scholarly journals Evaluation of Hemispheric Asymmetries in Marine Cloud Radiative Properties

2017 ◽  
Vol 30 (11) ◽  
pp. 4131-4147 ◽  
Author(s):  
Frida A.-M. Bender ◽  
Anders Engström ◽  
Robert Wood ◽  
Robert J. Charlson
Keyword(s):  
Hemispheric Asymmetry ◽  
Climate Models ◽  
Global Climate ◽  
Cloud Amount ◽  
Cloud Fraction ◽  
Global Climate Models ◽  
Radiative Properties ◽  
Contributing Factors ◽  
Cloud Albedo ◽  
Clear Sky

Abstract The hemispheric symmetry of albedo and its contributing factors in satellite observations and global climate models is evaluated. The analysis is performed on the annual mean time scale, on which a bimodality in the joint distribution of albedo and cloud fraction is evident, resulting from tropical and subtropical clouds and midlatitude clouds, respectively. Hemispheric albedo symmetry is not found in individual ocean-only latitude bands; comparing the Northern and Southern Hemisphere (NH and SH), regional mean albedo is higher in the NH tropics and lower in the NH subtropics and midlatitudes than in the SH counterparts. This follows the hemispheric asymmetry of cloud fraction. In midlatitudes and tropics the hemispheric asymmetry in cloud albedo also contributes to the asymmetry in total albedo, whereas in the subtropics the cloud albedo is more hemispherically symmetric. According to the observations, cloud contributions to compensation for higher clear-sky albedo in the NH come primarily from cloud albedo in midlatitudes and cloud amount in the subtropics. Current-generation climate models diverge in their representation of these relationships, but common features of the model–data comparison include weaker-than-observed asymmetry in cloud fraction and cloud albedo in the tropics, weaker or reversed cloud fraction asymmetry in the subtropics, and agreement with observed cloud albedo asymmetry in the midlatitudes. Models on average reproduce the NH–SH asymmetry in total albedo over the 60°S–60°N ocean but show higher occurrence of brighter clouds in the SH compared to observations. The albedo bias in both hemispheres is reinforced by overestimated clear-sky albedo in the models.

scholarly journals Improved Representation of Marine Stratocumulus Cloud Shortwave Radiative Properties in the CMIP5 Climate Models

2014 ◽  
Vol 27 (16) ◽  
pp. 6175-6188 ◽  
Author(s):  
Anders Engström ◽  
Frida A.-M. Bender ◽  
Johannes Karlsson
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Cloud Fraction ◽  
Global Climate Models ◽  
Satellite Observations ◽  
Radiative Properties ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Marine Stratocumulus ◽  
Cloud Albedo

Abstract The radiative properties of subtropical marine stratocumulus clouds are investigated in an ensemble of current-generation global climate models from phase 5 of the Climate Model Intercomparison Project (CMIP5). Using a previously documented method for determining regional mean cloud albedo, the authors find a closer agreement with observations in the CMIP5 models as compared to the previous generation of models (phase 3 of CMIP). The multimodel average indicates regional mean, monthly mean cloud albedos ranging from 0.32 to 0.5 among 26 models and five regions, to be compared with satellite observations that indicate a range from 0.32 to 0.39 for the same five regions. The intermodel spread in cloud fraction gives rise to a spread in albedo. Within models, there is a tendency for large cloud fraction to be related to low cloud albedo and vice versa, a relationship that dampens the intermodel variability in total albedo. The intramodel variability in albedo, for a given cloud fraction, is found to be up to twice as large in magnitude in models as in satellite observations. The reason for this larger variability in models is not settled, but possible contributing factors may be imperfect representation in the models of cloud type distribution or of sensitivity to meteorological variability or aerosols. Changes in aerosol loading are found to be the likely cause of an increase in cloud albedo over time. The radiative effect of such a scene brightening in marine stratocumulus cloud regions, from preindustrial times to present day, is estimated to be up to −1 W m−2 for the global ocean, but there are no observations to verify this number.

