An Investigation on Effect of Data Resolution on Vertical Wavenumber Spectrum of Gravity Waves From Radiosonde Observations

Abstract

Spectral structure of gravity waves (GWs) attracted much attention because it is related to wave dissipation mechanism and parameterization effect. Although many works have studied the spectral variation of GWs and attributed this change to factors such as height, season and latitude, impact of observational resolution on wave spectrum was rarely reported. By averaging and downsampling 5-m resolution radiosonde temperature, we construct two data sets with lower resolutions to investigate the effect of data resolution on vertical wavenumber spectrum of GWs. The constructed average and downsample data sets correspond to two measurement techniques in actual observations. The results indicate that a lower resolution causes a shallower slope of power spectrum density (PSD) due to its filter effect on high wavenumber spectrum close to the saturation spectrum. Nevertheless, there are some differences in spectral dependence on resolution between the two data. The shallowing slope is further enhanced in the downsample data due to significant increase of PSD amplitudes near maximum wavenumbers by superposition of subgrid scale perturbations, in contrast, slightly counteracted in the average data owing to weak attenuation of PSD amplitudes near maximum wavenumbers by smoothing. Hence, variation of observed wave spectrum may stem from resolution as well as data sampling technique, rather than only geophysical causes.