Diurnal and Seasonal Variations of Sensible and Latent Heat Fluxes at an Agricultural Site in Ile-Ife, Southwest Nigeria

2020 ◽  
Author(s):  
Adewale Ajao ◽  
Omodara Obisesan ◽  
Muritala Ayoola ◽  
Oluwagbemiga Jegede
Keyword(s):  
Latent Heat ◽  
Seasonal Variations ◽  
Bowen Ratio ◽  
Dry Season ◽  
Heat Fluxes ◽  
Wet Season ◽  
Mean Values ◽  
Diurnal Range ◽  
Southwest Nigeria ◽  
Agricultural Site

<p>Diurnal and seasonal variations of sensible heat (<em>H</em>) and latent heat (<em>LE</em>) fluxes observed at an agricultural site on the campus of Obafemi Awolowo University, Ile-Ife, southwest Nigeria have been reported in this paper. The deductions are made based on half-hourly flux data acquired from an open-path eddy covariance (OPEC) system measured continuously over a two-year observation period (2017-2018) at the study site. The study area is within tropical wet and dry climate of West Africa, thereby experiencing an alternating wet (that is, April – October) and dry (that is, December – February) seasons (monsoonal). Our results showed that peak hourly values of <em>H</em> and <em>LE</em> occurred at about 13:00 LT and 14:00 LT respectively, a lag of approximately one hour between them at the location. The diurnal range for <em>H</em> and <em>LE</em> during wet season was 75.3 W m<sup>-2</sup> and 177.0 W m<sup>-2</sup> respectively, while for dry season it was 182.0 W m<sup>-2</sup> and 89.9 W m<sup>-2</sup> respectively. The daily mean value of <em>H</em> for wet season was 19.7 ± 27.2 W m<sup>-2</sup> and it was 52.1 ± 63.5 W m<sup>-2 </sup>for <em>LE</em>. For dry season, daily mean values for <em>H</em> and <em>LE</em> were 44.0 ± 66.4 W m<sup>-2</sup> and 26.6 ± 33.7 W m<sup>-2</sup> respectively. A transition of seasons from wet (Bowen ratio, <em>Bo</em> < 1) to dry (<em>Bo</em> > 1) was observed in November and reversal in March.</p><p> </p><p><strong>Keywords</strong>: Diurnal and Seasonal Variations, Sensible and Latent Heat Fluxes, Tropical Wet and Dry Climate</p>

scholarly journals Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

2017 ◽  
Vol 21 (7) ◽  
pp. 3401-3415 ◽  
Author(s):  
Nobuhle P. Majozi ◽  
Chris M. Mannaerts ◽  
Abel Ramoelo ◽  
Renaud Mathieu ◽  
Alecia Nickless ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Latent Heat ◽  
Surface Energy Balance ◽  
Sensible Heat Flux ◽  
Dry Season ◽  
Energy Balance Closure ◽  
Net Radiation ◽  
Wet Season

Abstract. Flux towers provide essential terrestrial climate, water, and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based Earth observation and monitoring efforts, such as assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. In this paper, 15 years of Skukuza eddy covariance data, i.e. from 2000 to 2014, were analysed for surface energy balance closure (EBC) and partitioning. The surface energy balance closure was evaluated using the ordinary least squares regression (OLS) of turbulent energy fluxes (sensible (H) and latent heat (LE)) against available energy (net radiation (Rn) less soil heat (G)), and the energy balance ratio (EBR). Partitioning of the surface energy during the wet and dry seasons was also investigated, as well as how it is affected by atmospheric vapour pressure deficit (VPD), and net radiation. After filtering years with low-quality data (2004–2008), our results show an overall mean EBR of 0.93. Seasonal variations of EBR also showed the wet season with 1.17 and spring (1.02) being closest to unity, with the dry season (0.70) having the highest imbalance. Nocturnal surface energy closure was very low at 0.26, and this was linked to low friction velocity during night-time, with results showing an increase in closure with increase in friction velocity. The energy partition analysis showed that sensible heat flux is the dominant portion of net radiation, especially between March and October, followed by latent heat flux, and lastly the soil heat flux, and during the wet season where latent heat flux dominated sensible heat flux. An increase in net radiation was characterized by an increase in both LE and H, with LE showing a higher rate of increase than H in the wet season, and the reverse happening during the dry season. An increase in VPD is correlated with a decrease in LE and increase in H during the wet season, and an increase in both fluxes during the dry season.