Assessment of Arctic Cloud Cover Anomalies in Atmospheric Reanalysis Products Using Satellite Data

2016 ◽  
Vol 29 (17) ◽  
pp. 6065-6083 ◽  
Author(s):  
Yinghui Liu ◽  
Jeffrey R. Key
Keyword(s):  
Cloud Cover ◽  
Climate Models ◽  
Global Climate ◽  
Correlation Coefficients ◽  
Cloud Amount ◽  
Satellite Observation ◽  
Skill Score ◽  
Global Climate Models ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Cloud cover is one of the largest uncertainties in model predictions of the future Arctic climate. Previous studies have shown that cloud amounts in global climate models and atmospheric reanalyses vary widely and may have large biases. However, many climate studies are based on anomalies rather than absolute values, for which biases are less important. This study examines the performance of five atmospheric reanalysis products—ERA-Interim, MERRA, MERRA-2, NCEP R1, and NCEP R2—in depicting monthly mean Arctic cloud amount anomalies against Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations from 2000 to 2014 and against Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations from 2006 to 2014. All five reanalysis products exhibit biases in the mean cloud amount, especially in winter. The Gerrity skill score (GSS) and correlation analysis are used to quantify their performance in terms of interannual variations. Results show that ERA-Interim, MERRA, MERRA-2, and NCEP R2 perform similarly, with annual mean GSSs of 0.36/0.22, 0.31/0.24, 0.32/0.23, and 0.32/0.23 and annual mean correlation coefficients of 0.50/0.51, 0.43/0.54, 0.44/0.53, and 0.50/0.52 against MODIS/CALIPSO, indicating that the reanalysis datasets do exhibit some capability for depicting the monthly mean cloud amount anomalies. There are no significant differences in the overall performance of reanalysis products. They all perform best in July, August, and September and worst in November, December, and January. All reanalysis datasets have better performance over land than over ocean. This study identifies the magnitudes of errors in Arctic mean cloud amounts and anomalies and provides a useful tool for evaluating future improvements in the cloud schemes of reanalysis products.

scholarly journals The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific

2010 ◽  
Vol 10 (10) ◽  
pp. 4757-4774 ◽  
Author(s):  
M. C. Wyant ◽  
R. Wood ◽  
C. S. Bretherton ◽  
C. R. Mechoso ◽  
J. Bacmeister ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Climate Models ◽  
Global Climate ◽  
Cloud Fraction ◽  
Atmospheric Modeling ◽  
Global Climate Models ◽  
Model Assessment ◽  
Regional Models ◽  
Study Region ◽  
Forecast Models

Abstract. The Preliminary VOCALS Model Assessment (PreVOCA) aims to assess contemporary atmospheric modeling of the subtropical South East Pacific, with a particular focus on the clouds and the marine boundary layer (MBL). Models results from fourteen modeling centers were collected including operational forecast models, regional models, and global climate models for the month of October 2006. Forecast models and global climate models produced daily forecasts, while most regional models were run continuously during the study period, initialized and forced at the boundaries with global model analyses. Results are compared in the region from 40° S to the equator and from 110° W to 70° W, corresponding to the Pacific coast of South America. Mean-monthly model surface winds agree well with QuikSCAT observed winds and models agree fairly well on mean weak large-scale subsidence in the region next to the coast. However they have greatly differing geographic patterns of mean cloud fraction with only a few models agreeing well with MODIS observations. Most models also underestimate the MBL depth by several hundred meters in the eastern part of the study region. The diurnal cycle of liquid water path is underestimated by most models at the 85° W 20° S stratus buoy site compared with satellite, consistent with previous modeling studies. The low cloud fraction is also underestimated during all parts of the diurnal cycle compared to surface-based climatologies. Most models qualitatively capture the MBL deepening around 15 October 2006 at the stratus buoy, associated with colder air at 700 hPa.

Simulations of 20th and 21st century Arctic cloud amount in the global climate models assessed in the IPCC AR4

2008 ◽  
Vol 33 (7-8) ◽  
pp. 1099-1115 ◽  
Author(s):  
Steve Vavrus ◽  
Duane Waliser ◽  
Axel Schweiger ◽  
Jennifer Francis
Keyword(s):  
21St Century ◽  
Climate Models ◽  
Global Climate ◽  
Cloud Amount ◽  
Global Climate Models ◽  
Ipcc Ar4

scholarly journals Can a coupled meteorology–chemistry model reproduce the historical trend in aerosol direct radiative effects over the Northern Hemisphere?

