Variation of Projected Atmospheric Water Vapor in Central Asia Using Multi-Models from CMIP6

Using data from the Integrated Global Radiosonde Archive Version 2 (IGRA2) and the Multi Model Ensemble (MME) of four global climate models (GCMs), named CanESM5, IPSL-CM6A-LR, MIROC6, and MRI-ESM2-0, within the framework of phase 6 of the Coupled Model Intercomparison Project (CMIP6), we analyzed the changes in atmospheric total column water vapor (TCWV) over Central Asia in the future (2021–2100) under SSP-RCPs scenarios: SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0, and SSP5-8.5, relative to baseline period (1986–2005). Results showed that the annual mean TCWV from IGRA2 was consistent with the model output from 1979 to 2014 in Central Asia. Besides, the spatial distribution of TCWV in Central Asia during the baseline period was consistent between the models. The regional average value of Central Asia was between 10.8 mm and 12.4 mm, and decreased with elevation. TCWV will increase under different SSP-RCPs from 2021 to 2040, but showed different trends after 2040. It will increase under SSP1-1.9 and SSP1-2.6 scenarios from 2021 to 2050, and decrease after that. It will grow from 2021 to 2055 under SSP4-3.4 scenario, and then stay essentially constant. Under SSP2-4.5 and SSP4-6.0 scenarios, TCWV will rise rapidly during 2021–2065, but the growth will decline from 2065 to 2100. TCWV will continue to increase under SSP3-7.0 and SSP5-8.5 scenarios, and the largest increase is projected under SSP5-8.5 scenario. Change in near-surface temperature (Ts) matched the change in TCWV, but changes in precipitation and evapotranspiration are not significant during 2021–2100. In spite of the large variations in TCWV under different SSP-RCPs, the dominant characteristic in all scenarios shows that a large TCWV increase is demonstrated over areas with small TCWV amounts during the baseline period. On the contrary, increases will be small where the TCWV amounts had been large during the baseline period. The change in TCWV is highly correlated to the increase in Ts in Central Asia. Under SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0, and SSP5-8.5 scenarios, the higher the temperature due to higher radiative forcing, the steeper the regression slope between TCWV and Ts change. It is closest to the theoretical value of the Clausius-Clapeyron equation under SSP3-7.0 and SSP5-8.5 scenarios, but not presented under other scenarios. Spatially, steeper regression slopes during 2021–2100 have been found around the Caspian Sea in the southwest and in the high-elevation areas in the southeast of Central Asia, which is likely related to the abundant local water supply for evaporation.

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Why Do Global Climate Models Struggle to Represent Low-Level Clouds in the West African Summer Monsoon?

Journal of Climate ◽

10.1175/jcli-d-16-0451.1 ◽

2017 ◽

Vol 30 (5) ◽

pp. 1665-1687 ◽

Cited By ~ 29

Author(s):

Lisa Hannak ◽

Peter Knippertz ◽

Andreas H. Fink ◽

Anke Kniffka ◽

Gregor Pante

Keyword(s):

Climate Models ◽

Global Climate ◽

West African Monsoon ◽

High Elevation ◽

West African ◽

Global Climate Models ◽

The West ◽

Near Surface ◽

Low Level ◽

The Impact

Abstract Climate models struggle to realistically represent the West African monsoon (WAM), which hinders reliable future projections and the development of adequate adaption measures. Low-level clouds over southern West Africa (5°–10°N, 8°W–8°E) during July–September are an integral part of the WAM through their effect on the surface energy balance and precipitation, but their representation in climate models has received little attention. Here 30 (20) years of output from 18 (8) models participating in phase 5 of the Coupled Model Intercomparison Project (Year of Tropical Convection) are used to identify cloud biases and their causes. Compared to ERA-Interim reanalyses, many models show large biases in low-level cloudiness of both signs and a tendency to too high elevation and too weak diurnal cycles. At the same time, these models tend to have too strong low-level jets, the impact of which is unclear because of concomitant effects on temperature and moisture advection as well as turbulent mixing. Part of the differences between the models and ERA-Interim appear to be related to the different subgrid cloud schemes used. While nighttime tendencies in temperature and humidity are broadly realistic in most models, daytime tendencies show large problems with the vertical transport of heat and moisture. Many models simulate too low near-surface relative humidities, leading to insufficient low cloud cover and abundant solar radiation, and thus a too large diurnal cycle in temperature and relative humidity. In the future, targeted model sensitivity experiments will be needed to test possible feedback mechanisms between low clouds, radiation, boundary layer dynamics, precipitation, and the WAM circulation.

