1. Global Contributions of Incoming Radiation and Land Surface Conditions to Maximum Near‐Surface Air Temperature Variability and Trend
- Author
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Schwingshackl, Clemens, Hirschi, Martin, and Seneviratne, Sonia I.
- Abstract
The evolution of near‐surface air temperature is influenced by various dynamical, radiative, and surface‐atmosphere exchange processes whose contributions are still not completely quantified. Applying stepwise multiple linear regression to Coupled Model Intercomparison Project phase 5 (CMIP5) model simulations and focusing on radiation (diagnosed by incoming shortwave and incoming longwave radiation) and land surface conditions (diagnosed by soil moisture and albedo) about 79% of the interannual variability and 99% of the multidecadal trend of monthly mean daily maximum temperature over land can be explained. The linear model captures well the temperature variability in middle‐to‐high latitudes and in regions close to the equator, whereas its explanatory potential is limited in deserts. While radiation is an essential explanatory variable over almost all of the analyzed domain, land surface conditions show a pronounced relation to temperature in some confined regions. These findings highlight that considering local‐to‐regional processes is crucial for correctly assessing interannual temperature variability and future temperature trends. The evolution of near‐surface air temperature is mostly impacted by radiation, heat advection, and land‐atmosphere interactions. In this study, we quantify the impact of incoming shortwave and longwave radiation as well as soil moisture and albedo on year‐to‐year variability and long‐term trends of average daily maximum temperature. Applying a linear regression model to the output of climate models, about 80% of the year‐to‐year temperature variability and 99% of the long‐term temperature trend can be explained by the four considered radiation and land surface variables. The radiation components are essential for explaining the temperature evolution almost everywhere. Soil moisture and albedo impact temperature in some confined regions. Incoming longwave radiation contributes strongly to year‐to‐year variability in high latitudes and explains most of the long‐term temperature trend. Incoming shortwave radiation is important in the tropics and in middle‐to‐high latitude during winter. Albedo is of special importance in regions that experience varying snow cover in different years or snow cover changes with climate change. The impact of soil moisture is highest in regions, where it limits the amount of evapotranspiration. The results highlight the fact that local‐to‐regional processes are relevant both for year‐to‐year temperature variability and future temperature trends. The used linear regression model explains about 79% of interannual temperature variability and 99% of multidecadal temperature trendRadiation explains on average about 75% to 85% of the total explained variance, while land surface conditions contribute about 15% to 25%Radiation is essential for explaining temperature variability almost everywhere, land surface conditions in some confined regions
- Published
- 2018
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