Dry Tropical Climate Research Articles

Alkalinity and dissolved inorganic carbon exports from tropical and subtropical river catchments discharging to the Great Barrier Reef, Australia

AbstractDissolved inorganic carbon (DIC) transport by rivers is an important control on the pH and carbonate chemistry of the coastal ocean. Here, we combine DIC and total alkalinity (TAlk) concentrations from four tropical rivers of the Great Barrier Reef region in Australia with daily river discharge to quantify annual river loads and export rates. DIC in the four rivers ranged from 284 to 2,639 μmol kg−1 and TAlk ranged from 220 to 2,612 μmol kg−1. DIC:TAlk ratios were mostly greater than one suggesting elevated exports of free [CO2*]. This was pronounced in the Johnstone and Herbert rivers of the tropical wet north. The largest annual loads were transported in the two large river catchments of the southern Great Barrier Reef region, the Fitzroy and Burdekin rivers. The carbon stable isotopic composition of DIC suggests that carbonate weathering was the dominant source of DIC in the southern rivers, and silicate weathering was likely a source of DIC in the northern Wet Tropics rivers. Annual loads and export rates were strongly driven by precipitation and discharge patterns, the occurrence of tropical cyclones, and associated flooding events, as well as distinct seasonal dry and wet periods. As such, short‐lived hydrological events and long‐term (seasonal and inter‐annual) variation of DIC and TAlk that are pronounced in rivers of the tropical and subtropical wet and dry climate zone should be accounted for when assessing inorganic carbon loads to the coastal ocean and the potential to buffer against or accelerate ocean acidification.

Ecohydrology in a Brazilian tropical dry forest: thinned vegetation impact on hydrological functions and ecosystem services

Study regionThis study was developed in two paired catchments under a tropical dry climate with a tropical dry forest landcover subject to vegetation management in the Brazilian northeastern region. Water input is mostly from rainfall, concentrated in three to four months of the year and with a potential evaporation that is over twice the amount of rainfall that characterizes its hydric deficit. Study focusInteractions between hydrological functions, services and human actions to minimize environmental impacts, improve the availability of water of good quality and decrease degradation of the ecosystems; land use management effect on systems resilience, impact on surface runoff, soil loss, herbaceous and radicular biomass production, soil humidity and total organic carbon under altered vegetation cover. New hydrological insights for the regionStrategies to improve ecosystem services should rely on adequate management of vegetation to reduce surface flow. This reduction contributes to higher soil moisture contents, less intense erosive processes and resulting higher stocked soil carbon. The many techniques that improve resilience and ecosystem services in tropical dry forests lack an integrated view on how ecohydrological processes may be managed to favor the system. Vegetation thinning promotes underbrush development that dissipates rainfall and surface flow kinetic energy, increasing soil moisture content and carbon fixation and reducing soil loss.

Diurnal and seasonal variability of sensible and latent heat fluxes at an agricultural site in Ile-Ife, southwest Nigeria

In this paper, diurnal and seasonal variability of sensible heat (H) and latent heat (LE) fluxes have been investigated at an agricultural site in tropical wet and dry climate, Ile-Ife, Nigeria. Half-hourly averaged flux data for two complete years (2017–2018) of eddy covariance measurements at the study site was used to determine the seasonal trend of Bowen ratio (Bo). In wet season (April–October), diurnal range for both fluxes, H and LE, was 75.3 W m−2 and 177.0 W m−2, respectively. Conversely, in dry season (December–February), the range for H and LE was 182.0 W m−2 and 89.9 W m−2 respectively. For wet season, the daily mean value of H was 19.7 ± 27.2 W m−2 and LE was 52.1 ± 63.5 W m−2, while for dry season, H and LE were 44.0 ± 66.4 W m−2 and 26.6 ± 33.7 W m−2 respectively. A reversal of relative magnitudes of both fluxes was observed, such that the values of H were larger in dry season (Bo > 1) but lower in wet season (Bo < 1). There is a lag of about 1 h between H and LE.

