scholarly journals Anthropogenic Aerosol effects on Tropospheric Circulation and Sea Surface Temperature (1980–2020): Separating the role of Zonally Asymmetric Forcings

2021 ◽  
Author(s):  
Chenrui Diao ◽  
Yangyang Xu ◽  
Shang-Ping Xie
Keyword(s):  
Radiative Forcing ◽  
Western Hemisphere ◽  
Hadley Cell ◽  
High Latitudes ◽  
Aerosol Forcing ◽  
Eastern Hemisphere ◽  
Aerosol Emission ◽  
Tropospheric Circulation ◽  
Cooling Effects

Abstract. Anthropogenic Aerosols (AA) induce global and regional tropospheric circulation adjustments due to the radiative energy perturbations. The overall cooling effects of AA since the pre-industrial (PI) era, to mask a portion of global warming, have been the subject of many studies with large uncertainty remaining. The interhemispheric contrast in AA forcing has also been demonstrated to induce a major shift in atmospheric circulation. The zonally heterogeneous changes in AA emissions since the late 20th century, with a notable decline in the Western Hemisphere and continuous increase in the Eastern Hemisphere, received less attention. Here we utilize four sets of single-model initial-condition large-ensemble simulations with various combinations of external forcings to quantify the different radiative and circulation responses due to aerosol emissions changes during 1980-2020. In particular, we focus on the distinct climate responses to Fossil-Fuel (FF) related aerosol from Western Hemisphere (WH) versus Eastern Hemisphere (EH). The zonal and meridional redistribution of FF aerosols from WH to EH results in negative radiative forcing over Asia and positive radiative forcing over North America and Europe. This leads to a counterclockwise anomaly of zonal mean stream function over the tropics (i.e. a northward shift of Hadley cell) and stronger equatorward shift of the Northern Hemisphere (NH) jet stream, consistent with the thermal wind argument with the gradient of surface air temperature (SAT) as a predictive metric. Two sets of regional FF simulations (Fix_EastFF1920 and Fix_WestFF1920) are performed and reveals the dominating role of WH forcing due to aerosol reduction in the NH. The Aerosol reduction over WH mid-to-high latitudes dominates the warming over NH mid-to-high latitudes. The increased aerosol over the EH low-to-mid latitudes is confined more locally but also induces slight warming over the northeastern Pacific and North Atlantic. The competing role of FF forcing originating from EH and WH in shaping tropospheric circulation and surface climate response indicates the importance of both zonal and meridional distribution of aerosol forcing within the NH, and previous idealized models that only consider the zonal difference of aerosol emission may oversimplify the real aerosol forcing.

scholarly journals Anthropogenic aerosol effects on tropospheric circulation and sea surface temperature (1980–2020): separating the role of zonally asymmetric forcings

2021 ◽  
Vol 21 (24) ◽  
pp. 18499-18518
Author(s):  
Chenrui Diao ◽  
Yangyang Xu ◽  
Shang-Ping Xie
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Western Hemisphere ◽  
Hadley Cell ◽  
Jet Stream ◽  
High Latitudes ◽  
Aerosol Forcing ◽  
Eastern Hemisphere ◽  
Northeastern Pacific ◽  
Tropospheric Circulation

Abstract. Anthropogenic aerosols (AAs) induce global and regional tropospheric circulation adjustments due to the radiative energy perturbations. The overall cooling effects of AA, which mask a portion of global warming, have been the subject of many studies but still have large uncertainty. The interhemispheric contrast in AA forcing has also been demonstrated to induce a major shift in atmospheric circulation. However, the zonal redistribution of AA emissions since start of the 20th century, with a notable decline in the Western Hemisphere (North America and Europe) and a continuous increase in the Eastern Hemisphere (South Asia and East Asia), has received less attention. Here we utilize four sets of single-model initial-condition large-ensemble simulations with various combinations of external forcings to quantify the radiative and circulation responses due to the spatial redistribution of AA forcing during 1980–2020. In particular, we focus on the distinct climate responses due to fossil-fuel-related (FF) aerosols emitted from the Western Hemisphere (WH) versus the Eastern Hemisphere (EH). The zonal (west to east) redistribution of FF aerosol emission since the 1980s leads to a weakening negative radiative forcing over the WH mid-to-high latitudes and an enhancing negative radiative forcing over the EH at lower latitudes. Overall, the FF aerosol leads to a northward shift of the Hadley cell and an equatorward shift of the Northern Hemisphere (NH) jet stream. Here, two sets of regional FF simulations (Fix_EastFF1920 and Fix_WestFF1920) are performed to separate the roles of zonally asymmetric aerosol forcings. We find that the WH aerosol forcing, located in the extratropics, dominates the northward shift of the Hadley cell by inducing an interhemispheric imbalance in radiative forcing. On the other hand, the EH aerosol forcing, located closer to the tropics, dominates the equatorward shift of the NH jet stream. The consistent relationship between the jet stream shift and the top-of-atmosphere net solar flux (FSNTOA) gradient suggests that the latter serves as a rule-of-thumb guidance for the expected shift of the NH jet stream. The surface effect of EH aerosol forcing (mainly from low- to midlatitudes) is confined more locally and only induces weak warming over the northeastern Pacific and North Atlantic. In contrast, the WH aerosol reduction leads to a large-scale warming over NH mid-to-high latitudes that largely offsets the cooling over the northeastern Pacific due to EH aerosols. The simulated competing roles of regional aerosol forcings in driving atmospheric circulation and surface temperature responses during the recent decades highlight the importance of considering zonally asymmetric forcings (west to east) and also their meridional locations within the NH (tropical vs. extratropical).

