Assessment of turbulent scales over complex terrain in central Spain

In this work, a micrometeorological assessment of Atmospheric Boundary Layer paremeters is carried out in order to determine the characteristic turbulent scales over complex terrain in the Sierra de Guadarrama, a range in central Spain. Observational data series of temperature and wind velocity measured at high frecuency (10 Hz) are available. These data come from two different stations located in the Bosque de La Herrería and belonging to GuMNet (2020) (Guadarrama Monitoring Network).

Integral scales, both time and spatial, have been determined for different atmospheric conditions, defined by parameters such as wind direction or stability of stratification. Also, energy cascade phenomenon occurence is assessed. In order to carry this out, different time series analysis tools are used, such as autocorrelation functions in time, and normalised power spectra or wavelets. Results obtained are compared with previous works.

In general, results show that under no synoptic forcing there is a clear dependency on diurnal cycle, giving rise to the development of big integral scales at nighttime, while they are small during the day. When synoptic forcing prevails, the scales are also small, both at daytime and nighttime. Moreover, a correlation patterns method has been implemented for scales obtained at two different heights (4 and 8 meters) on the one hand and at two locations on the other. In the first case, integral scales are highly correlated, exceeding the threshold of 0.5. In the second case, temporal scales show high correlation values, but spatial ones do not.  In addition, the slopes of the spectra in the inertial subrange have  been obtained and compared to those over homogeneous terrain (Kaimal et al., 1972), getting similar results for velocity turbulent components but not in case of vertical kinematic momentum and heat fluxes.

 

References

GuMNet: Guadarrama Monitoring Network (UCM), https://www.ucm.es/gumnet/, 2020.

Kaimal, J. C., Wyngaard, J. C., Izumi, Y., and Coté, O. R.: Spectral characteristics of surface- layer turbulence, Quart. J. R. Met. Soc., 98, 563–589, 1972.