The seasonal-diurnal variation of surface winds observed at Adelaide Airport (South Australia) over 40 years is modelled in terms of the zonal-meridional wind vectors. Calms are assessed separately from the wind vectors. The joint probability density function of the wind vectors is modelled as the sum of a number of disjoint bivariate normal distributions in the zonal-meridional plane. An overview of the data suggests three diurnal mechanisms: sea-to-land breezes, land-to-sea breezes and downslope drainage flows off the Adelaide Hills, together with two non-diurnal large-scale weather mechanisms that are modulated by the annual migration of the sub-tropical ridge. It is shown that, typically, two of the three diurnal components contribute to the joint probability density function for any given hour of day and month, together with the two large-scale weather components. Optimisation is used to quantify the model parameters directly from the joint probability density function. The robustness of the methodology is verified using standard “Bootstrapping” methods. The model elucidates the principal climate mechanisms at Adelaide in terms of the seasonaldiurnal variation of the joint statistics of wind speed and direction using just the mean, annual, semi-annual, diurnal and semi-diurnal harmonics.

/pdf/a-statistical-model-of-the-seasonal-diurnal-wind-climate-at-1k8ob96rov.pdf

A statistical model of the seasonal-diurnal wind climate at Adelaide

High Resolution WRF Simulations for the Tel‐Aviv Metropolitan Area Reveal the Urban Fingerprint in the Sea‐breeze Hodograph

Studies on the Vertical Structure of Horizontal Wind Variability in the Surface Boundary Layer Over Sriharikota

The Haurwitz sea-breeze theory, and modifications by Kusuda and Alpert, are not generally applicable to observed winds in coastal regions, in part because they make no allowance for spatial evolution of wind hodographs. This is demonstrated by integrating the Haurwitz equations of motion to find trajectories of air reaching the shoreline at various times of day through the action of a large-scale pressure gradient force. Hodographs and momentum advection are computed from the trajectories. Hodograph size, shape, and orientation depend on distance from the shoreline, friction, spatial distribution of the time-varying part of the geostrophic wind (that parallel to the shore), and other factors. Differences between the hodographs found here and those found by Haurwitz, or by Kusuda and Alpert are largely related to nonlinearity.

D. O. Staley

Papers

The Surface Sea Breeze: Applicability of Haurwitz-Type Theory