The Local Biophysical Response to Land-Use Change in HadGEM2-ES

2019 ◽  
Vol 32 (22) ◽  
pp. 7611-7627 ◽  
Author(s):  
E. Robertson
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Latent Heat ◽  
Temperature Response ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Available Energy ◽  
Turbulent Heat Fluxes ◽  
The Tropics

Abstract The biophysical response to a local change in land use is calculated using the HadGEM2-ES Earth system model. The biophysical temperature response is found to be a small residual of three large opposing flux responses: available energy, sensible heat, and latent heat. Deforestation reduces available energy, which is balanced by a reduction in heat lost via turbulent fluxes. However, the changes in turbulent heat fluxes are not simply a response to the reduction in available energy; rather, they are a direct response to land-use change, caused by reduced roughness length and, in the tropics, an increase in the Bowen ratio. Evaluation against satellite-derived observational datasets shows that in response to deforestation, the model has too much albedo-driven cooling and too little latent-heat-driven warming, leading to a large cooling bias.

Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal

2013 ◽  
Vol 14 (3) ◽  
pp. 390-397 ◽  
Author(s):  
Sadhana Shrestha ◽  
Takashi Nakamura ◽  
Rabin Malla ◽  
Kei Nishida
Keyword(s):  
Groundwater Level ◽  
Seasonal Variations ◽  
Shallow Groundwater ◽  
Dry Season ◽  
Kathmandu Valley ◽  
Microbial Quality ◽  
Wet Season ◽  
Groundwater Levels ◽  
E Coli

To develop effective groundwater pollution control strategies for the Kathmandu Valley, Nepal, seasonal variations in microbial quality and their underlying mechanisms must be understood. However, to date, there are no studies that address these topics. In this study, groundwater samples from dug wells were collected during the dry and wet seasons from 2009 to 2012, and Escherichia coli (E. coli) and total coliforms were analysed. Three wells were monitored each month for a year. Microbial concentrations in shallow groundwater were significantly higher during the wet season than during the dry season. Analyses of rainfall and E. coli concentrations in different seasons indicated that a high level of faecal material infiltration during the rainy season may have caused the seasonal variations in microbial quality. A moderate to strong relationship between E. coli concentrations and groundwater level suggested that the rise in groundwater levels during the wet season may be another reason for this variation. This long time-scale survey detected a significant decline in the microbial quality of shallow groundwater during the wet season as compared with the dry season. We propose that the infiltration of contaminants and change in groundwater level are the two probable mechanisms for the observed seasonal differences.

scholarly journals Variational Computation of Sensible and Latent Heat Flux over Lake Superior

2018 ◽  
Vol 19 (2) ◽  
pp. 351-373
Author(s):  
Zuohao Cao ◽  
Murray D. Mackay ◽  
Christopher Spence ◽  
Vincent Fortin
Keyword(s):  
Heat Flux ◽  
Variational Method ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Gradient Method ◽  
Lake Superior ◽  
Coupled Model ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Flux Gradient

