Annual Weather Research Articles

Calculation method of corona loss in EHV/UHV system based on distributed parameter characteristic

For the calculation of corona loss of extra‐/ultra‐high voltage (EHV/UHV) transmission lines, especially the estimation of real‐time corona loss, there exists no accurate method. In this paper, a calculation method of corona loss in the EHV/UHV system based on a distributed parameter characteristic is proposed. Based on the π‐shaped equivalent circuit of the long‐line distributed parameter characteristic, and considering the voltage distribution along the line, a formula for calculating the corona loss under a variety of weather and annual average conditions is derived and the power equation for the corona loss of EHV/UHV system is established by the method. The example results show that the method is quite accurate. The calculation method of this paper can consider different weather conditions of the line sections to calculate the corona loss. It is more in line with the actual weather conditions on the surface of the EHV/UHV transmission lines. And the method can analyze the corona loss and its proportion to the total loss of the system under the annual average and different weather conditions. It is of great significance to the design and operation of an EHV/UHV system. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Design framework for variable refrigerant flow systems with enhancement of interoperability between BIM and energy simulation

Heating and cooling energy consumption of buildings accounts for a large portion of global energy use and is significantly affected by the air conditioning system in the buildings. In order to predict the energy performance of buildings, various energy simulation engines have been developed and recently applied to the BIM data of buildings. However, due to the interoperability between them, estimating heating and cooling energy at the design stage of the air conditioning system, in collaboration with the building model, still lacks of efficiency and accuracy. In this paper a highly efficient design framework with enhancement of interoperability that enables the designing of a variable refrigerant flow (VRF) type air conditioning system in BIM environments and to analyze its energy behavior is proposed. The framework covers i) computing the energy load of a building, ii) designing a VRF system that includes equipment selection, layout and piping, and iii) predicting energy consumption by the system with consideration of the building’s thermal properties and annual weather conditions. The novelty of the proposed approach lies in the fact that the layout and piping for air conditioning system are enabled inside a BIM environment to maximize interoperability. We implemented the framework as an add-in program to the commercial BIM software and present its accuracy in comparison with the reference data provided by ASHARE.

Improving High-Latitude Rice Nitrogen Management with the CERES-Rice Crop Model

Efficient use of nitrogen (N) fertilizer is critically important for China’s food security and sustainable development. Crop models have been widely used to analyze yield variability, assist in N prescriptions, and determine optimum N rates. The objectives of this study were to use the CERES-Rice model to simulate the N response of different high-latitude, adapted flooded rice varieties to different types of weather seasons, and to explore different optimum rice N management strategies with the combinations of rice varieties and types of weather seasons. Field experiments conducted for five N rates and three varieties in Northeast China during 2011–2016 were used to calibrate and evaluate the CERES-Rice model. Historical weather data (1960–2014) were classified into three weather types (cool/normal/warm) based on cumulative growing degree days during the normal growing season for rice. After calibrating the CERES-Rice model for three varieties and five N rates, the model gave good simulations for evaluation seasons for top weight (R2 ≥ 0.96), leaf area index (R2 ≥ 0.64), yield (R2 ≥ 0.71), and plant N uptake (R2 ≥ 0.83). The simulated optimum N rates for the combinations of varieties and weather types ranged from 91 to 119 kg N ha−1 over 55 seasons of weather data and were in agreement with the reported values of the region. Five different N management strategies were evaluated based on farmer practice, regional optimum N rates, and optimum N rates simulated for different combinations of varieties and weather season types over 20 seasons of weather data. The simulated optimum N rate, marginal net return, and N partial factor productivity were sensitive to both variety and type of weather year. Based on the simulations, climate warming would favor the selection of the 12-leaf variety, Longjing 21, which would produce higher yield and marginal returns than the 11-leaf varieties under all the management strategies evaluated. The 12-leaf variety with a longer growing season and higher yield potential would require higher N rates than the 11-leaf varieties. In summary, under warm weather conditions, all the rice varieties would produce higher yield, and thus require higher rates of N fertilizers. Based on simulation results using the past 20 years of weather data, variety-specific N management was a practical strategy to improve N management and N partial factor productivity compared with farmer practice and regional optimum N management in the study region. The CERES-Rice crop growth model can be a useful tool to help farmers select suitable precision N management strategies to improve N-use efficiency and economic returns.

