Energy Balance


Spatial and temporal variations in the flows of energy between the surface, the atmosphere, and space play a central role in establishing the large-scale atmosphere and ocean circulation patterns that ultimately drive both weather and climate on Earth. The sensitivity of the climate system to external forcings, including increasing greenhouse gas concentrations, is, therefore, governed by the energy imbalances they induce and the partitioning of these imbalances between the atmosphere, ocean, and cryosphere. We use the latest satellite observations to construct Earth’s energy budget from its component fluxes and understand the factors that modulate this balance on seasonal to decadal timescales. We have pioneered new methods for re-introducing balance constraints in observation-based energy and water cycle reconstructions and using these estimates to evaluate climate model predictions. We are also leading efforts to utilize measurements from spaceborne active sensors to quantify the influence of mixed-phase and multi-layered clouds on atmospheric and surface energy balance.

Reconstructing the Energy and Water Cycles

Efforts to balance the Earth’s energy budget using observational datasets result in unrealistically large imbalances both within the atmosphere and at the surface where net radiation at the surface tends to significantly exceed the associated turbulent heat fluxes, particularly over the global oceans.  These imbalances arise from the fact that measures of the component energy fluxes are typically derived independently and all have uncertainties. Under NASA’s Energy and Water Cycle Study (NEWS) we are working with a large team of investigators to reintroduce energy and water cycle closure constraints in modern reconstructions of Earth’s energy budget and water cycle.  The resulting balanced global and regional energy and water cycles provide a resource for studying variations in continental and ocean basin on seasonal to multiyear timescales.

The Role of Cloud Phase in Earth's Energy Budget

The effects of clouds on Earth’s energy budget depends strongly on the relative partitioning of liquid and ice phases within them. Separating the contributions of liquid, ice, and mixed-phase clouds to global cloud forcing has, however, been very challenging due to the inherent difficulty in discriminating cloud phase from satellite sensors.  Using the combination of active and passive sensors in the A-Train, our group is computing the radiative effects of the complete spectrum of global cloud regimes and determining their influence on different aspects of the climate such as the general circulation shown at the left.  Interestingly, while mixed-phase clouds comprise only 8% of total cloud occurrence, they account for nearly 20% of the global mean SW and LW cloud radiative effects.