Climatology of Wind, Kinetic Energy, and Temperature Spectra Using a High-Resolution Climate Model for Mid-Europe

Abstract

Spectra of wind, kinetic energy, and temperature are investigated for a dataset of 10 years of regional climate simulations for mid-Europe. The nonhydrostatic Consortium for Small-Scale Modeling (COSMO) model in Climate Mode [COSMO-CLM (CCLM)] climate model is used in a hindcast mode for 1991–2000. The three-step nesting chain starts with a CCLM run with 18-km resolution covering all of Europe nested in ERA-40 reanalyses and then a run with a resolution of 4.4 km is performed for mid-Europe. Finally, the 1.3-km run focuses on the region of mid-Germany and Luxembourg. In the present study, only results for the 4.4- and 1.3-km runs are shown. Different methods based on the Fourier and cosine transformations for the computation of the spectra are evaluated. The kinetic energy spectra show the expected slope in the mesoscale (up to the effective resolution), while the spectrum of the vertical wind shows a zero-slope behavior. The spectra of the horizontal wind components and temperature compare well to the observations. The effective model resolution was found to be about 7–10 (5–7) times the horizontal grid spacing for the one-dimensional (two-dimensional) spectral methods. A comparison between the different model resolutions shows a benefit of the 1.3-km simulations for the boundary layer for horizontal scales up to 25 km. The multiyear time-scale simulations allow for a climatological study of the seasonal cycle. The kinetic energy spectrum is found to have the largest values in summer.

The Horizontal Spectrum of Vertical Velocities near the Tropopause from Global to Gravity Wave Scales

“…The contributions from divergent and vertical waves perpendicular to the flight direction are not dominant at mesoscales in these measurements. The relatively small difference between 1D and 2D spectra at mesoscales is also supported by model results (Zentek et al 2016).…”

“…Vertical wind at large horizontal scales is mostly weak and difficult to determine (Holton 2012;Bony and Stevens 2019). Models and observations often show a maximum of w variance at the smallest resolved scales, leaving the ultimate explanation of this maximum open (Sharman et al 2012;Zentek et al 2016;Smith and Kruse 2017).…”

Regulating Fine‐Scale Resolved Convection in High‐Resolution Models for Better Hurricane Track Prediction

“…The zoomed‐in views (Figures 4c and 4d) show that the resolved convection with hord5 is noisier and less well‐organized than with hord6 . The variance spectrum of w500 in Figure 4g (Zentek et al., 2016) quantifies the spatial scale difference of resolved convection between the two experiments. The comparison indicates that vertical motions from the two model configurations mostly differ at the small horizontal scales, roughly below 4 times the model's grid spacing (approximately 13 km): the variance is much larger in the hord5 run than in the hord6 run at this spatial scale.…”

A model‐based comparison of extreme winds in the Arctic and around Greenland

“…Despite their importance, the intensity and frequency of near‐surface winds are underestimated in state‐of‐the‐art climate models because of the rather coarse horizontal resolution (Kolstad, ; Sproson et al ., ; DuVivier and Cassano, ; Moore et al ., ). The “effective resolution” is even lower and about 5–7 times the native grid resolution (Skamarock, ; Zentek et al ., ). A sufficiently high horizontal resolution of atmospheric models is therefore crucial to simulate these mesoscale wind phenomena.…”