Toward a Consistent Definition between Satellite and Model Clear-Sky Radiative Fluxes

AbstractA new method of determining clear-sky radiative fluxes from satellite observations for climate model evaluation is presented. The method consists of applying adjustment factors to existing satellite clear-sky broadband radiative fluxes that make the observed and simulated clear-sky flux definitions more consistent. The adjustment factors are determined from the difference between observation-based radiative transfer model calculations of monthly mean clear-sky fluxes obtained by ignoring clouds in the atmospheric column and by weighting hourly mean clear-sky fluxes with imager-based clear-area fractions. The global mean longwave (LW) adjustment factor is −2.2 W m−2 at the top of the atmosphere and 2.7 W m−2 at the surface. The LW adjustment factors are pronounced at high latitudes during winter and in regions with high upper-tropospheric humidity and cirrus cloud cover, such as over the west tropical Pacific, and the South Pacific and intertropical convergence zones. In the shortwave (SW), global mean adjustment is 0.5 W m−2 at TOA and −1.9 W m−2 at the surface. It is most pronounced over sea ice off of Antarctica and over heavy aerosol regions, such as eastern China. However, interannual variations in the regional SW and LW adjustment factors are small compared to those in cloud radiative effect. After applying the LW adjustment factors, differences in zonal mean cloud radiative effect between observations and climate models decrease markedly between 60°S and 60°N and poleward of 65°N. The largest regional improvements occur over the west tropical Pacific and Indian Oceans. In contrast, the impact of the SW adjustment factors is much smaller.

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The Surface Longwave Cloud Radiative Effect from Space Lidar Observations

10.5194/egusphere-egu21-2064 ◽

2021 ◽

Author(s):

Assia Arouf

Keyword(s):

Cloud Cover ◽

Temporal Variations ◽

Radiative Effect ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

Long Time ◽

The One ◽

Natural Climate ◽

The Impact ◽

Lidar Observations

Clouds exert important effects on Earth's surface energy balance through their effects on longwave (LW) and shortwave (SW) radiation. Indeed, clouds radiatively warm the surface in the LW domain by emitting LW radiation back to the ground. The surface LW cloud radiative effect (CRE) quantifies this warming effect. To study the impact of clouds on the interanual natural climate variability, we need to observe them on a long time scale over all kinds of surfaces. The CALIPSO space lidar provides these observations by sampling the atmosphere along its track over all kinds of surfaces for over than 14 years (2006-2020).In this work, we propose new estimates of the surface LW CRE from space-based lidar observations only. Indeed, we show from 1D atmospheric column radiative transfer calculations, that surface LW CRE at sea level linearly decreases with the cloud altitude. Thus, these computations allow to establish simple relationships between the surface LW CRE, and five cloud properties observed by the CALIPSO space lidar: the opaque cloud cover and altitude, the thin cloud cover, altitude, and emissivity. Over the 2008&#8211;2011, CALIPSO-based retrieval (27.7 W m-2) is 1.2 W m-2 larger than the one derived from combined space radar, lidar, and radiometer observations. Over the 2008&#8211;2018 period, the global mean CALIPSO-based retrieval (27.5 W m-2) is 0.1 W m-2 larger than the one derived from CERES space radiometer. Our estimates show that globally, opaque clouds warm the surface by 23.3 W m-2 and thin clouds contribute only by 4.2 W m-2. At high latitudes North and South over oceans, the largest surface LW opaque CRE occurs in fall (40.4 W m-2, 31.6 W m-2) due to the formation of additional opaque low clouds after sea ice melting over a warmer ocean.To quantify the cloud property that drives the temporal variations of the surface LW CRE, the surface LW CRE needs to be related by simple relationships to a finite number of cloud properties such as cloud opacity, cloud altitude and cloud cover. This study allows a decomposition and attribution approach of the surface LW CRE variations and shows that they are driven by the variations occurring in the opaque cloud properties. Moreover, opaque cloud cover drives over than 73% of global surface LW CRE interannual variations.

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Top-of-Atmosphere Direct Radiative Effect of Aerosols over Global Oceans from Merged CERES and MODIS Observations

Journal of Climate ◽

10.1175/jcli3504.1 ◽

2005 ◽

Vol 18 (17) ◽

pp. 3506-3526 ◽

Cited By ~ 139

Author(s):

Norman G. Loeb ◽

Natividad Manalo-Smith

Keyword(s):

