Warm Days Research Articles

The effects of climate change on the timing of peak fall foliage in Acadia National Park

ContextIn recent decades, most United States’ National Parks have experienced extreme temperature and precipitation regimes outside of their historical ranges of variability with unknown effects on fall phenology.ObjectivesWe determine 1) how seasonal climate in Acadia National Park, Maine and the timing of peak fall foliage have changed between 1950 and 2021; 2) how changes in seasonal climate have affected fall foliage; and 3) how we might expect the timing of fall foliage to change given future climate projections.MethodsWe use ERA5-Land data to analyze changes in climate. We couple remotely sensed data with archival research to determine changes in the timing of peak fall foliage. We use multivariate regressions to understand the relationship between climate and fall foliage. We use CESM2 data to predict the timing of peak fall foliage coloration through 2060.ResultsMinimum temperatures, maximum temperatures, precipitation, and the number of warm nights, hot nights, warm days, hot days, and downpour days have all significantly increased (p ≤ 0.05). The timing of peak fall foliage is now occurring almost two weeks later (p ≤ 0.05). September temperature and precipitation and May precipitation were positively correlated with delayed peak fall foliage. Early October precipitation was negatively correlated. Future climate projections predict the timing of peak fall foliage to occur between October 30 and November 2 by 2060.ConclusionUnderstanding how climate is affecting leaf senescence both is crucial in a national park where fall tourism brings large gains to the local economy and provides key information to park managers planning for a resilient, sustainable future.

Differential temperature sensitivity of intracellular metabolic processes and extracellular soil enzyme activities

Abstract. Predictions concerning the feedback of soil heterotrophic respiration to a warming climate often do not differentiate between the extracellular and intracellular steps involved in soil organic matter decomposition. This study examined the temperature sensitivities of intracellular metabolic processes and extracellular soil enzyme activities and how they are influenced by previous temperatures. We pre-incubated soils at 5, 15, or 26 ∘C to acclimatize the microbial communities to different thermal regimes for 60 d before measuring potential activities of β-glucosidase and chitinase (extracellular enzymes), glucose-induced respiration (intracellular metabolic processes), and basal respiration at a range of assay temperatures (5, 15, 26, 37, and 45 ∘C). A higher pre-incubation temperature decreased the soil pH and C/N ratio and decreased β-glucosidase potential activity and respiration but not chitinase potential activity. It is likely that this legacy effect on β-glucosidase and respiration is an indirect effect of substrate depletion rather than physiological acclimatation or genetic adaptation. Pre-incubation temperature effects on temperature sensitivity were subtle and restricted to extracellular activities, perhaps because of the short (60 d) duration of the pre-incubation at temperatures that were below the initial optimum (∼ 30 ∘C) for the mesophilic soil community. However, we found that the intracellular and extracellular steps differ in their temperature sensitivity, and this observation differs depending on the range of temperature used for Q10 estimates of temperature sensitivity. Between 5 and 15 ∘C intracellular and extracellular processes show equal temperature sensitivity, but between 15 and 26 ∘C intracellular metabolic processes were more temperature sensitive than extracellular enzyme activity, and between 26 and 37 ∘C extracellular enzyme activity was more temperature sensitive than intracellular metabolic processes. This result implies that depolymerization of higher molecular weight carbon is more sensitive to temperature changes at higher temperatures (e.g. higher temperatures on extremely warm days), but the respiration of the generated monomers is more sensitive to temperature changes at moderate temperatures (e.g. mean daily maximum soil temperature). However, studies using multiple soil types and a greater range of pre-incubation temperatures are required to generalize our results. Nevertheless, since climate change predictions currently indicate that there will be a greater frequency and severity of hot summers and heatwaves, it is possible that global warming may reduce the importance of extracellular depolymerization relative to intracellular metabolic processes as the rate-limiting step of soil organic matter mineralization. We conclude that extracellular and intracellular steps are not equally sensitive to changes in soil temperature and that the previous temperature a soil is exposed to may influence the potential activity, but not temperature sensitivity, of extracellular and intracellular processes.

