scholarly journals VARIABILIDADE SAZONAL E INTERANUAL DO MICROCLIMA EM ÁREA DE FLORESTA NO SUDOESTE DA AMAZÔNIA

2016 ◽  
Vol 38 ◽  
pp. 169
Author(s):  
Nara Luisa Reis de Andrade ◽  
Luciana Sanches ◽  
Renata Gonçalves Aguiar ◽  
João Gilberto de Souza Ribeiro ◽  
Osvaldo Borges Pinto Junior
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Seasonal Patterns ◽  
Interannual Variations ◽  
Net Radiation ◽  
Radiation Data ◽  
Energy Exchanges ◽  
A Site ◽  
Seasonal And Interannual Variations ◽  
Biological Reserve

The Amazon is a recognized global ecosystem, due to its high biodiversity and the magnitude of the mass and energy exchanges performed. In this study it sought to analyze the seasonal and interannual variations of microclimate in a site of tropical forest in southwestern Amazon. For this purpose, net radiation data were used, air temperature, relative humidity and wind speed collected in a micrometeorological tower belonging to the LBA, located in Jaru Biological Reserve, from 2004 to 2010. The results showed that existence of well-defined seasonal patterns was verified, with variations between wet, wet-dry, dry, dry-humid periods for all variables in question. Yet, through analysis of the interannual variations were observed warming of the increment signs and decreased moisture in the locality. This observation, although patchy, deserves special attention, since changes in the microclimate in the Amazon region may have yet unknown consequences.

scholarly journals Quantitative Analysis of the Impact of Meteorological Factors on Reference Evapotranspiration Changes in Beijing, 1958–2017

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2263 ◽  
Author(s):  
Wenhui Liu ◽  
Baozhong Zhang ◽  
Songjun Han
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Time Scales ◽  
Reference Evapotranspiration ◽  
Meteorological Factors ◽  
Sensitivity Coefficient ◽  
Sensitivity Factor ◽  
Net Radiation ◽  
Annual Time ◽  
Different Time Scales

The effects of meteorological factors on reference evapotranspiration (ET0) are variable on different time scales, although research tends to focus only on certain time scales. Therefore, using the meteorological data from 1958 to 2017 of Beijing, China, ET0 values over the last 60 years were calculated using Penman–Monteith method. The variation in ET0 values was thus analyzed against four meteorological factors over different time scales. The sensitivity of ET0 to these factors was assessed using a sensitivity coefficient, while the contribution of each factor to ET0 change was quantified by combining this sensitivity coefficient with the factor’s relative change rate over multiple time scales. The results showed that the sensitivity coefficient of relative humidity over different time scales were all negative, while the sensitivity coefficients of net radiation, temperature and wind speed were mostly positive. The main sensitivity factors of ET0 on different time scales varied. On annual time scales, the main factors were relative humidity and temperature. Over annual time scales, relative humidity and net radiation alternated as the main sensitivity factor; while over interannual time scales, the most sensitive factor was relative humidity during 1958–1979 and net radiation thereafter. The contribution of these four meteorological factors to ET0 also fluctuated greatly on intra-annual time scales. On daily time scales, the contributions of temperature and wind speed at the start and end of the year were large, while net radiation and relative humidity were dominant mid-year. On monthly to seasonal time scales, the contributions of these four meteorological factors to ET0 were notable. The contribution of relative humidity was largest in spring and autumn; net radiation was dominant in summer, while temperature and wind speed were dominant in winter. This research on the temporal variability of ET0 response factors is of great significance for understanding regional climate change.

Distribution of the radiative index of dryness and forest site quality in a mountainous watershed

1984 ◽  
Vol 14 (5) ◽  
pp. 717-721 ◽  
Author(s):  
S. J. Tajchman
Keyword(s):  
Complex Terrain ◽  
Forest Biomass ◽  
Aridity Index ◽  
Site Quality ◽  
Seasonal Effects ◽  
Forest Site ◽  
Net Radiation ◽  
Energy Exchanges ◽  
A Site

The radiative aridity index, β (i.e., the ratio of yearly sums of net radiation to those of the latent heat of precipitation), and forest biomass were obtained for 245 terrain segments [Formula: see text] in an Appalachian watershed. A hypothesis was tested that β can be used as a site quality indicator in complex terrain. Regression analysis yielded the following relationship between the average forest biomass of the watershed (Mo = 15.94 kg m−2), the biomass (Mi), the radiative aridity index (βi), and the azimuth (Ai) of terrain segments: Mi/M0 = 2βi[l−Ai/2π + (Ai/2π)4] ± 0.27. The value of the expression in the bracket reaches its maximum for Ai = 0 (north facing slopes), and a minimum for Ai = 227° (southwest facing slopes). A possible interpretation of the obtained relationship is that p represents long term (e.g., daily and seasonal) effects of water and energy exchanges of terrain segments on growth, and the expression in the bracket represents the aspect-related effects of daily fluctuations of microclimate of terrain segments on growth.

scholarly journals Evaluation of FAO-56 Procedures for Estimating Reference Evapotranspiration Using Missing Climatic Data for a Brazilian Tropical Savanna

