ◽  
Vol 32 (3) ◽  
pp. 917-934 ◽  
Author(s):  
Ying Li ◽  
David W. J. Thompson ◽  
Sandrine Bony ◽  
Timothy M. Merlis
Keyword(s):  
Climate Change ◽  
Radiative Effects ◽  
Considerable Uncertainty ◽  
Surface Warming ◽  
Thermodynamic Constraint ◽  
Poleward Shift ◽  
Cloud Radiative Effects ◽  
Underlying Mechanisms ◽  
High Clouds

Extratropical eddy-driven jets are predicted to shift poleward in a warmer climate. Recent studies have suggested that cloud radiative effects (CRE) may enhance the amplitude of such shifts. But there is still considerable uncertainty about the underlying mechanisms, whereby CRE govern the jet response to climate change. This study provides new insights into the role of CRE in the jet response to climate change by exploiting the output from six global warming simulations run with and without atmospheric CRE (ACRE). Consistent with previous studies, it is found that the magnitude of the jet shift under climate change is substantially increased in simulations run with ACRE. It is hypothesized that ACRE enhance the jet response to climate change by increasing the upper-tropospheric baroclinicity due to the radiative effects of rising high clouds. The lifting of the tropopause and high clouds in response to surface warming arises from the thermodynamic constraints placed on water vapor concentrations. Hence, the influence of ACRE on the jet shift in climate change simulations may be viewed as an additional “robust” thermodynamic constraint placed on climate change by the Clausius–Clapeyron relation. The hypothesis is tested in simulations run with an idealized dry GCM, in which the model is perturbed with a thermal forcing that resembles the ACRE response to surface warming. It is demonstrated that 1) the enhanced jet shifts found in climate change simulations run with ACRE are consistent with the atmospheric response to the radiative warming associated with rising high clouds, and 2) the amplitude of the jet shift scales linearly with the amplitude of the ACRE forcing.

scholarly journals Processes Controlling Tropical Tropopause Temperature and Stratospheric Water Vapor in Climate Models

2015 ◽  
Vol 28 (16) ◽  
pp. 6516-6535 ◽  
Author(s):  
Steven C. Hardiman ◽  
Ian A. Boutle ◽  
Andrew C. Bushell ◽  
Neal Butchart ◽  
Mike J. P. Cullen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Atmospheric Composition ◽  
Stratospheric Water Vapor ◽  
Vertical Advection ◽  
Radiative Processes ◽  
Microphysical Properties ◽  
Tropical Tropopause ◽  
The Tropics ◽  
Tropopause Temperature

Abstract A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.

scholarly journals Differences in tropical high clouds among reanalyses: origins and radiative impacts

2020 ◽  
Author(s):  
Jonathon S. Wright ◽  
Xiaoyi Sun ◽  
Paul Konopka ◽  
Kirstin Krüger ◽  
Andrea M. Molod ◽  
...  
Keyword(s):  
Water Content ◽  
Lower Stratosphere ◽  
Cloud Water ◽  
Radiative Heating ◽  
The Other ◽  
Radiative Effects ◽  
High Cloud ◽  
Cloud Water Content ◽  
Cloud Radiative Effects ◽  
The Tropics

Abstract. We examine differences among reanalysis high cloud products in the tropics, assess the impacts of these differences on radiation budgets at the top of the atmosphere and within the tropical upper troposphere and lower stratosphere (UTLS), and discuss their possible origins in the context of the reanalysis models. We focus on the ERA5, ERA-Interim, JRA-55, MERRA-2, and CFSR/CFSv2 reanalyses, with MERRA included in selected comparisons. As a general rule, JRA-55 produces the smallest tropical high cloud fractions and cloud water contents among the reanalyses, while MERRA-2 produces the largest. Accordingly, cloud radiative effects are relatively weak in JRA-55 and relatively strong in MERRA-2. Only MERRA-2 and ERA5 among the reanalyses produce tropical-mean values of outgoing longwave radiation (OLR) close to observed, but ERA5 tends to underestimate cloud effects while MERRA-2 tends to overestimate variability. ERA5 also produces distributions of longwave, shortwave, and total cloud radiative effects at top-of-atmosphere that are very consistent with observed. The other reanalyses all exhibit substantial biases in at least one of these metrics, although compensation between the longwave and shortwave effects helps to constrain biases in the total cloud effect for most reanalyses. The vertical distribution of cloud water content emerges as a key difference between ERA-Interim and the other reanalyses. Whereas ERA-Interim shows a monotonic decrease of cloud water content with increasing height, the other reanalyses all produce distinct anvil layers. The latter is in better agreement with observations and yields very different profiles of radiative heating in the UTLS. For example, whereas the altitude of the level of zero net radiative heating tends to be lower in convective regions than in the rest of the tropics in ERA-Interim, the opposite is true for the other four reanalyses. Differences in cloud water content also help to explain systematic differences in diabatic ascent in the tropical lower stratosphere among the reanalyses. We discuss several ways in which aspects of the cloud and convection schemes impact the tropical environment. Discrepancies in the vertical profile of moist static energy in convective regions are particularly noteworthy, as this metric is based exclusively on variables that are directly constrained by data assimilation.

