The objective of this work was to investigate the relationship between soil water content and rainfall with rice, beans, cassava and corn yields in the semiarid region of Northeast Brazil. Precipitation and modeled soil water content were compared to yields recorded at the county levels in this region. The results were also integrated over the area of the nine States that lie within the officially recognized region of semiarid climate in Brazil. The influence of water balance components was quantified by calculating their correlation coefficient with yields of the different crop species over the municipalities of the region. It was found that rainfall had higher correlation to crop yields over most of the region, while soil water content had lower values of correlation. This result is consistent with the fact that average root depth is 40 cm, lower than the layer of soil used in the model used to estimate soil water content (100 cm). Plants respond better to the precipitation in the top layers of soil, while the water storage in the deep layer of soil might be important only in other temporal and spatial scales of the hydrological cycle.
Soil moisture is a main factor for the study of drought impacts on vegetation. Drought is a regional phenomenon and affects the food security more than any other natural disaster. Currently, the monitoring of different types of drought is based on indexes that standardize in temporal and regional level allowing, thus, comparison of water conditions in different areas. Therefore, in order to assess the impact of soil moisture during periods of drought, drought Palmer Severity Index was estimated for the entire region of the territory. For this were used meteorological data (rainfall and evapotranspiration) and soil (field capacity, permanent wilting point and water storage in the soil). The data field capacity and wilting point were obtained from the physical properties of soil; while the water storage in soil was calculated considering the water balance model. The results of the PSDI were evaluated during the years 2000 to 2015, which correspond to periods with and without occurrence of drought. In order to assess the future drought projections, considering the set of the Coupled Model Intercomparison rainfall data Project Phase 5 (CMIP5). Climate projections precipitation in CMIP5 for the period 2071-2100 was extracted generating entitled forcing scenarios Representative Concentration Pathways -RCPs, and referred to as RCOP 8.5, corresponding to an approximate radiative forcing the end the twenty-first century of 8.5 Wm -2. The results showed that the PDSI is directly associated with climatological patterns of precipitation and soil moisture in any spatial and temporal scale (including future projections). Therefore, it is concluded that the PDSI is an important index to assess soil moisture different water conditions, as well as the association with economic and social information to create risk maps for subsidies to decision makers.Keywords: Soil moisture; Palmer Drought Severity Index; Future projections; Brazil. RESUMOA umidade do solo constitui-se num dos fatores principais para o estudo da seca, do clima e da vegetação. No caso da seca, esta é um fenômeno regional e afeta a segurança alimentar mais do que qualquer outro desastre natural. Atualmente, o monitoramento dos diversos tipos de seca é feito com base em índices que os padronizam em escala temporal e regional permitindo, com isso, a comparação das condições hídricas de diferentes áreas. Assim sendo, a fim de avaliar o impacto da umidade do solo durante os períodos de seca, o Índice de Severidade de Seca de Palmer foi estimado para toda a região do território brasileiro durante o período de 2000 a 2015, os quais incluem períodos com ocorrência de seca. Para isto foram utilizadas informações meteorológicas e pedológicas extraídas do modelo de balanço hídrico. A fim de avaliar as projeções de secas futuras, considerando o conjunto de dados de precipitação e de umidade do solo do Coupled Model Intercomparison Project Phase 5 (CMIP5) para o período de 2071-2100. Os resultados mostraram que o Índice de Seca de Palmer está diretamente associado ao...
This article presents a study of three different passive devices (spires, screens, and a carpet) separately and in various combinations, to simulate the atmospheric boundary layer (ABL) in a wind tunnel with a short test chamber (465×465x1200mm). The influence of distances between these devices on the formation of the ABL is established, and optimization of variation of thicknesses of the screens (thin, medium, and coarse) on pressure loss is explored. The results obtained in this work gave support for the analysis of the atmospheric flow and turbulence at Alcantara Launching Center (ALC) in order to launch Brazilian space vehicles under safe conditions. The results show that the "spires" and the thin screen are the devices that require the least area to form an ABL in a test chamber. The physical proximity of two devices (the spires and the medium screen) also influences the size of the ABL formed, which varies from 180 to 200 mm. The power law exponent ranged from 0.12 up to 0.14 after the insertion of a carpet.
An atmospheric Internal Boundary Layer (IBL) occurs when sudden changes in surface roughness disturb wind flows. The region of the Brazilian Alcantara Space Center (ASC), with its rocket launching pad located 150 m downwind of a 40 m coastal cliff, presents the formation of an IBL due to winds blowing inland from the ocean. Numerical simulations using the immersed boundary method, experiments in a wind tunnel using particle image velocimetry, and field observational data obtained from anemometric towers were used to study this IBL. The results demonstrated that it is dependent on the geometry of the coastal cliff: its height is around 17 and 15 m for slopes of the coastal cliff of 90º and 135º, respectively. The numerical results show a good agreement with the experimental data and the field observations, but with an overestimation of the vorticity field. The IBL significantly influences the wind flow at the launching pad.
SUMMARYThis work presents a numerical method suitable for the study of the development of internal boundary layers (IBL) and their characteristics for flows over various types of coastal cliffs. The IBL is an important meteorological occurrence for flows with surface roughness and topographical step changes. A two-dimensional flow program was used for this study. The governing equations were written using the vorticity-velocity formulation. The spatial derivatives were discretized by high-order compact finite differences schemes. The time integration was performed with a low storage fourth-order Runge-Kutta scheme. The coastal cliff (step) was specified through an immersed boundary method. The validation of the code was done by comparison of the results with experimental and observational data. The numerical simulations were carried out for different coastal cliff heights and inclinations. The results show that the predominant factors for the height of the IBL and its characteristics are the upstream velocity, and the height and form (inclination) of the coastal cliff.
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