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Volume 9, issue 2 | Copyright

Special issue: The 8th EGU Leonardo Conference: From evaporation to precipitation:...

Earth Syst. Dynam., 9, 915-937, 2018
https://doi.org/10.5194/esd-9-915-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Jun 2018

Research article | 29 Jun 2018

Recent changes of relative humidity: regional connections with land and ocean processes

Sergio M. Vicente-Serrano1, Raquel Nieto2, Luis Gimeno2, Cesar Azorin-Molina3, Anita Drumond2, Ahmed El Kenawy1,4, Fernando Dominguez-Castro1, Miquel Tomas-Burguera5, and Marina Peña-Gallardo1 Sergio M. Vicente-Serrano et al.
  • 1Instituto Pirenaico de Ecología, Consejo Superior de Investigaciones Científicas (IPE–CSIC), Saragossa, Spain
  • 2Environmental Physics Laboratory, Universidade de Vigo, Ourense, Spain
  • 3Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
  • 4Department of Geography, Mansoura University, Mansoura, Egypt
  • 5Estación Experimental Aula Dei, Consejo Superior de Investigaciones Científicas (EEAD-CSIC), Saragossa, Spain

Abstract. We analyzed changes in surface relative humidity (RH) at the global scale from 1979 to 2014 using both observations and the ERA-Interim dataset. We compared the variability and trends in RH with those of land evapotranspiration and ocean evaporation in moisture source areas across a range of selected regions worldwide. The sources of moisture for each particular region were identified by integrating different observational data and model outputs into a Lagrangian approach. The aim was to account for the possible role of changes in air temperature over land, in comparison to sea surface temperature (SST), but also the role of land evapotranspiration and the ocean evaporation on RH variability. The results demonstrate that the patterns of the observed trends in RH at the global scale cannot be linked to a particular individual physical mechanism. Our results also stress that the different hypotheses that may explain the decrease in RH under a global warming scenario could act together to explain recent RH trends. Albeit with uncertainty in establishing a direct causality between RH trends and the different empirical moisture sources, we found that the observed decrease in RH in some regions can be linked to lower water supply from land evapotranspiration. In contrast, the empirical relationships also suggest that RH trends in other target regions are mainly explained by the dynamic and thermodynamic mechanisms related to the moisture supply from the oceanic source regions. Overall, while this work gives insights into the connections between RH trends and oceanic and continental processes at the global scale, further investigation is still desired to assess the contribution of both dynamic and thermodynamic factors to the evolution of RH over continental regions.

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We analyzed changes in surface relative humidity (RH) at the global scale from 1979 to 2014 and compared the variability and trends in RH with those in land evapotranspiration and ocean evaporation in moisture source areas across a range of selected regions worldwide. Our results stress that the different hypotheses that may explain the decrease in RH under a global warming scenario could act together to explain recent RH trends.
We analyzed changes in surface relative humidity (RH) at the global scale from 1979 to 2014 and...
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