Warm Humid Zone Research Articles

Tree Ring Blue Intensity-Based August Temperature Reconstruction for Subtropical Central China

Tree-ring blue intensity (BI) has the potential to provide information on past summer temperatures of a similar quality to that of tree-ring maximum latewood density and at a substantially reduced cost. To explore the applicability of BI in subtropical regions, the inverted BI for the earlywood, latewood, and the delta BI (DBI) parameters, together with tree-ring width of subalpine fir (Abies fargesii Franch.) in the Shennongjia area of China, were measured, and the corresponding chronologies were developed. The relationships of these chronologies with the monthly mean temperature and monthly precipitation were explored via correlation analysis. Results show that the DBI chronology is closely related to the temperature in August of the current year, indicating that BI, specifically delta BI, data are suitable for use in dendroclimatology studies in subtropical areas. The resultant mean temperature August reconstruction, based on DBI, explains 40.8% of the temperature variance and is robustly validated using independent periods from the calibration. This pilot study not only highlights the potential of DBI for temperature reconstruction in China but also offers valuable insights into historical climate variations in the Shennongjia region. Moreover, it shows the potential for utilizing such tree-ring data from low-latitude regions to derive past climate data in subtropical warm-humid zones.

Agroecological-based modeling of meteorological drought at 12-month time scale in the Western Cape Province of South Africa

To mitigate the effects of drought in water-stressed agro-ecological zones (AEZs), it is crucial to implement efficient monitoring of drought characteristics and establish proactive water-use strategies. The Western Cape (WC) province is being confronted with an escalating threat of diminished water availability due to unsustainable human activities. The objective of this study was to assess the spatio-temporal characteristics of meteorological drought within a 12-month timescale in the WC province of South Africa spanning from 1980 to 2020. The University of East Anglia's Climate Research Unit provided precipitation datasets from fifteen stations across the six AEZs of the WC province. These datasets were processed using the Standardized Precipitation Index (SPI). The Mann–Kendall (M–K) test was used to analyze the precipitation trend and SPI values at a significance level of p < 0.05. The results indicated substantial negative trends in annual precipitation across all AEZs. An examination of seasonal precipitation patterns revealed a rise in summer precipitation in subtropical cool-arid regions and subtropical warm semi-arid regions, with increases of 0.4 and 0.2 mm/year, respectively. Conversely, the overall annual precipitation trend fell by -1.0 mm/year in both AEZs. The SPI values consistently fell within the range of -2 to 0 in the subtropical warm-arid, subtropical cool-arid, and subtropical cool-arid zones. Conversely, the SPI values were consistently positive in the subtropical warm-arid, subtropical cool-humid, and subtropical warm-humid zones. This finding suggests that there will be persistent drought conditions that will affect agricultural production, surface flows in rivers, and groundwater levels across the WC province.

Assessment of sandcrete hollow blocks’ thermal performance as a walling material for tropical buildings in Lokoja, Nigeria

PurposeUnderstanding the thermal performance of sandcrete hollow block walls in the tropic is very essential for occupants' well-being, productivity and efficiency, due to its widespread application in buildings in the study area. Lokoja, in Nigeria, lies in the warm humid zone with its attendant's high temperatures all year round. Thus, providing an acceptable walling material that will control the high indoor air temperature becomes imperative. This paper assessed sandcrete hollow blocks as a walling material used in Lokoja, to determine the thermal performances for effective thermal comfort of the residents.Design/methodology/approachIt involves the construction of a habitable model building with the commonly available sandcrete hollow blocks in the area. One unit of Cryopak iMINI Temperature and Relative Humidity Data Logger called new generation intelligent iMINI with Serial Number and Product Code MX-CI-145–0009 and MX-HE-S-16-L was installed, to record the indoor air temperature and relative humidity data at an interval of one hour, for 12 months covering dry and wet seasons. The results of the recorded data were downloaded to an excel spread sheet for assessment and analysis throughout the seasons. The values were computed using the temperature–humidity index (THI) equation, with a view to determine the indoor thermal comfort level category.FindingsThe study revealed that sandcrete hollow block walls provide thermal discomfort of the indoor environment for both seasons, with attendant adverse effects in the comfort of the occupants. The paper concludes that proper orientation of buildings, planting of trees, use of low absorbing or reflective surface materials, application of cavity walls to receive insulation materials in between the hollow spaces provided, instead of the single walling as well as providing shading device elements, can improve users' comfort and also ameliorate the heat effect on the external surface of building transferred into the interior by conduction, radiation or convection within the area and in the tropics at large. Other thermally eco-friendly wall materials available in Lokoja includes timber, stabilized laterite–cement blocks, burnt bricks and earth-mud bricks which can be used to replace sandcrete hollow block walls. These alternative wall materials are used for construction of residential and office buildings by the colonial government of Sir Fredrick Lugard in the study area.Practical implicationsThe application of sandcrete hollow blocks as a wall material is in vogue, not minding its thermal discomfort to the users and the environment; this is due to its availability and ease of production. The acceptability of this walling material requires holistic study to unravel the best way to reduce the thermal discomfort inherent in its application.Originality/valueThe author succeeded in revealing the thermal performance of sandcrete hollow blocks as walling material in Lokoja, the study area. It is a first attempt at understanding the performance for human comfort in the area. This will greatly assist the resident and other researchers to improve on the application of sandcrete hollow blocks as walling material towards ensuring that maximum indoor thermal comfort is achieved.