Modelling of an energy-efficient open double-glazing unit for the main climatic conditions of Mexico

The annual thermal evaluation of an open double-glazing unit (ODGU) is presented. The ODGU was modelled using two double-glazing configurations: DCC (clear glass + air + clear glass) and DCA (clear glass + air + absorbent glass). Numerical simulations were performed for the warmest design-day on each month of 2016 in four different climatic conditions in Mexico. The pseudo-transient simulations were carried out using an in-house code based on the finite volume method. To obtain the results, 5856 computational runs were necessary. From the results, the DCA configuration was observed to show the best thermal performance to reduce heat flux that passes through the inside space in the extreme warm dry climate with average reductions of 97 W/m2, followed by the semi-arid climate with 84 W/m2 and the tropical wet and dry climate with 82 W/m2 on a yearly basis. On an annual average, the DCA configuration in the extreme warm dry climate reached almost twice the mass flow rates than those observed in the temperate climate. From the numerical simulations, we have concluded that the use of the low-cost DCA configuration in warm climates was the best solar passive strategy for saving energy in buildings throughout the year.

A framework to estimate heat energy loss in building operation

Abstract Heat energy loss in buildings occurs by two means, namely Fabric Heat Loss and Ventilation Heat Loss. Loss occurs when energy flows out through building envelope from inner warmer air to cooler air located external to the building. The purpose of this study is to identify and estimate the proportion of Heat Energy Loss that is directly caused by construction components from the building envelope. The novelty of this research is to propose a methodological framework that characterizes the Heat Energy Loss in buildings during the operation phase, taking into consideration the local climate data in which buildings are located. Reliance is on the use of a systematic approach that makes the work readily available to practitioners and experts in the area of energy efficiency. A case example of a single-family house is examined in three different climate classifications for validating the proposed method of this work. Results reveal that Fabric Heat Loss is the main factor of the Heat Energy Loss in buildings; responsible for more than 81% of the total Heat Energy Loss in buildings. Openings and exterior walls play a significant role in curbing such energy loss; accounting for around 70% of the total Fabric Heat Loss in buildings. This work points out that the percentage of energy efficiency improvement of Fabric Heat Loss is similar and directly proportional to the percentage of reduction in U-values of building components; as U-value reduces by 6.66%, the energy efficiency of Fabric Heat Loss improves by 6.66%. Besides, the analysis conducted indicates that lower air change rate would lessen the Ventilation Heat Loss in buildings. Finally, this work illustrates that Heat Energy Loss in tropical climates and dry climates could reach a value of 16% and 8%, respectively, compared to Heat Energy Loss in moist subtropical mid-latitude climates.

Genetic Variability and Heritability among Sugarcane Genotypes in Plant Crop for Some Agronomic Traits under Tropical Dry Climate of Ferké, Ivory Coast

Aims: The study aimed to determine the best performing cane genotypes among 29 clones tested under sprinkler irrigation, in comparison with a check variety (R579).&#x0D; Study Design: The experimental design used was a randomized complete block (RCB) with 30 cane genotypes in three replications. Every plot consisted of two dual rows of five meters with 0.5 and 1.90 m of inter-row spacing, i.e. 19 m² per plot and about 600 m² for the whole experiment.&#x0D; Place and Duration of Study: It was carried out on a commercial sugarcane plantation of Ferké 2 located in the northern part of the country, over 10 months as a late season crop from late May 2018 to late March 2019.&#x0D; Methodology: Over each micro-plot, data were collected at harvest from both dual rows consisted of millable stalk number/ha, cane yield, juice quality traits (sucrose, purity, and recoverable sucrose), fiber content, and damaged internodes by stem borer Eldana saccharina.&#x0D; Results: Based on sugar yields, seven cane genotypes were equivalent to the check variety R579 which gave 17.6 t/ha. Their yield performances ranged from 12.2 to 15.4 t of sugar/ha and from 134.2 to 160.8 t of cane/ha compared to 176.0 t/ha for the check. Higher heritability values ranging from 52 to 85% were observed in traits like sugar yield, juice purity, juice sucrose, recoverable sucrose, sucrose percent, fiber content and stem borer infestations. Differences between PCV and GCV for most traits were small, indicating high prospects for genetic progress through selection under conditions of this study.&#x0D; Conclusions: Findings obtained need to be confirmed over the 2019-20 cropping season in first ratoon crop to determine promising cane genotypes for the advanced selection stage.

