Fig. 1
The model domain and orography. The border of the extension zone is denoted with the black line.
Fig. 2
(a) A kinetic energy spectrum, obtained as a sum of rotational and divergent energy and a spectrum obtained from u and v wind components at a model level close to 530 hPa. A randomly selected date is 20 July, 18 UTC run, 6-hour forecast and the spectra are produced by the detrending procedure. Short dotted lines have slopes and . The dashed line is Lindborg (1999) functional fit [eq. (71)] to aircraft observations. (b) The difference between kinetic energy computed from the wind components and from rotational and divergent energy using the two biperiodisation techniques normalised by the kinetic energy computed from the wind components. The result is averaged over all model levels and over one-month period.
Fig. 3
Energy spectra averaged over model levels between 9 and 11 km. VOR denotes rotational kinetic energy (blue line), DIV divergent kinetic energy (red line), VOR+DIV denotes total kinetic energy as a sum of the rotational and divergent components (black line) whereas U+V stands for the total kinetic energy computed from the velocity components (green line).
Fig. 4
Monthly and vertically averaged spectra of rotational (blue), divergent (red) and total kinetic energy (black) in (a) the free troposphere, (b) the planetary boundary layer (PBL) and (c) the stratosphere. (d) Divergent kinetic energy in various layers.
Fig. 5
Spectrum of the model surface geopotential height. The dotted lines are and , the dashed line is the best linear fit ().
Fig. 6
Monthly and vertically averaged spectra of rotational (a) and divergent kinetic energy (b) in the free troposphere with the spread included. The shaded area encloses plus/minus one standard deviation.
Fig. 7
The slope of the spectra of rotational (blue), divergent (red) and total kinetic energy (black) as a function of pressure. Spectra were fitted in the range between 150 and 30 km. The thin grey line represents −5/3.
Fig. 8
The scale at which divergent kinetic energy exceeds rotational kinetic energy as a function of pressure.
Fig. 9
(a) The fraction of divergent energy in the total kinetic energy in the same layer for stratosphere (black), free troposphere (blue) and PBL (red). (b) The fraction of divergent energy in the total kinetic energy across all model levels for stratosphere (black), free troposphere (blue), PBL (red) and all model levels (green).
Fig. 10
Distribution of divergent energy contribution with respect to altitude and horizontal scale. Divergent energy is expressed as the fraction of the total kinetic energy at each model level. Contour interval is 0.05 (5%).
Fig. 11
Vertical distribution of the average fraction of divergent energy in the total kinetic energy. The averaging is done over the scales below 300 km.
Fig. 12
Distribution of divergent energy contribution with respect to altitude and horizontal scale, based on the biperiodization using the extension zone.
Fig. 13
Vertical distribution of the average fraction of divergent energy in the total kinetic energy for both biperiodization techniques.
Fig. A1
Extension of the zonal wind component at model level close to 500 hPa for a random date and a random model-grid row.