Abstract Sensible and latent heat fluxes over Lake Superior are computed using a variational approach with a Bowen ratio constraint and inputs of 7 years of half-hourly temporal resolution observations of hydrometeorological variables over the lake. In an advancement from previous work focusing on the sensible heat flux, in this work computations of the latent heat flux are required so that a new physical constraint of the Bowen ratio is introduced. Verifications are made possible for fluxes predicted by a Canadian operational coupled atmosphere–ocean model due to recent availabilities of observed and model-predicted fluxes over Lake Superior. The observed flux data with longer time periods and higher temporal resolution than those used in previous studies allows for the examination of detailed performances in computing these fluxes. Evaluations utilizing eddy-covariance measurements over Lake Superior show that the variational method yields higher correlations between computed and measured sensible and latent heat fluxes than a flux-gradient method. The variational method is more accurate than the flux-gradient method in computing these fluxes at annual, monthly, daily, and hourly time scales. Under both unstable and stable conditions, the variational method considerably reduces mean absolute errors produced by the flux-gradient approach in computing the fluxes. It is demonstrated with 2 months of data that the variational method obtains higher correlation coefficients between the observed and the computed sensible and latent heat fluxes than the coupled model predicted, and yields lower mean absolute errors than the coupled model. Furthermore, comparisons are made between the coupled-model-predicted fluxes and the fluxes computed based on three buoy observations over Lake Superior.

scholarly journals Environmental Determinants Influencing Seasonal Variations of Bird Diversity and Abundance in Wetlands, Northern Region (Ghana)

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Collins Ayine Nsor ◽  
Edward Adzesiwor Obodai
Keyword(s):  
Seasonal Variations ◽  
Bird Community ◽  
Iucn Red List ◽  
Northern Region ◽  
Dry Season ◽  
Bird Diversity ◽  
Environmental Determinants ◽  
Wet Season ◽  
Bird Abundance ◽  
Bubulcus Ibis

The study assessed major environmental determinants influencing bird community in six wetlands over a 2-year period. A combination of visual and bird sounding techniques was used to determine the seasonal variations in bird abundance, while ordination techniques were performed to determine the influence of environmental factors on bird assemblage. A total of 1,169 birds from 25 species and 885 individuals from 23 species were identified in the wet and dry season, respectively. The shallow close marshes supported the greatest number of birds (P<0.05) compared to the riparian wetlands. Bird diversity was significantly higher in the wet season than in the dry season (F=4.101,P<0.05). Cattle egret (Bubulcus ibis) and marsh warbler (Acrocephalus palustris) were the most abundant. Using the IUCN “Red List” database guide, we noted that 96.2% of birds identified were least concern (LC). The yellow weaver bird (Ploceous megarhrynchus) was the only vulnerable species (VU) and represented 3.8%. From the three variables tested, bushfire and farming practices were the major threats and cumulatively explained 15.93% (wet season) and 14.06% (dry season) variations in bird diversity and abundance. These findings will help wetland managers design conservation measures to check current threats on birds from becoming vulnerable in the future.

scholarly journals Effects of Effluents on the Quality of River Rido, Kaduna- State, Nigeria

2020 ◽  
Vol 12 (1) ◽  
pp. 159-170
Author(s):  
Louis Buggu ◽  
Funmilayo Yusufu - Alfa ◽  
Abigail Abenu
Keyword(s):  
Heavy Metals ◽  
Treatment Plant ◽  
World Health Organisation ◽  
Dry Season ◽  
World Health ◽  
Wet Season ◽  
Mean Values ◽  
The World ◽  
Effluent Discharge

This study examines the effect of discharged effluents on the quality of river Rido in Kaduna. Ten water samples were collected and tested for Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb), Manganese (Mn), Mercury (Hg), Nickel (Ni) and Zinc (Zn). The results revealed that in  the dry season,  six heavy metals, namely As, Cd, Cu, Mn, Ni and Zn, presented mean values that were  higher  after the point of effluent discharge; while Cr, Fe and Pb  had lower values and Hg was not detected. In the wet season all the heavy metals tested, except Hg, increased in values after the point of effluent discharge. The values of As, Cd,  Fe, Mn, Ni and Pb after the discharge point, in dry and wet seasons, were greater than the maximum tolerable limits set by the Standard Organisation of Nigeria (SON) and the World Health Organisation (WHO).  The values recorded for Zn and Cu at both dry and wet seasons were below the limit set by the Standard Organisation of Nigeria (SON) and the World Health Organisation (WHO), but the value of Cr was lower than the maximum tolerable limit only in the dry season.  The contamination of the river with heavy metals poses a grave danger to human health, as its water is used for diverse purposes. The wastewater treatment plant of KRPC should be rehabilitated and the wastewater can be pre-treated before it is discharged into the river.

