Evaluation of methods for estimating atmospheric emissivity in Mato-Grossense Cerrado

Silva, Jonh Billy; Gaio, Denilton Carlos; Curado, Leone Francisco Amorim; Nogueira, José de Souza; Júnior, Luiz Claudio Galvão do Valle; Rodrigues, Thiago Rangel

doi:10.4136/ambi-agua.2288

Cited by 7 publications

(4 citation statements)

References 22 publications

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“…Over the last few decades, the hydrological cycle and climate of the Brazilian savanna (locally known as Cerrado) have been heavily affected by human activities, especially by the expansion of irrigation and the replacement of native vegetation by crops [1][2][3][4][5][6]. Due to…”

Section: Introductionmentioning

confidence: 99%

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

Júnior

Vourlitis

Curado

et al. 2021

Water

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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.

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Section: Introductionmentioning

confidence: 99%

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

Júnior

Vourlitis

Curado

et al. 2021

Water

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“…where P W is the partial water pressure/actual vapor pressure in hectopascal expressed as a function of relative humidity, RH (%) and temperature [70,71]:…”

Section: Methods and Data Processingmentioning

confidence: 99%

Impacts of cloudiness on near surface radiation and temperature in Nigeria, West Africa

et al. 2020

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This study investigates impacts of cloudiness on surface radiation budget and temperature from 1983 to 2018 in Nigeria, West Africa. The National Aeronautics and Space Administration meteorological datasets were used to achieve this objective. Net radiation (R) increased latitudinally from the coast to the inland areas. The least value of R was obtained in wet season which coincided with the period when cloud cover was at its optimal. We obtained significant decreasing trends (− 0.110 to − 0.536 Wm −2 year −1) in R but significant increasing trends in cloud cover in most parts of the region. Under clear-sky conditions, however, significant increasing trends (0.256-0.807 Wm −2 year −1) in R were obtained. Annual mean temperature showed significant upward trends under all-sky (0.009-0.059 °C year −1) and clear-sky (0.019-0.072 °C year −1) conditions. Furthermore, significant negative correlations (− 0.70 ≤ r ≤ − 0.95) were obtained between monthly values of cloud cover and R over the country. However, r values for cloud cover and temperature were positive over Sahel (r ~ 0.65) but negative over Guinea (r ~ 0.45); both significant at p < 0.05. Changes in R were accounted for by 21 to 26% variations in cloud cover, while fluctuation in temperature was explained by about 14% variation in cloud cover over Sahel region at p < 0.05. Our results revealed that the surface radiation budget was significantly perturbed by variations in cloudiness which resulted in net cloud-radiative cooling (− 30 Wm −2) over Guinea but warming over Savannah (25 Wm −2) and Sahel (50 Wm −2) zones.

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“…Over the last few decades, the Brazilian savanna (locally known as Cerrado) hydrological cycle and climate have been heavily affected by human activities, especially the replacement of native vegetation by agricultural crops (Giambelluca et al 2009;Rodrigues et al 2014;Oliveira et al 2014;Nóbrega et al 2018;Silva et al 2019;Valle Júnior et al 2020). Due to this irrigated agricultural expansion, it is important to have good management of available water resources.…”

Section: Introductionmentioning

confidence: 99%

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

Júnior

Vourlitis

Curado

et al. 2021

Preprint

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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.

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Evaluation of methods for estimating atmospheric emissivity in Mato-Grossense Cerrado

Cited by 7 publications

References 22 publications

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

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

Impacts of cloudiness on near surface radiation and temperature in Nigeria, West Africa

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

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