Improvement on Window Glassing for an Enhanced Indoor Thermal Environment of Tropical Office Buildings

The intense solar radiation absorbed through the window glassing and transmitted into the indoor environment constitute thermal discomfort and increased cooling energy demand for buildings in the tropical climatic zone. This is because tropical climates are generally characterised by hot thermal distress almost all the year round. The need for improvement on window glassing of office buildings arise as a result of the global consensus on reducing energy demand of building sector. In office buildings, higher level of thermal and visual comfort is required for productive work performance within the indoor environment. This place office buildings in a position to enhance the realisation of a sustainable environment in the tropical climatic zone. This paper focus on effect of two types of window glassing on indoor air temperature and achieving improvement on single pane ordinary clear glassing window through the use of low-solar gain low-emissivity windows of two existing office buildings in the warm-humid zone of the tropical climate of Nigeria. An experimental investigation was scheduled during rainy and dry seasons of the year to collect outdoor and indoor microclimatic data of air temperatures in the west-facing natural ventilated office spaces within the existing office buildings through the use of Tiny Tag Ultra 2 Dual Channel Temperature/Relative Humidity (TGU-4500) Data loggers. Data collected were sorted and analysed through descriptive statistics. Improvement on single glassing window of existing office building was obtained through calculation of heat gain characteristics and comparison with that of low-solar gain low-emissivity glass window heat gain characteristics. Results showed that single pane ordinary clear glassing window exhibits higher indoor temperatures in the monitored office space. 89.54% improvement was recorded by using low-solar gain low-emissivity glass window over single pane clear glass window in the investigated office buildings. The study therefore recommends the use of low-solar gain glass low-emissivity window in office buildings within the warm-humid zone of tropical climate of Nigeria.

Factorial Design of Concrete Production in Hot and Warm Humid Zones in South East Nigeria

This study narrates the quality of concrete production as slump wet in warm and hot zones. The quality of concrete mixture is of inevitable concern to all stakeholders in the construction industry in the zones when the climatic conditions of the zones are considered. Absence of National standards, environmental and climatic conditions and other factors are the main factors that affect the quality of concrete produced in the area. The affected mix ratio is examined and all the prevailing construction/production practices are considered. All necessary measures for improving the quality of concrete produced are surveyed considering the relationships between various variables used in the mixture. Three major factors (variables) that are found to be influencing the quality of concrete in the south east, Nigeria. The absence or lack of implementing the existing building code, climatic conditions in the zones and types of construction materials available, all remain the major variable influencing the quality of present concrete production in the zones of south east, Nigeria.

Thermal behavior of a phase change material in a building roof with and without reflective coating in a warm humid zone

In this paper, the heat transfer in a concrete roof with an intermediate layer of PCM was studied numerically. Three positions and three thicknesses of the PCM layer and two values of solar absorptance (gray and white) of the roof were evaluated. The period studied was a typical summer week of a city in Mexico with warm humid weather. The interior boundary was in contact with the indoor air at a constant temperature. The unsteady two-dimensional model was solved by the Finite Volume Method using an implicit scheme. For the gray roof, the greatest reduction in the temperature of the interior surface (6.4°C) and in the heat gains (22.2%) was obtained when a PCM layer with a thickness of 2 cm is close to the interior surface. For the white roof, the results of the maximum temperatures of the interior surface and the heat gains between the different thicknesses and positions of the PCM layer showed negligible differences. However, the melting cycles of the PCM layer were affected as it was closer to the interior surface of the roof, and its thickness increased. The incorporation of a white reflective coating reduced the maximum interior surface temperature and the cooling load by 14.7–15.4⋄C, and 58.1–62.7%, respectively.

Radial growth response of Pinus yunnanensis to rising temperature and drought stress on the Yunnan Plateau, southwestern China

The relative influence of energy and water availability on tree growth at specific sites under warming conditions remains insufficiently understood on the Yunnan Plateau, which obstructs the rational selection and development of forest management measures in the context of climate change. In this study, a dendroecological investigation was conducted in four sites on the Yunnan Plateau to evaluate growth trends and climate responses of Pinus yunnanensis under warming and drought stress across cold-dry (CD), warm-humid (WH), warm (WR), and hot-dry (HD) zones. The effects of energy and water availability on the radial growth of P. yunnanensis varied in different sites and showed site-specific characteristics. The radial growth of P. yunnanensis in the CD zone benefited from rising temperatures, especially in the pre-growing season and core growing season. However the radial growth of P. yunnanensis in the WH zone was restricted by excess water in the core growing season. The radial growth of P. yunnanensis in the WR and HD zones became increasingly limited by temperature and drought stress, and the growth switched from responding to energy stress to moisture stress. The sensitivity of P. yunnanensis to climate factors in the warm-humid zone and humid seasons was relatively stable; in contrast, this species was vulnerable to warming and drought stress under harsh growth conditions and showed considerable instability. Intense warming in the future may cause a significant variation of tree growth response to climate. It would trigger a noticeable redistribution effect of energy and water availability on forest growth, which motivates assessments of climate-growth relationships, not only at large spatial scales, but also in specific sites. This research provides a basis for the adoption of effective forest management measures for specific sites according to their response characteristics associated with the distribution of climate drivers.