Environmental Response in Coupled Energy and Water Cloud Impact Parameters Derived from A-Train Satellite, ERA-Interim and MERRA-2

2021 ◽  
Keyword(s):  
Climate Models ◽  
Water Cycle ◽  
Cloud Microphysics ◽  
Dynamic Regime ◽  
Radiative Heating ◽  
Radiative Effects ◽  
Surface Cooling ◽  
Heating Efficiency ◽  
Cloud Radiative Effects ◽  
Impact Parameters

Abstract Understanding the connections between latent heating from precipitation and cloud radiative effects is essential for accurately parameterizing cross-scale links between cloud microphysics and global energy and water cycles in climate models. While commonly examined separately, this study adopts two cloud impact parameters (CIPs), the surface radiative cooling efficiency, Rc, and atmospheric radiative heating efficiency, Rh, that explicitly couple cloud radiative effects and precipitation to characterize how efficiently precipitating cloud systems influence the energy budget and water cycle using A-Train observations and two reanalyses. These CIPs exhibit distinct global distributions that suggest cloud energy and water cycle coupling are highly dependent on cloud regime. The dynamic regime (ω500) controls the sign of Rh, while column water vapor (CWV) appears to be the larger control on the magnitude. The magnitude of Rc is highly coupled to the dynamic regime. Observations show that clouds cool the surface very efficiently per unit rainfall at both low and high sea surface temperature (SST) and CWV, but reanalyses only capture the former. Reanalyses fail to simulate strong Rh and moderate Rc in deep convection environments but produce stronger Rc and Rh than observations in shallow, warm rain systems in marine stratocumulus regions. While reanalyses generate fairly similar climatologies in the frequency of environmental states, the response of Rc and Rh to SST and CWV results in systematic differences in zonal and meridional gradients of cloud atmospheric heating and surface cooling relative to A-Train observations that may have significant implications for global circulations and cloud feedbacks.

scholarly journals On the Role of Clouds and Moisture in Tropical Waves: A Two-Dimensional Model Study

2006 ◽  
Vol 63 (8) ◽  
pp. 2140-2155 ◽  
Author(s):  
Danče Zurovac-Jevtić ◽  
Sandrine Bony ◽  
Kerry Emanuel
Keyword(s):  
Water Vapor ◽  
Large Scale ◽  
Active Role ◽  
Small Scale ◽  
Tropical Atmosphere ◽  
Two Dimensional ◽  
Mean Flow ◽  
Radiative Effects ◽  
Model Study ◽  
Cloud Radiative Effects

Abstract Observations show that convective perturbations of the tropical atmosphere are associated with substantial variations of clouds and water vapor. Recent studies suggest that these variations may play an active role in the large-scale organization of the tropical atmosphere. The present study investigates that possibility by using a two-dimensional, nonrotating model that includes a set of physical parameterizations carefully evaluated against tropical data. In the absence of cloud–radiation interactions, the model spontaneously generates fast upwind (eastward) moving planetary-scale oscillations through the wind-induced surface heat exchange mechanism. In the presence of cloud–radiative effects, the model generates slower upwind (eastward) propagating modes in addition to small-scale disturbances advected downwind (westward) by the mean flow. Enhanced cloud–radiative effects further slow down upwind propagating waves and make them more prominent in the spectrum. On the other hand, the model suggests that interactions between moisture and convection favor the prominence of moist Kelvin-like waves in tropical variability at the expense of small-scale advective disturbances. These numerical results, consistent with theoretical predictions, suggest that the interaction of water vapor and cloud variations with convection and radiation plays an active role in the large-scale organization of the tropical atmosphere.

Interpreting the inter-model spread in regional precipitation projections in the tropics: role of surface evaporation and cloud radiative effects

2016 ◽  
Vol 47 (9-10) ◽  
pp. 2801-2815 ◽  
Author(s):  
Boutheina Oueslati ◽  
Sandrine Bony ◽  
Camille Risi ◽  
Jean-Louis Dufresne
Keyword(s):  
Radiative Effects ◽  
Surface Evaporation ◽  
Cloud Radiative Effects ◽  
The Tropics ◽  
Precipitation Projections

Water Vapor Radiative Effects On Spain

2018 ◽  
Author(s):  
Javier Vaquero-Martínez
Keyword(s):  
Water Vapor ◽  
Radiative Effects
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