Is a 100% renewable European power system feasible by 2050?

In this study, we model seven scenarios for the European power system in 2050 based on 100% renewable energy sources, assuming different levels of future demand and technology availability, and compare them with a scenario which includes low-carbon non-renewable technologies. We find that a 100% renewable European power system could operate with the same level of system adequacy as today when relying on European resources alone, even in the most challenging weather year observed in the period from 1979 to 2015. However, based on our scenario results, realising such a system by 2050 would require: (i) a 90% increase in generation capacity to at least 1.9 TW (compared with 1 TW installed today), (ii) reliable cross-border transmission capacity at least 140 GW higher than current levels (60 GW), (iii) the well-managed integration of heat pumps and electric vehicles into the power system to reduce demand peaks and biogas requirements, (iv) the implementation of energy efficiency measures to avoid even larger increases in required biomass demand, generation and transmission capacity, (v) wind deployment levels of 7.5 GW y−1 (currently 10.6 GW y−1) to be maintained, while solar photovoltaic deployment to increase to at least 15 GW y−1 (currently 10.5 GW y−1), (vi) large-scale mobilisation of Europe’s biomass resources, with power sector biomass consumption reaching at least 8.5 EJ in the most challenging year (compared with 1.9 EJ today), and (vii) increasing solid biomass and biogas capacity deployment to at least 4 GW y−1 and 6 GW y−1 respectively. We find that even when wind and solar photovoltaic capacity is installed in optimum locations, the total cost of a 100% renewable power system (∼530 €bn y−1) would be approximately 30% higher than a power system which includes other low-carbon technologies such as nuclear, or carbon capture and storage (∼410 €bn y−1). Furthermore, a 100% renewable system may not deliver the level of emission reductions necessary to achieve Europe’s climate goals by 2050, as negative emissions from biomass with carbon capture and storage may still be required to offset an increase in indirect emissions, or to realise more ambitious decarbonisation pathways.

Factors affecting spontaneous vocal activity of Tawny Owls Strix aluco and implications for surveying large areas

To use vocalizations properly for the estimation of owl population size, it is important to identify how environmental factors affect owl calling behaviour. Here, we analyse how intrinsic and extrinsic factors modify the vocal activity of Tawny Owls Strix aluco in two areas of northern Spain. From March 2013 to May 2015, we radiotracked 20 Tawny Owls and also undertook a systematic survey in which we collected data on spontaneous vocal activity (hoot/call) of the tagged owls, plus their mates and neighbours (36 untagged owls). After 223 nights in Valle de Mena and 224 in Duranguesado we obtained a total of 8791 records of vocal activity. The annual proportion of surveys on which an owl called was 6.3% and did not differ between the study areas. Vocal activity of Tawny Owls varied with sex, annual cycle stage and weather. Male owls were significantly more vocal than females year‐round, and vocal activity peaked during the incubation and post‐breeding periods. Wind and rain adversely affected vocal activity of both sexes throughout the year. Tagged owls were detected more often than untagged owls, which we interpret as an observer effect because the systematic survey ensured that short distances to tagged owls increased the probability of detecting vocal activity. In fact, 2.8% of variation in vocal activity was due to detectability differences between tagged and untagged owls. We conclude that if fieldwork is carried out during the optimum period of the year for vocal detection (i.e. incubation, which in our case was around mid‐April), and under good weather conditions (dry and calm nights), censuses based on spontaneous vocal activity would detect only approximately 12% of the true Tawny Owl population.

Comparison of rain attenuation estimation in high frequency in Indonesia region for LAPAN communication satellite

Rain attenuation is one of the factors taken into consideration in the telecommunication system using frequencies above 10 GHz. As a tropical country, Indonesia has an annual average weather of high rainfall, causing the atmospheric conditions to contain a lot of water vapor. At frequencies above 10 GHz, the rain greatly affects the attenuation of the signal transmitted from/to telecommunication satellites. The objective of the research is to know the rain attenuation value estimation that used in link budget communication design to compensate the appropriate margin in LAPAN communication satellite. The study compared the rain attenuation estimation using ITU-R, Global Crane, and DAH modelling. The highest estimated rainfall value is found in Pare-pare using the Global Crane method. The result of the calculation with ITU-R model is the closest method for rain attenuation prediction in LAPAN communication satellite. The study recommends that the method to be used in the design of high frequency communication satellite operating in Indonesia is the ITU-R modelling.

