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

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 (fifth-generation European Centre for Medium-range Weather Forecasts – ECMWF – reanalysis), ERA-Interim (ECMWF Interim Reanalysis), JRA-55 (Japanese 55-year Reanalysis), MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, Version 2), and CFSR/CFSv2 (Climate Forecast System Reanalysis/Climate Forecast System Version 2) reanalyses. 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, long-wave 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 long-wave radiation (OLR) close to those observed, but ERA5 tends to underestimate cloud effects, while MERRA-2 tends to overestimate variability. ERA5 also produces distributions of long-wave, short-wave, and total cloud radiative effects at the top of the atmosphere that are very consistent with those observed. The other reanalyses all exhibit substantial biases in at least one of these metrics, although compensation between the long-wave and short-wave effects helps to constrain biases in the total cloud radiative effect for most reanalyses. The vertical distribution of cloud water content emerges as a key difference between ERA-Interim and 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 radiative heating 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 profiles of temperature and specific humidity in convective regions are particularly noteworthy, as these variables are directly constrained by data assimilation, are widely used, and feed back to convective behaviour through their relationships with thermodynamic stability.

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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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Insights into the diurnal cycle of global Earth outgoing radiation using a numerical weather prediction model

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5129-2018 ◽

2018 ◽

Vol 18 (7) ◽

pp. 5129-5145 ◽

Cited By ~ 4

Author(s):

Jake J. Gristey ◽

J. Christine Chiu ◽

Robert J. Gurney ◽

Cyril J. Morcrette ◽

Peter G. Hill ◽

...

Keyword(s):

Water Content ◽

Land Surface ◽

Convective Cloud ◽

Short Wave ◽

Cloud Water ◽

Diurnal Variations ◽

Satellite Observations ◽

Outgoing Radiation ◽

Cloud Water Content ◽

Cloud Development

Abstract. A globally complete, high temporal resolution and multiple-variable approach is employed to analyse the diurnal cycle of Earth's outgoing energy flows. This is made possible via the use of Met Office model output for September 2010 that is assessed alongside regional satellite observations throughout. Principal component analysis applied to the long-wave component of modelled outgoing radiation reveals dominant diurnal patterns related to land surface heating and convective cloud development, respectively explaining 68.5 and 16.0 % of the variance at the global scale. The total variance explained by these first two patterns is markedly less than previous regional estimates from observations, and this analysis suggests that around half of the difference relates to the lack of global coverage in the observations. The first pattern is strongly and simultaneously coupled to the land surface temperature diurnal variations. The second pattern is strongly coupled to the cloud water content and height diurnal variations, but lags the cloud variations by several hours. We suggest that the mechanism controlling the delay is a moistening of the upper troposphere due to the evaporation of anvil cloud. The short-wave component of modelled outgoing radiation, analysed in terms of albedo, exhibits a very dominant pattern explaining 88.4 % of the variance that is related to the angle of incoming solar radiation, and a second pattern explaining 6.7 % of the variance that is related to compensating effects from convective cloud development and marine stratocumulus cloud dissipation. Similar patterns are found in regional satellite observations, but with slightly different timings due to known model biases. The first pattern is controlled by changes in surface and cloud albedo, and Rayleigh and aerosol scattering. The second pattern is strongly coupled to the diurnal variations in both cloud water content and height in convective regions but only cloud water content in marine stratocumulus regions, with substantially shorter lag times compared with the long-wave counterpart. This indicates that the short-wave radiation response to diurnal cloud development and dissipation is more rapid, which is found to be robust in the regional satellite observations. These global, diurnal radiation patterns and their coupling with other geophysical variables demonstrate the process-level understanding that can be gained using this approach and highlight a need for global, diurnal observing systems for Earth outgoing radiation in the future.

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Fluorescing aerosols and clouds: investigations of co-existence

EPJ Web of Conferences ◽

10.1051/epjconf/201817605010 ◽

2018 ◽

Vol 176 ◽

pp. 05010

Author(s):

Jens Reichardt ◽

Ronny Leinweber ◽

Anne Schwebe

Keyword(s):

Optical Properties ◽

Water Content ◽

Atmospheric Aerosols ◽

Fluorescence Spectra ◽

Cloud Water ◽

The Other ◽

Cloud Water Content ◽

Meteorological Observatory ◽

First Time

RAMSES of the Lindenberg Meteorological Observatory, Germany, is the first multipurpose lidar to routinely measure the fluorescence spectra of atmospheric aerosols. Combined with the other measurement parameters (cloud water content and optical properties, moisture and temperature), this capability allows one to study the co-existence of clouds and fluorescing aerosols for the first time. The fluorescence receiver is briefly described, and measurement examples are presented and discussed.

