Microburst detection with the WRF model: effective resolution and forecasting indices

Microbursts are meteorological phenomena in the lower troposphere which can produce damaging surface winds and pose a severe risk to aircraft flying close to the ground. As these events usually span less than 4 km and 15 min, the spatiotemporal resolution is a challenge for numerical simulations. Although research of microburst using operative mesoscale models is scarce, the Weather Research and Forecasting (WRF) model has been used in the diagnosis of this phenomenon. In this paper, such model is used to simulate several microburst conducive days using two different boundary conditions. The energy spectra of the simulations are computed to evaluate the effective resolution of the model. The results are in line with previous studies and produce no notable differences among the boundary conditions. Nonetheless, the energy spectra show an overenergetic troposphere at microscale resolutions, rendering the effective resolution inadequate for microburst forecasting using the simulated physics variables. Thus, mesoscale indices are analyzed as a prognostic tool. The wind index, the wet microburst severity index and the microburst windspeed potential index do not show high forecasting performances, even though improving the results of climatology. Also, notable differences among the boundary conditions can be seen. The most consistent results are achieved by the wet microburst severity index

Overview of the main radiation transport codes

Accurate predictions of expected radiation dose levels on Mars are often provided by specific radiation transport codes that have been adapted to space conditions. Unsurprisingly, several of the main space agencies and institutions involved in space research and technology tend to work with their own in-house radiation codes. We present the codes that are related to the simulation of the radiation on Mars' surface under different scenarios. All of these codes have similar fields of application, but they differ with respect to several aspects, including the energy range and types of projectiles considered as well as the models of nuclear reactions considered

Impacts of afternoon and evening sea-breeze fronts on local turbulence, and on CO2 and radon-222 transport

We investigated sharp disruptions of local turbulence and scalar transport due to the arrival of sea-breeze fronts (SBFs). To this end, we employed a comprehensive 10-year observational database from the Cabauw Experimental Site for Atmospheric Research (CESAR, the Netherlands). Sea-breeze (SB) days were selected using a five-filter algorithm, which accounts for large-scale conditions and a clear mesoscale-frontal signal associated with the land-sea contrast. Among those days (102 in all, 8.3%), based on the value of the sensible-heat flux at the onset of SB, we identified three atmospheric boundary-layer (ABL) regimes: convective, transition and stable. In the convective regime, the thermally driven convective boundary layer is only slightly altered by a small enhancement of the shear when the SBF arrives. Regarding the transition regime, we found that the ABL afternoon transition is accelerated. This was quantified by estimating the contributions of shear and buoyancy to the turbulent kinetic energy. Other relevant disruptions are the sharp reduction in ABL depth (similar to 250 m/hr) and the sudden increase in average wind speed (> 2 m/s). In the stable regime, the arrival of the SB leads to disturbances in the wind profile at the surface layer. We observed a deviation of more than 1 m/s in the observed surface-layer wind profile compared with the profile calculated using Monin-Obukhov Similarity Theory (MOST). Our findings furthermore reveal the determinant role of the SB direction in the transport of water vapour, CO2 and Rn-222. The return of continental air masses driven by the SB circulation generates sharp CO2 increases (up to 14 ppm in half an hour) in a few SB events. We suggest that the variability in Rn-222 evolution may also be influenced by other non-local processes such as the large-scale footprint from more remote sources