Correction Of Ship-based Turbulent Wind Velocity And Characterization Of Turbulent In The North West Pacific

Along with the global weather and climate change getting increasingly fierce, theinteraction of atmosphere with geosphere, hydrosphere and other systems attractincreasing attention of people. Over seventy percent of the earth’s surface covered byoceans, the exchange of material and energy through the turbulent motion between theocean and the upper atmosphere in the boundary layer is vital to the sea-airinteraction.Ship-based turbulent wind velocities were measured in the North West Pacificfrom September to November in2005. Using the corrected turbulent wind velocity,we estimated a few turbulent parameters in the North West Pacific during theobservational period, and we finally come to a few conclusions.1. The analysis results of turbulent wind velocity power spectrum showed anunexpected peak in frequency ranges of0.06-0.26Hz, which was believed due to theplatform rocking. This study proposed a new approach, i.e., improved filteringcorrection, to minimize the interference from the rocking of the platform on the signalof turbulent wind velocity. When power spectral densities and frequencies wereplotted in a dual-logarithm coordinates system, they should have a linear relationshipin the inertial zone. Thus, the power spectral densities out of the range from0.06to0.26Hz were used to linearly fit the trend line of the power spectra between0.06to0.26Hz. Combined the original power spectra and the trend line inversion, thecorrected power spectra were calculated. The new power spectra were compared withthe spectra corrected by considering the ship-gesture, and the results were comparable.Both of approaches can remove the interference from the platform rocking effectively.Through the inverse Fourier transform, the new turbulent wind velocity was obtained.Using the corrected turbulent wind velocity, the estimated turbulent parameters showthat the new approach is valid to reduce the influence of the platform rocking. 2. During the voyage in the North West Pacific, atmospheric thermal action wasstrong, leading to weak instable and instable stratifications. Using the correctedturbulent wind velocity, we estimated a few turbulent parameters during theobservational period. When dimensionless velocity standard deviation is plottedagainst the stability parameter (z/L), their relationship accords with the1/3power law.Intensities of turbulence in u, v and w direction are estimated to be0.091,0.076and0.043. The friction velocity is the function of the averaged wind velocity and can beexpressed asu*=0.0375*U0.0278. The drag coefficient is estimated to be(1.30±0.26)×10-3, which is similar to the values reported in this sea region.3. When the platform is moving, the observation influence factors of theturbulent wind velocity observation are more complex. We adopt a few steps such asthe singularity processing, ship-gesture adjustment, improved filtering correction,coordinate conversion, singularity with large magnitude scale rejection, and lineartrend removal to minimize the interference from the movement and the rocking of theplatform, and the influence of the platform obstacles to wind velocity observation.After a series of correction steps, the characterization of turbulent such as therelationship between dimensionless velocity standard deviation (σ u/u*,σ v/u*,σ w/u*) and the stability parameter (z/L), intensities of turbulence in u, v and wdirection, the friction velocity, and the drag coefficient are very consistent with stopthe ship material. The data quality of the sailing stations can be used to estimate theflux of the turbulent.4. In the North West Pacific the mean sensible heat flux and latent heat flux are6.8W/m2and107.6W/m2. While the mean Bowen ratio during this voyage is about0.063, latent heat flux is much higher than sensible heat flux, and the heat flux aremost positive, i.e., the heat is transmitted from marine to atmosphere. The dailychanges of the mean sensible heat flux and the latent heat flux are both not obvious.During the day, because of the solar radiation the temperature of sea surface roseslightly, which makes the latent heat flux is slightly higher than night.5. This study compares the mean heat flux result of ECMWF and OAFlux products from September to November,2005, in the North West Pacific. Comparedwith observation experiment, the heat flux result of ECMWF is bigger. The OAFlux’sresult of sensible heat flux and latent heat flux is similar to our study in the NorthWest Pacific, and the Bowen ratio is between0.05and0.09, which is also consistentwith our study and the values reported in this sea region. Thus, the OAFlux productsare constructed from an optimal blending of several kinds of data source, such assatellite retrievals and three atmospheric reanalysis. The OAFlux project improves theestimates of latent and sensible heat fluxes through utilizing the best possible surfacemeteorological variables and the best possible bulk flux algorithm (COARE3.0). Thisalgorithm is shown to be accurate within five percent for wind speeds of0–10m/s andten percent for wind speeds between10and20m/s.