Regional Wind Speed Comparison of Climate Models, Era-Interim Reanalysis and Observations

Thursday, 18 December 2014
Sium Tesfai Gebremariam and Belay Demoz, Howard University, Washington, DC, United States
Global Climate models have been evolving and improving over the years. Seven Model simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) are compared to reanalysis dataset to ascertain how well they simulate wind speed trends and variability over North America region. Trend values for the period 1979-2005 are calculated using a linear least square analysis with trend uncertainties computed using the standard error, where temporal autocorrelation is employed for non randomness of the datasets. Results showed strong regional difference in surface wind speed trends among individual models, as well as between models and reanalysis dataset. Furthermore, comparison of horizontal wind speed climatology, trends and variability among models, reanalysis and radiosonde observations at station level were performed. Result showed that CMIP5 models have wind speed bias (ranging from -5m/s to 5 m/s) for both annual and seasonal averages, specifically during JJA and DJF seasons. Furthermore, CMIP5 underestimated the radiosonde observed wind speed interannual and intra-annual variability in the troposphere. Overall, the trends estimated from CMIP5, radiosonde and ERA-Interim reanalysis product are not statistically significant for the period 1979-2005. Lastly, implications of this study on future satellite missions and the data to be collected are also investigated. It is shown that future satellites need to provide approximately 0.5 km resolution data to resolve the jet stream variability.