scholarly journals Environmental Impact of Heavy Metals from Poultry Waste Discharged into the Olosuru Stream, Ikire, Southwestern Nigeria

2019 ◽  
Vol 9 (22) ◽  
Author(s):  
Abayomi Tolulope Oyewale ◽  
Taiwo Adekanmi Adesakin ◽  
Adedeji Idowu Aduwo
Keyword(s):  
Heavy Metals ◽  
Environmental Impact ◽  
Anthropogenic Activities ◽  
Sampling Period ◽  
Dry Season ◽  
World Health ◽  
Poultry Waste ◽  
Wet Season ◽  
Southwestern Nigeria ◽  
Southwest Nigeria

Background. Water supplies can be contaminated by anthropogenic activities. The poultry industry uses a variety of heavy metals as additives in chicken feed, but excretion, runoff and dumping of heavy metals can threaten water bodies and have adverse effects on human health. Objectives. The aim of the present study was to determine the environmental impact of heavy metals from poultry waste discharged into the Olosuru stream, located in Ikire, southwest Nigeria. Methods. In order to study changes in heavy metal loads, samples were collected six times during the wet season (September, October 2014 and April 2015) and dry season (November 2014, January and February 2015). The inhabitants of Olosuru village use water for domestic and agriculture purposes from the Olosuru stream which is located only a few meters from a poultry farm discharge point. Three stations were sampled, upstream to downstream, with 500 meter distance between each point. Results. Selected heavy metals concentrations in the Olosuru stream were all above the World Health Organization (WHO) standard for drinking water. The highest mean concentrations of heavy metals were recorded at the downstream station, while arsenic, iron and lead showed significant spatial and seasonal differences. Seasonally, the highest iron concentrations were recorded in the dry season (0.104±0.401 mg/L), while the mean concentrations of other heavy metals recorded during the sampling period were higher during the wet season. Conclusions. Concentrations of heavy metals in the present study were above acceptable limits. Poultry waste discharged into the Olosuru stream, can have negative impacts on the stream and health implications for local residents. Competing Interests. The authors declare no competing financial interests.

scholarly journals Components of near-surface energy balance derived from satellite soundings – Part 2: Noontime latent heat flux

2014 ◽  
Vol 11 (24) ◽  
pp. 7369-7382 ◽  
Author(s):  
K. Mallick ◽  
A. Jarvis ◽  
G. Wohlfahrt ◽  
G. Kiely ◽  
T. Hirano ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Vegetation Index ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Simple Method ◽  
Near Surface ◽  
Available Energy

Abstract. This paper introduces a relatively simple method for recovering global fields of latent heat flux. The method focuses on specifying Bowen ratio estimates through exploiting air temperature and vapour pressure measurements obtained from infrared soundings of the AIRS (Atmospheric Infrared Sounder) sensor onboard NASA's Aqua platform. Through combining these Bowen ratio retrievals with satellite surface net available energy data, we have specified estimates of global noontime surface latent heat flux at the 1°×1° scale. These estimates were provisionally evaluated against data from 30 terrestrial tower flux sites covering a broad spectrum of biomes. Taking monthly average 13:30 data for 2003, this revealed promising agreement between the satellite and tower measurements of latent heat flux, with a pooled root-mean-square deviation of 79 W m−2, and no significant bias. However, this success partly arose as a product of the underspecification of the AIRS Bowen ratio compensating for the underspecification of the AIRS net available energy, suggesting further refinement of the approach is required. The error analysis suggested that the landscape level variability in enhanced vegetation index (EVI) and land surface temperature contributed significantly to the statistical metric of the predicted latent heat fluxes.

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