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

Temporal trends (1971-2007) in 10-m wind speeds from homogeneous observational data sets from 540 weather stations and reanalysis data sets are quantified and compared. Also, possible physical cause of inconsistencies between the data sets and temporal trends and variability in wind speeds are investigated. Annual mean wind speeds from the observational data exhibit pronounced downward trends especially in the upper percentiles and during spring. The NCEP/NCAR reanalysis reproduces the observed wind speeds, seasonality and temporal trends better than the ERA-40 even though it shows larger interannual fluctuations. The warm and cold AO and ENSO phases have significant influence on probability distribution of wind speeds, thus internal climate variability is a major source of both interannual and long-term variability.