scholarly journals The Large-Scale Dynamical Response of Clouds to Aerosol Forcing

2017 ◽  
Vol 30 (21) ◽  
pp. 8783-8794 ◽  
Author(s):  
Brian Soden ◽  
Eui-Seok Chung
Keyword(s):  
Atmospheric Circulation ◽  
Radiative Forcing ◽  
Large Scale ◽  
Energy Transport ◽  
Hadley Cell ◽  
Dynamical Response ◽  
Aerosol Radiative Forcing ◽  
Aerosol Forcing ◽  
Meridional Displacement ◽  
Cloud Response

Radiative kernels are used to quantify the instantaneous radiative forcing of aerosols and the aerosol-mediated cloud response in coupled ocean–atmosphere model simulations under both historical and future emission scenarios. The method is evaluated using matching pairs of historical climate change experiments with and without aerosol forcing and accurately captures the spatial pattern and global-mean effects of aerosol forcing. It is shown that aerosol-driven changes in the atmospheric circulation induce additional cloud changes. Thus, the total aerosol-mediated cloud response consists of both local microphysical changes and nonlocal dynamical changes that are driven by hemispheric asymmetries in aerosol forcing. By comparing coupled and fixed sea surface temperature (SST) simulations with identical aerosol forcing, the relative contributions of these two components are isolated, exploiting the ability of prescribed SSTs to also suppress changes in the atmospheric circulation. The radiative impact of the dynamical cloud changes is found to be comparable in magnitude to that of the microphysical cloud changes and acts to further amplify the interhemispheric asymmetry of the aerosol radiative forcing. The dynamical cloud response is closely linked to the meridional displacement of the Hadley cell, which, in turn, is driven by changes in the cross-equatorial energy transport. In this way, the dynamical cloud changes act as a positive feedback on the meridional displacement of the Hadley cell, roughly doubling the projected changes in cross-equatorial energy transport compared to that from the microphysical changes alone.

The response of the ozone layer under abrupt 4xCO2 in CMIP6

2021 ◽  
Author(s):  
Gabriel Chiodo ◽  
William T. Ball ◽  
Peer Nowack ◽  
Clara Orbe ◽  
James Keeble ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Models ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Cmip5 Models ◽  
Radiative Efficiency ◽  
Tropospheric Circulation ◽  
Column Ozone ◽  
The Relationship

<p>Previous studies indicate a possible role of stratospheric ozone chemistry feedbacks in the climate response to 4xCO2, either via a reduction in equilibrium climate sensitivity (ECS) or via changes in the tropospheric circulation (Nowack et al., 2015; Chiodo and Polvani, 2017). However, these effects are subject to uncertainty. Part of the uncertainty may stem from the dependency of the feedback on the pattern of the ozone response, as the radiative efficiency of ozone largely depends on its vertical distribution (Lacis et al., 1990). Here, an analysis is presented of the ozone layer response to 4xCO2 in chemistry–climate models (CCMs) which participated to CMIP inter-comparisons. In a previous study using CMIP5 models, it has been shown that under 4xCO2, ozone decreases in the tropical lower stratosphere, and increases over the high latitudes and throughout the upper stratosphere (Chiodo et al., 2018). It was also found that a substantial portion of the spread in the tropical column ozone is tied to inter-model spread in tropical upwelling, which is in turn tied to ECS. Here, we revisit this connection using 4xCO2 data from CMIP6, thereby exploiting the larger number of CCMs available than in CMIP5. In addition, we explore the linearity of the ozone response, by complementing the analysis with simulations using lower CO2 forcing levels (2xCO2). We show that the pattern of the ozone response is similar to CMIP5. In some models (e.g. WACCM), we find larger ozone responses in CMIP6 than in CMIP5, partly because of the larger ECS and thus larger upwelling response in the tropical pipe. In this presentation, we will discuss the relationship between radiative forcing, transport and ozone, as well as further implications for CMIP6 models.</p>