Combined effect of ambient temperature and solar radiation on maned sloths' behaviour and detectability

AbstractChanges in ambient temperature and solar radiation may affect sloths' metabolic rate and body temperature, with consequent changes in activities, postures and microhabitat selection. Although the separate effect of temperature and solar radiation on sloth's behaviour have been previously studied, the combined effect of these climatic factors on behavioural aspects of sloths has never been systematically evaluated in field conditions. Here we evaluated the influence of hourly ambient temperature variation on maned sloth (Bradypus torquatus) activities, postures and tree crown positions, under sunny and cloudy conditions; and tested if any of the animal posture and position increase their exposure to human detection. We performed 350 h of visual observation on eight maned sloths, equipped with radio‐backpacks, in northern Bahia, Brazil, recording their activities, and their resting postures and positions on tree crowns. We also recorded the time taken to visualize the sloths on 58 days to analyse if sloths' detection is affected by posture and position. Higher ambient temperature, within a range of 21–33°C, increased the sloths' activity levels in cloudy conditions but reduced their activity in sunny conditions. Increasing ambient temperature also reduced the frequency of huddled posture and increased the frequency of extended posture and permanence in the inner tree crown. Lastly, the postures and positions did not influence sloths' detectability. Thus, the direction of the temperature–activity relationship depends on climatic conditions (sunny/cloudy), and individuals rely on resting postures and positions to thermoregulate. The warmer and drier future climate, expected to occur in the northern Atlantic Forest, may impose change in the diurnal activity levels and postural pattern for this threatened species, leading maned sloths to reduce its activity on sunny and warmer days and adopting an extended posture.

Evaluation of Changes in Temperature Extremes in Vamsadhara River Basin, Odisha, India

With an emphasis on extreme events, several climate change indices that were derived from daily temperature data were computed and studied. Odisha is a coastal state of India which is severely prone to extreme events. With climate change, extreme events are also increasing in the world especially in coastal regions. Vamsadhara river basin which is situated at Odisha is selected for the study. The objective of this study was to compute and analyze the Expert Team on Climate Change Detection and Indices (ETCCDI) extreme indices using CLIMPACT software. 14 temperature indices were used to analyze the signals of climate change in the study area. The IMD data for the period 1961-2022 has been used for the study. The trend detection of indices was done through Mann-Kendall test and magnitude of trend was calculated using Sen’s Slope estimator. The result showed that warm days (TX90), Diurnal temperature range (DTR) and Warm Spell Duration Index (WSDI) are increasing with 1%, 10% and 1% level of significance respectively. This indicates that indices associated with warming are increasing in river basin. The cold night (TX10) indices found to be decreasing with 10% level of significance and TNx showed a negative trend at 10% level of significance.

Optimizing the Pump Storage System for Hot Water Showering at Swimming Pools

Previous studies have demonstrated the energy- and water-saving potentials of showering facilities in residential buildings. However, the prospect of public showering places where multiple showerheads usually worked together according to their opening hours has often been overlooked and rarely investigated. This study measured the water flow rate in a water supply pipe to understand the water-use patterns and water consumption of showering facilities in a swimming pool. The measurements were carried out on typical cold and warm days. The results showed that the average water consumption was 50.5 L/person in December (T = 19.7 °C) and 38.6 L/person in April (T = 24.5 °C). The fluctuation of the water flow rate demonstrated a water demand pattern for the showering facilities, where the maximum water flow rate was more than twice the average level, indicating inefficient working modes of the water supply pump. To improve the current situation, an appropriately sized water tank was suggested to be installed, which could ensure a more stable water flow rate in the main supply pipe, enhancing the water supply system efficiency and saving energy for the water pump. These results contribute to establishing the design data for optimizing water tank design in swimming pools or similar buildings with public showering demand and illustrate the energy-saving potential of water supply systems in showering facilities. Nevertheless, the results of this study are only based on theoretical calculations. More comprehensive field studies with a water tank are required to confirm these findings and better elucidate the effects.

