The wind industry in the United States has experienced a remarkably rapid expansion of capacity i... more The wind industry in the United States has experienced a remarkably rapid expansion of capacity in recent years and this fast growth is expected to continue in the future 1-3. While converting wind's kinetic energy into electricity, wind turbines modify surface-atmosphere exchanges and the transfer of energy, momentum, mass and moisture within the atmosphere 4-6. These changes, if spatially large enough, may have noticeable impacts on local to regional weather and climate. Here we present observational evidence for such impacts based on analyses of satellite data for the period of 2003-2011 over a region in west-central Texas, where four of the world's largest wind farms are located 7. Our results show a significant warming trend of up to 0.72 • C per decade, particularly at night-time, over wind farms relative to nearby non-wind-farm regions. We attribute this warming primarily to wind farms as its spatial pattern and magnitude couples very well with the geographic distribution of wind turbines. Despite debates regarding the possible impacts of wind farms on regional to global scale weather and climate 8-12 , modelling studies agree that they can significantly affect local scale meteorology 6,13-16 by increasing surface roughness, changing the stability of the atmospheric boundary layer (ABL) and enhancing turbulence in the rotor wakes 4-6. However, these studies are based primarily on numerical simulations of regional and global models, which owing to lack of observations only crudely represent the effects of wind turbines by explicitly increasing either surface roughness length or turbulence kinetic energy. Evidently, more realistic model parameterizations should be developed and modelling results should be validated against the observations. Although observed data on wind speed and turbulence in and around operational wind farms are readily available, information on other meteorological variables does not exist in the public domain. A recent study using the only available observed temperature data from an operational wind farm shows a warming effect at night and a cooling effect during the day 6. However, the observed data are from only two meteorological towers for a period of 1.5 months. Hence more observational evidence, particularly on larger scales and for longer periods, is needed. Satellites provide information on global spatial sampling at regular temporal intervals and thus have the potential to accurately monitor and detect the impacts of large wind farms with spatial detail. This study aims to search for observational evidence of such impacts from land surface temperature (LST) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) with spatial resolutions finer than most wind farms and temporal resolutions covering both days and nights. LST is the radiometric
Features of atmospheric water vapor and water vapor transport fields during the Pacific Explorato... more Features of atmospheric water vapor and water vapor transport fields during the Pacific Exploratory Mission (PEM) in the Tropical Pacific were studied using the data from the National Centers for Environmental Prediction (NCEP) reanalyses, the Global Precipitation Climatology Project, the Climate Analysis Center, and the European Center for Medium-Range Weather Forecasts, with a focus on PEM-Tropics B. Vertically integrated values of the moisture quantities such as the precipitable water and the zonal and meridional water vapor fluxes were examined. Moisture transports across boundaries of major sectors over the tropical Pacific and their budgets were estimated. The differences of the precipitable water between PEM-Tropics B and PEM-Tropics A were highlighted owing to its importance for atmospheric chemistry. During PEM-Tropics B, the NCEP reanalyses showed that there existed clearly a moist Walker circulation over the northern tropical Pacific during the whole period and a moist Hadley circulation over the eastern Pacific during the first half of the mission. The southwest sector where the South Pacific Convergence Zone (SPCZ) was located had the largest areal mean precipitation and the northeast sector had the smallest, whereas the estimated evaporation rates for both regions were comparable. A more vigorous moist circulation during the second half period led to enhanced precipitation for all the regions except the southeast sector. An interesting and potentially very important meteorological phenomenon during PEM-Tropics B was the double Intertropical Convergence Zone (ITCZ) structure over the eastern tropical Pacific. We suggest that this structure, along with the similar double convective zones over the western tropical Pacific (i.e., ITCZ and SPCZ), may act as double barriers for the interhemispheric exchanges for this particular season with implications for photochemistry in both hemispheres.
The wind industry in the United States has experienced a remarkably rapid expansion of capacity i... more The wind industry in the United States has experienced a remarkably rapid expansion of capacity in recent years and this fast growth is expected to continue in the future 1-3. While converting wind's kinetic energy into electricity, wind turbines modify surface-atmosphere exchanges and the transfer of energy, momentum, mass and moisture within the atmosphere 4-6. These changes, if spatially large enough, may have noticeable impacts on local to regional weather and climate. Here we present observational evidence for such impacts based on analyses of satellite data for the period of 2003-2011 over a region in west-central Texas, where four of the world's largest wind farms are located 7. Our results show a significant warming trend of up to 0.72 • C per decade, particularly at night-time, over wind farms relative to nearby non-wind-farm regions. We attribute this warming primarily to wind farms as its spatial pattern and magnitude couples very well with the geographic distribution of wind turbines. Despite debates regarding the possible impacts of wind farms on regional to global scale weather and climate 8-12 , modelling studies agree that they can significantly affect local scale meteorology 6,13-16 by increasing surface roughness, changing the stability of the atmospheric boundary layer (ABL) and enhancing turbulence in the rotor wakes 4-6. However, these studies are based primarily on numerical simulations of regional and global models, which owing to lack of observations only crudely represent the effects of wind turbines by explicitly increasing either surface roughness length or turbulence kinetic energy. Evidently, more realistic model parameterizations should be developed and modelling results should be validated against the observations. Although observed data on wind speed and turbulence in and around operational wind farms are readily available, information on other meteorological variables does not exist in the public domain. A recent study using the only available observed temperature data from an operational wind farm shows a warming effect at night and a cooling effect during the day 6. However, the observed data are from only two meteorological towers for a period of 1.5 months. Hence more observational evidence, particularly on larger scales and for longer periods, is needed. Satellites provide information on global spatial sampling at regular temporal intervals and thus have the potential to accurately monitor and detect the impacts of large wind farms with spatial detail. This study aims to search for observational evidence of such impacts from land surface temperature (LST) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) with spatial resolutions finer than most wind farms and temporal resolutions covering both days and nights. LST is the radiometric
Features of atmospheric water vapor and water vapor transport fields during the Pacific Explorato... more Features of atmospheric water vapor and water vapor transport fields during the Pacific Exploratory Mission (PEM) in the Tropical Pacific were studied using the data from the National Centers for Environmental Prediction (NCEP) reanalyses, the Global Precipitation Climatology Project, the Climate Analysis Center, and the European Center for Medium-Range Weather Forecasts, with a focus on PEM-Tropics B. Vertically integrated values of the moisture quantities such as the precipitable water and the zonal and meridional water vapor fluxes were examined. Moisture transports across boundaries of major sectors over the tropical Pacific and their budgets were estimated. The differences of the precipitable water between PEM-Tropics B and PEM-Tropics A were highlighted owing to its importance for atmospheric chemistry. During PEM-Tropics B, the NCEP reanalyses showed that there existed clearly a moist Walker circulation over the northern tropical Pacific during the whole period and a moist Hadley circulation over the eastern Pacific during the first half of the mission. The southwest sector where the South Pacific Convergence Zone (SPCZ) was located had the largest areal mean precipitation and the northeast sector had the smallest, whereas the estimated evaporation rates for both regions were comparable. A more vigorous moist circulation during the second half period led to enhanced precipitation for all the regions except the southeast sector. An interesting and potentially very important meteorological phenomenon during PEM-Tropics B was the double Intertropical Convergence Zone (ITCZ) structure over the eastern tropical Pacific. We suggest that this structure, along with the similar double convective zones over the western tropical Pacific (i.e., ITCZ and SPCZ), may act as double barriers for the interhemispheric exchanges for this particular season with implications for photochemistry in both hemispheres.
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