Modeling Water and Nutrient Movement in Sandy Soils Using HYDRUS-2D.

Models help to describe and predict complex processes and scenarios that are difficult to understand or measure in environmental management systems. Thus, model simulations were performed (i) to calibrate HYDRUS-2D for water and solute movement as a possible decision support system for Candler and Immokalee fine sand using data from microsprinkler and drip irrigation methods, (ii) to validate the performance of HYDRUS-2D using field data of microsprinkler and drip irrigation methods, and (iii) to investigate Br, NO, and water movement using annual or seasonal weather data and variable fertigation scenarios. The model showed reasonably good agreement between measured and simulated values for soil water content ( = 0.87-1.00), Br ( = 0.63-0.96), NO-N ( = 0.66-0.98), P ( = 0.25-0.78), and K ( = 0.44-0.99) movement. The model could be successfully used for scheduling irrigation and predicting nutrient leaching for both microsprinkler and drip irrigation systems on Florida's sandy soils.

Erosion of Coastal Archaeological Sites on Santa Rosa Island, California

The damage and loss of coastal archaeological sites from shoreline transgression and other near-coastal processes is common around the world. It negatively impacts our ability to address important research questions including those about the colonization of the New World, which likely occurred along the Pacific Coast. Differences in geomorphic context, annual weather patterns, topography, vegetation, bedrock, and land-use history lead to distinct localized patterns of erosion even within small geographic regions. We assessed near-coastal erosion on Santa Rosa Island, California, by monitoring annual change at 16 controlled points on 11 archaeological sites from 2013 to 2017 and by comparing it to the local geomorphic context and annual weather patterns. Overall, erosion through this period was greatest on the northwest coast of the island, which is directly in the path of prevailing winds and most winter storms, and least on the more protected west and south coasts. The 2016–2017 winter was the rainiest and had the most annual erosion in general; however, erosion at sites along gulley walls was lowest that year. By monitoring annual erosion and weather and associating them with variations in erosional processes, we can better understand threats to valuable cultural resources and take appropriate steps for mitigating their losses and the loss of archaeological data.

Effect of applied weather data sets in simulation of building energy demands: Comparison of design years with recent weather data

Building energy demands in long-term studies are mostly calculated using the averaged weather data sets, reflecting the changes in environmental conditions over time, thus the different energy consumption each year. This paper reviews and discusses the coupled effects of warming trend in global mean surface temperatures, application of different design weather datasets, and utilization of different methods of building energy assessment on the calculated energy demands. The possible inaccuracies of building energy analyses caused by those three factors are investigated on the example of a residential house in Central Europe. For that purpose eight different weather data sets for Prague, Czech Republic are selected and simulations in two different scales are performed. The analysis of the effect of recent weather data is performed by an improved methodology. First, the simulation brings an increased precision as an advanced hygrothermal model is used for energy calculations. Second, the building performance is assessed, contrary to the Czech national standards, using both heating and cooling energy demands. The simulation results confirm the warming trend in the time period of 2013–2017 as the average heating demands are 3.95% lower and the average cooling demands 3.96% higher in a comparison with the Test Reference Year. In the extreme years, a 12–15% decrease of energy consumed for heating and up to 20% increase of energy necessary for cooling is found. This is in accordance with the presumed warming trend that has been widely discussed during the last few decades. Furthermore, the presented results verify the critical and positive design weather years as suitable for application in the simulation of heating and cooling energy demands in the Czech Republic.

Seston Fatty Acid Responses to Physicochemical Changes in Subalpine Lake Lunz, Austria.

Rapid increase in lake temperature can cause a shift toward the dominance of warm temperature tolerant species, including Cyanobacteria that are deficient in polyunsaturated fatty acids (PUFA) supporting consumer growth and reproduction. To increase our understanding of how changes in physicochemical lake parameters affect phytoplankton composition and the provision of dietary quality to consumers in subalpine oligotrophic lakes, we conducted a multiannual study (2013–2015) in the 34‐m‐deep Lake Lunz and investigated interannual changes in (a) water temperature, transparency, and lake inflow; (b) seston (<30‐μm particle size class) biomass and taxonomy; and (c) seston nutritional quality, assessed by its PUFA composition. The phytoplankton taxonomic composition within this seston size class varied mostly by changes in physical parameters (temperature, conductivity, lake transparency, and days of full ice cover). The dietary quality of seston varied mostly with lake physical parameters and, to a lesser extent, with phytoplankton taxonomic composition, suggesting that the nutritional quality at the base of the food web in Lake Lunz is likely to respond directly to changes in lake physical parameters. This multiannual data set, combining monthly values for physicochemical variables, grazable phytoplankton composition, and fatty acids in seston, provides nutritional information of how annual weather changes may induce changes at the base of the food web in this and perhaps also other oligotrophic subalpine lakes.

