Description: The energy budgets over land and oceans are still afflicted with considerable uncertainties, despite their key importance for terrestrial and maritime climates. We evaluate these budgets as represented in 43 CMIP5 climate models with direct observations from both surface and space and identify substantial biases, particularly in the surface fluxes of downward solar and thermal radiation. These flux biases in the various models are then linearly related to their respective land and ocean means to infer best estimates for present day downward solar and thermal radiation over land and oceans. Over land, where most direct observations are available to constrain the surface fluxes, we obtain 184 and 306 Wm−2 for solar and thermal downward radiation, respectively. Over oceans, with weaker observational constraints, corresponding estimates are around 185 and 356 Wm−2. Considering additionally surface albedo and emissivity, we infer a surface absorbed solar and net thermal radiation of 136 and −66 Wm−2 over land, and 170 and −53 Wm−2 over oceans, respectively. The surface net radiation is thus estimated at 70 Wm−2 over land and 117 Wm−2 over oceans, which may impose additional constraints on the poorly known sensible/latent heat flux magnitudes, estimated here near 32/38 Wm−2 over land, and 16/100 Wm−2 over oceans. Estimated uncertainties are on the order of 10 and 5 Wm−2 for most surface and TOA fluxes, respectively. By combining these surface budgets with satellite-determined TOA budgets we quantify the atmospheric energy budgets as residuals (including ocean to land transports), and revisit the global mean energy balance.

Description: The energy budgets over land and oceans are still afflicted with considerable uncertainties, despite their key importance for terrestrial and maritime climates. We evaluate these budgets as represented in 43 CMIP5 climate models with direct observations from both surface and space and identify substantial biases, particularly in the surface fluxes of downward solar and thermal radiation. These flux biases in the various models are then linearly related to their respective land and ocean means to infer best estimates for present day downward solar and thermal radiation over land and oceans. Over land, where most direct observations are available to constrain the surface fluxes, we obtain 184 and 306 Wm-2 for solar and thermal downward radiation, respectively. Over oceans, with weaker observational constraints, corresponding estimates are around 185 and 356 Wm-2. Considering additionally surface albedo and emissivity, we infer a surface absorbed solar and net thermal radiation of 136 and -66 Wm-2 over land, and 170 and -53 Wm-2 over oceans, respectively. The surface net radiation is thus estimated at 70 Wm-2 over land and 117 Wm-2 over oceans, which may impose additional constraints on the poorly known sensible/latent heat flux magnitudes, estimated here near 32/38 Wm-2 over land, and 16/100 Wm-2 over oceans. Estimated uncertainties are on the order of 10 and 5 Wm-2 for most surface and TOA fluxes, respectively. By combining these surface budgets with satellite-determined TOA budgets we quantify the atmospheric energy budgets as residuals (including ocean to land transports), and revisit the global mean energy balance. This study has recently been published online in Climate Dynamics.

Description: The energy budgets over land and oceans are key determinants of terrestrial and maritime climates. Traditionally, however, large uncertainties have been inherent in the estimates of these budgets, which is still reflected in largely differing energy budgets in the latest generation of global climate models (CMIP5). We combine a comprehensive set of radiation observations with 43 state-of-the-art global climate models from CMIP5 to infer best estimates for downward solar and thermal radiation averaged over land and ocean surfaces. Over land, where most direct observations are available to constrain the surface fluxes, we obtain 185 and 305 Wm-2 for the solar and thermal downward radiation, respectively. Over oceans, with weaker observational constraints, our best estimates are around 186 and 356 Wm-2 for the solar and thermal downward radiation. These values closely agree, mostly within 3 Wm-2, with the respective quantities independently derived by recent state-of-the-art reanalyses (ERA-Interim) and satellite-derived products (surface CERES EBAF). This remarkable consistency enhances confidence in the determined flux magnitudes, which so far caused large uncertainties in the energy budgets and often hampered an accurate simulation of surface climates in models. Considering additionally surface albedo and emission, we infer an absorbed solar and net thermal radiation over land of 138 and -67 Wm-2, and over ocean of 170 and -53 Wm-2, respectively. Best estimates for the surface net radiation thus amount to 71 Wm-2 over land and 117 Wm-2 over oceans, which may provide better constraints for the respective sensible and latent heat fluxes. Combining these surface budgets with satellite-determined TOA budgets (CERES-EBAF) results in an atmospheric solar absorption of 75 and 82 Wm-2 and a net atmospheric thermal emission of -165 and -190 Wm-2 over land and oceans, respectively.

