Developing Aviation Turbulence Diagnostics based on Convectively Induced Gravity Wave Drag

Convection is one of the major sources generating turbulence. Near-cloud turbulence (NCT) occurs above the convection under the clear-air weather conditions, mostly due to breaking of convective gravity waves (CGWs). The current operational forecasting systems of aviation turbulence do not include diagnostics related to NCT, resulting in relatively low forecasting performance in summertime. In the present study, we develop diagnostics of NCT utilizing the parameterization scheme of CGWs proposed by Chun and Baik, used in climate models, in two ways by calculating (i) drag of CGWs (CGWD) and (ii) turbulent kinetic energy (TKE) using the minimum Richardson number including the effect of CGWs (Rim_CGW). Feasibility of the approaches is examined based on a numerical simulation for the real case that occurred over the border area between Missouri and Illinois on 9 March 2006. The numerical simulation is conducted using the Advanced Research Weather Research and Forecasting (ARW-WRF) model with three domains with horizontal grid spacings of 30, 10, and 3.3 km, respectively, at 82 vertical layers from the surface to 26.3 km. The regions of non-zero GWDC calculated in 10 km horizontal domain are well matched with those of the observed NCTs outside an active shallow convection. The value of GWDC for the moderate or greater (MOG)-level observed NCTs is 0.1 m/s/hr, and the diffusion coefficients corresponding to the CGWD is 2.39 m²/s. This leads to eddy dissipation rate (EDR) of 0.095 m^2/3/s, based on the formulation by Bertin et al. TKE is also calculated in 10 km horizontal domain using diffusion coefficient that is derived using Rim_CGW, and resultant EDR is 0.1 m^2/3/s. The estimated EDRs in the two approaches are comparable. It is noteworthy that TKE calculated here is subgrid-scale TKE by  including the effect of CGWs, where TKE does not exist from the planetary boundary layer scheme. The results demonstrate that the CGW parameterization represents reasonably well the aviation turbulence related to breaking of CGWs in clear air condition, at least the current case. Sensitivity of the results to model resolution will be also presented in the conference.