Stability analysis for grain yield of winter wheat in a long-term field experiment

ABSTRACTThe current study is based on a long-term field experiment that was conducted at the Rauischholzhausen field station of the University of Giessen (Germany). It includes six different crop rotation systems (CRSs), three mineral nitrogen (N) fertilization treatments and the varying annual weather conditions (AWCs) over 25 years (1993–2017). To ensure new insight into wheat cropping systems that have high yield stability, the dataset was assessed using different methods of stability analysis, including eco-valence, biplot and risk analysis. The results show that the factors which influence grain yield variation in winter wheat can be ranked in the following order: (1) N fertilization; (2) AWC; and (3) CRS. Compared to winter rye as the preceding cereal crop, field bean as the preceding legume crop had a clearly positive effect on the grain yield stability of winter wheat. Furthermore, the higher N fertilization level led to more stable grain yields of winter wheat for all investigated CRSs. Overall, in this study, crop rotation and N fertilization had a high impact on the yield stability of winter wheat. These are important factors to consider in agronomic management decisions under the increasingly difficult environmental conditions caused by climate change.

Consumption, habit formation, and savings: Evidence from a rural household panel survey

AbstractProtecting consumption from the effects of uninsured risk is vital for rural farming households, who tend to be poor and live close to subsistence level. Income uncertainty and habit formation play important roles in the consumption and savings. Variability in weather conditions has a strong linkage with variability in agricultural income in developing countries. This study analyzes consumption and saving decisions of rural farm households in India. Using household panel data for 4 years, we estimated consumption equation accounting for habit formation under income uncertainty. Our findings suggest an evidence for habit formation among rural households. Additionally, we found that both annual and seasonal weather risks significantly influence savings among rural households. Findings from this study also suggest a robust and vibrant farm economy and that the nonfarm economy could contribute to the economic well‐being of rural farming households.

Multi-year data from satellite- and ground-based sensors show details and scale matter in assessing climate's effects on wetland surface water, amphibians, and landscape conditions.

Long-term, interdisciplinary studies of relations between climate and ecological conditions on wetland-upland landscapes have been lacking, especially studies integrated across scales meaningful for adaptive resource management. We collected data in situ at individual wetlands, and via satellite for surrounding 4-km2 landscape blocks, to assess relations between annual weather dynamics, snow duration, phenology, wetland surface-water availability, amphibian presence and calling activity, greenness, and evapotranspiration in four U.S. conservation areas from 2008 to 2012. Amid recent decades of relatively warm growing seasons, 2012 and 2010 were the first and second warmest seasons, respectively, dating back to 1895. Accordingly, we observed the earliest starts of springtime biological activity during those two years. In all years, early-season amphibians first called soon after daily mean air temperatures were ≥ 0°C and snow had mostly melted. Similarly, satellite-based indicators suggested seasonal leaf-out happened soon after snowmelt and temperature thresholds for plant growth had occurred. Daily fluctuations in weather and water levels were related to amphibian calling activity, including decoupling the timing of the onset of calling at the start of season from the onset of calling events later in the season. Within-season variation in temperature and precipitation also was related to vegetation greenness and evapotranspiration, but more at monthly and seasonal scales. Wetland water levels were moderately to strongly associated with precipitation and early or intermittent wetland drying likely reduced amphibian reproduction success in some years, even though Pseudacris crucifer occupied sites at consistently high levels. Notably, satellite-based indicators of landscape water availability did not suggest such consequential, intra-seasonal variability in wetland surface-water availability. Our cross-disciplinary data show how temperature and precipitation interacted to affect key ecological relations and outcomes on our study landscapes. These results demonstrate the value of multi-year studies and the importance of scale for understanding actual climate-related effects in these areas.

Does Tillage or Fertilizer Provide Resilience to Extreme Weather in Southern Illinois?

