No abstract

Air temperature and photoperiod play an important role in the seedling development for tropical forest species. Both variables are sensitive to climate, and so evaluating thermal and photoperiodic effects on seedling development is fundamental, especially for climate change studies. Methods to quantify thermal time and the energy required for plants to reach a development stage include air temperature and cardinal temperatures. The photoperiod will also affect physiological reactions of a plant and thus its development. Here we evaluated the six thermal time methods widely used to compute thermal requirement, and identified the influence of the photoperiod from the 2015 and 2016 growing seasons and 12 sowing dates in Itajubá, Minas Gerais state, Brazil, on seedling development of three native tropical forest species Psidium guajava L. (Myrtaceae), Citharexylum myrianthum Cham. (Verbenaceae), and Bixa orellana L. (Bixaceae). The method used to quantify thermal time influenced the analytical results of seedling development; the one that considered three cardinal temperatures and compared them with the mean air temperature (Method 5) performed better in computing thermal requirements. The influence of photoperiod on seedling development was inconclusive for the three species, but all three developed better in mild temperatures (between 13.3 °C and 26.9 °C) with a photoperiod shorter than 13 h.

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Como há poucos estudos na literatura que descrevem a estrutura física das baixas térmicas no noroeste da Argentina (BNOA), isso torna-se o objetivo do presente trabalho. Para isso, são utilizados dados da Global Forecast System Analysis (GFSanl - Sistema de Previsão Global). O caso de BNOA em estudo teve gênese no dia 29 de outubro de 2009 às 0600 UTC e perdurou até o dia 03 de novembro às 1200 UTC. Sua estrutura vertical mostra máximo aquecimento e vorticidade relativa ciclônica entre a superfície e 750 hPa ao longo das longitudes de 70º a 65º W. Em níveis médios, durante todo o ciclo de vida da BNOA, predominou uma crista no escoamento atmosférico. A influência de sistemas transientes causa a desconfiguração da BNOA.   Analysis of an episode of Thermal Low of Northwest Argentina A B S T R A C TIn South America, there are two favorable places for the genesis of thermal lows (low pressure system with semi-stationary feature): Chaco region and the northwest of Argentina. Thermal lows developed in these regions receive their names. So, the purpose of this study is to describe the physical structure of thermal low occurred over the northwest of Argentina (TLNA). For this reason, data from the Global Analysis of the Forecasting System (GFSanl - Global Forecasting System) are used. TLNA had genesis on October 29, 2009 at 0600 UTC and decayed on November 03 at 1200 UTC. Its vertical structure shows the maximum heating and the cyclonic relative vorticity between the surface and 750 hPa along the longitudes 70º-65º W. At middle levels, throughout the TLNA's lifecycle, a ridge in the atmospheric flow predominated. The influence of the transient systems causes the deconfiguration of TLNA.Keywords: thermal low; northwestern Argentina; anticyclone; transient systems

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This study analyzes the correlation between the spread of COVID-19 and meteorological variables (air temperature, relative humidity, wind speed, and precipitation) in urban-rural cities located in southeastern Brazil. Spearman's correlation coefficients were used for the statistical analysis. Results show that air temperature and wind speed were positively correlated with COVID-19 cases, while air relative humidity showed negative correlation. As seen in several recent studies, climate factors and the spread of COVID-19 seem to be related. Our study corroborates this hypothesis for less densely populated and less polluted regions. We hope that our findings help worldwide scientific efforts towards understanding this disease and how it spreads in different regions.