Naslov  Lowlevel turbulence characteristics over inhomogeneous surface during wintertime 
Autor  Karmen Babić 
Voditelj/Mentor  Zvjezdana Bencetić Klaić

Sažetak rada  In this dissertation, the local similarity scaling approach was examined based on the multilevel measurements of atmospheric turbulence in the wintertime (December 2008 February 2009) stable atmospheric boundary layer (SBL) established over a heterogeneous surface influenced by mixed agricultural, industrial and forest surfaces. The 62 m tower (levels 20, 32, 40, 55 and 62 m above ground) was situated in the middle of some 120 m × 480 m area of hc = 18 m high walnut trees. The heterogeneity of the surface was characterized by spatial variability of both roughness and topography. In a first step local similarity theory in terms of fluxvariance and fluxgradient relationships was investigated. Nieuwstadts local scaling approach was found to be suitable for the representation of all three wind velocity components. The roughness sublayer (RSL) influenced wind variances, and consequently the turbulent kinetic energy (TKE) and correlation coefficients at the lowest measurement level, but not the wind shear profile. After removing data points associated with the flux Richardson number (Rf) greater than 0.25, the observations support the classical linear expressions for the dimensionless wind shear ([phi]m) even over inhomogeneous terrain. Levelingoff of [phi]m at higher values of stability parameter was found to be a result of the large number of data characterized by smallscale turbulence (Rf > 0.25). Deviations from linear expressions were shown to be mainly due to smallscale turbulence rather than due to the surface heterogeneities, supporting the universality of the linear relationship. Additionally, the fluxgradient dependence on stability did not show different behavior for different wind regimes, indicating that the stability parameter is a sufficient predictor for fluxgradient relationships. Data followed the local zless scaling for [phi]m when the prerequisite Rf[less than or equal to]0.25 was imposed. Further investigations focused on the combined influence of the RSL found above tall vegetation and the internal boundary layer (IBL) on the turbulence spectral characteristics and TKE budget. The traditional surface layer scaling was tested against the canopy scaling, which is generally valid for the RSL. It was found that canopy scaling can be successfully applied even within the transition layer. For the present complex site local isotropy was not found. Vertical velocity spectra were smaller than horizontal spectra. Similarly, dissipation rates ([epsilon]) determined only from vertical spectra were smaller than [epsilon] estimates based on horizontal components. Therefore, it was necessary to normalize vertical wind speed spectra with [phi][epsilon]w in order to get good correspondence with the Kansas spectral models. Extending the analysis to the Olesen approach, applied for the first time to the SBL over heterogeneous terrain, normalized spectra collapsed to one single curve. Finally, analyzing the budget terms of the TKE equation, nonequilibrium conditions were found. The nonlocal dynamics are considered to be the main reason for the observed imbalance of TKE in the transition layer as well as for the observed breakdown of zless regime in the strongly stable conditions above heterogeneous surface. In the RSL, the turbulent transport of TKE above vegetated canopies is considered to be the main cause of the observed TKE imbalance in the neutral conditions. A less systematic behavior of the residual term was observed indicating that the advection term has more pronounced influence on the RSL than the upper levels. 
Ključne riječi  stabilni granični sloj lokalno skaliranje šumski pokrov podsloj hrapavosti turbulentna kinetička energija (TKE) spektralni modeli budžet TKE 
Naslov na drugom jeziku (hrvatski)  Karakteristike prizemne turbulencije zimi iznad nehomogene podloge 
Povjerenstvo za obranu  Branko Grisogono (predsjednik povjerenstva) Mathias W. Rotach (član povjerenstva) Zvjezdana Bencetić Klaić (član povjerenstva) Željko Večenaj (član povjerenstva)

Ustanova koja je dodijelila akademski/stručni stupanj  Sveučilište u Zagrebu Prirodoslovnomatematički fakultet 
Ustrojstvena jedinica niže razine  Geofizički odsjek 
Mjesto  Zagreb 
Država obrane  Hrvatska 
Znanstveno područje, polje, grana  PRIRODNE ZNANOSTI Geofizika Meteorologija s klimatologijom