Core Ideas Dry weather causes maximum reduction in yields of corn and soybean. Precipitation during silking increases yields of corn. In cold years, no‐till yielded 7.5% higher than alternate tillage and chisel tillage. Fertilizer placement had significant effects on corn yields during normal and dry weather years only. Understanding the influence of past “extreme” weather during critical growth stages of corn (Zea mays L.) and soybean (Glycine max L.) production may help us to predict how management practices could influence yield under climate change scenarios. This study evaluated the influence of tillage (moldboard plow [MP], alternate [AT], chisel [ChT], and no‐till [NT]) and fertilizer (N+NPK starter, NPK+NPKstarter, and NPK) management on yield during extreme weather events (cold, hot, wet, and dry) occurring at critical growth stages of corn and soybean under continuous–corn [CC; 1970–1990] and corn–soybean [CS; 1991–2015] rotations located in a somewhat poorly drained Bethalto silt loam near Belleville, IL. Results showed that during dry years, corn yield was 3.8% higher with NPK treatment as compared to NPK+NPKstarter fertilizer treatment. Soybean yield was not influenced by any type of fertilizer treatments during extreme and normal weather events. Corn yields were significantly affected by tillage in cold years in which NT yielded 7.5% higher than AT and ChT treatments; however, during wet years, ChT and MP yielded 8.5 and 7.3% (respectively) higher than NT. During cold years, soybean yield in AT was higher by 12.3 and 9.4% than MP and ChT treatments, respectively. As compared to normal weather years, corn yield was highest with all tillage treatments during wet years, showing beneficial influence of precipitation on corn yield during critical growth stage (silking). Our study results showed that dry weather has maximum potential for causing a reduction in corn and soybean yields under all tillage treatments.

Quantifying temporal change in plant population attributes: insights from a resurrection approach.

Rapid evolution in annual plants can be quantified by comparing phenotypic and genetic changes between past and contemporary individuals from the same populations over several generations. Such knowledge will help understand the response of plants to rapid environmental shifts, such as the ones imposed by global climate change. To that end, we undertook a resurrection approach in Spanish populations of the annual plant Arabidopsis thaliana that were sampled twice over a decade. Annual weather records were compared to their historical records to extract patterns of climatic shifts over time. We evaluated the differences between samplings in flowering time, a key life-history trait with adaptive significance, with a field experiment. We also estimated genetic diversity and differentiation based on neutral nuclear markers and nucleotide diversity in candidate flowering time (FRI and FLC) and seed dormancy (DOG1) genes. The role of genetic drift was estimated by computing effective population sizes with the temporal method. Overall, two climatic scenarios were detected: intense warming with increased precipitation and moderate warming with decreased precipitation. The average flowering time varied little between samplings. Instead, within-population variation in flowering time exhibited a decreasing trend over time. Substantial temporal changes in genetic diversity and differentiation were observed with both nuclear microsatellites and candidate genes in all populations, which were interpreted as the result of natural demographic fluctuations. We conclude that drought stress caused by moderate warming with decreased precipitation may have the potential to reduce within-population variation in key life-cycle traits, perhaps as a result of stabilizing selection on them, and to constrain the genetic differentiation over time. Besides, the demographic behaviour of populations probably accounts for the substantial temporal patterns of genetic variation, while keeping rather constant those of phenotypic variation.

Spatiotemporal Mining of BSS Data for Characterising Seasonal Urban Mobility Dynamics

Digital traces of individual mobility can be revealed from the origin-destination sensing systems of BSS (Bicycle Sharing System). This record enables wide analysis of human mobility traits in urban area including pattern, trend, and anomalies. This study investigates and compares trip history of BSS open data from two cities, London and New York, along a year period with respect to annual weather data as explanatory factors. This aims to get insights about seasonal urban mobility dynamics both temporally and spatially. Results show that, for both cities, there are differences as well as similarities of temporal correlation level between riding behaviour of BSS users and hour of the day, day of the week, season, and local weather. Practically, the most correlated factor can be further considered and used as predictive features. Meanwhile, the proposed spatial analysis shows the positive bikes imbalance occurs in the morning, mostly at inner stations because of inward flow, and vice versa. This spatial extent can be used for redistribution purpose, specifically in order to provide enough resources at the highly visited stations before peak time occurs.

