Search results for "scale [mass]"
showing 10 items of 997 documents
Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory
2018
We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4 EeV measured using the Pierre Auger Observatory. For the energy bins [4,8] EeV and $E\geq 8$ EeV, the most significant signal is a dipolar modulation in right ascension at energies above 8 EeV, as previously reported. In this paper we further scrutinize the highest-energy bin by splitting it into three energy ranges. We find that the amplitude of the dipole increases with energy above 4 EeV. The growth can be fitted with a power law with index $\beta=0.79\pm 0.19$. The directions of the dipoles are consistent with an extragalactic origin of these anisotropies at all the energies considered. Addi…
A one-dimensional simulation of the interaction between land surface processes and the atmosphere
1992
A one-dimensional soil-vegetation model is developed for future incorporation into a mesoscale model. The interaction of land surface processes with the overlying atmosphere is treated in terms of three coupled balance equations describing the energy and moisture transfer at the ground and the energy state of the vegetation layer. For a complete description of the interaction, the coupled processes of heat and moisture transport within the soil are included as a multilayer soil model. As model verification, successful reproductions of the observed energy fluxes over vegetated surfaces from the HAPEX-MOBILHY experiment in southwestern France and from the LOTREX-10E/HIBE88 field experiment in…
Bias correction of dynamically downscaled precipitation to compute soil water deficit for explaining year-to-year variation of tree growth over north…
2017
This paper documents the accuracy of a post-correction method applied to precipitation regionalized by the Weather Research and Forecasting (WRF) Regional Climate Model (RCM) for improving simulated rainfall and feeding impact studies. The WRF simulation covers Burgundy (northeastern France) at a 8-km resolution and over a 20-year long period (1989–2008). Previous results show a strong deficiency of the WRF model for simulating precipitation, especially when convective processes are involved. In order to reduce such biases, a Quantile Mapping (QM) method is applied to WRF-simulated precipitation using the mesoscale atmospheric analyses system SAFRAN («Système d'Analyse Fournissant des Rense…
Design, construction and commissioning of the Braunschweig Icing Wind Tunnel
2018
Beyond its physical importance in both fundamental and climate research, atmospheric icing is considered as a severe operational condition in many engineering applications like aviation, electrical power transmission and wind-energy production. To reproduce such icing conditions in a laboratory environment, icing wind tunnels are frequently used. In this paper, a comprehensive overview on the design, construction and commissioning of the Braunschweig Icing Wind Tunnel is given. The tunnel features a test section of 0.5 m × 0.5 m with peak velocities of up to 40 m s−1. The static air temperature ranges from −25 to +30 °C. Supercooled droplet icing with liquid water contents up to 3 g m−3 c…
Comparative assessment of RAMS and WRF short-term forecasts over Eastern Iberian Peninsula using various in-situ observations, remote sensing product…
2018
The Regional Atmospheric Modeling System (RAMS) and the Weather Research and Forecasting (WRF) mesoscale models are being used for weather and air quality studies as well as forecasting tools in Numerical Weather Prediction (NWP) systems. In the current study, we perform a comparative assessment of these models under distinct typical atmospheric conditions, classified according to the dominant wind flow and cloudiness, over Eastern Iberian Peninsula. This study is focused on the model representation of key physical processes in terms of meteorology and surface variables during a 7-days period in summer 2011. The hourly outputs produced by these two models are compared not only with observed…
Sting Jets in Simulations of a Real Cyclone by Two Mesoscale Models
2010
AbstractThe existence of sting jets as a potential source of damaging surface winds during the passage of extratropical cyclones has recently been recognized. However, there are still very few published studies on the subject. Furthermore, although it is known that other models are capable of reproducing sting jets, in the published literature only one numerical model [the Met Office Unified Model (MetUM)] has been used to numerically analyze these phenomena. This article aims to improve our understanding of the processes that contribute to the development of sting jets and show that model differences affect the evolution of modeled sting jets. A sting jet event during the passage of a cycl…
Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolut…
2017
Abstract. Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave characteristics due to differing atmospheric background conditions. While wave breaking occurred at altitudes between 25 and 30 km during the first event due to weak stratospheric winds, waves propagated to altitudes above 30 km and interfacial waves formed in the troposphere at a stratospheric intrusion layer during the second event. Global an…
Exploring the linkage between dew point temperature and precipitation extremes: A multi-time-scale analysis on a semi-arid Mediterranean region
2021
Abstract Understanding warming climate implications on precipitation is of crucial importance, especially for areas particularly subjected to climate changes and land use/cover modifications, which could be extremely vulnerable to phenomena typically caused by rainfall extremes, such as floods and landslides. Past decade has been witnessing an increasing interest on simple modeling approaches based on the observation of commonly available meteorological variables and their physical linkages. In particular, based on the well-known thermodynamic Clausius-Clapeyron (CC) equation, it was widely investigated the scaling relation between rainfall extremes and variables representative of the near …
Large-scale Rossby wave and synoptic-scale dynamic analyses of the unusually late 2016 heatwave over Europe
2018
This paper analyses the late summer heatwave over Europe in 2016. Central, western and southwestern Europe were primarily affected by the high temperatures. Seville, Spain, for example, experienced the highest September temperature on record on 5 September 2016, reaching a maximum of 44.8°C, and temperatures in Trier, Germany reached 34.2°C on 13 September 2016. The heatwave was marked by three distinct peaks, accompanied by record‐breaking values for 500hPa geopotential heights and, to a lesser extent, 850hPa temperatures. These peaks were associated with the arrival of high‐amplitude Rossby wave packets in western Europe. The latter originated several days before the event over western No…
Improving RAMS and WRF mesoscale forecasts over two distinct vegetation covers using an appropriate thermal roughness length parameterization
2019
Land Surface Models (LSM) have shown some difficulties to properly simulate day-time 2-m air and surface skin temperatures. This kind of models are coupled to atmospheric models in mesoscale modelling, such as the Regional Atmospheric Modeling System (RAMS) and the Weather Research and Forecasting (WRF) Model. This model coupling is used within Numerical Weather Prediction Systems (NWP) in order to forecast key physical processes for agricultural meteorology and forestry as well as in ecological modelling. The current study first evaluates the surface energy fluxes and temperatures simulated by these two state-of-the-art NWP models over two distinct vegetated covers, one corresponding to a …