scholarly journals The Climatic Importance of Uncertainties in Regional Aerosol–Cloud Radiative Forcings over Recent Decades

2015 ◽  
Vol 28 (17) ◽  
pp. 6589-6607 ◽  
Author(s):  
Leighton A. Regayre ◽  
Kirsty J. Pringle ◽  
Lindsay A. Lee ◽  
Alexandru Rap ◽  
Jo Browse ◽  
...  
Keyword(s):  
Time Scales ◽  
Radiative Forcing ◽  
Large Scale ◽  
Regional Patterns ◽  
Aerosol Radiative Forcing ◽  
Aerosol Cloud ◽  
The North ◽  
Aerosol Forcing ◽  
Aerosol Emission ◽  
Surface Temperatures

Abstract Regional patterns of aerosol radiative forcing are important for understanding climate change on decadal time scales. Uncertainty in aerosol forcing is likely to vary regionally and seasonally because of the short aerosol lifetime and heterogeneous emissions. Here the sensitivity of regional aerosol cloud albedo effect (CAE) forcing to 31 aerosol process parameters and emission fluxes is quantified between 1978 and 2008. The effects of parametric uncertainties on calculations of the balance of incoming and outgoing radiation are found to be spatially and temporally dependent. Regional uncertainty contributions of opposite sign cancel in global-mean forcing calculations, masking the regional importance of some parameters. Parameters that contribute little to uncertainty in Earth’s global energy balance during recent decades make significant contributions to regional forcing variance. Aerosol forcing sensitivities are quantified within 11 climatically important regions, where surface temperatures are thought to influence large-scale climate effects. Substantial simulated uncertainty in CAE forcing in the eastern Pacific leaves open the possibility that apparent shifts in the mean ENSO state may result from a forced aerosol signal on multidecadal time scales. A likely negative aerosol CAE forcing in the tropical North Atlantic calls into question the relationship between Northern Hemisphere aerosol emission reductions and CAE forcing of sea surface temperatures in the main Atlantic hurricane development region on decadal time scales. Simulated CAE forcing uncertainty is large in the North Pacific, suggesting that the role of the CAE in altering Pacific tropical storm frequency and intensity is also highly uncertain.

Morphological types of spermatheca in Coreidae: bearing on intra-familial classification and tribal-groupings (Hemiptera: Heteroptera)

Zootaxa ◽  
2020 ◽  
Vol 4834 (4) ◽  
pp. 451-501
Author(s):  
DOMINIQUE PLUOT-SIGWALT ◽  
PIERRE MOULET
Keyword(s):  
Western Hemisphere ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Spermathecal Duct ◽  
Eastern Hemisphere ◽  
Intermediate Part ◽  
Muscular Pump ◽  
Familial Classification

The morphology of the spermatheca is described in 109 species of 86 genera representing all four currently recognised subfamilies of Coreidae, covering the undivided Hydarinae, both tribes of Pseudophloeinae, all three tribes of Meropachyinae and 27 of the 32 tribes of Coreinae. Three types of spermatheca are recognised. Type I is bipartite, consisting only of a simple tube differentiated into distal seminal receptacle and proximal spermathecal duct and lacks the intermediate part present in most Pentatomomorpha, in which it serves as muscular pump. Type II is also bipartite but more elaborate in form with the receptacle generally distinctly wider than the duct. Type III is tripartite, with receptacle, duct and an often complex intermediate part. Four subtypes are recognised within type III. Type I is found only in Hydarinae and type II only in Pseudophloeinae. Type III is found in both Coreinae and Meropachyinae. Subtype IIIA (“Coreus-group”) unites many tribes from the Eastern Hemisphere and only one (Spartocerini) from the Western Hemisphere. Subtypes IIIB (“Nematopus-group”) and IIID (“Anisoscelis-group”) are confined to taxa from the Western Hemisphere and subtype IIIC (“Chariesterus-group”) is found in tribes from both hemispheres. The polarity of several characters of the intermediate part and some of the spermathecal duct is evaluated, suggesting autapomorphies or apomorphies potentially relevant to the classification of Coreidae at the sufamilial and tribal levels. Characters of the intermediate part strongly indicate that the separation of Meropachyinae and Coreinae as currently constituted cannot be substantiated. The tribes Anisoscelini, Colpurini, Daladerini and Hyselonotini are heterogeneous, each exhibiting two subtypes of spermatheca, and probably polyphyletic. Two tribes, Cloresmini and Colpurini, requiring further investigation remain unplaced. This study demonstrates the great importance of characters of the spermatheca, in particular its intermediate part, for research into the phylogeny and taxonomy of Pentatomomorpha. 