London's weather and the everyday: two centuries of newspaper reports

AbstractThis study surveys 200 years of London's weather and its public reporting in newspapers to reveal some of the recurring modes of reporting and linguistic styles that are used to describe and make sense of the human experience of weather. These modes include: the cultural anxieties prompted by ‘unusual weather’, the visual dramas of ‘great storms’, the weather as culpable, and the bench‐marking of extreme weather. Even as the broader processes and patterns of our climate are changing, at the level of the everyday the human and cultural experience of weather remains remarkably familiar.

Weather determines the occurrence of wheat stem base diseases in biogas cropping systems

Renewable energy produced at biogas plants has tremendously increased the demand for digestible biomass in central Europe over the last twenty years. As a consequence, new crop rotations combining conventional and recently introduced bioenergy crops are tested in long-term field trials. The aim of this work was to determine risks for soilborne wheat stem base diseases in new bioenergy crop rotations. Crop rotations tested consisted of maize, sorghum, cereals, grasslegume mixtures, and phacelia. Field trials with five rotations were established at four different sites in Germany, whereby winter wheat was grown at the end of each rotation. Field trials were set up in a block or strip plot design in 2005 and 2006. After eight years, stem base diseases of winter wheat were visually assessed during milk ripeness. ‘Random forests’, a non-parametric statistical method, was used to select the most important variables describing weather, soil productivity and rotation. Subsequently, disease incidences were modeled with generalized linear models. Disease incidence was high for Fusarium foot rot (47%), moderately high for eyespot (30%), and low for sharp eyespot (4%). An increasing number of days with high precipitation during six weeks after sowing, and less growing degree days from February through June led to higher eyespot incidence (R2 = 60%). Fusarium foot rot incidence was correlated to high mean precipitation during six weeks after sowing, and low number of growing degree days from February through June (R2 = 78%). In contrast to the eyespot model, year and region had additional explanatory power to the Fusarium foot rot model. Based on the results of this study we could show that annual weather patterns had a high impact on eyespot and Fusarium foot rot incidences, while the effect of rotation was low. Although unexplained site and year-specific effects require further investigations, weather patterns identified by applying an innovative variable selection method provide a valuable starting point for developing and improving forecasting models for Fusarium foot rot.

What determines irrigation efficiency when farmers face extreme weather events? A field survey of the major wheat producing regions in China

Water availability is a major constraint on grain production in China, therefore, improving irrigation efficiency is particularly important when agriculture faces extreme weather events. This paper first calculates irrigation efficiency with a translog stochastic frontier production function and then investigates what happens when extreme weather events occur via a Tobit model. The estimated results reveal several important features of irrigation practices: i) irrigation efficiency is lower when extreme weather events occur; ii) large variations in irrigation efficiency occur across irrigation facilities; iii) the farm plots exhibit an extreme distribution across efficiency levels; and iv) water-saving techniques, technology adoption, and the maintenance of farmers’ economic resilience are major determinants of irrigation efficiency. Based on these results we propose the following recommendations: i) farmers should balance crop yield and water use; undertake relevant training programs and adopt water-saving techniques; ii) local governments and researchers should help farmers to find the optimal level of irrigation water use based on their own circumstances and provide better water-saving techniques and training programs rather than simply encouraging farmers to invest in irrigation facilities in the most extreme weather years; and iii) the income level of farm households should be increased so as to improve their resilience to natural disasters.

Experimental Study on Fire Performance of Weathered Cedar

ABSTRACTHistoric buildings have significant cultural, scientific, and aesthetic value, and show the accomplishments of past eras. Unfortunately, many of wooden historic buildings are destroyed by fire disasters. The reaction-to-fire performance of timber was changed after several hundred years of natural weathering. In this study, the effect of weathering on the reaction-to-fire performance of untreated and fire retardant treated timber are investigated. The conventionally treated cedars were weathered in accordance with a standard construction material durability test method (JSTM J7001), three accelerated weathering test methods (J60, J20 and J4), and a standard weathering method (NT FIRE 053 Method A), respectively. Then, the effect of weathering on phosphoric acid and paraffin treated timber samples was examined by comparing the reaction-to-fire performance of chemically treated timber before and after weathering. The results show that the use of fire retardant can reduce the ignition time, the peak heat release rate (pHRR) and total heat release (THR). The weathering process increases both the pHRR and THR, but reduces the ignition time, which infer a relationship between the two processes of sufficient pyrolysis.