UDK  55 PRIRODNE ZNANOSTI Geologija. Meteorologija. Hidrologija 
Vrsta studija  sveučilišni 
Stupanj  poslijediplomski doktorski 
Naziv studijskog programa  Fizika 
Akademski / stručni naziv  doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika 
Kratica akademskog / stručnog naziva  dr. sc. 
Vrsta rada  disertacija 
Jezik  engleski 
Datum obrane  20160920 
Datum promocije  20160920 
Sažetak rada na drugom jeziku (engleski)  In this dissertation, the local similarity scaling approach was examined based on the multilevel measurements of atmospheric turbulence in the wintertime (December 2008 February 2009) stable atmospheric boundary layer (SBL) established over a heterogeneous surface influenced by mixed agricultural, industrial and forest surfaces. The 62 m tower (levels 20, 32, 40, 55 and 62 m above ground) was situated in the middle of some 120 m × 480 m area of hc = 18 m high walnut trees. The heterogeneity of the surface was characterized by spatial variability of both roughness and topography. In a first step local similarity theory in terms of fluxvariance and fluxgradient relationships was investigated. Nieuwstadts local scaling approach was found to be suitable for the representation of all three wind velocity components. The roughness sublayer (RSL) influenced wind variances, and consequently the turbulent kinetic energy (TKE) and correlation coefficients at the lowest measurement level, but not the wind shear profile. After removing data points associated with the flux Richardson number (Rf) greater than 0.25, the observations support the classical linear expressions for the dimensionless wind shear ([phi]m) even over inhomogeneous terrain. Levelingoff of [phi]m at higher values of stability parameter was found to be a result of the large number of data characterized by smallscale turbulence (Rf > 0.25). Deviations from linear expressions were shown to be mainly due to smallscale turbulence rather than due to the surface heterogeneities, supporting the universality of the linear relationship. Additionally, the fluxgradient dependence on stability did not show different behavior for different wind regimes, indicating that the stability parameter is a sufficient predictor for fluxgradient relationships. Data followed the local zless scaling for [phi]m when the prerequisite Rf[less than or equal to]0.25 was imposed. Further investigations focused on the combined influence of the RSL found above tall vegetation and the internal boundary layer (IBL) on the turbulence spectral characteristics and TKE budget. The traditional surface layer scaling was tested against the canopy scaling, which is generally valid for the RSL. It was found that canopy scaling can be successfully applied even within the transition layer. For the present complex site local isotropy was not found. Vertical velocity spectra were smaller than horizontal spectra. Similarly, dissipation rates ([epsilon]) determined only from vertical spectra were smaller than [epsilon] estimates based on horizontal components. Therefore, it was necessary to normalize vertical wind speed spectra with [phi][epsilon]w in order to get good correspondence with the Kansas spectral models. Extending the analysis to the Olesen approach, applied for the first time to the SBL over heterogeneous terrain, normalized spectra collapsed to one single curve. Finally, analyzing the budget terms of the TKE equation, nonequilibrium conditions were found. The nonlocal dynamics are considered to be the main reason for the observed imbalance of TKE in the transition layer as well as for the observed breakdown of zless regime in the strongly stable conditions above heterogeneous surface. In the RSL, the turbulent transport of TKE above vegetated canopies is considered to be the main cause of the observed TKE imbalance in the neutral conditions. A less systematic behavior of the residual term was observed indicating that the advection term has more pronounced influence on the RSL than the upper levels. 
Ključne riječi na drugom jeziku (engleski)  Stable boundary layer Local scaling Forest canopy Roughness sublayer Turbulent kinetic energy Spectral models TKE budget 
Opseg  147 str. 
Verzija  obranjena verzija 
Vrsta resursa  tekst 
Prava pristupa  Rad u otvorenom pristupu 
Uvjeti korištenja rada  
URN:NBN  https://urn.nsk.hr/urn:nbn:hr:217:047214 
Repozitorij  https://repozitorij.pmf.unizg.hr 