scholarly journals Cloud Radiative Effects and Precipitation in Extratropical Cyclones

2016 ◽  
Vol 29 (18) ◽  
pp. 6483-6507 ◽  
Author(s):  
James B. Polly ◽  
William B. Rossow
Keyword(s):  
Radiative Heating ◽  
Extratropical Cyclones ◽  
Radiative Effects ◽  
Local Pressure ◽  
Wind Speeds ◽  
Modeling Analysis ◽  
Flux Profile ◽  
Pressure Anomaly ◽  
Cloud Radiative Effects ◽  
Sky Conditions

Abstract Clouds associated with extratropical cyclones complicate the well-developed theory of dry baroclinic waves through feedback on their dynamics by precipitation and cloud-altered radiative heating. The relationships between cyclone characteristics and the diabatic heating associated with cloud radiative effects (CREs) and latent heat release remain unclear. A cyclone tracking algorithm [NASA’s Modeling, Analysis, and Prediction (MAP) Climatology of Midlatitude Storminess (MCMS)] is used to identify over 106 cyclones in 33 years of the ERA-Interim and collect the properties of each disturbance. Considering storm intensity as related to wind speeds, which depend on the pressure gradient, the distribution of cyclone properties is investigated using groups defined by their depth (local pressure anomaly) and the radius of the region within closed pressure contours to investigate variations with longitude (especially ocean and land), hemisphere, and season. Using global data products of cloud radiative effects on in-atmosphere net radiation [the ISCCP radiative flux profile dataset (ISCCP-FD)] and precipitation (GPCP), composites are assembled for each cyclone group and for “nonstormy” locations. On average, the precipitation rate and the CRE are approximately the same among all cyclone groups and do not strongly differ from nonstormy conditions. The variance of both precipitation and CRE increases with cyclone size and depth. In larger, deeper storms, maximum precipitation and CRE increase, but so do the amounts of nonprecipitating and clear-sky conditions.

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 The Role of Cloud Radiative Heating in Determining the Location of the ITCZ in Aquaplanet Simulations

2016 ◽  
Vol 29 (8) ◽  
pp. 2741-2763 ◽  
Author(s):  
Bryce E. Harrop ◽  
Dennis L. Hartmann
Keyword(s):  
Hadley Circulation ◽  
Radiative Heating ◽  
Moisture Convergence ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Onset Of Convection ◽  
Cloud Radiative Effect ◽  
Cloud Radiative Effects ◽  
The Mean ◽  
The Impact

Abstract The relationship between the tropical circulation and cloud radiative effect is investigated. Output from the Clouds On–Off Klimate Intercomparison Experiment (COOKIE) is used to examine the impact of cloud radiative effects on circulation and climate. In aquaplanet simulations with a fixed SST pattern, the cloud radiative effect leads to an equatorward contraction of the intertropical convergence zone (ITCZ) and a reduction of the double ITCZ problem. It is shown that the cloud radiative heating in the upper troposphere increases the temperature, weakens CAPE, and inhibits the onset of convection until it is closer to the equator, where SSTs are higher. Precipitation peaks at higher values in a narrower band when the cloud radiative effects are active, compared to when they are inactive, owing to the enhancement in moisture convergence. Additionally, cloud–radiation interactions strengthen the mean meridional circulation and consequently enhance the moisture convergence. Although the mean tropical precipitation decreases, the atmospheric cloud radiative effect has a strong meridional gradient, which supports stronger poleward energy flux and speeds up the Hadley circulation. Cloud radiative heating also enhances cloud water path (liquid plus ice), which, combined with the reduction in precipitation, suggests that the cloud radiative heating reduces precipitation efficiency in these models.

scholarly journals Comparison of Radiative Energy Flows in Observational Datasets and Climate Modeling

2016 ◽  
Vol 55 (1) ◽  
pp. 93-117 ◽  
Author(s):  
Ehrhard Raschke ◽  
Stefan Kinne ◽  
William B. Rossow ◽  
Paul W. Stackhouse ◽  
Martin Wild
Keyword(s):  
Climate Modeling ◽  
Radiative Flux ◽  
Radiative Energy ◽  
Trade Wind ◽  
Radiative Effects ◽  
Ancillary Data ◽  
Global Modeling ◽  
Lower Altitude ◽  
Clear Sky ◽  
Cloud Radiative Effects