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Monte Carlo-based subgrid parameterization of vertical velocity and stratiform cloud microphysics in ECHAM5.5-HAM2

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7551-2013 ◽

2013 ◽

Vol 13 (15) ◽

pp. 7551-7565 ◽

Cited By ~ 9

Author(s):

J. Tonttila ◽

P. Räisänen ◽

H. Järvinen

Keyword(s):

Monte Carlo ◽

Water Content ◽

Vertical Velocity ◽

Cloud Microphysics ◽

Cloud Water ◽

Radiative Effects ◽

Reference Simulation ◽

Cloud Water Content ◽

Cloud Radiative Effects ◽

The Impact

Abstract. A new method for parameterizing the subgrid variations of vertical velocity and cloud droplet number concentration (CDNC) is presented for general circulation models (GCMs). These parameterizations build on top of existing parameterizations that create stochastic subgrid cloud columns inside the GCM grid cells, which can be employed by the Monte Carlo independent column approximation approach for radiative transfer. The new model version adds a description for vertical velocity in individual subgrid columns, which can be used to compute cloud activation and the subgrid distribution of the number of cloud droplets explicitly. Autoconversion is also treated explicitly in the subcolumn space. This provides a consistent way of simulating the cloud radiative effects with two-moment cloud microphysical properties defined at subgrid scale. The primary impact of the new parameterizations is to decrease the CDNC over polluted continents, while over the oceans the impact is smaller. Moreover, the lower CDNC induces a stronger autoconversion of cloud water to rain. The strongest reduction in CDNC and cloud water content over the continental areas promotes weaker shortwave cloud radiative effects (SW CREs) even after retuning the model. However, compared to the reference simulation, a slightly stronger SW CRE is seen e.g. over mid-latitude oceans, where CDNC remains similar to the reference simulation, and the in-cloud liquid water content is slightly increased after retuning the model.

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PROFILING OF CLOUD WATER CONTENT BY ACTIVE-PASSIVE SENSING

Telecommunications and Radio Engineering ◽

10.1615/telecomradeng.v73.i13.20 ◽

2014 ◽

Vol 73 (13) ◽

pp. 1141-1152

Author(s):

Ye. N. Belov ◽

B. A. Kabanov ◽

Stanislav I. Khomenko ◽

G. I. Khlopov ◽

A. M. Linkova ◽

...

Keyword(s):

Water Content ◽

Cloud Water ◽

Passive Sensing ◽

Cloud Water Content

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RETRIEVING CLOUD WATER CONTENT OVER LAND USING SATELLITE-BASED PASSIVE MICROWAVE OBSERVATIONS

Journal of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering) ◽

10.2208/jscejhe.74.5_i_1219 ◽

2018 ◽

Vol 74 (5) ◽

pp. I_1219-I_1224

Author(s):

Rie SETO ◽

Toshio KOIKE ◽

Shinjiro KANAE

Keyword(s):

Water Content ◽

Cloud Water ◽

Passive Microwave ◽

Cloud Water Content ◽

Land Using

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Understanding the Extratropical Liquid Water Path Feedback in Mixed-Phase Clouds with an Idealized Global Climate Model

Journal of Climate ◽

10.1175/jcli-d-21-0334.1 ◽

2022 ◽

pp. 1-48

Author(s):

Yi Ming

Keyword(s):

Water Content ◽

Liquid Water ◽

Climate Model ◽

Global Climate Model ◽

Cloud Water ◽

Mixed Phase ◽

Liquid Water Path ◽

Water Path ◽

Cloud Water Content ◽

Mixed Phase Clouds

Abstract A negative shortwave cloud feedback associated with higher extratropical liquid water content in mixed-phase clouds is a common feature of global warming simulations, and multiple mechanisms have been hypothesized. A set of process-level experiments performed with an idealized global climate model (a dynamical core with passive water and cloud tracers and full Rotstayn-Klein single-moment microphysics) show that the common picture of the liquid water path (LWP) feedback in mixed-phase clouds being controlled by the amount of ice susceptible to phase change is not robust. Dynamic condensate processes—rather than static phase partitioning—directly change with warming, with varied impacts on liquid and ice amounts. Here, three principal mechanisms are responsible for the LWP response, namely higher adiabatic cloud water content, weaker liquid-to-ice conversion through the Bergeron-Findeisen process, and faster melting of ice and snow to rain. Only melting is accompanied by a substantial loss of ice, while the adiabatic cloud water content increase gives rise to a net increase in ice water path (IWP) such that total cloud water also increases without an accompanying decrease in precipitation efficiency. Perturbed parameter experiments with a wide range of climatological LWP and IWP demonstrate a strong dependence of the LWP feedback on the climatological LWP and independence from the climatological IWP and supercooled liquid fraction. This idealized setup allows for a clean isolation of mechanisms and paints a more nuanced picture of the extratropical mixed-phase cloud water feedback than simple phase change.

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