Evaluating the effects of land use and cover change on the decrease of surface wind speed over China in recent 30 years using a statistical downscaling method

Climate Dynamics, Mar 2016

The long-term decrease of surface wind speed (SWS) has been revealed by previous studies in China in recent decades, but the reasons for the SWS decrease remain uncertain. In this paper, we evaluated the effects of land use and cover change (LUCC) on the SWS decrease during 1980–2011 over the Eastern China Plain (ECP) region using a combined method of statistical downscaling and observation minus reanalysis data, which was used to improve the climate prediction of general circulation models and to evaluate the influence of LUCC on climate change. To exclude the potential influence of LUCC on SWS observation, a statistical downscaling model (SDM) was established during 1980–1992 because a lower extent of LUCC occurred during this period than in later periods. The skill of the SDM was checked by comparing the results of different predictor combinations. Then, SDM was used to improve the wind speed data at 10 m above the surface in the ERA-Interim reanalysis data (V10m-ERA) during 1993–2011, which decreased the error in the reanalysis wind speed as far as possible. Then, the difference between the station observed SWS (V10m-OBV) and the downscaled SWS (V10m-SDM) during 1993–2011 (SWSD) was considered the quantitative estimation of the influence of the LUCC on SWS in this period. The V10m-SDM can capture both the large-scale and local characteristics in the observation, and their patterns are very similar. V10m-SDM has better performance in the spatial–temporal changes than does V10m-ERA with respect to V10m-OBV. The impact of LUCC on the SWS was pronounced, the SWSD was −0.24 m s−1 in 1993, and the SWSD reached −0.56 m s−1 in 2011. LUCC could induce a 0.17 m s−1 wind speed decrease per 10 year in the ECP region during 1993–2011. Furthermore, each 10 % rise of the urbanization rate could cause an approximately 0.12 m s−1 decrease in wind speed. Additionally, pressure-gradient force was eliminated as the primary cause of the observed long-term decrease of SWS in ECP by composite analysis and temporal serial analysis, and the rise of the surface drag force caused by LUCC was identified as an important factor inducing the SWS decrease during 1993–2011 in ECP region. Moreover, the results from different time lengths used to construct SDM were compared, and the uncertainties in SWSD were evaluated by different SDMs established by different time periods.

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Evaluating the effects of land use and cover change on the decrease of surface wind speed over China in recent 30 years using a statistical downscaling method

Clim Dyn Evaluating the effects of land use and cover change on the decrease of surface wind speed over China in recent 30 years using a statistical downscaling method Jian Wu 0 1 Jinlin Zha 0 1 Deming Zhao 0 1 0 Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029 , People's Republic of China 1 Department of Atmospheric Science, Yunnan University , Kunming 650091 , People's Republic of China The long-term decrease of surface wind speed (SWS) has been revealed by previous studies in China in recent decades, but the reasons for the SWS decrease remain uncertain. In this paper, we evaluated the effects of land use and cover change (LUCC) on the SWS decrease during 1980-2011 over the Eastern China Plain (ECP) region using a combined method of statistical downscaling and observation minus reanalysis data, which was used to improve the climate prediction of general circulation models and to evaluate the influence of LUCC on climate change. To exclude the potential influence of LUCC on SWS observation, a statistical downscaling model (SDM) was established during 1980-1992 because a lower extent of LUCC occurred during this period than in later periods. The skill of the SDM was checked by comparing the results of different predictor combinations. Then, SDM was used to improve the wind speed data at 10 m above the surface in the ERA-Interim reanalysis data (V10mERA) during 1993-2011, which decreased the error in the reanalysis wind speed as far as possible. Then, the difference between the station observed SWS (V10m-OBV) and the downscaled SWS (V10m-SDM) during 1993-2011 (SWSD) was considered the quantitative estimation of the influence of the LUCC on SWS in this period. The V10mSDM can capture both the large-scale and local characteristics in the observation, and their patterns are very similar. Surface wind speed; Statistical downscaling method; Pressure-gradient force; LUCC 1 Introduction The distinct decrease of the surface wind speed (SWS) has been reported by several studies in different regions, such as in the Mediterranean and Adriatic areas (Pirazzoli and Tomasin 2003) , the Black Sea region (Garmsshov and Polonskii 2011) , Europe (Najac et al. 2009; Smits et al. 2005) , North America (Greene et al. 2012; He et al. 2010; Pryor et al. 2007; Tuller 2004; Enloe 2003; Klink 2002) , East Asia (Vautard et al. 2010) , and China (Hu et al. 2011; McVicar et al. 2010; Jiang et al. 2010; Xu et al. 2006) . The causes of these observed decreases in SWS remain unclear. Possible reasons for the SWS change include the influences of large-scale circulation and local changes in land use and cover change (LUCC). Some studies relate the decrease of the SWS with the weakening of large-scale circulation, Niño–Southern Oscillation (ENSO), and climate change. Pryor and Ledolter (2010), Pryor et al. (2005) and Enloe (2003) found some relations between the SWS change and ENSO, and Klink (2007) emphasized the importance of the pressure-gradient force (PGF) in the change of SWS, which means that the PGF should be a major cause of SWS change. Sušelj et al. (2010) showed that decreases in SWS were determined by the weakening of large-scale circulation. Xu et al. (2006) reported links between the weakening of the monsoon driving force and the SWS decrease in China, and Jiang et al. (2010) revealed a strong correlation between the changes in large-scale circulation and the SWS. Guo et al. (2011) reported a decreasing trend of the geostrophic current on the 850 hPa level in China; therefore, they noted that the decrease of SWS was caused by the weakening of circulation at high altitude. Other studies found the cause of the SWS decrease to be anthropogenic activities (Gao et al. 2015; Pere et al. 2011) , including the increase of surface roughness, which is induced by anthropogenic LUCC. Vautard et al. (2010) addressed the decreases in SWS could be determined by increases in surface roughness. Li et al. (2008) used the observation minus reanalysis (OMR) method to investigate the impact of the LUCC on the SWS, and their results suggest that the observed significant decrease of mean wind speeds was due to urbanization and other land-use changes in the last 40 years. In addition, SWS in urban areas was found to be lower than that in suburban regions in Shanghai (Zhou and Yu 1988) and Beijing (Li et al. 2011; Xu et al. 2009) , two of China’s megacities, which linked the decrease of SWS to the increase in building area and height. Wu et al. (2016) used the frictional wind model (FWM), in which a balance among PGF, the Coriolis force, and the drag force was reached, to separate the effects of the PGF and LUCC on the SWS change and to quantitatively estimate the influence of the LUCC on the SWS change over the Eastern China Plain (ECP) region during the period of 1980–2011. Their results show that the drag c (...truncated)


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Jian Wu, Jinlin Zha, Deming Zhao. Evaluating the effects of land use and cover change on the decrease of surface wind speed over China in recent 30 years using a statistical downscaling method, Climate Dynamics, 2016, pp. 131-149, Volume 48, Issue 1-2, DOI: 10.1007/s00382-016-3065-z