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Search Results: 1 - 10 of 7962 matches for " Sin Chan Chou "
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Future Changes in Temperature and Precipitation Extremes in the State of Rio de Janeiro (Brazil)  [PDF]
Wanderson Luiz Silva, Claudine Dereczynski, Sin Chan Chou, Iracema Cavalcanti
American Journal of Climate Change (AJCC) , 2014, DOI: 10.4236/ajcc.2014.34031
Abstract: In this study, we document the air temperature and precipitation changes between present-day conditions and those projected for the period 2041-2070 in the state of Rio de Janeiro (Brazil) by means of Eta driven by HadCM3 climate model output, considering the variation among its four ensemble members. The main purpose is to support studies of vulnerability and adaptation policy to climate change. In relation to future projections of temperature extremes, the model indicates an increase in average minimum (maximum) temperature of between +1.1°C and +1.4°C (+1.0°C and +1.5°C) in the state by 2070, and it could reach maximum values of between +2.0°C and +3.5°C (+2.5°C and +4.5°C). The model projections also indicate that cold nights and days will be much less frequent in Rio de Janeiro by 2070, while there will be significant increases in warm nights and days. With respect to annual total rainfall, the Northern Region of Rio de Janeiro displays the greatest variation among members, indicating changes ranging from a decrease of -350 mm to an increase of +300 mm during the 21st century. The southern portion of the state has the largest increase in annual total rainfall occurring due to heavy rains, ranging from +50 to +300 mm in the period 2041-2070. Consecutive dry days will increase, which indicates poorly time distributed rainfall, with increased rainfall concentrated over shorter time periods.
Downscaling Climate Projections over La Plata Basin  [PDF]
Caroline Mour?o, Sin Chan Chou, José Marengo
Atmospheric and Climate Sciences (ACS) , 2016, DOI: 10.4236/acs.2016.61001
Abstract: Regional Climate Models are important tools, which are increasingly being used in studies of impacts and adaptation to climate change at local scale. The goal of this work is to assess the climate change over the La Plata Basin, using the Eta Regional model with a resolution of 10 km. Initial and boundary conditions used by the model are provided by the Eta-20 km model and the HadGEM2-ES Global model. The RCP 4.5 scenario was used for simulations of the future climate. The evaluation of the present climate (1961-1990) shows that the model represents well the spatial and temporal distribution of precipitation and temperature in the region. The model underestimates precipitation over large areas in summer, and overestimates in Southern Brazil in winter. Simulated temperature shows a good correlation with CRU data, with bias less than 1°C. The bias of temperature and precipitation in this simulation setup for the La Plata Basin is substantially reduced in comparison with previous literature using regional models. The climatic projections are shown in timeslices: 2011-2040, 2041-2070, and 2071-2099. In the three timeslices, the simulation project has a trend for an increase in precipitation during summer in Argentina, Uruguay, and southernmost Brazil. This increase is only projected in Southern Brazil during winter. The negative anomaly of precipitation appears in a large portion of the model domain during summer and is limited to some states in Southeast and Central-West Brazil in winter. The area with largest warming is projected in the northern portion of the domain. The projected increase in temperature reaches about 4°C in 2071-2099.
Evaluation of two Eta Model versions for weather forecast over South America
Marcelo E. Seluchi,Sin Chan Chou
Geofísica internacional , 2001,
Abstract: A comparison of performance of two versions of the Eta/CPTEC model is presented. The new version is an update of an earlier operational one and includes representation of soil and vegetation types. The soil/vegetation model contains two underground layers and a canopy layer. Evaluation was carried out by comparing the mean and root mean square errors of several variables for an ensemble of 15 meteorological situations, using the NCEP analyses, upper air soundings and precipitation data over South America. Precipitation forecasts were evaluated by the equitable threat score (ETS) and the bias score (BIAS).The mean errors from both versions show similarities during the first 24 hours of forecast, but surface temperature is more accurately predicted by the updated model. After 48 hours, temperature and humidity forecasts show better skill in the new version too. Over subtropical South America differences are more evident in temperature and humidity, less so for geopotential heights and practically nonexistent for horizontal winds. The precipitation forecasts for the updated version have equitable threat scores slightly higher and similar bias scores during the first 24 hours. After 48 hours this version tends to overestimate the rainfall, while its spatial distribution remains unaffected.