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1763
Author(s):  
Luiz Claudio Galvão do Valle Júnior ◽  
George L. Vourlitis ◽  
Leone Francisco Amorim Curado ◽  
Rafael da Silva Palácios ◽  
José de S. Nogueira ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Water Resource Management ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Climatic Conditions ◽  
Climatic Variables ◽  
Climatic Data ◽  
Wet Season ◽  
Radiation Data

The Brazilian savanna (Cerrado) has been heavily impacted by agricultural activities over the last four to five decades, and reliable estimates of reference evapotranspiration (ETo) are needed for water resource management and irrigation agriculture. The Penman–Monteith (PM) is one of the most accepted models for ETo estimation, but it requires many inputs that are not commonly available. Therefore, assessing the FAO guidelines to compute ETo when meteorological data are missing could lead to a better understanding of which variables are critically important for reliable estimates of ETo and how climatic variables are related to water requirements and atmospheric demands. In this study, ETo was computed for a grass-dominated part of the Cerrado from April 2010 to August 2019. We tested 12 different scenarios considering radiation, relative humidity, and/or wind speed as missing climatic data using guidelines given by the FAO. Our results presented that wind speed and actual vapor pressure do not affect ETo estimates as much as the other climatic variables; therefore, in the Cerrado’s conditions, wind speed and relative humidity measurements are less required than temperature and radiation data. When radiation data were missing, the computed ETo was overestimated compared to the benchmark. FAO procedures to estimate the net radiation presented good results during the wet season; however, during the dry season, their results were overestimated because the method could not estimate negative Rn. Our results indicate that radiation data have the highest impact on ETo for our study area and presumably for regions with similar climatic conditions. In addition, those FAO procedures for estimating radiation are not suitable when radiation data are missing.

scholarly journals Evaluation of FAO-56 procedures for estimating reference evapotranspiration using missing climatic data for a Brazilian tropical savanna

2021 ◽  
Author(s):  
Luiz Claudio Valle Junior ◽  
George Vourlitis ◽  
Leone Francisco Curado ◽  
Rafael Palacios ◽  
José Nogueira ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Climatic Data ◽  
Wet Season ◽  
Resources Management ◽  
Radiation Data ◽  
D Values ◽  
Irrigation Agriculture

Since the Brazilian Cerrado has been heavily impacted by agricultural activities over the last four to five decades, reference evapotranspiration (ETo) plays a pivotal role in water resources management for irrigation agriculture. The Penman-Monteith (PM) is one of the most accepted models for ETo estimation, but it requires many inputs that are not commonly available. Therefore, assessing the FAO guidelines to compute ETo when meteorological data are missing could lead to a better understanding of how climatic variables are related to water requirements and atmospheric demands for a grass-mixed savanna region and which variable impacts the estimates the most. In this study, ETo was computed from April 2010 to August 2019. We tested twelve different scenarios considering radiation, relative humidity, and/or wind speed as missing climatic data using guidelines given by FAO. When wind speed and/or relative humidity data were the only missing data, the PM method showed the lowest errors in the ETo estimates and correlation coefficient (r) and Willmott’s index of agreement (d) values close to 1.0. When radiation data were missing, computed ETo was overestimated compared to the benchmark. FAO procedures to estimate the net radiation presented good results during the wet season; however, during the dry season, their results were overestimated, especially because the method could not estimate negative Rn. Therefore, we can infer that radiation data have the highest impact on ETo for our study area and also regions with similar conditions and FAO guidelines are not suitable when radiation data are missing.

scholarly journals Evaluation of FAO-56 Procedures for Estimating Reference Evapotranspiration Using Missing Climatic Data for a Brazilian Tropical Savanna

2021 ◽  
Author(s):  
Luiz Cláudio Galvão Valle Júnior ◽  
George Louis Vourlitis ◽  
Leone Francisco Amorim Curado ◽  
Rafael da Silva Palácios ◽  
José de Souza Nogueira ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Climatic Data ◽  
Wet Season ◽  
Resources Management ◽  
Radiation Data ◽  
D Values ◽  
Irrigation Agriculture

Abstract Since the Brazilian Cerrado has been heavily impacted by agricultural activities over the last four to five decades, reference evapotranspiration (ETo) plays a big role in water resources management for irrigation agriculture. The Penman-Monteith (PM) is one of the most accepted models for ETo estimation, but it requires many inputs that are not commonly available. Therefore, assessing the FAO guidelines to compute ETo when meteorological data are missing could lead to a better understanding of how climatic variables are related to water requirements and atmospheric demands for a grass-mixed savanna region and which variable impacts the estimates the most. ETo was computed from April 2010 to August 2019. We tested twelve different scenarios considering radiation, relative humidity, and/or wind speed as missing climatic data using guidelines given by FAO. When wind speed and/or relative humidity data were the only missing data, the PM method showed the lowest errors in the ETo estimates and correlation coefficient (r) and Willmott’s index of agreement (d) values close to 1.0. When radiation data were missing, computed ETo was overestimated compared to the benchmark. FAO procedures to estimate net radiation presented good results during the wet season; however, during the dry season, their results were overestimated, especially because the method could not estimate negative Rn. Therefore, we can infer that radiation data have the largest impact on ETo for our study area and regions with similar conditions and FAO guidelines are not suitable when radiation data are missing.