Thermodynamic analysis of the scheme­cycle design of a heating­coolingmachinefor an individual house

The direction of the research is the thermodynamic analysis of the scheme-cycle designof a heating and cooling machine for an individual house powered by autonomous solar photovoltaic system of providing private consumers with the year-roundheating and cooling in conditions of dry tropical climate. For the analysis, a single-stage compressor refrigerating machine was used, which operates in two modes: refrigeration forair conditioning and heat pump for heating, covering all rooms in the house. Change of the modes is made seasonally or during the day depending on the ambient temperature. The energy efficiency of the refrigerationcycle(“energy” problem) associated with the properties of the working fluid, and cycle size(“transport”problem) associated with the scheme-cycle design, equipment mass and investment costs,were determined. The study used the working fluids R404a, R134a, R410, R290, R600a, R32, which are neither prohibited nor expired. Calculations were performed separately for each mode. The results showed that the R290, R600a working fluids have a high efficiency in both modes, R404A, R410, R32 have the same energy efficiency, differing by no more than 10%, R134a is incompetitivein the heating mode. Among the cyclesizes, R32, R410 have the advantagewith the valueshalf the size of R290, R404A, R600a and R134a are not included in the alternative group. Based on the thermodynamic analysis and monitoring of the market of working fluids, only R32 can be recommended for real projects. A separate thermodynamic analysis of thescheme-cycle designs for CO 2 – the real prospect of refrigeration equipmentwas carried out.

SISTEM PENDUKUNG KEPUTUSAN CERDAS KESESUAIAN LAHAN DENGAN JENIS TANAMAN PANGAN: STUDI KASUS KABUPATEN SIKKA

Sikka District is an area with a dry tropical climate. Most of the plants especially food crops in Sikka District depend on rainfall. The lack of rain coupled with the weather anomalies occurring in Sikka District make Sikka District categorised in the area threatened by food insecurity. Food crop cultivation often experiences obstacles, one of which is in determining the suitability of agricultural land for the advancement of certain food crops because the productivity of food crops depends on the quality of the area used. Therefore, this study aimed to develop a smart decision support system to determine land suitability with food crops. This study used a fuzzy analytic hierarchy process to determine the value of alternatives based on parameters that affect the relevance of the land with the type of food crop. The results showed that corn food crops were the best alternative crop with a value of 0.339 of the three alternative food crops studied and then use the method fuzzy inference system to calculate the amount of land suitability. Kopong Village and Geliting Village were the best villages with land suitability values 81.Keywords: fuzzy analytic hierarchy process, fuzzy inference system, intelligent decision support systems, land suitability

Soil Physical Attributes Under Eucalyptus stands With Non-living and Living Plants

The conservation of ecosystems has benefited from planted forests which provide reforested wood reducing the pressure on deforestation of natural forests. Soil physical attributes determine soil water storage capacity; therefore, they play an important role on plant roots&amp;rsquo; development which may compromise plant&amp;rsquo;s survival. The study tested the influence of soil physical and water attributes on the survival of Eucalyptus spp. clones under dry tropical climate. Two areas were selected, including one with living plants and a second with non-living plants of Eucalyptus spp. clones. Moreover, five soil profiles were studied in each area and the parameters estimated were soil bulk density, total porosity, saturated hydraulic conductivity, soil water retention curve, pores size distribution, available water capacity, and S index. Soil physical and hydric attributes did not differ between the area with living plants and the one with non-living plants. The saturated hydraulic conductivity in the area surface layer was high for both the living plants and non-living palnts; 331 mm h-1 and 294 mm h-1, respectively. The S index (to give the value) indicated that the structure was suitable for the development of Eucalyptus trees. Furthermore, it was possible to affirm that soil physical and water attributes of the studied areas were promising for the cultivation of Eucalyptus spp. in the dry tropical climate.