Information Service ◽

Radiant Energy ◽

Energy System ◽

Surface Fluxes ◽

Radiative Effect ◽

Distribution Models ◽

Radiative Fluxes ◽

Clear Sky ◽

Moderate Resolution Imaging Spectroradiometer ◽

Global Oceans

Abstract The direct radiative effect of aerosols (DREA) is defined as the difference between radiative fluxes in the absence and presence of aerosols. In this study, the direct radiative effect of aerosols is estimated for 46 months (March 2000–December 2003) of merged Clouds and the Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) Terra global measurements over ocean. This analysis includes the contribution from clear regions in both clear and partly cloudy CERES footprints. MODIS–CERES narrow-to-broadband regressions are developed to convert clear-sky MODIS narrowband radiances to broadband shortwave (SW) radiances, and CERES clear-sky angular distribution models (ADMs) are used to estimate the corresponding top-of-atmosphere (TOA) radiative fluxes that are needed to determine the DREA. Clear-sky MODIS pixels are identified using two independent cloud masks: (i) the NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) algorithm that is used for inferring aerosol properties from MODIS on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product (NOAA SSF); and (ii) the standard algorithm that is used by the MODIS aerosol group to produce the MODIS aerosol product (MOD04). Over global oceans, direct radiative cooling by aerosols for clear scenes that are identified from MOD04 is estimated to be 40% larger than for clear scenes from NOAA SSF (5.5 compared to 3.8 W m−2). Regionally, differences are largest in areas that are affected by dust aerosol, such as oceanic regions that are adjacent to the Sahara and Saudi Arabian deserts, and in northern Pacific Ocean regions that are influenced by dust transported from Asia. The net total-sky (clear and cloudy) DREA is negative (cooling) and is estimated to be −2.0 W m−2 from MOD04, and −1.6 W m−2 from NOAA SSF. The DREA is shown to have pronounced seasonal cycles in the Northern Hemisphere and large year-to-year fluctuations near deserts. However, no systematic trend in deseasonalized anomalies of the DREA is observed over the 46-month time series that is considered.

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Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Top-of-Atmosphere (TOA) Edition-4.0 Data Product

Journal of Climate ◽

10.1175/jcli-d-17-0208.1 ◽

2018 ◽

Vol 31 (2) ◽

pp. 895-918 ◽

Cited By ~ 176

Author(s):

Norman G. Loeb ◽

David R. Doelling ◽

Hailan Wang ◽

Wenying Su ◽

Cathy Nguyen ◽

...

Keyword(s):

Regional Differences ◽

Radiant Energy ◽

Energy System ◽

Polar Regions ◽

Marine Stratocumulus ◽

Clear Sky ◽

Data Product ◽

Cloud Radiative Effect ◽

Global Mean

The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) top-of-atmosphere (TOA), Edition 4.0 (Ed4.0), data product is described. EBAF Ed4.0 is an update to EBAF Ed2.8, incorporating all of the Ed4.0 suite of CERES data product algorithm improvements and consistent input datasets throughout the record. A one-time adjustment to shortwave (SW) and longwave (LW) TOA fluxes is made to ensure that global mean net TOA flux for July 2005–June 2015 is consistent with the in situ value of 0.71 W m−2. While global mean all-sky TOA flux differences between Ed4.0 and Ed2.8 are within 0.5 W m−2, appreciable SW regional differences occur over marine stratocumulus and snow/sea ice regions. Marked regional differences in SW clear-sky TOA flux occur in polar regions and dust areas over ocean. Clear-sky LW TOA fluxes in EBAF Ed4.0 exceed Ed2.8 in regions of persistent high cloud cover. Owing to substantial differences in global mean clear-sky TOA fluxes, the net cloud radiative effect in EBAF Ed4.0 is −18 W m−2 compared to −21 W m−2 in EBAF Ed2.8. The overall uncertainty in 1° × 1° latitude–longitude regional monthly all-sky TOA flux is estimated to be 3 W m−2 [one standard deviation (1 σ)] for the Terra-only period and 2.5 W m−2 for the Terra– Aqua period both for SW and LW fluxes. The SW clear-sky regional monthly flux uncertainty is estimated to be 6 W m−2 for the Terra-only period and 5 W m−2 for the Terra– Aqua period. The LW clear-sky regional monthly flux uncertainty is 5 W m−2 for Terra only and 4.5 W m−2 for Terra– Aqua.

