Vertical structure of cloud radiative heating in the tropics: confronting the EC-Earth v3.3.1/3P model with satellite observations

Abstract. Understanding the coupling of clouds to large-scale circulation is one of the grand challenges for the global climate research community. In this context, realistically modelling the vertical structure of cloud radiative heating (CRH) and/or cooling in Earth system models is a key premise to understand this coupling. Here, we evaluate CRH in two versions of the European Community Earth System Model (EC-Earth) using retrievals derived from the combined radar and lidar data from the CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. One model version is also used with two different horizontal resolutions. Our study evaluates large-scale intraseasonal variability in the vertical structure of CRH and cloud properties and investigates the changes in CRH during different phases of the El Niño–Southern Oscillation (ENSO), a process that dominates the interannual climate variability in the tropics. EC-Earth generally captures both the intraseasonal and meridional pattern of variability in CRH over the convectively active and stratocumulus regions and the CRH during the positive and negative phases of ENSO. However, two key differences between model simulations and satellite retrievals emerge. First, the magnitude of CRH, in the upper troposphere, over the convectively active zones is up to twice as large in the models compared to the satellite data. Further dissection of net CRH into its shortwave and longwave components reveals noticeable differences in their vertical structure. The shortwave component of the radiative heating is overestimated by all model versions in the lowermost troposphere and underestimated in the middle troposphere. These over- and underestimates of shortwave heating are partly compensated by an overestimate of longwave cooling in the lowermost troposphere and heating in the middle troposphere. The biases in CRH can be traced back to disagreement in cloud amount and cloud water content. There is no noticeable improvement of CRH by increasing the horizontal resolution in the model alone. Our findings highlight the importance of evaluating models with satellite observations that resolve the vertical structure of clouds and cloud properties.

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Vertical cloud radiative heating in the tropics: Confronting the EC-Earth model with satellite observations

10.5194/gmd-2020-277 ◽

2020 ◽

Author(s):

Erik Johansson ◽

Abhay Devasthale ◽

Michael Tjernström ◽

Annica M. L. Ekman ◽

Klaus Wyser ◽

...

Keyword(s):

Large Scale ◽

Vertical Structure ◽

Southern Oscillation ◽

Satellite Observations ◽

Radiative Heating ◽

Earth System ◽

Middle Troposphere ◽

Cloud Properties ◽

Cloud Water Content ◽

The Tropics

Abstract. Understanding the coupling of clouds to large-scale circulation is one of the grand challenges for the global climate research community. In this context, realistically modelling the vertical structure of cloud radiative heating/cooling (CRH) in Earth system models is a key premise to understand these couplings. Here, we evaluate CRH in two versions of the European Community Earth System Model (EC-Earth) using retrievals derived from the combined radar and lidar data from the CloudSat and CALIPSO satellites. One model version is also used with two different horizontal resolutions. Our study evaluates large-scale intraseasonal variability in the vertical structure of CRH and cloud properties and investigates the changes in CRH during different phases of the El Niño Southern Oscillation (ENSO), a process that dominates the interannual climate variability in the tropics. EC-Earth generally captures both the intraseasonal and meridional pattern of variability in CRH over the convectively active and stratocumulus regions and the CRH during the positive and negative phases of ENSO. However, two key differences between model simulations and satellite retrievals emerge. First, the magnitude of CRH over the convectively active zones is up to twice as large in the models compared to the satellite data. Further dissection of net CRH into its shortwave and longwave components reveals noticeable differences in their vertical structure. The shortwave component of the radiative heating is overestimated by all model versions in the lowermost troposphere and underestimated in the middle troposphere. These over- and underestimates of shortwave heating are partly compensated by an overestimate of longwave cooling in the lowermost troposphere and heating in the middle troposphere. The biases in CRH can be traced back to disagreements in cloud amount and cloud water content. There is no noticeable improvement of CRH by increasing the horizontal resolution in the model alone. Our findings highlight the importance of evaluating models with satellite observations that resolve the vertical structure of clouds and cloud properties.

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Molecular cloud formation by compression of magnetized turbulent gas subjected to radiative cooling

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa468 ◽

2020 ◽

Vol 493 (3) ◽

pp. 3098-3113 ◽

Cited By ~ 5

Author(s):

Ankush Mandal ◽

Christoph Federrath ◽

Bastian Körtgen

Keyword(s):