Long-term conservation horticulture in mango orchards : comparative effects of conventional and conservation management practices on an Alfisol under seasonally dry tropical savanna climate

Long-term conservation horticulture in mango orchards : comparative effects of conventional and conservation management practices on an Alfisol under seasonally dry tropical savanna climate

Species diversity and community structure of butterfly in urban forest fragments at Lucknow, India

The survey was carried out between September 2015-August 2016 in five different localities in Lucknow like Bijli Pasi Quila, Smriti Upvan, Vanasthali Park, Butchery Ground and BSNVPG College Campus, Lucknow, 26.84’N latitude and 80.92’E longitude, is located at an elevation of 126 meters above sea level and in the plain of northern India. Its location is responsible for the diverse weather patterns and climate change. The region has tropical dry equable climate having three main seasons; cold, hot and rainy season. Temperature of the city ranges from 23.8- 45.8°C in summer and 4.6-29.7°C in winter. During the study, butterflies were collected mainly with the help of circular aerial net, which were then placed in killing jar. Killed butterflies were stored in the insect box by proper pinning them for identification. During the course of study, 30 species of butterflies, belonging to 26 genera, representing 5 families, were recorded in Lucknow. 11 Species from nymphalidae, 7 sp. pieridae, 5 sp. from lycaenidae, 3 sp. From hesperidae and 3 sp. from papilionidae were recorded in all selective sites. The butterflies observed were categorized into groups based on their relative numbers; most common &gt;9-10, common 6-8, rare 3-5, very rare 0-2. This study is used for academic as well as applied importance.

Experimental Study of the Thermo-physical Properties of Lateritic Blocks Used in the Habitat in Dry Tropical Climate

Experimental Study of the Thermo-physical Properties of Lateritic Blocks Used in the Habitat in Dry Tropical Climate

Low-latitude vegetation and climate dynamics at the Paleocene-Eocene transition – A study based on multiple proxies from the Jathang section in northeastern India

We present a multi-proxy study of an upper Paleocene-lower Eocene succession from the paleo-equatorial region. The study is carried out on a coal-bearing, shallow-marine succession exposed at Jathang, east Khasi hills, Meghalaya, northeastern India. The succession was deposited in a low-energy, coastal marsh-bay complex. Dinoflagellate cyst biostratigraphy yields a late Paleocene to early Eocene age for the section. The deposits of the lower part of the succession represent a transgressive systems tract (TST) defined by seven parasequences, each starting with bay sediments deposited during transgression, followed by a shallowing-upward bay fill-marsh deposit. In the vertical succession, each parasequence acquires an increasingly marine character, culminating in a maximum flooding surface at the Paleocene-Eocene boundary. It is followed by four shallowing upward parasequences deposited in a highstand systems tract (HST). Enhanced chemical weathering and high terrestrial supply are testified by raised SiO2 and Al2O3 contents and high percentages of terrestrial palynomorphs. The pollen flora recovered from the Jathang section was used for quantitative paleoclimate and vegetation reconstructions. The Coexistence Approach was applied based on Nearest Living Relatives (NLRs) of sixty fossil species recorded at different stratigraphic levels. Seven climate variables were determined for the fossil assemblages, and, as a measure of the seasonality of climate, the number of dry months was estimated. Our study shows that during the Paleocene there existed warm, seasonally dry tropical climate conditions with mean annual temperature at ca. 24–26 °C and mean annual precipitation at ca. 700–1800 mm, and with a dry season of 5–6 months. Particularly warm and wet, perhumid climate conditions with 26–27 °C and 2200–3200 mm mean annual precipitation with a dry period of 2–3 months were reconstructed for the latest Paleocene-earliest Eocene interval. The study shows a distinct vegetational turnover from palm-dominated, seasonally dry tropical forest during the Paleocene to highly diversified dicotyledonous megathermal rainforest during the latest Paleocene-early Eocene. The present study demonstrates that the reduced duration of the dry period during the latest Paleocene-earliest Eocene, due to a more active hydrological cycle, played a major role in determining the climate and shaping the vegetation cover in the paleo-equatorial region. There is evidence from our data that seasonality of rainfall is the determining factor for the tropical forest vegetation pattern of the equatorial region rather than mean annual rainfall condition. As the main trigger for the observed step-wise changes of the hydrology along the studied succession, the fast northward movement of the Indian Plate is inferred.