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Feedback between dust particles and atmospheric processes over West Africa during dust episodes in March 2006 and June 2007

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-10771-2010 ◽

2010 ◽

Vol 10 (22) ◽

pp. 10771-10788 ◽

Cited By ~ 61

Author(s):

T. Stanelle ◽

B. Vogel ◽

H. Vogel ◽

D. Bäumer ◽

C. Kottmeier

Keyword(s):

West Africa ◽

Mineral Dust ◽

Dust Storms ◽

Dust Particles ◽

Total Emission ◽

Radiative Effect ◽

Radiative Fluxes ◽

Dust Layer ◽

Emission Fluxes ◽

The Impact

Abstract. We used the comprehensive model system COSMO-ART to quantify the impact of mineral dust on the radiative fluxes, the temperature and the feedback between dust particles and their emissions. We simulated two dust storms over West Africa in March 2006 and in June 2007. Simulations with and without coupling of the actual dust concentration with the radiative fluxes and the thermodynamics were carried out for each case. The model results for the 2006 case were compared with observations of the AMMA campaign. At the surface the shortwave radiative effect of mineral dust can be described by a linear relation between the changes in net surface radiation and the aerosol optical depth (AOD). For an AOD at 450 nm of 1 the average shortwave radiation reduction amounts −140 W m−2 during noon. The longwave radiative effect of mineral dust is nonlinear, with an average increase of +70 W m−2 for an AOD (450 nm) of 1. At the top of the atmosphere the effect of the dust layer with an AOD of 1 on radiative fluxes is not as significant as at the surface. It is slightly positive for the shortwave and approximately 26 W m−2 for the longwave radiation. The height range and the extension of the dust layer determine the effect of dust particles on the 2 m temperature. When the dust layer is attached to the surface and lasts for several days it leads to an increase of the surface temperature even during daytime. In case of an elevated dust layer there is a decrease in 2 m temperature of up to 4 K during noon. It is shown, that the temperature changes caused by mineral dust may result in horizontal temperature gradients which also modify near surface winds. Since surface wind thresholds decide the uptake of dust from the surface, a feedback on total emission fluxes is established. The coupled model provides an increase in the total emission fluxes of dust particles by about 16% during the dust storm in March 2006 and 25% during the dust episode in June 2007.

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Earth’s Global Mean Energy Flow System as the Solution of Four Radiative Transfer Constraint Equations

10.21203/rs.3.rs-818026/v1 ◽

2021 ◽

Author(s):

Miklos Zagoni

Keyword(s):

Optical Depth ◽

Energy Flow ◽

Flow System ◽

Lower Boundary ◽

Longwave Radiation ◽

Net Radiation ◽

Data Set ◽

Clear Sky ◽

Cloud Radiative Effect ◽

Global Mean

Abstract Schwarzschild’s equation in two-stream approximation provides a constraint on the net radiation at the lower boundary, as unequivocally connects it to fluxes at the upper boundary (top-of-atmosphere): surface net radiation, balanced by the non-radiative fluxes in radiative-convective equilibrium, is equal to half of the outgoing longwave radiation (OLR), independent of the optical depth. This paper controls this equation on satellite observations and proved to be valid within -2.19 W/m2 for clear-sky, in the annual global mean. The all-sky version of the relationship can easily be constructed, separating atmospheric radiation transfer from the longwave cloud radiative effect (LWCRE); it is valid with a difference of 2.76 W/m2 on the same data set. The equation provides a total (greenhouse) relationship as well, where the surface energy income is given as a function of OLR and the optical depth. This equation is controlled at a particular optical depth of two, and found to be verified with a difference of -2.72 W/m2 for clear-sky in the global mean. An all-sky form is created by including LWCRE, justified within 2.42 W/m2 on the same data set. The four equations together have a mean bias of 0.07 W/m2. This set of equations, using evident definitions between the all-sky and clear-sky fluxes has a solution for the involved components of the global mean energy flow system. Implications on the global mean clear-sky and cloudy energy flow systems are assessed, and the all-sky energy budget is constructed as a weighted sum of the clear and cloudy fluxes.

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Radiative Effect of Clouds at Ny-Ålesund, Svalbard, as Inferred from Ground-Based Remote Sensing Observations

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0080.1 ◽

2020 ◽

Vol 59 (1) ◽

pp. 3-22 ◽

Cited By ~ 6

Author(s):

Kerstin Ebell ◽

Tatiana Nomokonova ◽

Marion Maturilli ◽

Christoph Ritter

Keyword(s):