Molecular Cloud ◽

Large Scale ◽

Turnover Rate ◽

Radiative Heating ◽

Cloud Formation ◽

Neutral Medium ◽

Contraction Rate ◽

Mhd Turbulence ◽

Cloud Properties ◽

Hydrodynamical Simulations

ABSTRACT Complex turbulent motions of magnetized gas are ubiquitous in the interstellar medium (ISM). The source of this turbulence, however, is still poorly understood. Previous work suggests that compression caused by supernova shockwaves, gravity, or cloud collisions, may drive the turbulence to some extent. In this work, we present three-dimensional (3D) magnetohydrodynamic (MHD) simulations of contraction in turbulent, magnetized clouds from the warm neutral medium of the ISM to the formation of cold dense molecular clouds, including radiative heating and cooling. We study different contraction rates and find that observed molecular cloud properties, such as the temperature, density, Mach number, and magnetic field strength, and their respective scaling relations, are best reproduced when the contraction rate equals the turbulent turnover rate. In contrast, if the contraction rate is significantly larger (smaller) than the turnover rate, the compression drives too much (too little) turbulence, producing unrealistic cloud properties. We find that the density probability distribution function evolves from a double lognormal representing the two-phase ISM, to a skewed, single lognormal in the dense, cold phase. For purely hydrodynamical simulations, we find that the effective driving parameter of contracting cloud turbulence is natural to mildly compressive (b ∼ 0.4–0.5), while for MHD turbulence, we find b ∼ 0.3–0.4, i.e. solenoidal to naturally mixed. Overall, the physical properties of the simulated clouds that contract at a rate equal to the turbulent turnover rate, indicate that large-scale contraction may explain the origin and evolution of turbulence in the ISM.

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

10.5194/acp-2019-1187 ◽

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.

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Earth system feedbacks following large-scale tropical forest restoration

10.5194/bg-2020-432 ◽

2020 ◽

Author(s):

Alexander Koch ◽

Chris Brierley ◽

Simon L. Lewis

Keyword(s):

Land Use ◽

Forest Restoration ◽

Large Scale ◽

Paris Agreement ◽

Climate Feedback ◽

Substantial Contribution ◽

System Response ◽

Earth System ◽

Negative Emissions ◽

The Tropics

Abstract. To achieve the Paris Agreement requires aggressive mitigation strategies alongside negative emission technologies. Recent studies suggest that increasing tree cover can make a substantial contribution to negative emissions, with the tropics being the most suitable region from a biogeophysical perspective. Yet these studies typically do not account for subsequent carbon cycle and climate feedback processes of large-scale land use change. Here we quantify the maximum potential temperature and CO2 benefits from pantropical forest restoration, including earth system feedbacks, using a fully-coupled, emission-driven Earth System Model (HadGEM2-ES). We perform an idealised experiment where all land use in the tropics is stopped and vegetation is allowed to recover, on top of an aggressive mitigation scenario (RCP 2.6). We find that tropical restoration of 1529 Mha increases carbon stored in live biomass by 130 Pg C by 2100 CE. Whilst avoiding deforestation and tropical restoration in the tropics removes 42 Pg C compared to RCP 2.6, feedback processes mean that carbon in the atmosphere only reduces by 18 Pg C by 2100. The resulting, small CO2 (9 ppm) benefit does not translate to a detectable reduction in global surface air temperature compared to the control experiment. The greatest carbon benefit is achieved 30–50 years after restoration before the Earth System response adjusts to the new land-use regime and declining fossil fuel use. We identify three model-independent key points: (i) the carbon benefit of restoration is CO2-scenario dependent, (ii) in a world that follows Paris Agreement emission cuts restoration is best deployed immediately, and (iii) the ocean carbon feedbacks will reduce the efficacy of negative emissions technologies. We conclude that forest restoration can reduce peak CO2 mid-century, but can only be a modest contribution to negative emissions.

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Recent evolution of stratospheric aerosol load from ground-based lidars and satellites: impact of volcanic eruptions and wildfires.

10.5194/egusphere-egu2020-11246 ◽

2020 ◽

Author(s):

Sergey Khaykin ◽

Sophie Godin-Beekmann ◽

Ghassan Taha ◽

Artem Feofilov ◽

Adam Bourassa ◽

...

Keyword(s):

Large Scale ◽

Background Level ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Satellite Observations ◽