scholarly journals Role of sea surface temperature responses in simulation of the climatic effect of mineral dust aerosol

2011 ◽  
Vol 11 (12) ◽  
pp. 6049-6062 ◽  
Author(s):  
X. Yue ◽  
H. Liao ◽  
H. J. Wang ◽  
S. L. Li ◽  
J. P. Tang
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Radiative Forcing ◽  
Mineral Dust ◽  
Dust Aerosol ◽  
Sea Surface ◽  
Climatic Effect ◽  
Radiative Effects ◽  
Climate Simulations

Abstract. Mineral dust aerosol can be transported over the nearby oceans and influence the energy balance at the sea surface. The role of dust-induced sea surface temperature (SST) responses in simulations of the climatic effect of dust is examined by using a general circulation model with online simulation of mineral dust and a coupled mixed-layer ocean model. Both the longwave and shortwave radiative effects of mineral dust aerosol are considered in climate simulations. The SST responses are found to be very influential on simulated dust-induced climate change, especially when climate simulations consider the two-way dust-climate coupling to account for the feedbacks. With prescribed SSTs and dust concentrations, we obtain an increase of 0.02 K in the global and annual mean surface air temperature (SAT) in response to dust radiative effects. In contrast, when SSTs are allowed to respond to radiative forcing of dust in the presence of the dust cycle-climate interactions, we obtain a global and annual mean cooling of 0.09 K in SAT by dust. The extra cooling simulated with the SST responses can be attributed to the following two factors: (1) The negative net (shortwave plus longwave) radiative forcing of dust at the surface reduces SST, which decreases latent heat fluxes and upward transport of water vapor, resulting in less warming in the atmosphere; (2) The positive feedback between SST responses and dust cycle. The dust-induced reductions in SST lead to reductions in precipitation (or wet deposition of dust) and hence increase the global burden of small dust particles. These small particles have strong scattering effects, which enhance the dust cooling at the surface and further reduce SSTs.

Observational Constraints on Past Attributable Warming and Predictions of Future Global Warming

2006 ◽  
Vol 19 (13) ◽  
pp. 3055-3069 ◽  
Author(s):  
Peter A. Stott ◽  
John F. B. Mitchell ◽  
Myles R. Allen ◽  
Thomas L. Delworth ◽  
Jonathan M. Gregory ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Temperature Change ◽  
Greenhouse Warming ◽  
Gas Emissions ◽  
Aerosol Forcing ◽  
Future Global Warming ◽  
Cooling Effects ◽  
The Impact

Abstract This paper investigates the impact of aerosol forcing uncertainty on the robustness of estimates of the twentieth-century warming attributable to anthropogenic greenhouse gas emissions. Attribution analyses on three coupled climate models with very different sensitivities and aerosol forcing are carried out. The Third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3), Parallel Climate Model (PCM), and GFDL R30 models all provide good simulations of twentieth-century global mean temperature changes when they include both anthropogenic and natural forcings. Such good agreement could result from a fortuitous cancellation of errors, for example, by balancing too much (or too little) greenhouse warming by too much (or too little) aerosol cooling. Despite a very large uncertainty for estimates of the possible range of sulfate aerosol forcing obtained from measurement campaigns, results show that the spatial and temporal nature of observed twentieth-century temperature change constrains the component of past warming attributable to anthropogenic greenhouse gases to be significantly greater (at the 5% level) than the observed warming over the twentieth century. The cooling effects of aerosols are detected in all three models. Both spatial and temporal aspects of observed temperature change are responsible for constraining the relative roles of greenhouse warming and sulfate cooling over the twentieth century. This is because there are distinctive temporal structures in differential warming rates between the hemispheres, between land and ocean, and between mid- and low latitudes. As a result, consistent estimates of warming attributable to greenhouse gas emissions are obtained from all three models, and predictions are relatively robust to the use of more or less sensitive models. The transient climate response following a 1% yr−1 increase in CO2 is estimated to lie between 2.2 and 4 K century−1 (5–95 percentiles).