Regional upper Albian–lower Cenomanian sequence boundaries, Texas Comanche shelf: Is timing related to oceanic tectonics?

The Albian–lower Cenomanian Comanchean Series on the Comanche Shelf, Texas and northern Mexico is a laboratory to calibrate the numerical ages of mixed carbonate-siliciclastic cycles. The stratigraphic contacts of the long-term cycles formed during subaerial exposure followed by marine drowning. Correlation of these cycle contacts in different basins tests their synchroneity and the hypothesis of eustasy. Petrographic and geochemical evidence of Early Cretaceous meteoric diagenesis differs across the shelf because the Comanche Shelf spanned the subtropical arid belt and the mid-latitude warm humid zone. The contact between the Fredericksburg and Washita groups is Al SB Wa1, which is a composite subaerial unconformity and transgressive drowning surface that is traced from southeastern Oklahoma to El Paso and down-dip to the shelf margin.Chronostratigraphy of the Comanchean Series Fredericksburg and Washita groups is constrained by multiple biostratigraphic data of ammonites, caprinid rudists, and foraminifers. The lower upper Albian Al SB Wa1 is dated by the Dipoloceras cristatum Zone below and the Mortoniceras pricei Zone above. Caprinid zones in carbonate facies are integrated with ammonites and foraminifers to provide a complementary correlation criterion. This contact is coeval with a condensed interval in Europe and flooding sequences in western Asia and northern Africa.Depleted carbon isotope ratios indicate subaerial exposure below sequence boundaries at base of Washita Group, at base of the lower Cenomanian Del Rio Formation and base of the Cenomanian Woodbine-Eagle Ford groups. These contacts are coeval with sequences in Europe, Africa, Asia, and South America. Late Albian–early Cenomanian sea-level changes provide a chronologic scale for significant oceanic plate reorganization dated at about 100 Ma.

Performance of desiccant air conditioning system with geothermal energy under different climatic conditions

Energy saving still and continue a major seek in our life, due to the continuous increase in energy consumptions. So, a desiccant air conditioning system with geothermal energy is conducted in the current study. The thermal analysis of air conditioning system with its different components desiccant wheel, solar collector, heat exchanger, ground heat exchanger and water spray evaporative cooler is presented. Three different air conditioning cycles are simulated in the current study for different zones like: hot-dry zone, warm-dry zone, hot-humid zone and the warm-humid zone. The results show that the desiccant air conditioning system successfully provides a better thermal comfort condition in different climates. This hybrid system significantly decreases the supplied air temperature from 12.7 to 21.7°C at different climate zones. When ωin,air and TReg increasing, COP decreases and the ventilation cycle provides the better COP. The highest COP value of the desiccant air conditioning system is about 1.03 while the lowest value is about 0.15. The SHR of makeup cycle is higher than that ventilation cycle at warm and hot-humid zone and vice versa at warm and hot-dry zone. The highest SHR value of the desiccant air conditioning system is about 0.99 while the lowest value is about 0.2. The Tsup,air, ωsup,air, COP and SHR isolines may easily be used for pre-evaluating of various cooling cycles in different climates. The hybrid system provides a human thermal comfort at different climates.

Potentials of Passive Solar Design in Energy Conservation in Buildings in the Warm Humid Climate

The achievement of energy efficiency in the building sub-sector is considered a very important issue in contemporary research and development efforts by engineers, architects and environmentalists. This is because of its direct impact on national economies and indirectly on the environment and the general well being of future generations. This paper attempts an evaluation of the potentials of passive design in the warm humid zone of Nigeria by assessing the level of energy conservation in building through solar orientation. Model experimental buildings were constructed and comfort factors (indoor and out door temperature, relative humidity, solar radiation, etc) measured, and the climatic and technical (construction) factors determined for each of the model buildings using known methods. Regression model on the effect of solar radiation on the climatic and technical factors reflecting the amount of heat energy required to achieve an acceptable comfort level for each building was formulated. Results from the study show that there is strong evidence of tremendous potentials in passive design as ecotechique for energy conservation in buildings.

Climatic Classification for Building Design in India

A study on climatic data for nearly 225 stations spread over the whole country has been carried out to determine climatic zones which may meet common basic design features in buildings and requirements of heat flow computations. The country is categorised in four major types of climates viz, hot-dry, warm-humid, temperate and cold and a sub-group “Composite”. The greater part of the country falls under composite followed by warm—humid zone.