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Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations

Journal of Climate ◽

10.1175/jcli-d-19-0023.1 ◽

2019 ◽

Vol 32 (19) ◽

pp. 6467-6490 ◽

Cited By ~ 8

Author(s):

Kimmo Ruosteenoja ◽

Timo Vihma ◽

Ari Venäläinen

Keyword(s):

North Atlantic ◽

Climate Models ◽

Global Climate ◽

Arctic Sea Ice ◽

Global Climate Models ◽

Near Surface ◽

Wind Speeds ◽

The North ◽

Seasonal Wind ◽

Projected Changes

Abstract Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.

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Modeled Arctic sea ice evolution through 2300 in CMIP5 extended RCPs

The Cryosphere Discussions ◽

10.5194/tcd-8-1383-2014 ◽

2014 ◽

Vol 8 (1) ◽

pp. 1383-1406 ◽

Cited By ~ 1

Author(s):

P. J. Hezel ◽

T. Fichefet ◽

F. Massonnet

Keyword(s):

Sea Ice ◽

Radiative Forcing ◽

Climate Models ◽

Global Climate ◽

Arctic Sea Ice ◽

Global Climate Models ◽

The Arctic ◽

Sea Ice Extent ◽

Arctic Sea ◽

Arctic Sea Ice Extent

Abstract. Almost all global climate models and Earth system models that participated in the Coupled Model Intercomparison Project 5 (CMIP5) show strong declines in Arctic sea ice extent and volume under the highest forcing scenario of the Radiative Concentration Pathways (RCPs) through 2100, including a transition from perennial to seasonal ice cover. Extended RCP simulations through 2300 were completed for a~subset of models, and here we examine the time evolution of Arctic sea ice in these simulations. In RCP2.6, the summer Arctic sea ice extent increases compared to its minimum following the peak radiative forcing in 2044 in all 9 models. RCP4.5 demonstrates continued summer Arctic sea ice decline due to continued warming on longer time scales. These two scenarios imply that summer sea ice extent could begin to recover if and when radiative forcing from greenhouse gas concentrations were to decrease. In RCP8.5 the Arctic Ocean reaches annually ice-free conditions in 7 of 9 models. The ensemble of simulations completed under the extended RCPs provide insight into the global temperature increase at which sea ice disappears in the Arctic and reversibility of declines in seasonal sea ice extent.

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An Equatorial Ocean Bottleneck in Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-11-00059.1 ◽

2012 ◽

Vol 25 (1) ◽

pp. 343-349 ◽

Cited By ~ 19

Author(s):

Kristopher B. Karnauskas ◽

Gregory C. Johnson ◽

Raghu Murtugudde

Keyword(s):

Ocean Circulation ◽

Radiative Forcing ◽

Climate Models ◽

Global Climate ◽

Critical Role ◽

Tropical Pacific ◽

Global Climate Models ◽

Momentum Balance ◽

Equatorial Ocean ◽

The Tropical Pacific

Abstract The Equatorial Undercurrent (EUC) is a major component of the tropical Pacific Ocean circulation. EUC velocity in most global climate models is sluggish relative to observations. Insufficient ocean resolution slows the EUC in the eastern Pacific where nonlinear terms should dominate the zonal momentum balance. A slow EUC in the east creates a bottleneck for the EUC to the west. However, this bottleneck does not impair other major components of the tropical circulation, including upwelling and poleward transport. In most models, upwelling velocity and poleward transport divergence fall within directly estimated uncertainties. Both of these transports play a critical role in a theory for how the tropical Pacific may change under increased radiative forcing, that is, the ocean dynamical thermostat mechanism. These findings suggest that, in the mean, global climate models may not underrepresent the role of equatorial ocean circulation, nor perhaps bias the balance between competing mechanisms for how the tropical Pacific might change in the future. Implications for model improvement under higher resolution are also discussed.