2015 ◽  
Vol 15 (17) ◽  
pp. 9997-10018 ◽  
Author(s):  
J. Xing ◽  
R. Mathur ◽  
J. Pleim ◽  
C. Hogrefe ◽  
C.-M. Gan ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Global Climate ◽  
Eastern China ◽  
Global Climate Models ◽  
Shortwave Radiation ◽  
Historical Trend ◽  
Clear Sky ◽  
Northern Pacific ◽  
Central Atlantic

Abstract. The ability of a coupled meteorology–chemistry model, i.e., Weather Research and Forecast and Community Multiscale Air Quality (WRF-CMAQ), to reproduce the historical trend in aerosol optical depth (AOD) and clear-sky shortwave radiation (SWR) over the Northern Hemisphere has been evaluated through a comparison of 21-year simulated results with observation-derived records from 1990 to 2010. Six satellite-retrieved AOD products including AVHRR, TOMS, SeaWiFS, MISR, MODIS-Terra and MODIS-Aqua as well as long-term historical records from 11 AERONET sites were used for the comparison of AOD trends. Clear-sky SWR products derived by CERES at both the top of atmosphere (TOA) and surface as well as surface SWR data derived from seven SURFRAD sites were used for the comparison of trends in SWR. The model successfully captured increasing AOD trends along with the corresponding increased TOA SWR (upwelling) and decreased surface SWR (downwelling) in both eastern China and the northern Pacific. The model also captured declining AOD trends along with the corresponding decreased TOA SWR (upwelling) and increased surface SWR (downwelling) in the eastern US, Europe and the northern Atlantic for the period of 2000–2010. However, the model underestimated the AOD over regions with substantial natural dust aerosol contributions, such as the Sahara Desert, Arabian Desert, central Atlantic and northern Indian Ocean. Estimates of the aerosol direct radiative effect (DRE) at TOA are comparable with those derived by measurements. Compared to global climate models (GCMs), the model exhibits better estimates of surface-aerosol direct radiative efficiency (Eτ). However, surface-DRE tends to be underestimated due to the underestimated AOD in land and dust regions. Further investigation of TOA-Eτ estimations as well as the dust module used for estimates of windblown-dust emissions is needed.

Internal variability and unforced trends of all-sky and clear-sky SSR: quantitative estimates using CMIP6

2021 ◽  
Author(s):  
Boriana Chtirkova ◽  
Doris Folini ◽  
Lucas Ferreira Correa ◽  
Martin Wild
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Grid Cell ◽  
Internal Variability ◽  
Global Climate Models ◽  
Geographical Region ◽  
Positive Trend ◽  
Surface Solar Radiation ◽  
Anthropogenic Effect ◽  
Clear Sky

<p>Quantifying trends in surface solar radiation (SSR) of unforced simulations is of substantial importance when one tries to quantify the anthropogenic effect in forced trends, as the net effect may be dampened or amplified by the internal variability of the system. In our analysis, we consider trends on different temporal scales (10, 30, 50 and 100 years) from 58 global climate models, participating in the Coupled Model Intercomparison Project - Phase 6 (CMIP6). We calculate the trends at the grid-box level for all-sky and clear-sky SSR using annual mean data of the multi-century pre-industrial control (piControl) experiments. The trends from both variables are found to depend strongly on the geographical region, as the most pronounced trends of the all-sky variable are observed in the Tropical Pacific, while the largest clear-sky trends are found in the large desert regions. Inspecting for each grid cell the statistical distribution of occurring N-year trends  shows that they are normally distributed in the majority of grid cells for both all-sky and clear-sky SSR. The 75-th percentile taken from these distributions (i.e. a positive trend with a 25 % chance of occurrence) varies with geographical region, taking values in the ranges 0.79 - 12.03 Wm<sup>-2</sup>/decade for 10-year trends, 0.15 - 2.05 Wm<sup>-2</sup>/decade for 30-year trends, 0.07 - 0.92 Wm<sup>-2</sup>/decade for 50-year trends and 0.02 - 0.29 Wm<sup>-2</sup>/decade for 100-year trends for all-sky SSR. The unforced trends become less significant on longer timescales – the trend medians, corresponding to the above ranges, are 3.18 Wm<sup>-2</sup>/decade, 0.62 Wm<sup>-2</sup>/decade, 0.29 Wm<sup>-2</sup>/decade, 0.10 Wm<sup>-2</sup>/decade respectively. The trends for clear-sky SSR are found to differ from the all-sky SSR by a factor of 0.16 on average, independent of the trend length. The model spread becomes greater at longer trend timescales, the differences being more substantial between large model families rather than between individual models. To elucidate the dominant causes of variability in different regions, we examine the correlations of the SSR variables with ambient aerosol optical thickness at 550 nm, atmosphere mass content of water vapour, cloud area fraction and albedo.</p>