AbstractThis study examines radiative flux distributions and local spread of values from three major observational datasets (CERES, ISCCP, and SRB) and compares them with results from climate modeling (CMIP3). Examinations of the spread and differences also differentiate among contributions from cloudy and clear-sky conditions. The spread among observational datasets is in large part caused by noncloud ancillary data. Average differences of at least 10 W m−2 each for clear-sky downward solar, upward solar, and upward infrared fluxes at the surface demonstrate via spatial difference patterns major differences in assumptions for atmospheric aerosol, solar surface albedo and surface temperature, and/or emittance in observational datasets. At the top of the atmosphere (TOA), observational datasets are less influenced by the ancillary data errors than at the surface. Comparisons of spatial radiative flux distributions at the TOA between observations and climate modeling indicate large deficiencies in the strength and distribution of model-simulated cloud radiative effects. Differences are largest for lower-altitude clouds over low-latitude oceans. Global modeling simulates stronger cloud radiative effects (CRE) by +30 W m−2 over trade wind cumulus regions, yet smaller CRE by about −30 W m−2 over (smaller in area) stratocumulus regions. At the surface, climate modeling simulates on average about 15 W m−2 smaller radiative net flux imbalances, as if climate modeling underestimates latent heat release (and precipitation). Relative to observational datasets, simulated surface net fluxes are particularly lower over oceanic trade wind regions (where global modeling tends to overestimate the radiative impact of clouds). Still, with the uncertainty in noncloud ancillary data, observational data do not establish a reliable reference.

A Brief Review of Wind Effects on Buildings and Structures

1966 ◽  
Vol 70 (665) ◽  
pp. 553-560 ◽  
Author(s):  
C. Scruton
Keyword(s):  
Air Flow ◽  
Pressure Fluctuations ◽  
Ground Level ◽  
Vertical Gradient ◽  
Proximity Effects ◽  
Wind Tunnels ◽  
Wind Loading ◽  
Local Pressure ◽  
Wind Speeds ◽  
Random Forcing

SummaryPresent day structural forms and methods of fabrication have considerably increased the importance of wind as a design consideration. For estimations of the overall stability of a structure and of the local pressure distribution on the cladding, a knowledge of the maximum steady or time-averaged wind loads is usually sufficient. Mind tunnel tests to determine the wind loading coefficients are often made in smooth uniform flow, but for more accurate data account must be taken of the effects of the vertical gradient of wind speed and the turbulence of natural winds. Further research is needed into these effects and also into methods of obtaining a sufficient representation of the natural wind in the wind tunnel.There are a number of ways by which wind excites structures into oscillation; among these are vortex excitation, galloping, proximity effects including buffeting, stalling flutter and classical flutter. The vortex and galloping excitation might be expected to be especially sensitive to the turbulence properties of the air flow. Also, in the absence of any mechanism for instability, atmospheric turbulence may directly excite oscillations through the random forcing by the pressure fluctuations which it produces. Further understanding of this problem must come through research into the effects of turbulence (and to the extent to which these effects may be disregarded), but the range of the conditions is so vast and complicated that it seems unlikely that sufficient aerodynamic and wind data will be accumulated to permit the response of a proposed structure to be calculated with reasonable certainty, and for major projects it is anticipated that comprehensive tests on aeroelastic models in wind tunnels with appropriate turbulent air flow will continue to offer the more reliable predictions.The air flow around buildings is of concern inasmuch as it influences the dispersal of combustion and other gases from the smokestack and also in its effect on the speeds and turbulence of the wind over areas used by pedestrians. The erection of a tall building may cause an increase in wind speeds and gustiness at ground level. These problems of the external flow over buildings are readily examined in wind tunnels. For this purpose tunnels with large working sections are desirable to permit a sufficiently wide area of the neighbourhood to be represented.

scholarly journals The cloud-free global energy balance and inferred cloud radiative effects: an assessment based on direct observations and climate models

2018 ◽  
Vol 52 (7-8) ◽  
pp. 4787-4812 ◽  
Author(s):  
Martin Wild ◽  
Maria Z. Hakuba ◽  
Doris Folini ◽  
Patricia Dörig-Ott ◽  
Christoph Schär ◽  
...  
Keyword(s):  
Energy Balance ◽  
Climate Models ◽  
Radiative Effects ◽  
Global Energy ◽  
Global Energy Balance ◽  
Direct Observations ◽  
Cloud Radiative Effects

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.

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