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Evaluating Climate Model Simulations of the Radiative Forcing and Radiative Response at Earth’s Surface

Journal of Climate ◽

10.1175/jcli-d-18-0137.1 ◽

2019 ◽

Vol 32 (13) ◽

pp. 4089-4102 ◽

Cited By ~ 2

Author(s):

Ryan J. Kramer ◽

Brian J. Soden ◽

Angeline G. Pendergrass

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Climate Model ◽

Hydrological Cycle ◽

Global Climate ◽

Global Climate Models ◽

Lapse Rate ◽

Radiation Budget ◽

Model Simulations ◽

Climate Model Simulations

Abstract We analyze the radiative forcing and radiative response at Earth’s surface, where perturbations in the radiation budget regulate the atmospheric hydrological cycle. By applying a radiative kernel-regression technique to CMIP5 climate model simulations where CO2 is instantaneously quadrupled, we evaluate the intermodel spread in surface instantaneous radiative forcing, radiative adjustments to this forcing, and radiative responses to surface warming. The cloud radiative adjustment to CO2 forcing and the temperature-mediated cloud radiative response exhibit significant intermodel spread. In contrast to its counterpart at the top of the atmosphere, the temperature-mediated cloud radiative response at the surface is found to be positive in some models and negative in others. Also, the compensation between the temperature-mediated lapse rate and water vapor radiative responses found in top-of-atmosphere calculations is not present for surface radiative flux changes. Instantaneous radiative forcing at the surface is rarely reported for model simulations; as a result, intermodel differences have not previously been evaluated in global climate models. We demonstrate that the instantaneous radiative forcing is the largest contributor to intermodel spread in effective radiative forcing at the surface. We also find evidence of differences in radiative parameterizations in current models and argue that this is a significant, but largely overlooked, source of bias in climate change simulations.

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Projecting Rainfall Changes over the South American Altiplano

Journal of Climate ◽

10.1175/jcli-d-11-00051.1 ◽

2011 ◽

Vol 24 (17) ◽

pp. 4577-4583 ◽

Cited By ~ 53

Author(s):

Marie Minvielle ◽

René D. Garreaud

Keyword(s):

Climate Models ◽

Greenhouse Gas Emission ◽

Global Climate ◽

Strong Dependence ◽

Zonal Flow ◽

Central Andes ◽

High Elevation ◽

Global Climate Models ◽

South American ◽

Westerly Flow

Consistent with its high elevation (>4000 m) and subtropical location (15°–25°S), the central Andes are expected to become warmer during the twenty-first century, affecting the population, ecosystems, and glaciers on the so-called South American Altiplano. Future changes in regional precipitation (even its sign) have been more difficult to estimate, partly because of the low resolution of current global climate models (GCMs) relative to the cross-mountain scale of the Andes. Nevertheless, summer season rainfall over the Altiplano exhibits a strong dependence on the magnitude of the zonal flow in the free troposphere, as quantified in this work using station data. Since GCMs indicate a consistent increase in westerly flow over the central Andes, hindering moisture transport from the interior of the continent, a simple regression analysis suggests a significant reduction (10%–30%) in Altiplano precipitation by the end of this century under moderate-to-strong greenhouse gas emission scenarios.

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The Surface-Pressure Signature of Atmospheric Tides in Modern Climate Models

Journal of the Atmospheric Sciences ◽

10.1175/2010jas3560.1 ◽

2011 ◽

Vol 68 (3) ◽

pp. 495-514 ◽

Cited By ~ 11

Author(s):

Curt Covey ◽

Aiguo Dai ◽

Dan Marsh ◽

Richard S. Lindzen

Keyword(s):

Surface Pressure ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Global Climate Models ◽

Atmospheric Tides ◽

Intergovernmental Panel ◽

Near Surface ◽

Low Altitude ◽

Upper Boundary

Abstract Although atmospheric tides driven by solar heating are readily detectable at the earth’s surface as variations in air pressure, their simulations in current coupled global climate models have not been fully examined. This work examines near-surface-pressure tides in climate models that contributed to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC); it compares them with tides both from observations and from the Whole Atmosphere Community Climate Model (WACCM), which extends from the earth’s surface to the thermosphere. Surprising consistency is found among observations and all model simulations, despite variation of the altitudes of model upper boundaries from 32 to 76 km in the IPCC models and at 135 km for WACCM. These results are consistent with previous suggestions that placing a model’s upper boundary at low altitude leads to partly compensating errors—such as reducing the forcing of the tides by ozone heating, but also introducing spurious waves at the upper boundary, which propagate to the surface.

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General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-17941-2011 ◽

2011 ◽

Vol 11 (6) ◽

pp. 17941-18160 ◽

Cited By ~ 4

Author(s):

M. Kulmala ◽

A. Asmi ◽

H. K. Lappalainen ◽

U. Baltensperger ◽

J.-L. Brenguier ◽

...

