Analytical evaluation of mesoscale fluxes and pressure field

Abstract

Abstract. Terrain in natural areas is never homogeneous: there may be a variety of vegetation types and patches of vegetated and unvegetated areas which can modify the mesoscale atmospheric flow. Moreover, horizontal thermal inhomogeneities in the planetary boundary layer are a well known source of mesoscale circulation systems such as land and sea breezes, mountain-valley winds, and urban heat island circulations. Since those phenomena are not resolved in regional scale numerical models, therefore an analytic procedure able to evaluate the relative importance of mesoscale and turbulent heat fluxes associated with surface thermal heterogeneities is of crucial importance in the optic of developing a parameterization of mesoscale effects generated by these heterogeneities for use in larger scale models. In the present paper we analyze how small a horizontal variation in surface heating can be and still produce a significant mesoscale circulation, how the heat and momentum fluxes associated to mesoscale flows can penetrate deeply into the mid-troposphere, and how they modify tropospheric relevant climate parameters, such as the atmospheric static stability. In addition, we evaluate the terms of the pressure gradient force, nonlinear and linear, non-hydrostatic and hydrostatic, as function of time and space scales of the mesoscale flow. The present paper is mainly a review of analytical results, the numerical comparison and verification using RAMS is in progress.

Land use/land cover changes and climate: modeling analysis and observational evidence

“…A spatial heterogeneity of approximately 10-20 km has often been considered sufficient for creating mesoscale circulations under convective conditions though smaller scales approximately 2-5 km are also often sufficient to trigger changes in boundary layer dynamics. [138][139][140] For the monsoon effects, the threshold may be larger. The irrigation effects for northwest India, for instance, suggest that the required landscape change is probably on the order of 50-100 km to affect the synoptic convergence patterns.…”

“…The conclusion from these studies is that LULCC can result in mesoscale and regional climate change if the areal coverage of the landscape conversion is large enough. A spatial heterogeneity of approximately 10–20 km has often been considered sufficient for creating mesoscale circulations under convective conditions though smaller scales approximately 2–5 km are also often sufficient to trigger changes in boundary layer dynamics 138–140. For the monsoon effects, the threshold may be larger.…”

Community Modeling and Long-Term Predictions of the Integrated Water Cycle. Report from the September 2012 Workshop

“…Pielke et al (2011) argues that "LULCC can result in mesoscale and regional climate change if the areal coverage of the landscape conversion is large enough. A spatial heterogeneity of approximately 10-20 km has often been considered sufficient for creating mesoscale circulations under convective conditions though smaller scales approximately 2-5 km are also often sufficient to trigger changes in boundary layer dynamics (Baldi et al, 2005). For the monsoon effects, the threshold may be larger.…”