Remote Sensing ◽

The Arctic ◽

Radiative Effect ◽

Liquid Water Path ◽

Ice Clouds ◽

Surface Warming ◽

Clear Sky ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

The Difference

AbstractFor the first time, the cloud radiative effect (CRE) has been characterized for the Arctic site Ny-Ålesund, Svalbard, Norway, including more than 2 years of data (June 2016–September 2018). The cloud radiative effect, that is, the difference between the all-sky and equivalent clear-sky net radiative fluxes, has been derived based on a combination of ground-based remote sensing observations of cloud properties and the application of broadband radiative transfer simulations. The simulated fluxes have been evaluated in terms of a radiative closure study. Good agreement with observed surface net shortwave (SW) and longwave (LW) fluxes has been found, with small biases for clear-sky (SW: 3.8 W m−2; LW: −4.9 W m−2) and all-sky (SW: −5.4 W m−2; LW: −0.2 W m−2) situations. For monthly averages, uncertainties in the CRE are estimated to be small (~2 W m−2). At Ny-Ålesund, the monthly net surface CRE is positive from September to April/May and negative in summer. The annual surface warming effect by clouds is 11.1 W m−2. The longwave surface CRE of liquid-containing cloud is mainly driven by liquid water path (LWP) with an asymptote value of 75 W m−2 for large LWP values. The shortwave surface CRE can largely be explained by LWP, solar zenith angle, and surface albedo. Liquid-containing clouds (LWP > 5 g m−2) clearly contribute most to the shortwave surface CRE (70%–98%) and, from late spring to autumn, also to the longwave surface CRE (up to 95%). Only in winter are ice clouds (IWP > 0 g m−2; LWP < 5 g m−2) equally important or even dominating the signal in the longwave surface CRE.

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A tropical West Pacific OH minimum and implications for stratospheric composition

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-4827-2014 ◽

2014 ◽

Vol 14 (9) ◽

pp. 4827-4841 ◽

Cited By ~ 42

Author(s):

M. Rex ◽

I. Wohltmann ◽

T. Ridder ◽

R. Lehmann ◽

K. Rosenlof ◽

...

Keyword(s):

Transport Model ◽

Source Region ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

The West ◽

Model Calculations ◽

West Pacific ◽

Stratospheric Composition ◽

The Impact

Abstract. Most of the short-lived biogenic and anthropogenic chemical species that are emitted into the atmosphere break down efficiently by reaction with OH and do not reach the stratosphere. Here we show the existence of a pronounced minimum in the tropospheric column of ozone over the West Pacific, the main source region for stratospheric air, and suggest a corresponding minimum of the tropospheric column of OH. This has the potential to amplify the impact of surface emissions on the stratospheric composition compared to the impact when assuming globally uniform OH conditions. Specifically, the role of emissions of biogenic halogenated species for the stratospheric halogen budget and the role of increasing emissions of SO2 in Southeast Asia or from minor volcanic eruptions for the increasing stratospheric aerosol loading need to be reassessed in light of these findings. This is also important since climate change will further modify OH abundances and emissions of halogenated species. Our study is based on ozone sonde measurements carried out during the TransBrom cruise with the RV Sonne roughly along 140–150° E in October 2009 and corroborating ozone and OH measurements from satellites, aircraft campaigns and FTIR instruments. Model calculations with the GEOS-Chem Chemistry and Transport Model (CTM) and the ATLAS CTM are used to simulate the tropospheric OH distribution over the West Pacific and the transport pathways to the stratosphere. The potential effect of the OH minimum on species transported into the stratosphere is shown via modeling the transport and chemistry of CH2Br2 and SO2.

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The Role of Cloud Radiative Heating in Determining the Location of the ITCZ in Aquaplanet Simulations

Journal of Climate ◽

10.1175/jcli-d-15-0521.1 ◽

2016 ◽

Vol 29 (8) ◽

pp. 2741-2763 ◽

Cited By ~ 33

Author(s):

Bryce E. Harrop ◽

Dennis L. Hartmann

Keyword(s):

Hadley Circulation ◽

Radiative Heating ◽

Moisture Convergence ◽

Radiative Effect ◽

Radiative Effects ◽

Onset Of Convection ◽

Cloud Radiative Effect ◽

Cloud Radiative Effects ◽

The Mean ◽

The Impact

Abstract The relationship between the tropical circulation and cloud radiative effect is investigated. Output from the Clouds On–Off Klimate Intercomparison Experiment (COOKIE) is used to examine the impact of cloud radiative effects on circulation and climate. In aquaplanet simulations with a fixed SST pattern, the cloud radiative effect leads to an equatorward contraction of the intertropical convergence zone (ITCZ) and a reduction of the double ITCZ problem. It is shown that the cloud radiative heating in the upper troposphere increases the temperature, weakens CAPE, and inhibits the onset of convection until it is closer to the equator, where SSTs are higher. Precipitation peaks at higher values in a narrower band when the cloud radiative effects are active, compared to when they are inactive, owing to the enhancement in moisture convergence. Additionally, cloud–radiation interactions strengthen the mean meridional circulation and consequently enhance the moisture convergence. Although the mean tropical precipitation decreases, the atmospheric cloud radiative effect has a strong meridional gradient, which supports stronger poleward energy flux and speeds up the Hadley circulation. Cloud radiative heating also enhances cloud water path (liquid plus ice), which, combined with the reduction in precipitation, suggests that the cloud radiative heating reduces precipitation efficiency in these models.

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