scholarly journals Understanding the Varied Influence of Midlatitude Jet Position on Clouds and Cloud Radiative Effects in Observations and Global Climate Models

2016 ◽  
Vol 29 (24) ◽  
pp. 9005-9025 ◽  
Author(s):  
Kevin M. Grise ◽  
Brian Medeiros
Keyword(s):  
Vertical Velocity ◽  
Climate Models ◽  
Global Climate ◽  
Storm Track ◽  
Cloud Amount ◽  
Global Climate Models ◽  
Radiative Effects ◽  
Velocity Anomalies ◽  
Cooling Effects ◽  
Cloud Radiative Effects

Abstract This study examines the dynamical mechanisms responsible for changes in midlatitude clouds and cloud radiative effects (CRE) that occur in conjunction with meridional shifts in the jet streams over the North Atlantic, North Pacific, and Southern Oceans. When the midlatitude jet shifts poleward, extratropical cyclones and their associated upward vertical velocity anomalies closely follow. As a result, a poleward jet shift contributes to a poleward shift in high-topped storm-track clouds and their associated longwave CRE. However, when the jet shifts poleward, downward vertical velocity anomalies increase equatorward of the jet, contributing to an enhancement of the boundary layer estimated inversion strength (EIS) and an increase in low cloud amount there. Because shortwave CRE depends on the reflection of solar radiation by clouds in all layers, the shortwave cooling effects of midlatitude clouds increase with both upward vertical velocity anomalies and positive EIS anomalies. Over midlatitude oceans where a poleward jet shift contributes to positive EIS anomalies but downward vertical velocity anomalies, the two effects cancel, and net observed changes in shortwave CRE are small. Global climate models generally capture the observed anomalies associated with midlatitude jet shifts. However, there is large intermodel spread in the shortwave CRE anomalies, with a subset of models showing a large shortwave cloud radiative warming over midlatitude oceans with a poleward jet shift. In these models, midlatitude shortwave CRE is sensitive to vertical velocity perturbations, but the observed sensitivity to EIS perturbations is underestimated. Consequently, these models might incorrectly estimate future midlatitude cloud feedbacks in regions where appreciable changes in both vertical velocity and EIS are projected.

scholarly journals Global indirect aerosol effects: a review

2005 ◽  
Vol 5 (3) ◽  
pp. 715-737 ◽  
Author(s):  
U. Lohmann ◽  
J. Feichter
Keyword(s):  
Climate Models ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Global Climate Models ◽  
Cloud Albedo ◽  
Aerosol Forcing ◽  
Ice Nuclei ◽  
Cloud Characteristics ◽  
Climate Simulations ◽  
Aerosol Effects

Abstract. Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei, they may inhibit freezing and they could have an influence on the hydrological cycle. While the cloud albedo enhancement (Twomey effect) of warm clouds received most attention so far and traditionally is the only indirect aerosol forcing considered in transient climate simulations, here we discuss the multitude of effects. Different approaches how the climatic implications of these aerosol effects can be estimated globally as well as improvements that are needed in global climate models in order to better represent indirect aerosol effects are discussed in this paper.

scholarly journals Quantification of Monthly Mean Regional-Scale Albedo of Marine Stratiform Clouds in Satellite Observations and GCMs