Keyword(s):

Air Quality ◽

Radiative Forcing ◽

Climate Models ◽

Global Climate ◽

Global Scale ◽

Global Climate Models ◽

Modeling Tools ◽

Emissions Inventory ◽

Airborne Measurements ◽

Aerosol Cloud

Abstract. In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) the first comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. This work enabled EUCAARI to improve our understanding of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.

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Reducing uncertainties in satellite estimates of aerosol-cloud interactions over the subtropical ocean by integrating vertically resolved aerosol observations

10.5194/acp-2019-892 ◽

2019 ◽

Author(s):

David Painemal ◽

Fu-Lung Chang ◽

Richard Ferrare ◽

Sharon Burton ◽

Zhujun Li ◽

...

Keyword(s):

Climate Models ◽

Global Climate ◽

Cloud Condensation Nuclei ◽

Cloud Droplet ◽

Global Climate Models ◽

Orthogonal Polarization ◽

Near Surface ◽

Aerosol Cloud ◽

Error Characterization ◽

Aerosol Cloud Interactions

Abstract. Satellite quantification of aerosol effects on clouds relies on aerosol optical depth (AOD) as a proxy for aerosol concentration or cloud condensation nuclei (CCN). However, the lack of error characterization of satellite-based results hampers their use for the evaluation and improvement of global climate models. We show that the use of AOD for assessing aerosol-cloud interactions (ACI) is inadequate over vast oceanic areas in the subtropics. Instead, we postulate that a more physical approach that consists of matching vertically resolved aerosol data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite at the cloud-layer height with Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) cloud retrievals reduces uncertainties in satellite-based ACI estimates. Combined aerosol extinction coefficients (σ) below cloud-top (σBC) from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and cloud droplet number concentrations (Nd) from Aqua-MODIS yield high correlations across a broad range of σBC values, with σBC quartile correlations > 0.78. In contrast, CALIOP-based AOD yields correlations with MODIS Nd of less than 0.62 for the two lower AOD quartiles. Moreover, σBC explains 41 % of the spatial variance in MODIS Nd, whereas AOD only explains 17 %, primarily caused by the lack of spatial covariability in the eastern Pacific. Compared with σBC, near-surface σ weakly correlates in space with MODIS Nd, accounting for a 16 % variance. It is concluded that the linear regression calculated from ln(Nd)−ln(σBC) (the standard method for quantifying ACI) is more physically meaningful than that derived from the Nd−AOD pair.

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Response of shortwave cloud radiative effect to greenhouse gases and aerosols and its impact on daily maximum temperature

10.5194/acp-2019-1159 ◽

2020 ◽

Author(s):

Tao Tang ◽

Drew Shindell ◽

Yuqiang Zhang ◽

Apostolos Voulgarakis ◽

Jean-Francois Lamarque ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Global Climate ◽

Global Climate Models ◽

Maximum Temperature ◽

Boreal Summer ◽

Daily Maximum Temperature ◽

Daily Maximum ◽

Sulfate Aerosols ◽

Multilinear Regression

Abstract. Shortwave cloud radiative effects (SWCRE), defined as the difference of shortwave radiative flux between all-sky and clear-sky conditions, have been reported to play an important role in influencing the Earth’s energy budget and temperature extremes. In this study, we employed a set of global climate models to examine the SWCRE responses to CO2, black carbon (BC) aerosols and sulfate aerosols in boreal summer over the Northern Hemisphere. We found that CO2 causes positive SWCRE changes over most of the NH, and BC causes similar positive responses over North America, Europe and East China but negative SWCRE over India and tropical Africa. When normalized by effective radiative forcing, the SWCRE from BC is roughly 3–5 times larger than that from CO2. SWCRE change is mainly due to cloud cover changes resulting from the changes in relative humidity (RH) and, to a lesser extent, changes in circulation and stability. The SWCRE response to sulfate aerosols, however, is negligible compared to that for CO2 and BC. Using a multilinear regression model, it is found that mean daily maximum temperature (Tmax) increases by 0.15 K and 0.13 K per W m−2 increase in local SWCRE under the CO2 and BC experiment, respectively. When domain-averaged, the SWCRE change contribution to summer mean Tmax changes was 10–30 % under CO2 forcing and 30–50 % under BC forcing, varying by region, which can have important implications for extreme climatic events and socio-economic activities.

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