Browsing by Subject "Energy budget"

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  • Räisänen, Jouni (2017)
    An energy balance decomposition of temperature changes is conducted for idealized transient CO2-only simulations in the fifth phase of the Coupled Model Intercomparison Project. The multimodel global mean warming is dominated by enhanced clear-sky greenhouse effect due to increased CO2 and water vapour, but other components of the energy balance substantially modify the geographical and seasonal patterns of the change. Changes in the net surface energy flux are important over the oceans, being especially crucial for the muted warming over the northern North Atlantic and for the seasonal cycle of warming over the Arctic Ocean. Changes in atmospheric energy flux convergence tend to smooth the gradients of temperature change and reduce its land-sea contrast, but they also amplify the seasonal cycle of warming in northern North America and Eurasia. The three most important terms for intermodel differences in warming are the changes in the clear-sky greenhouse effect, clouds, and the net surface energy flux, making the largest contribution to the standard deviation of annual mean temperature change in 34, 29 and 20 % of the world, respectively. Changes in atmospheric energy flux convergence mostly damp intermodel variations of temperature change especially over the oceans. However, the opposite is true for example in Greenland and Antarctica, where the warming appears to be substantially controlled by heat transport from the surrounding sea areas.
  • Räisänen, Jouni (2019)
    Energetics of interannual temperature variability in the years 1980-2016 is studied using two reanalysis data sets. Monthly temperature anomalies are decomposed to contributions from the net surface energy flux, atmospheric energy convergence minus storage (CONV), and processes that affect the top-of-the-atmosphere radiation balance. The analysis reveals a strong compensation between the net surface heat flux and CONV over the ice-free oceans, with the former driving the temperature variability over the tropical oceans and the latter at higher latitudes. CONV also makes a dominant contribution to temperature anomalies in the winter hemisphere extratopical continents. During the summer half-year and in the tropics, however, variations in cloudiness dominate the temperature variability over land, while the contribution of CONV is modest or even negative. The latter reflects the diffusion-like behaviour of short-term atmospheric variability, which acts to spread out the local, to a large extent cloud-induced temperature anomalies to larger areas. The ERA-Interim and MERRA2 reanalyses largely agree on the general energy budget features of interannual temperature variability, although substantial quantitative differences occur in some of the individual terms.