State of the climate in 2013

In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earths surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series. © 2014, American Meteorological Society. All rights reserved

Hydrosphere

The hydrosphere refers to the water on or surrounding the surface of the globe whether it is liquid, frozen or floating ice, in the soil or as water vapor in the atmosphere. The hydrosphere is the major setting for the earth’s hydrologic cycle. This article explores its origin, types, and distribution on earth as well as its role in the ecosystem. It concludes by highlighting the influence of human beings on quality and quantity of earth’s water

Estruturas automáticas para controle de água nos canais em lavoura de arroz irrigado Automatic structures for water control in channels on irrigated rice crops

O Rio Grande do Sul apresenta a maior área irrigada do Brasil, devido principalmente à lavoura de arroz irrigado por inundação. Um dos fatores que contribuem para reduzir a eficiência de irrigação nessas lavouras é o baixo grau de controle exercido pelas estruturas de distribuição de água. Os objetivos deste trabalho foram projetar e construir dois protótipos de estruturas hidráulicas para controle automático de vazão em canais de irrigação e comparar sua sensibilidade de controle de vazão com a sensibilidade de duas comportas fixas. Os protótipos construídos - uma comporta hidromecânica automática e um regulador automático de vazão - foram instalados à entrada de um canal secundário, juntamente com uma comporta-gaveta e uma comporta-vertedor, que são as estruturas mais utilizadas para controle de vazão no RS. Provocou-se uma variação de 0,20 m na altura da lâmina de água a montante, determinando-se a vazão em cada estrutura. A menor variação de vazão com a alteração da lâmina foi de 5,6%, obtida com o regulador automático de vazão, seguido da comporta-gaveta com 23,7%, da comporta hidromecânica com 30,5%, e da comporta vertedor com 1.177,2%.<br>In Brazil, the State that presents the largest extension of irrigated lands is Rio Grande do Sul, mainly due to rice that grows under flooded conditions. One of the factors that contribute to decrease the efficiency of irrigation is the low degree of control obtained with the structures used on water distribution. The objectives of this work were to design and build two hydraulic structures for automatic flow control on irrigation channels, and to compare the flow control sensitivity of the built prototypes with two types of gates that are widely used in the rice fields at the Rio Grande do Sul State. The constructed prototypes - a hydro-mechanical gate and an automatic flow regulator - were installed at the entrance of a secondary channel, next to a sluice gate and a weir. The upstream water depth was ranged from 0.9 m to 0.7 m, and the flow in each structure was measured with "H" flumes. The lower flow variation as a function of the water depth in the principal channel was 5.6%, obtained with the automatic flow regulator, followed by the sluice gate with 23.7%, the hydro-mechanical gate with 30.5% and the weir with 1,177.2%