Changes in near‐surface wind speed in China: 1969–2005

Abstract

This study extends upon previous analyses and details near-surface wind speed change in China and its monsoon regions from 1969 to 2005, using a new dataset consisting of 652 stations. Moreover, causes of wind speed changes are examined. Major results show that most stations in China have experienced significant weakening in annual and seasonal mean wind during the study period. The averaged rate of decrease in annual mean wind speed over China is −0.018 ms −1 a −1 . Decrease in seasonal mean wind differs. The largest rate of decline is in spring at −0.021 ms −1 a −1 and the least is in summer at −0.015 ms −1 a −1 . Spatially, large declines are found in northern China, the Tibetan Plateau and the coastal areas in east and southeast China, while central and south-central China have the least change in their wind speed. Significant weakening of wind speed has occurred primarily in strong wind categories. Decreases in light wind categories are trivial, and light wind has even increased slightly in parts of central China. These changes indicate reduced fluctuations in wind and wind storms in recent decades, contributing to decreased frequency and magnitude of dust storms. The trivial changes in summer winds in east and southeast China suggest fairly steady monsoon winds over the decades.A main cause of the weakening wind is shown to be the weakening in the lower-tropospheric pressure-gradient force, a result pointing to climate variation as the primary source of the wind speed change. Superimposed on the climate effect is the urban effect. While analysis of winds between urban and rural stations reinstate the urban frictional effect, a peculiar stronger increase in wind at urban stations than at rural stations after the abrupt urbanization since 1990 indicates a new aspect of the urban effect on wind speed.

Homogenization of Tianjin monthly near-surface wind speed using RHtestsV4 for 1951–2014

“…8, the wind speed series after adjustment at all 10 stations were coincident, with a reducing trend at the 95% significant level. This result is consistent with current researches on assessment of observed near-surface wind speed trends in China (Rong and Liang 2008;Cheng 2010;Zou et al 2010;Fu et al 2011;Guo et al 2011;Chen et al 2013;Zhang et al 2014;Xiong 2015), and also similar to trends reported for other parts of the world (Pryor et al 2009;Wan et al 2010;William and Martha 2014). Based on the adjusted data, the trends in the regional average annual and seasonal (spring, summer, autumn, and winter) wind speed series were −0.277, −0.325, −0.228, −0.223, and −0.336 m s −1 /10a, respectively (Fig.…”

“…The statistics based on the adjusted data here were generally consistent with those from Li et al (2011), who evaluated the regional trends (Table 4). Both this study and the prior study indicate that the decreasing amplitudes of wind speed trend in spring and winter were much larger than those in summer and autumn; this is also reflected in studies on annual and seasonal wind speed change over China (Xu et al 2006;Jiang et al 2010;Guo et al 2011;Fu et al 2011;and Chen et al 2013). Accordingly, based on the adjusted data, characteristics of near-surface wind speed change in Tianjin are consistent with those of regional background climate in China.…”

Wind speed trends over China: quantifying the magnitude and assessing causality

“…The ERA-40 reanalysis output does not exhibit a significant trend in 10-m wind speeds over China from 1971 to 2001, while spatial average NCEP/NCAR reanalysis wind speed exhibits negative trends at the rate of −0.13 m s -1 /decade over the past 37 years (Figure 2(a)). In addition, as discussed by Guo et al (2010), the temporal evolution of annual mean wind speed shows two phases: robust declines in the 1970s and 1980s, followed by a period of much smaller trends after 1990 (Figure 2(b)). Consistent with prior analyses of station data (Guo et al, 2010;Jiang et al, 2010), time series of the annual wind speed percentiles indicate that the downward trend in the upper percentiles is more pronounced than in lower percentiles.…”

“…The proportion of stations exhibiting an upward trend over China is larger than that estimated by Fu et al (2011) and Guo et al (2010), but still represents only a small fraction of the total number of time series considered. Fifty-four percent of grid cells in the NCEP/NCAR product exhibit significant negative trends, while 3% show increases.…”

“…For example, Guo et al (2010) (Vautard et al, 2010). Here we extend these prior analyses by specifically comparing temporal trends and seasonality as derived from the in situ data with those from global reanalysis data sets.…”