Eastern Australia ◽

Stratospheric Circulation ◽

The Tropics ◽

Global Mean

&#160; &#160; During the last 2 years (2018-2019) a series of volcanic eruptions led to remarkable enhancements in stratospheric aerosol load. These are eruptions of Ambae (July 2018, Vanuatu), Raikoke (June 2019, Russia) and Ulawun (July 2019, Papua New Guinea). In this study we examine the evolution of the stratospheric aerosol bulk optical properties following these events in consideration of large-scale stratospheric circulation. We use long-term aerosol records by ground-based lidars in both hemispheres together with global observations by various satellite missions (OMPS-LP, SAGE III, OSIRIS, CALIOP) and discuss the consistency between these datasets. &#160;In addition, we evaluate the preliminary lower stratosphere aerosol product by ESA Aeolus mission through intercomparison with ground-based lidars.&#160; &#160;The 28-yr Observatoire de Haute Provence (OHP) lidar record shows that Raikoke eruption has led to the strongest enhancement of stratospheric aerosol optical depth (SAOD) in the northern extratropics since Pinatubo eruption. Satellite observations suggest that the stratospheric plume of Raikoke has dispersed throughout the entire Northern hemisphere and ascended up to 27 km altitude. The eruption of Ulawun in the tropics has further boosted the stratospheric aerosol load and by Fall 2019, the global mean SAOD was a factor of 2.5 higher than its background level.&#160; &#160; At the turn of the year 2020, while both Raikoke and Ulawun aerosols were still present in the stratosphere, a dramatic bushfire event accompanied by vigorous fire-induced thunderstorms (PyroCb) in eastern Australia caused a massive injection of smoke into the stratosphere. The early detections of stratospheric smoke by OMPS-LP suggest that the zonal-mean SAOD perturbation caused by this event exceeds the previous record-breaking PyroCb-related perturbation after the British Columbia fires in August 2017. We use satellite observations of aerosol and trace gases (H2O, CO) to characterize the stratospheric impact of the wildfires and contrast it with that of volcanic eruptions.

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Stratospheric dryness: model simulations and satellite observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-1313-2007 ◽

2007 ◽

Vol 7 (5) ◽

pp. 1313-1332 ◽

Cited By ~ 92

Author(s):

J. Lelieveld ◽

C. Brühl ◽

P. Jöckel ◽

B. Steil ◽

P. J. Crutzen ◽

...

Keyword(s):

Water Vapor ◽

General Circulation ◽

Large Scale ◽

Middle Atmosphere ◽

Circulation Model ◽

Satellite Observations ◽

Radiative Heating ◽

Mixing Ratios ◽

Tropical Tropopause ◽

Mass Fluxes

Abstract. The mechanisms responsible for the extreme dryness of the stratosphere have been debated for decades. A key difficulty has been the lack of comprehensive models which are able to reproduce the observations. Here we examine results from the coupled lower-middle atmosphere chemistry general circulation model ECHAM5/MESSy1 together with satellite observations. Our model results match observed temperatures in the tropical lower stratosphere and realistically represent the seasonal and inter-annual variability of water vapor. The model reproduces the very low water vapor mixing ratios (below 2 ppmv) periodically observed at the tropical tropopause near 100 hPa, as well as the characteristic tape recorder signal up to about 10 hPa, providing evidence that the dehydration mechanism is well-captured. Our results confirm that the entry of tropospheric air into the tropical stratosphere is forced by large-scale wave dynamics, whereas radiative cooling regionally decelerates upwelling and can even cause downwelling. Thin cirrus forms in the cold air above cumulonimbus clouds, and the associated sedimentation of ice particles between 100 and 200 hPa reduces water mass fluxes by nearly two orders of magnitude compared to air mass fluxes. Transport into the stratosphere is supported by regional net radiative heating, to a large extent in the outer tropics. During summer very deep monsoon convection over Southeast Asia, centered over Tibet, moistens the stratosphere.

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Tropospheric ozone variability in the tropics from ENSO to MJO and shorter timescales

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-8037-2015 ◽

2015 ◽

Vol 15 (14) ◽

pp. 8037-8049 ◽

Cited By ~ 24

Author(s):

J. R. Ziemke ◽

A. R. Douglass ◽

L. D. Oman ◽

S. E. Strahan ◽

B. N. Duncan

Keyword(s):

Tropospheric Ozone ◽

Large Scale ◽

Climate Model ◽

Transport Model ◽

Southern Oscillation ◽

Longwave Radiation ◽

Chemical Transport Model ◽

Enso Variability ◽

Earth Observing System ◽

The Tropics

Abstract. Aura OMI and MLS measurements are combined to produce daily maps of tropospheric ozone beginning October 2004. We show that El Niño-Southern Oscillation (ENSO) related inter-annual change in tropospheric ozone in the tropics is small in relation to combined intra-seasonal/Madden–Julian Oscillation (MJO) and shorter timescale variability by a factor of ~ 3–10 (largest in the Atlantic). Outgoing longwave radiation (OLR), taken as a proxy for convection, suggests that convection is a dominant driver of large-scale variability of tropospheric ozone in the Pacific from inter-annual (e.g., ENSO) to weekly periods. We compare tropospheric ozone and OLR satellite observations with two simulations: (1) the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) that uses observed sea surface temperatures and is otherwise free-running, and (2) the NASA Global Modeling Initiative (GMI) chemical transport model (CTM) that is driven by Modern Era Retrospective-Analysis for Research and Applications (MERRA) analyses. It is shown that the CTM-simulated ozone accurately matches measurements for timescales from ENSO to intra-seasonal/MJO and even 1–2-week periods. The CCM simulation reproduces ENSO variability but not shorter timescales. These analyses suggest that a model used to delineate temporal and/or spatial properties of tropospheric ozone and convection in the tropics must reproduce both ENSO and non-ENSO variability.