Modeling of Heat Transfer in a Habitat Built in Local Materials in Dry Tropical Climate

Modeling of Heat Transfer in a Habitat Built in Local Materials in Dry Tropical Climate

Designing an Energy-Efficient Building in a Context of Helping Self-Build

This article presents a study of the performance of a typical building with walls made of local materials. The work consisted in evaluating the thermal comfort in a building built of cut lateritic blocks. This study is a contribution to the development of thermal regulations in Burkina Faso, a country with a dry tropical climate. It will also contribute to solve housing problems in rural and peri-urban areas through the construction of decent housing. The proposed standard building was modelled using TRNSYS software and the simulation determined the atmosphere (relative air temperatures and humidity) in the building's rooms. Air temperature values range from 25.5°C to 31.6°C in the Yako side block rooms. A reduction in the temperature and relative humidity values of the internal air and a high damping of the internal thermal amplitudes have been observed. However, the temperature values have shown that thermal comfort is not achieved in the rooms during the hot periods of the year. This comfort is improved with the use of Reo blocks, because there is a decrease from 1.0 to 1.5°C in the monthly average values of the internal temperature. However, comfort deteriorates when the walls are made of Bobo-Dioulasso lateritic bricks due to the minimum increase in the average temperature of 0.5°C. The values of energy consumption ratios, thermal phase shift times and damping factors show that the building has good energy performance.

Determination of Parameters Influencing Thermal Comfort in a Building

This paper presents a theoretical and an experimental study on the determination of thermal phase shift time and damping factors of building walls. The work consisted in evaluating the thermal comfort in a building. This study is a contribution to put in place a thermal regulation in Burkina Faso, a country with a dry tropical climate. This regulation will, in its application, reduce the energy consumption related to air conditioning in buildings. To do this, we theoretically determine the parameters influencing this comfort using the admittance method. This method makes it possible to analyze the thermal response of a building to a periodic energy demand. It is based on the modeling of the building component by the quadrupole method resulting from the writing of the thermal problem in the form of transfer matrix products. The principle is to link the flows and temperatures of both sides of a homogeneous wall through the equation of heat and the Fourier transform. The calculation method is validated by experimental results. For simple sheet walls based on their compositions, damping factors range from about 37.9% to 79.7% and thermal phase shift time from about 3.9 hours to 7.4 hours. However, the values of these parameters are better when the walls are double-sheeted, the maximum value of the damping factor is 11.5% and the minimum value of the thermal phase shift time is 9.7 h. The values of Mean Bias Difference (MBD) and Root Mean Square Difference (RMSD) show that the theoretical and experimental results are quite concordant. The admittance method can be used to evaluate the performance of building walls.

Characterisation of Rice Production Systems in Northern Agro-Ecological Zone, Uganda

Rice growing is an important source of food and income to the farming community in the northern agro-ecological zone (NAEZ) of Uganda. NAEZ comprised of 16 districts which form Acholi and Lango sub-regions and it is categorized by tropical dry climate with bimodal rainfall patterns. However, inspite of the importance of rice in the NAEZ, very little information exists that could support prioritization of development in the sector. This paper therefore, bridges information gap by analyzing characteristics of rice production system in the study area based on data obtained from a field survey conducted during 2016. The study used cross-sectional design to collect data which was analysed using the descriptive statistics of the STATA computer package. The results revealed marked difference in households’ characteristics, production output and input utilization, production practices and constraints between lowland and upland systems. The study has concluded that: climate variability, pest and diseases, lack of improved seed variety, labour related constraints and lack of specialization are potential causes of low rice production and productivity in the NAEZ. However, to improve production performance of the systems, the study recommends promotion of climate smart farming in rice and further research into system based effects of climate on productivity as well as farmers’ adaptation to climate variability.

Is the spatial pattern of a tree population in a seasonally dry tropical climate explained by density‐dependent mortality?

AbstractSpatial pattern of tropical plants is initially generated by limited seed dispersal, but the role of density‐dependent and independent mechanisms as modifiers of these patterns across ontogeny is poorly understood. We investigated whether density‐dependent mortality (DDM) and environmental heterogeneity can drive spatial pattern across the ontogeny of a tree in a seasonally dry tropical climate. We used Moran's I correlograms and spatial analysis by distance indices (SADIE) to assess the spatial patterns of the pre‐ and post‐germinative stages of Cordia oncocalyx (Boraginaceae), an abundant tree endemic in the deciduous thorny woodland in the northeastern Brazilian semiarid region. We also used RDA to analyse the effect of DDM and environmental heterogeneity (measured by microtopography and canopy openness) in the mortality and recruitment. Seeds, seedlings, juveniles and adults showed aggregated spatial patterns; infants and immatures were randomly distributed; adults, seeds and seedlings attracted each other while adult, juveniles and immatures repulsed each other. Infant and seedling mortality rates were related to DDM and the recruitment from infant to juvenile was more influenced by spatial heterogeneity. Attraction was determined by local dispersal; repulsion was related to DDM and environment heterogeneity, which allowed the return to aggregation in adult stage. Together, these results indicated that spatial pattern can change across ontogeny, in which the initial stages are responsive to DDM and the final stages are influenced by spatial heterogeneity.

