11 research outputs found
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Observational constraints on atmospheric and oceanic cross-equatorial heat transports: revisiting the precipitation asymmetry problem in climate models
Satellite based top-of-atmosphere (TOA) and surface radiation budget observations are combined with mass corrected vertically integrated atmospheric energy divergence and tendency from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Hemispheric contrasts in the energy budget terms are used to determine the radiative and combined sensible and latent heat contributions to the cross-equatorial heat transports in the atmosphere (AHT_EQ) and ocean (OHT_EQ). The contrast in net atmospheric radiation implies an AHT_EQ from the northern hemisphere (NH) to the southern hemisphere (SH) (0.75 PW), while the hemispheric difference in sensible and latent heat implies an AHT_EQ in the opposite direction (0.51 PW), resulting in a net NH to SH AHT_EQ (0.24 PW). At the surface, the hemispheric contrast in the radiative component (0.95 PW) dominates, implying a 0.44 PW SH to NH OHT_EQ. Coupled model intercomparison project phase 5 (CMIP5) models with excessive net downward surface radiation and surface-to-atmosphere sensible and latent heat transport in the SH relative to the NH exhibit anomalous northward AHT_EQ and overestimate SH tropical precipitation. The hemispheric bias in net surface radiative flux is due to too much longwave surface radiative cooling in the NH tropics in both clear and all-sky conditions and excessive shortwave surface radiation in the SH subtropics and extratropics due to an underestimation in reflection by clouds
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The curious nature of the hemispheric symmetry of the Earth’s water and energy balances
This paper presents new estimates of the hemispheric
energy balance based on an assembly of radiative flux
and ocean heat data. Further, it provides an overview of recent simulations with fully coupled climate models to investigate
the role of its representation in causing tropical precipitation
biases. The energy balance portrayed here features a small
hemispheric imbalance with slightly more energy being
absorbed by the Southern hemisphere. This yields a net transport
of heat towards the NH composing of a northward crossequatorial
heat transport by the oceans and a southward heat
flow in the atmosphere. The turbulent fluxes and hemispheric
precipitation balance to about 3 Wm−2 with slightly larger
total accumulation occurring in the NH. CloudSat data indicate
more frequent precipitation in the SH implying more
intense precipitation in the NH. Fully coupled climate model
simulations show that reducing hemispheric energy balance
biases does little to reduce existing biases in tropical
precipitation
An Imperative to Monitor Earth\u27s Energy Imbalance
The current Earth\u27s energy imbalance (EEI) is mostly caused by human activity, and is driving global warming. The absolute value of EEI represents the most fundamental metric defining the status of global climate change, and will be more useful than using global surface temperature. EEI can best be estimated from changes in ocean heat content, complemented by radiation measurements from space. Sustained observations from the Argo array of autonomous profiling floats and further development of the ocean observing system to sample the deep ocean, marginal seas and sea ice regions are crucial to refining future estimates of EEI. Combining multiple measurements in an optimal way holds considerable promise for estimating EEI and thus assessing the status of global climate change, improving climate syntheses and models, and testing the effectiveness of mitigation actions. Progress can be achieved with a concerted international effort