2011 ◽  
Vol 50 (10) ◽  
pp. 2139-2148 ◽  
Author(s):  
Frida A.-M. Bender ◽  
Robert J. Charlson ◽  
Annica M. L. Ekman ◽  
Louise V. Leahy
Keyword(s):  
Climate Models ◽  
System Modeling ◽  
Regional Scale ◽  
Radiant Energy ◽  
Energy System ◽  
Cloud Fraction ◽  
Satellite Observations ◽  
Radiative Properties ◽  
Cloud Albedo ◽  
Stratiform Clouds

AbstractPlanetary albedo—the reflectivity for solar radiation—is of singular importance in determining the amount of solar energy taken in by the Earth–atmosphere system. Modeling albedo, and specifically cloud albedo, correctly is crucial for realistic climate simulations. A method is presented herein by which regional cloud albedo can be quantified from the relation between total albedo and cloud fraction, which in observations is found to be approximately linear on a monthly mean scale. This analysis is based primarily on the combination of cloud fraction data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and albedo data from the Clouds and the Earth’s Radiant Energy System (CERES), but the results presented are also supported by the combination of cloud fraction and proxy albedo data from satelliteborne lidar [Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)]. These data are measured and derived completely independently from the CERES–MODIS data. Applied to low-level marine stratiform clouds in three regions (off the coasts of South America, Africa, and North America), the analysis reveals regionally uniform monthly mean cloud albedos, indicating that the variation in cloud shortwave radiative properties is small on this scale. A coherent picture of low “effective” cloud albedo emerges, in the range from 0.35 to 0.42, on the basis of data from CERES and MODIS. In its simplicity, the method presented appears to be useful as a diagnostic tool and as a constraint on climate models. To demonstrate this, the same method is applied to cloud fraction and albedo output from several current-generation climate models [from the Coupled Model Intercomparison Project, phase 3 (CMIP3), archive]. Although the multimodel mean cloud albedo estimates agree to within 20% with the satellite-based estimates for the three focus regions, model-based estimates of cloud albedo are found to display much larger variability than do the observations, within individual models as well as between models.

Uncertainty in Forced and Natural Arctic Solar Absorption Variations in CMIP6 Models

2021 ◽  
Vol 34 (3) ◽  
pp. 931-948
Author(s):  
Anne Sledd ◽  
Tristan L’Ecuyer
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Global Climate ◽  
Coupled Model ◽  
Internal Variability ◽  
Global Climate Models ◽  
Shortwave Radiation ◽  
The Arctic ◽  
Solar Absorption ◽  
Clear Sky

AbstractThe Arctic is rapidly changing, with increasingly dramatic sea ice loss and surface warming in recent decades. Shortwave radiation plays a key role in Arctic warming during summer months, and absorbed shortwave radiation has been increasing largely because of greater sea ice loss. Clouds can influence this ice–albedo feedback by modulating the amount of shortwave radiation incident on the Arctic Ocean. In turn, clouds impact the amount of time that must elapse before forced trends in Arctic shortwave absorption emerge from internal variability. This study determines whether the forced climate response of absorbed shortwave radiation in the Arctic has emerged in the modern satellite record and global climate models. From 18 years of satellite observations from CERES-EBAF, we find that recent declines in sea ice are large enough to produce a statistically significant trend (1.7 × 106 PJ or 3.9% per decade) in observed clear-sky absorbed shortwave radiation. However, clouds preclude any forced trends in all-sky absorption from emerging within the existing satellite record. Across 18 models from phase 6 of the Coupled Model Intercomparison Project (CMIP6), the predicted time to emergence of absorbed shortwave radiation trends varies from 8 to 39 and from 8 to 35 years for all-sky and clear-sky conditions, respectively, across two future scenarios. Furthermore, most models fail to reproduce the observed cloud delaying effect because of differences in internal variability. Contrary to observations, one-third of models suggest that clouds may reduce the time to emergence of absorbed shortwave trends relative to clear skies, an artifact that may be the result of inaccurate representations of cloud feedbacks.

Sign in / Sign up

Export Citation Format

Share Document