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Tropospheric column ozone response to ENSO in GEOS-5 assimilation of OMI and MLS ozone data

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-7091-2016 ◽

2016 ◽

Vol 16 (11) ◽

pp. 7091-7103 ◽

Cited By ~ 13

Author(s):

Mark A. Olsen ◽

Krzysztof Wargan ◽

Steven Pawson

Keyword(s):

El Niño ◽

Large Scale ◽

El Nino ◽

Southern Oscillation ◽

Convective Transport ◽

Vertical Transport ◽

Small Scale ◽

Middle Latitudes ◽

Column Ozone ◽

The Tropics

Abstract. We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Niño Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Niño 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Niño 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9-year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Niño influence on tropospheric ozone in the middle latitudes.

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Physical Processes Controlling the Tide in the Tropical Lower Atmosphere Investigated Using a Comprehensive Numerical Model

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0080.1 ◽

2017 ◽

Vol 74 (8) ◽

pp. 2467-2487 ◽

Cited By ~ 6

Author(s):

T. Sakazaki ◽

K. Hamilton

Keyword(s):

Linear Theory ◽

Large Scale ◽

Regional Climate ◽

Atmospheric Model ◽

Solar Heating ◽

Radiative Heating ◽

Lower Atmosphere ◽

Limited Area ◽

Daily Variations ◽

The Tropics

Abstract The lower-atmospheric circulation in the tropics is strongly influenced by large-scale daily variations referred to as atmospheric solar tides. Most earlier studies have used simplified linear theory to explain daily variations in the tropics. The present study employs a comprehensive limited-area atmospheric model and revisits some longstanding issues related to atmospheric tidal dynamics. The tides in the tropical lower atmosphere are realistically simulated in the control experiment with a near-global (75°S–75°N) version of the model. Sensitivity experiments with different aspects of the solar heating suppressed showed that the semidiurnal (S2) tide near the surface can be attributed roughly equally to stratospheric and tropospheric direct solar heating and that the diurnal (S1) tide is excited almost entirely by tropospheric direct solar heating as well as solar heating of Earth’s surface. Linear theory with forcing only by direct radiative heating predicts the phase of the S2 barometric oscillation should be ~0910 LT versus the ~0945 LT phase seen in low-latitude observations. The roles of (i) convective and latent heating and (ii) mechanical dissipation, in determining the S2 phase, are assessed in the model. It is found that the former effect delays the phase by ~25 min and the latter by ~5 min; these two effects together explain the observed phase. When the model is run in limited-area domains comparable to those used in typical regional climate studies the S2, but not S1, tide is found to be significantly weaker than observed, even using atmospheric reanalysis data to drive the lateral boundaries.

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Combined biogeophysical and biogeochemical effects of large-scale forest cover changes in the MPI earth system model

Biogeosciences Discussions ◽

10.5194/bgd-7-387-2010 ◽

2010 ◽

Vol 7 (1) ◽

pp. 387-428 ◽

Cited By ~ 3

Author(s):

S. Bathiany ◽

M. Claussen ◽

V. Brovkin ◽

T. Raddatz ◽

V. Gayler

Keyword(s):

Land Surface ◽

Large Scale ◽

Forest Canopy ◽

Forest Cover ◽

Co2 Concentration ◽

Earth System Model ◽

System Model ◽

Climate Mitigation ◽

Earth System ◽

The Tropics

Abstract. Afforestation and reforestation have become popular instruments of climate mitigation policy, as forests are known to store large quantities of carbon. However, they also modify the fluxes of energy, water and momentum at the land surface. Previous studies have shown that these biogeophysical effects can counteract the carbon drawdown and, in boreal latitudes, even overcompensate it due to large albedo differences between forest canopy and snow. This study investigates the role forest cover plays for global climate by conducting deforestation and afforestation experiments with the earth system model of the Max Planck Institute for Meteorology (MPI-ESM). Complete deforestation of the tropics (18.75° S–15° N) exerts a global warming of 0.4 °C due to an increase in CO2 concentration by initially 60 ppm and a decrease in evapotranspiration in the deforested areas. In the northern latitudes (45° N–90° N), complete deforestation exerts a global cooling of 0.25 °C after 100 years, while afforestation leads to an equally large warming, despite the counteracting changes in CO2 concentration. Earlier model studies are qualitatively confirmed by these findings. As the response of temperature as well as terrestrial carbon pools is not of equal sign at every land cell, considering forests as cooling in the tropics and warming in high latitudes seems to be true only for the spatial mean, but not on a local scale.

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