scholarly journals Convectively Coupled Equatorial Waves. Part I: Horizontal and Vertical Structures

2007 ◽  
Vol 64 (10) ◽  
pp. 3406-3423 ◽  
Author(s):  
Gui-Ying Yang ◽  
Brian Hoskins ◽  
Julia Slingo
Keyword(s):  
Composite Structures ◽  
Wave Structure ◽  
Wave Theory ◽  
Western Hemisphere ◽  
Equatorial Waves ◽  
Kelvin Wave ◽  
Ambient Flow ◽  
Convectively Coupled Equatorial Waves ◽  
Eastern Hemisphere ◽  
Equatorial Wave

Abstract Multilevel 15-yr ECMWF Re-Analysis (ERA-15) and satellite-observed brightness temperature (Tb) data for the period May–October 1992 are used to examine the horizontal and vertical structures of convectively coupled equatorial waves. Dynamical waves are isolated using a methodology developed previously. Composite structures of convectively coupled equatorial waves are obtained using linear regression/correlation between convection (Tb) and dynamical structures. It is found that the relationship depends on the ambient flow and the nature of the convective coupling, and varies between off-equatorial- and equatorial-centered convection, different hemispheres, and seasons. The Kelvin wave structure in the Western Hemisphere is generally consistent with classic equatorial wave theory and has its convection located in the region of low-level convergence. In the Eastern Hemisphere the Kelvin wave tends to have convection in the region of enhanced lower-tropospheric westerlies and a tilted vertical structure. The Kelvin wave also tends to have a third peak in zonal wind amplitude at 500 hPa and exhibits upward propagation into the lower stratosphere. Lower-tropospheric westward-moving mixed Rossby–gravity (WMRG) and n = 1 Rossby (R1) wave structures and their relationship with convection are consistent with classic equatorial wave theory and the implied lower-tropospheric convergences. In the Eastern Hemisphere the WMRG and R1 waves have first baroclinic mode structures in the vertical. However, in the Western Hemisphere, the R1 wave has a barotropic structure. In the Eastern Hemisphere the R1 wave, like the Kelvin wave, tends to have equatorial convection in the region of enhanced lower-level westerlies, suggesting that enhanced surface energy fluxes associated with these waves may play an important organizing role for equatorial convection in this warm-water hemisphere. In the upper troposphere, eastward-moving Rossby–gravity (EMRG) and n = 1 gravity waves are found in the Eastern Hemisphere, and eastward-moving WMRG and R1 waves are found in the Western Hemisphere, suggestive of Doppler shifting of waves by the ambient flow.

Aschersonia aleyrodis. [Descriptions of Fungi and Bacteria].

1984 ◽  
Author(s):  
B. L. Brady
Keyword(s):  
Costa Rica ◽  
Geographical Distribution ◽  
Solomon Islands ◽  
Western Hemisphere ◽  
Scale Insects ◽  
Infected Host ◽  
Santo Domingo ◽  
Eastern Hemisphere ◽  
Aschersonia Aleyrodis ◽  
The Relationship

Abstract A description is provided for Aschersonia aleyrodis. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Scale insects (Coccidae) and whitefly (Aleyrodidae). GEOGRAPHICAL DISTRIBUTION: Costa Rica, Cuba, India, Jamaica, Santo Domingo, Solomon Islands, USA. According to Mains (1959) A. aleyrodis is very common in the Western hemisphere whereas A. placenta is common in the Eastern hemisphere. DISEASE: When the genus Aschersonia Montagne was described in 1848 the species were regarded as parasites of the leaves of the plants on which the insect hosts were located and it was only in 1894 that Webber recognized A. aleyrodis as entomogenous. Early work and the relationship with the ascomycete genus Hypocrella is extensively treated and illustrated in colour by Petch (1921). Sutton (1980) states that approximately 50 taxa have been described in the genus which is wholly entomogenous. Infection is mainly of young larvae, but mature larvae and pupae are also attacked. Larvae in the early stages of infection become swollen and by the time that hyphae emerge around the edge of the infected host the latter is already dead.

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