Processes controlling the evolution of deep moist convection in the summertime West African Sahel

Deep moist convection and mesoscale convective systems (MCSs) are integral to the West African monsoon and, as the main rain-producing mechanism in the Sahel, are essential to the livelihoods of millions. Current operational forecasting models struggle to predict rainfall with a good precision. It is therefore necessary to study the processes controlling deep moist convection in detail, in order to understand them better and to be able to evaluate simulations to identify errors for future model development. In this thesis properties of cold pools from Sahelian MCSs were characterised from surface observations. It was observed that early season cold pools were stronger and drier, likely due to drier mid-levels before the monsoon onset. The properties of observed cold pools were used to evaluate a Unified Model (UM) convection-permitting simulation. The comparison showed that simulated cold pools are generally weaker than observed. Cold pools and MCS structure were further investigated in two case studies. This enabled an analysis of MCS vertical structure. Processes controlling the diurnal cycle of convection were analysed using observations and UM simulations. This showed that while surface CAPE follows a diurnal cycle with a maximum in the afternoon and minimum in the early morning, elevated CAPE was found to have a nearly opposite cycle, due to advection of high equivalent potential temperature air overnight by the nocturnal low-level jet. In addition, the low-level jet provides low-level wind shear which balances the cold-pool related vorticity and helps to maintain the MCS until morning, when the jet decays and MCSs tend to dissipate. The jet also creates moisture flux convergence overnight, supporting MCSs. Finally, mechanisms underlying storm initiation and regeneration were analysed in UM simulations, showing the roles of soil moisture boundaries, pre-existing cold pools and bookend vortices

Business plan of a small company

Předmětem této bakalářské práce je vypracování všech aspektů podnikatelského plánu malé firmy. První část práce je zaměřená na teoretická východiska této problematiky. Ve druhé části je zpracován konkrétní podnikatelský plán společnosti PROFA, s.r.o. Podnikatelským záměrem společnosti je balíček služeb týkající se servisu pro profesionální sportovce. Výstupem práce je konkrétní znění všech částí podnikatelského plánu a budoucí možnost využít tuto práci pro založení skutečného podniku.ObhájenoThe main subject of this thesis is a business plan of a small company. The first part deals with the theoretical basis. The second part is focused on specific business plan of the company PROFA, s.r.o. The company's purpose is to offer a service package to professional athletes. The output of this thesis is a description of all parts of this specific business plan and the possibility to use it to start a new business in the future

A Characterization of Cold Pools in the West African Sahel

Cold pools are integral components of squall-line mesoscale convective systems and the West African Monsoon, but are poorly represented in operational global models. Observations of thirty-eight cold pools made at Niamey during the 2006 AMMA (African Monsoon Multidisciplinary Analysis) campaign (1 June to 30 September 2006), are used to generate a seasonal characterization of cold-pool properties by quantifying related changes in surface meteorological variables. Cold pools were associated with temperature decreases of 2 to 14 ͦC, pressure increases of 0 to 8 hPa and wind gusts of 3 to 22 m s-1. Comparison with published values of similar variables from the Great Plains of the USA showed comparable differences. The leading part of most cold pools had decreased water vapour mixing ratios compared to the environment, with moister air, likely related to precipitation, approximately 30 minutes behind the gust front. A novel diagnostic used to quantify how consistent observed cold pool temperatures are with saturated or unsaturated descent from mid-levels (Fractional Evaporational Energy Deficit, FEED) shows that early-season cold pools are consistent with less saturated descents. Early season cold pools were relatively colder, windier and wetter, consistent with drier mid-levels, although this was only statistically significant for the change in moisture. Late season cold pools tended to decrease equivalent potential temperature from the pre-cold-pool value, whereas earlier in the season changes were smaller, with more increases. The role of cold pools may therefore change through the season, with early season cold-pools more able to feed subsequent convection

The 2015 Indian summer monsoon onset - phenomena, forecasting and research flight planning

From May to July 2016, as part of the INCOMPASS project, the Facility for Airborne Atmospheric Measurements (FAAM, jointly funded by the Met Office and NERC) BAe-146 research aircraft travelled to India to record key aspects of the Indian summer monsoon onset and evolution. As part of the planning for the campaign, partners in the UK and India took part in a dry-run forecasting exercise during 2015, to assess the reliability of the forecast products and develop a set of flight plans, in advance of the real campaign, and to get a real-time feel for the monsoon onset. 5-day forecasts from the Met Office and the Indian National Centre for Medium Range Weather Forecasting (NCMRWF) showed good skill in terms of predicting the advance of rainfall in regions key for the campaign in north and south India, and captured transitions from active (wet) monsoon conditions to break (dry) periods and back again. Key phenomena seen during the dry-run exercise include (1) a western disturbance, which had a major effect on the extreme pre-monsoon heatwave conditions over India; (2) dry intrusions, which are thought to be important in the progression of the monsoon onset against the synoptic flow; and (3) cyclones Ashobaa and Komen

Modeling Haboob Dust Storms in Large-Scale Weather and Climate Models

Recent eld campaigns have shown that haboob dust storms, formed by convective cold pool outflows, contribute a significant fraction of dust uplift over the Sahara and Sahel in summer. However, in-situ observations are sparse and haboobs are frequently concealed by clouds in satellite imagery. Furthermore, most large-scale weather and climate models lack haboobs, because they do not explicitly represent convection. Here a one-year long model run with explicit representation of convection delivers the first full seasonal cycle of haboobs over northern Africa. Using conservative estimates, the model suggests that haboobs contribute one fifth of the annual dust-generating winds over northern Africa, one fourth between May and October, and one third over the western Sahel during this season. A simple parameterization of haboobs has recently been developed for models with parameterized convection, based on the downdraft mass flux of convection schemes. It is applied here to two model runs with different horizontal resolutions, and assessed against the explicit run. The parameterization succeeds in capturing the geographical distribution of haboobs and their seasonal cycle over the Sahara and Sahel. It can be tuned to the different horizontal resolutions, and different formulations are discussed with respect to the frequency of extreme events. The results show that the parameterization is reliable and may solve a major and long-standing issue in simulating dust storms in large-scale weather and climate models

Business plan of a small company

Předmětem této bakalářské práce je vypracování všech aspektů podnikatelského plánu malé firmy. První část práce je zaměřená na teoretická východiska této problematiky. Ve druhé části je zpracován konkrétní podnikatelský plán společnosti PROFA, s.r.o. Podnikatelským záměrem společnosti je balíček služeb týkající se servisu pro profesionální sportovce. Výstupem práce je konkrétní znění všech částí podnikatelského plánu a budoucí možnost využít tuto práci pro založení skutečného podniku.ObhájenoThe main subject of this thesis is a business plan of a small company. The first part deals with the theoretical basis. The second part is focused on specific business plan of the company PROFA, s.r.o. The company's purpose is to offer a service package to professional athletes. The output of this thesis is a description of all parts of this specific business plan and the possibility to use it to start a new business in the future