Climate Change Index: A Proposed Methodology for Assessing Susceptibility to Future Climatic Extremes  [PDF]
Manyu Chang, Claudine Dereczynski, Marcos A. V. Freitas, Sin Chan Chou
American Journal of Climate Change (AJCC) , 2014, DOI: 10.4236/ajcc.2014.33029
Abstract: A Climate Change Index (CCI) was designed to assess the degree of susceptibility to the climatic extremes projected for the future. Climate projections for the period 2041-2070 are extracted from the numerical integrations of INPE’s Eta-HadCM3 model, using the SRES A1B emissions scenario. Five indicators were chosen to represent the climatic extremes: Total annual precipitation, precipitation on the days of heavy rain, the maximum number of consecutive dry days in the year and the annual mean maximum and mean minimum temperatures. The methodology was applied to the state of Paraná. The results point to a very strong warming in 99% of the municipalities, with temperature increases between 6 and 8 times greater than the variance observed in the present climate. On the other hand, projections of precipitation do not indicate major changes in relation to present behavior.
Hydrological Processes and Climate Change in Hydrographic Regions of Brazil  [PDF]
Alfredo Ribeiro Neto, Adriano Rolim da Paz, José Antonio Marengo, Sin Chan Chou
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.812087
Abstract: The objective of this work is to assess the impacts of IPCC AR5 climate change scenarios on water resources and hydrological processes across the entire Brazilian territory. Hydrological simulations are carried out in total drainage area of about 11,535,645 km2 and average stream flow of about 272,460 m3/s. The study area consists of different climates and land covers such as the Amazon Forest, Northeast Semiarid, Brazilian Savannah, Pantanal wetlands and temperate climate in the South. The atmospheric forcing to drive the large-scale hydrological model MGB-IPH is derived from the downscaling of two global climate models, HadGEM2-ES and MIROC5, by the Eta Regional Climate Model, at 20 km resolution. The Eta model provided the downscaling of the baseline (1961-1990) and three time-slices (2011-2040, 2041-2070 and 2071-2099). These projections adopted two emission scenarios, the RCP 4.5 and RCP 8.5. The change in the average and extremes of precipitation, evapotranspiration, rates of river discharge and soil moisture were assessed. The simulations showed the response of the hydrographic regions due to change of precipitation and potential evapotranspiration in the scenarios. Water availability decreases in almost the entire study area (exception for the South) and the major basins for hydroelectric power generation are affected. The Northwest, Amazon and a small area along the Northeast Atlantic coast exhibited intensification of the extremes discharges, where the anomaly is positive for high-flow (Q10) and negative for low-flow (Q95). The results highlight the most climatic sensitive regions in Brazil in terms of hydrological variables and water resources.
Impacts of Climate Change on the Hydrology of a Small Brazilian Headwater Catchment Using the Distributed Hydrology-Soil-Vegetation Model  [PDF]
Lívia Alves Alvarenga, Carlos Rogério de Mello, Alberto Colombo, Sin Chan Chou, Luz Adriana Cuartas, Marcelo Ribeiro Viola
American Journal of Climate Change (AJCC) , 2018, DOI: 10.4236/ajcc.2018.72021
Abstract: Climate change is one of the greatest issues for human society. The objective of this study is to assess the impacts of future climate change on seasonal average discharge and monthly water budget in a small headwater catchment, located on the Grande River basin, in Minas Gerais, Brazil. The assessment is carried out using the hydrology model, DHSVM. The atmospheric forcing to drive the Distributed Hydrology-Soil-Vegetation Model (DHSVM) is derived from the downscaling of the HadGEM2-ES projections by the Eta Regional Climate Model, at 5-km high resolution. The projections assume the RCP4.5 and RCP8.5 IPCC AR5 emission scenarios. Baseline period was taken between 1961 and 1990. The projections are assessed in three time slices (2011-2040, 2041-2070 and 2071-2099). The climate change is assessed in time slices of 30 years and in comparison against the baseline period to evaluate the hydrological changes in the catchment. The results showed differences in the hydrological behavior between the emission scenarios and though time slices. Reductions in the magnitude of the seasonal average discharge and monthly water budget may alter the water availability. Under the RCP4.5 scenario, results show greater reductions in the water availability in the first time slice, whereas under RCP8.5 scenario greater reductions are indicated in the third time slice.