Impacts of large-scale circulation patterns on the temperature extremes in the cold regions of China with global warming

The cold regions of China (CRC) are important and vulnerable freshwater recharge areas on land, and any changes in them are related to the survival of millions of people in East Asia. However, for nearly half a century, in cold regions, the extreme temperature response to global warming is still poorly understood. In this study, we systematically studied the temperature extreme changes in cold regions of China since 1961 and discussed the possible circulation factors in detail. The results showed that 1) the warming magnitudes in cold nights and warm nights are greater than those in cold days and warm days, and decreases in cold nights and cold days and increases in warm days and warm nights appeared in almost all of cold regions of China. Most of the temperature indices displayed the largest magnitudes of warming in winter. 2) Spatially, for most of the temperature extremes, the stations located at Qinghai–Tibet Plateau (TPC) and Northwest China (NWC) showed a larger warming trend than that shown by the station at Northeast China (NEC). 3) The responses of temperature extremes at different cold regions to each circulation index are variable. Atlantic Multidecadal Oscillation (AMO) has a significant relationship with almost all the indices in cold regions of China. Almost all the temperature extremes of TPC and NWC showed closely relationship with the North Atlantic Oscillation (NAO), especially for diurnal temperature range (DTR), daily maximum temperature, and the cold extremes. Multivariate ENSO Index (MEI) is significantly related to most the temperature indices of Northwest China and Northeast China. However, MEI has a significant impact on only TPC’s diurnal temperature range and warmest night (TNx). 4) Atlantic Multidecadal Oscillation displayed significant relationships with most the temperature extremes in every season in cold regions of China. However, the summer and winter MEI and the summer and winter North Atlantic Oscillation showed significant impacts on only diurnal temperature range, daily minimum temperatures (TNm), and TNx.

Snížení základního odtoku kvůli evapotranspiraci povrchové a podzemní vody z mokřadu v povodí Liběchovky: porovnání měření a výpočtu Oudinovou metodou

This study is focused on the base flow decrease due to surface water and groundwater evapotranspiration (ET) in wetlands of the Liběchovka catchment. Evapotranspiration in wetlands can significantly affect stream discharge, and its influence will probably still increase in the future due to the global rise of temperatures caused by climate change. The study site is located in the upper part of Liběchovka catchment (Fig. 1). This wetland hosts a small stream supplied by rather steady groundwater inflow, representing the favourable site for detection of the effect of ET. V notch weir and two piezometers were used to monitor stream discharge and wetland water table in 30 minute periods (Fig. 2). Diurnal periodical oscillations of water flow and water table caused by ET were observed (Fig. 3). They occurred in the summer part of the year, especially on sunny days without rain. The amplitude of water table level oscillation was increasing with increasing temperature (Fig. 4). Calculation showed that evapotranspiration reduced the water flow, on average, by 15 % on the warm sunny days. The maximum daily reduction was up to 32 %. Direct measurements were compared with the potential ET calculated using the Oudin’s method (Oudin 2005). The ET from the measurement was 45 % of the potential ET calculated by Oudin’s method. In the next step, the Oudin’s method was used to calculate the potential ET of all wetlands in Liběchovka catchment upstream from the Želízy village, where gauging station of ČHMÚ is situated. The original discharge not reduced by the wetland ET was defined as the sum of the wetland potential ET and the mean annual measured discharge. Due to the ET from wetlands (years 2015–2020), the discharge was reduced on average by 13 %. If only the summer months of July and August were considered, it was reduced, on average, by 26 % and by 39 % in the driest day recorded in this period. To estimate the role of groundwater abstraction on the Liběchovka stream during the period of 2015–2020, the sum of measured stream discharge, groundwater abstraction and wetland ET was calculated. From this sum, 71.5 % represented the directly measured water flow, 18.2 % was the groundwater abstraction, and 10.3 % was the wetland ET (Fig. 8).

Annual evaluation of a modified wall with PCM to reduce energy consumption and CO2 emissions in Southeast Mexico

This research shows the numerical thermal evaluation of walls commonly used in Mexico under Merida, Yucatan weather conditions. At first, the thermal behavior of the hollow block wall (HB) was compared with the red brick wall (RB) for the warmest and coldest days of the year. Afterward, the annual thermal evaluation of an HB with and without a PCM layer (HBP) was carried out. The PCM layer was a 10 mm thick layer of RT25HC, located between the HB and the plaster facing the indoor. The results showed that the HB reduces the heat flow by 14.6% during the warmest day and increases it by 1.9% during the coldest day, compared to the RB wall. Besides, the HBP reduced the heat flux up to 48.7% regarding HB and showed a time lag in the maximum temperature of up to 3.86 h during the warmest day. Also, the PCM layer reduced the monthly CO2 emissions of the HB up to 56.4%. Therefore, incorporating a PCM layer on HB is highly recommended for buildings in Merida and similar climatic regions to reduce their energy demand and carbon footprint.