scholarly journals Responses of natural runoff to recent climatic changes in the Yellow River basin, China

2013 ◽  
Vol 10 (4) ◽  
pp. 4489-4514 ◽  
Author(s):  
Y. Tang ◽  
Q. Tang ◽  
F. Tian ◽  
Z. Zhang ◽  
G. Liu
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Yellow River ◽  
Climatic Changes ◽  
Low Flow ◽  
Mean Annual Precipitation ◽  
The Yellow River ◽  
Net Radiation ◽  
Recent Period ◽  
Zero Flow

Abstract. The Yellow River, the second longest river in China, experienced frequent zero flow in the lower reaches of the mainstream in the 1990s. In recent years, the zero-flow phenomenon has almost disappeared. Besides engineering measures implemented to maintain ecological flows, the changes in natural runoff might have contributed to replenish the river. In this study, we used the Soil and Water Assessment Tool (SWAT) model and runoff elasticity analyses to assess the impacts of climatic changes on the natural streamflow at the Huayuankou station. The results show that there was little increase of precipitation but substantial recovery of natural runoff in the recent period (2003–2011) compared with the low flow period (1991–2002). The recent precipitation was slightly greater (~2% of the mean annual precipitation in the baseline period of 1960–1990) than precipitation in the low flow period. However, the natural runoff in the recent period was much larger (~14% baseline runoff) than runoff in the low flow period. The decreasing runoff in the low flow period was mainly caused by the decline in precipitation while the runoff recovery in the recent period was largely affected by the contributions from the climatic variables other than the precipitation. In the recent period, precipitation could account for a reduction of 21% baseline runoff whereas the others – net radiation, wind speed, air temperature, and relative humidity – accounted for an increase of 7.5% baseline runoff. The runoff reduction (~10.4% baseline runoff) caused by the changes in temperature and relative humidity was offset by the contribution from the decreasing net radiation and wind speed which resulted in an increase of ~17.9% baseline runoff.

scholarly journals A Reliability Based Model for Wind Turbine Selection

2013 ◽  
Vol 2 (2) ◽  
pp. 69-74 ◽  
Author(s):  
A.K. Rajeevan ◽  
P.V. Shouri ◽  
Usha Nair
Keyword(s):  
Power Generation ◽  
Wind Speed ◽  
Wind Turbine ◽  
Wind Power ◽  
Point Of View ◽  
Cube Root ◽  
Mathematical Relationship ◽  
Turbine Generator ◽  
Wind Turbine Generator ◽  
A Site

A wind turbine generator output at a specific site depends on many factors, particularly cut- in, rated and cut-out wind speed parameters. Hence power output varies from turbine to turbine. The objective of this paper is to develop a mathematical relationship between reliability and wind power generation. The analytical computation of monthly wind power is obtained from weibull statistical model using cubic mean cube root of wind speed. Reliability calculation is based on failure probability analysis. There are many different types of wind turbinescommercially available in the market. From reliability point of view, to get optimum reliability in power generation, it is desirable to select a wind turbine generator which is best suited for a site. The mathematical relationship developed in this paper can be used for site-matching turbine selection in reliability point of view.

scholarly journals Potential Evapotranspiration Reduction and Its Influence on Crop Yield in the North China Plain in 1961–2014

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Wanlin Dong ◽  
Chao Li ◽  
Qi Hu ◽  
Feifei Pan ◽  
Jyoti Bhandari ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Crop Yield ◽  
North China Plain ◽  
North China ◽  
Potential Evapotranspiration ◽  
The North ◽  
The North China Plain ◽  
Sunshine Hours ◽  
Humidity Index

Climate change has caused uneven changes in hydrological processes (precipitation and evapotranspiration) on a space-temporal scale, which would influence climate types, eventually impact agricultural production. Based on data from 61 meteorological stations from 1961 to 2014 in the North China Plain (NCP), the spatiotemporal characteristics of climate variables, such as humidity index, precipitation, and potential evapotranspiration (ET0), were analyzed. The sensitivity coefficients and contribution rates were applied to ET0. The NCP has experienced a semiarid to humid climate from north to south due to the significant decline of ET0 (−13.8 mm decade−1). In the study region, 71.0% of the sites showed a “pan evaporation paradox” phenomenon. Relative humidity had the most negative influence on ET0, while wind speed, sunshine hours, and air temperature had a positive effect on ET0. Wind speed and sunshine hours contributed the most to the spatiotemporal variation of ET0, followed by relative humidity and air temperature. Overall, the key climate factor impacting ET0 was wind speed decline in the NCP, particularly in Beijing and Tianjin. The crop yield in Shandong and Henan provinces was higher than that in the other regions with a higher humidity index. The lower the humidity index in Hebei province, the lower the crop yield. Therefore, potential water shortages and water conflict should be considered in the future because of spatiotemporal humidity variations in the NCP.

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