Global terrestrial stilling: does Earth's greening play a role?

• Published in: Environmental Research Letters
• Main Authors: Zeng, Zhenzhong, Piao, Shilong, Li, Laurent, Ciais, Philippe, Li, Yue, Cai, Xitian, Yang, Long, Liu, Maofeng, Wood, Eric
• Other Authors: Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University Beijing, Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Orange Labs Cesson-Sévigné, Orange Labs, The First Institute of Oceanography, SOA, Department of Civil and Environmental Engineering, Princeton University
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: terrestrial stilling; Earth's greening; surface wind speed; surface roughness; leaf area index; weather station; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Sea ice; Southern Ocean
• Online Access: https://hal.science/hal-02412929; https://hal.science/hal-02412929/document; https://hal.science/hal-02412929/file/HAL-146-Zeng_2018_Environ._Res._Lett._13_124013.pdf; https://doi.org/10.1088/1748-9326/aaea84

International audience Previous studies have documented that surface wind speed (u) has been increasing over the ocean but decreasing over land for the past several decades. The decreasing u at the surface over land has been referred to as terrestrial stilling. A plausible hypothesis for terrestrial stilling is an increase in surface roughness associated with changes in land surface (e.g. enhanced vegetation growth, landscape fragmentation or urbanization). One of the most widespread land surface changes is enhanced vegetation leaf area index (LAI) known as greening, particularly over the middle to high latitudes of the Northern Hemisphere where strong stilling is observed from weather station data. In this study, we examine the hypothesis that enhanced vegetation LAI is a key driver of global terrestrial stilling. We first characterized the trend in u over the ocean using long-term satellite altimeter measurements, and the trend in u over land using continuous wind records from 4305 in situ meteorological stations. We then performed initial condition ensemble Atmospheric Model Intercomparison Project-type simulations using two state-of-the-art Earth system models (IPSL-CM and CESM) to isolate the response of u to the historical increase in LAI (representing the greening) for the period 1982-2011. Both models, forced with observed sea surface temperature and sea ice and with LAI from satellite observation, captured the observed strengthening of Pacific trade winds and Southern Ocean westerly winds. However, these simulations did not reproduce the weakening of surface winds over land as significantly as it appears in the observations (−0.006 m s −1 versus −0.198 m s −1 during 1982-2011), indicating that enhanced LAI (greening) is not a dominant driver for terrestrial stilling.