A case study of a winter heavy rainfall event over the Serra do Mar in Brazil
Seluchi, Marcelo E.;Chan Chou, Sin;Gramani, Marcelo;
Geofísica internacional , 2011,
Abstract: serra do mar is a mountainous region vulnerable to landslides due to frequent summer heavy rainfall and steep slopes. these mountains are located in southeastern brazil and lie along the coastal region. major cities, industries, roads and pipelines are established in the serra do mar. a reference of landslides occurred in the winter of 2004. this is a rare case in the dry season and the civil defense was caught unprepared. we investigate the causes of these landslides in order to provide some guidance to forecasters and policy makers. rain was mainly from stratiform clouds associated with a relatively intense cold front which persisted for about 6 days in the region. the cold front became stationary on the coast of the state of sao paulo as the post-frontal anticyclone, which was initially cold, acquired a barotropic structure and, consequently, a semi stationary behavior. the large scale circulation determined the persistence of southerly and southeasterly winds near the surface. after reaching the continent, these winds were lifted by the serra do mar mountain chain. the progression of a shortwave trough to upper levels was not the major cause of heavy precipitation, but contributed to enhance the thermodynamic instability and increase rainfall, which caused the landslides in the serra do mar.
Indicadores de turbulência a partir de previs?es do modelo regional ETA
Lyra, André de Arruda;Chan, Chou Sin;Dereczynski, Claudine Pereira;
Revista Brasileira de Meteorologia , 2007, DOI: 10.1590/S0102-77862007000200003
Abstract: the clear air turbulence (cat) which is frequently observed near jet stream regions, usually in the layer between 10,000 and 12,000 m, may cause serious damages to aviation, reaching airplanes without warning. therefore, predictions of this phenomenon can help to prevent physical damages and discomfort for the crew and passengers. numerical weather prediction models have been used as powerful tools for operational forecasts of this phenomenon, by application of some indices in the determination of the turbulence areas. in this work, the brown, ellrod and richardson number indices, calculated from eta model outputs, are used to detect turbulence. the verification was accomplished for 2 events on 24 june 2003 and 17 august 2006 and was based on sigwx charts. the results show that the three indices correlated well with sigwx charts. this study showed that the use of eta model forecasts could help to understand the mechanism of turbulence and to increase the forecast lead time to about 48h or 72h, as compared to 24-h forecast sigwx maps.
Projecting Extreme Changes in Summer Rainfall in South America by the Middle of the 21st Century  [PDF]
Paula Andrea M. Fonseca, José Augusto P. Veiga, Francis Wagner S. Correia, Adriane L. Brito, M?nica R. Queiroz, André A. Lyra, Sin Chan Chou
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.44067

Extreme rainfall events can be considered a natural manifestation of the environment in which they are embedded and foreknowledge about their future behavior is very important, especially for decision makers. In this context, we aimed to explore the future behavior of extreme rainfall intensity through numerical simulations with the ETA model. The model was forced with a scenario of high greenhouse gas emissions for the middle of the 21st Century as described for A1B emission scenario. We detailed the main changes in accumulated rainfall produced by heavy events, very heavy events and rare events over a broad area of South America with a focus on the tropical sector. The methodology applied here is capable of separating extreme events and establishing the quantity of rainfall yielded by them. We have found that in the near future (2041-2050) rare events will tend to increase over the Amazon basin, followed by reductions in heavy and very heavy events. Conversely, heavy, very heavy and rare events are expected to decline over north-east Brazil. Furthermore, increases were found for heavy, very heavy and rare events over southern Brazil.

Previs?es meteorológicas do Modelo Eta para subsidiar o uso de modelos de previs?o agrícola no Centro-Sul do Brasil
Vieira Junior, Pedro Abel;Dourado Neto, Durval;Chou, Sin Chan;Martin, Thomas Newton;
Ciência Rural , 2009, DOI: 10.1590/S0103-84782008005000076
Abstract: the objective of this study was to evaluate the 120-day precipitation and maximum and minimum temperature forecasts by eta model over 24 locations around the mid-southern of brazil. the evaluation was based on comparing observed time series of precipitation and temperatures from 1997 to 2002 to 30, 60 and 120-day forecasts of eta model over these 24 locations. mean, median and standard deviation were used in the evaluation. the results show that these forecasts generally underestimate rain and temperature range. the smallest precipitation errors occurred in itumbiara and rio verde, whereas the largest errors occurred in porangatu and manduri. the smallest maximum temperature errors occurred in brasília, manduri and piracicaba whereas the largest errors in barreiras and porangatu. despite the systematic errors exhibited by the precipitation and temperature forecasts, these errors can be removed and the corrected values input into the crop models.
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