Description: Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 26 (2013): 2719–2740, doi:10.1175/JCLI-D-12-00436.1.

Description: The estimate of surface irradiance on a global scale is possible through radiative transfer calculations using satellite-retrieved surface, cloud, and aerosol properties as input. Computed top-of-atmosphere (TOA) irradiances, however, do not necessarily agree with observation-based values, for example, from the Clouds and the Earth’s Radiant Energy System (CERES). This paper presents a method to determine surface irradiances using observational constraints of TOA irradiance from CERES. A Lagrange multiplier procedure is used to objectively adjust inputs based on their uncertainties such that the computed TOA irradiance is consistent with CERES-derived irradiance to within the uncertainty. These input adjustments are then used to determine surface irradiance adjustments. Observations by the Atmospheric Infrared Sounder (AIRS), Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS) that are a part of the NASA A-Train constellation provide the uncertainty estimates. A comparison with surface observations from a number of sites shows that the bias [root-mean-square (RMS) difference] between computed and observed monthly mean irradiances calculated with 10 years of data is 4.7 (13.3) W m−2 for downward shortwave and −2.5 (7.1) W m−2 for downward longwave irradiances over ocean and −1.7 (7.8) W m−2 for downward shortwave and −1.0 (7.6) W m−2 for downward longwave irradiances over land. The bias and RMS error for the downward longwave and shortwave irradiances over ocean are decreased from those without constraint. Similarly, the bias and RMS error for downward longwave over land improves, although the constraint does not improve downward shortwave over land. This study demonstrates how synergetic use of multiple instruments (CERES, MODIS, CALIPSO, CloudSat, AIRS, and geostationary satellites) improves the accuracy of surface irradiance computations.

Description: The work was supported by theNASACERES and, in part, Energy Water Cycle Study (NEWS) projects.

Description: 2013-11-01

Description: The energy budget over terrestrial surfaces is a key determinant of the land surface climate and governs a variety of physical, chemical and biological surface processes. The purpose of the present study is to establish new reference estimates for the different components of the energy balance over global land surfaces. Thanks to the impressive progress in space-based observation systems in the past decade, we now know the energy exchanges between our planet and the surrounding space with unprecedented accuracy. However, the energy flows at the Earth’s surface have not been established with the same accuracy, since they cannot be directly measured from satellites. Accordingly, estimates on the magnitude of the fluxes at terrestrial surfaces largely vary, and latest climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) still show significant differences in their simulated energy budgets on a land mean basis, which prevents a consistent simulation of the land surface processes in these models. In the present study we use to the extent possible direct observations of surface radiative fluxes from the Global Energy Balance Archive (GEBA) and the Baseline Surface Radiation Network (BSRN) to better constrain the simulated fluxes over global land surfaces. These model-calculated fluxes stem from the comprehensive set of more than 40 global climate from CMIP5 used in the latest IPCC report AR5. The CMIP5 models overall still show a tendency to overestimate the downward solar and underestimate the downward thermal radiation at terrestrial surfaces, a long standing problem in climate modelling. Based on the direct radiation observations and the bias structure of the CMIP5 models we infer best estimates for the downward solar and thermal radiation averaged over global land surfaces. They amount to 184 Wm-2 and 306 Wm-2, respectively. These values closely agree with the respective quantities independently derived by recent state-of-the-art reanalyses (ERA-Interim) and satellite-derived products (surface CERES EBAF). This remarkable consistency enhances confidence in the determined flux magnitudes, which so far caused large uncertainties in the energy budgets and often hampered an accurate simulation of surface climates in models. Using in addition a land mean surface albedo estimate of 0.26, we determine an average absorbed solar radiation at land surfaces of 136 Wm-2. Our best estimate for the upward thermal radiation at land surfaces (essentially based on the Stefan Boltzmann law) is 372 Wm-2, and combined with the above best estimate of 306 Wm-2 for the downward thermal radiation, this results in a net thermal radiation of -66 Wm-2 averaged over global land surfaces. Adding the absorbed solar and net thermal radiation, our best estimate of the land mean surface net radiation amounts to 70 Wm-2, which is the energy available for the sensible and latent heat fluxes. Latest estimates of terrestrial latent heat fluxes indicate a land mean value slightly below 40 Wm-2. In our best estimate of the global land mean energy balance we thus adopt a land mean latent heat flux of 38 Wm-2, leaving a land mean sensible heat flux of 32 Wm-2 as residual to close the energy balance over terrestrial surfaces. A diagram of the global land mean energy balance including these new estimates and the related discussion has recently been published in Climate Dynamics (Wild et al. 2015).