Assessment of carbon sequestration potential of revegetated coal mine overburden dumps: A chronosequence study from dry tropical climate

Development of secondary forest as post-mining land use in the surface coal mining degraded sites is of high research interest due to its potential to sequester atmospheric carbon (C). The objectives of this study were to assess the improvement in mine soil quality and C sequestration potential of the post–mining reclaimed land with time. Hence, this study was conducted in reclaimed chronosequence sites (young, intermediate and old) of a large open cast coal project (Central Coal Fields Limited, Jharkhand, India) and results were compared to a reference forest site (Sal forest, Shorea robusta). Mine soil quality was assessed in terms of accretion of soil organic carbon (SOC), available nitrogen (N) and soil CO2 flux along with the age of revegetation. After 14 years of revegetation, SOC and N concentrations increased three and five-fold, respectively and found equivalent to the reference site. Accretion of SOC stock was estimated to be 1.9 Mg C ha−1year−1. Total ecosystem C sequestered after 2–14 years of revegetation increased from 8 Mg C ha−1 to 90 Mg C ha−1 (30–333 Mg CO2 ha−1) with an average rate of 6.4 Mg C ha−1year−1. Above ground biomass contributes maximum C sequestrate (50%) in revegetated site. CO2 flux increased with age of revegetation and found 11, 33 and 42 Mg CO2 ha−1year−1 in younger, intermediate and older dumps, respectively. Soil respiration in revegetated site is more influenced by the temperature than soil moisture. Results of the study also showed that trees like, Dalbergia sissoo and Heterophragma adenophyllum should be preferred for revegetation of mine degraded sites.

Plant water resource partitioning and isotopic fractionation during transpiration in a seasonally dry tropical climate

Abstract. Lake Chala (3°19′ S, 37°42′ E) is a steep-sided crater lake situated in equatorial East Africa, a tropical semiarid area with a bimodal rainfall pattern. Plants in this region are exposed to a prolonged dry season, and we investigated if (1) these plants show spatial variability and temporal shifts in their water source use; (2) seasonal differences in the isotopic composition of precipitation are reflected in xylem water; and (3) plant family, growth form, leaf phenology, habitat and season influence the xylem-to-leaf water deuterium enrichment. In this study, the δ2H and δ18O of precipitation, lake water, groundwater, plant xylem water and plant leaf water were measured across different plant species, seasons and plant habitats in the vicinity of Lake Chala. We found that plants rely mostly on water from the short rains falling from October to December (northeastern monsoon), as these recharge the soil after the long dry season. This plant-available, static water pool is only slightly replenished by the long rains falling from February to May (southeastern monsoon), in agreement with the two water worlds hypothesis, according to which plants rely on a static water pool while a mobile water pool recharges the groundwater. Spatial variability in water resource use exists in the study region, with plants at the lakeshore relying on a water source admixed with lake water. Leaf phenology does not affect water resource use. According to our results, plant species and their associated leaf phenology are the primary factors influencing the enrichment in deuterium from xylem water to leaf water (εl/x), with deciduous species giving the highest enrichment, while growth form and season have negligible effects. Our observations have important implications for the interpretation of δ2H of plant leaf wax n-alkanes (δ2Hwax) from paleohydrological records in tropical East Africa, given that the temporal variability in the isotopic composition of precipitation is not reflected in xylem water and that leaf water deuterium enrichment is a key factor in shaping δ2Hwax. The large interspecies variability in xylem–leaf enrichment (24 ± 28 ‰) is potentially troublesome, taking into account the likelihood of changes in species assemblage with climate shifts.