Permafrost degradation at two monitored palsa mires in north-west Finland

Abstract. Palsas and peat plateaus are expected to disappear from many regions, including Finnish Lapland. However, detailed long-term monitoring data of the degradation process on palsas are scarce. Here, we present the results of the aerial photography time series analysis (1959–2021), annual real-time kinematic (RTK) GNSS and active layer monitoring (2007–2021), and annual unoccupied aerial system surveys (2016–2021) at two palsa sites (Peera and Laassaniemi, 68∘ N) located in north-west Finland. We analysed temporal trends of palsa degradation and their relation to climate using linear regression. At both sites, the decrease in palsa area by −77 % to −90 % since 1959 and height by −16 % to −49 % since 2007 indicate substantial permafrost degradation throughout the study periods. The area loss rates are mainly connected to winter air temperature changes at Peera and winter precipitation changes at Laassaniemi. The active layer thickness (ALT) has varied annually between 2007 and 2021 with no significant trend and is related mainly to the number of very warm days during summer, autumn rainfall of previous year, and snow depths at Peera. At Laassaniemi, the ALT is weakly related to climate and has been decreasing in the middle part of the palsa during the past 8 years despite the continuous decrease in palsa volume. Our findings imply that the ALT in the inner parts of palsas do not necessarily reflect the overall permafrost conditions and underline the importance of surface position monitoring alongside the active layer measurements. The results also showed a negative relationship between the ALT and snow cover onset, indicating the complexity of climate–permafrost feedbacks in palsa mires.

Analysis of trends in extreme temperature indices over selected areas in Peninsular Malaysia from 1991-2020

This study investigates the temporal variations of extreme temperature trends across three stations in Peninsular Malaysia with different settings, Petaling Jaya represents urban station, while Kluang and Batu Embun represent rural areas from 1991-2020. Eleven extreme warm and cold indices trends were analysed using the Mann-Kendall test, with Sen’s slope as a magnitude estimator. The findings revealed that the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature increased significantly at all stations by 0.04°C yr–1, 0.02°C yr–1, and 0.05°C yr–1, respectively. The station in the rural area shows a significant increment of an average of 0.03°C yr–1 for mean and warm extreme indices. Despite that, there were no changes in the total number of warm days and nights and cold days and nights for all settings. For the cold temperature indices, there were significant decreasing trends for the annual minimum of maximum temperature in rural areas, while urban station did not exhibit changes. All stations also exhibit similar annual patterns when compared although significantly higher readings were observed during El Niño events.

On the Seasonal and Spatial Dependence of Extreme Warm Days in Antarctica

AbstractThe spatial distribution of trends in temperature extremes over Antarctica remains largely unknown. Here we investigate the seasonal and spatial characteristics of extreme warm occurrence across Antarctica. The Antarctic inland areas show significant positive trends in the number of extreme warm days in austral spring and summer. The trends in the seasonal mean of daily maximum temperature show strong coherence with the trends in extreme warm occurrences. In addition, the long‐term longwave radiation, water vapor flux and regional atmospheric circulation changes are closely connected to the trends of extreme warm days in all seasons outside of summer; the summer longwave radiation and interior wind trends show little coherence with warm extreme trends, indicating other processes at play driving extreme warm days in summer.

Future transition in climate extremes over Western Ghats of India based on CMIP6 models.

The effect of climate change on the tropical river catchments in the Western Ghats of India is studied using the Coupled Model Intercomparison Project-6 data (CMIP-6). Multi-model ensembles of rainfall and temperature are constructed using the Random Forest ensemble technique for bias-corrected GCMs in the near future (2014-2050) and far future (2051-2100) horizons. For the two catchments each in the southern, central, and northern Ghats, the trend in minimum and maximum temperatures, precipitation, and other indices are calculated. By 2100, dry sub-humid and humid catchments will see a higher increase in mean annual temperature than per-humid central catchments. In future decades, the warm days and nights increase by 45-50% and 40-70%, respectively, with twofold warming in the winter season. Under a climate change scenario, annual rainfall increases in Vamanapuram, Ulhas, and Purna, while Chaliyar, Netravati, and Aghanashini catchments experience a decrease in rainfall in the far future with an increase in pre-monsoon rainfall. The southern catchments are anticipated to have contrasting variations in the rainfall extremes; northern catchments face a substantial increase in very wet to extremely wet days and medium to heavy rainfall. In all catchments (excluding Vamanapuram), cumulative wet days increase with a decrease in cumulative dry days. After the mid-twenty-first century, humid to per-humid catchments encompass an increase in cool nights, whereas it disappears in dry sub-humid catchments of the Ghat. Interestingly, warming tendencies begin to slow down after 2050. This investigation can assist in comprehending the regional climate extremes in the Western Ghats to formulate better climate risk planning and adaptation strategies.

The Relative Warming Rates of Heat Events and Median Days in the Pacific Northwest from Observations and a Regional Climate Model

Abstract This paper examines the trends in hot summer days for the Pacific Northwest in observations and a regional climate model ensemble. Hot days are identified by the temperature threshold for several percentile values computed over 10-yr intervals (85th, 90th, and 95th percentiles and absolute maximum) to differentiate heat events of different intensities and are compared to the median temperature (50th percentile). For the stations analyzed, the observed rate of warming during hot days is not statistically different from the warming rate of median days since the 1950s. However, for projections to 2100, hot days show a statistically significant increase in the warming rate of the hottest days compared to the warming rate for median days. Depending on location, the 95th-percentile daily maximum temperature shows a warming rate of up to 0.2°C decade−1 above the median warming rate. The divergence in the trends of median and extreme temperature shows substantial regional variation depending on local terrain and coastlines. The warming trend during hot days is related to the unique circulation patterns during heat events, which respond to different feedbacks and amplifying effects in the land–atmosphere system from those that prevail during typical days. The regional climate model simulations are taken from an ensemble of the Weather Research and Forecasting (WRF) Model simulations forced by 12 global climate model simulations from phase 5 of the Climate Model Intercomparison Project (CMIP5) using the RCP8.5 emissions scenario and 12-km grid spacing. Significance Statement The heatwave of June 2021 had substantial societal and ecological impacts, illustrating vulnerability to record-shattering events. This paper addresses whether climate change can cause heat events in the Pacific Northwest to warm at a more rapid rate than typical days. Based on observations, in the recent past, the hottest days warmed at about the same rate as typical days in the recent past. However, results from a high-resolution climate model show a higher rate of warming during the warmest days relative to median days under the most aggressive future emissions scenario. This effect could cause heatwaves to become more intense relative to typical days by 2100, making adaptation to extreme events more difficult.

Do bone elasticity and postmortem interval affect forensic fractographic analyses?

Forensic fractographic features of bone reliably establish crack propagation in perimortem injuries. We investigated if similar fracture surface features characterize postmortem fractures. Experimentally induced peri- and postmortem fractures were used to assess if fractographic features vary as bone elasticity decreases during the postmortem interval (PMI). Thirty-seven unembalmed, defleshed human femoral shafts from males and females aged 33-81 years were fractured at varying PMIs with a drop test frame using a three-point bending setup and recorded with a high-speed camera. Vital statistics, cause of death, PMI length, temperature, humidity, collagen percentage, water loss, fracture energy, and fractography scores were recorded for each sample. Results showed that fractographic features associated with perimortem fractures were expressed in PMIs up to 40,600 accumulated degree hours (ADH), or 60 warm weather days. Hackle was the most consistently expressed feature, occurring in all fractures regardless of ADH. The most variable characteristics were wake features (78.4%) and arrest ridges (70.3%). Collagen percentage did not correlate strongly with ADH (r=-0.04, p=0.81); however, there was a strong significant correlation between ADH and water loss (r=0.74, p < 0.001). Multinomial logistic regression showed no association between fractographic feature expression and ADH or collagen percentage. In conclusion, forensic fractographic features reliably determine initiation and directionality of crack propagation in experimentally induced PMIs up to 40,600 ADH, demonstrating the utility of this method into the recent postmortem interval. This expression of reliable fractographic features throughout the early PMI intimates these characteristics may not be useful standalone features for discerning peri- versus postmortem fractures.

Extending the culture of cleavage-stage embryos to the blastocyst stage after warming increases the chance of live birth: does it have a regenerative effect?

We aimed to evaluate the effect of extending the culture of cleavage-stage embryos to the blastocyst stage in vitrified-warmed cycles on pregnancy outcomes. This is a retrospectively designed pilot study of a single center. All patients who applied for freeze-all cycle procedures during in vitro fertilization treatment were included in the study. Patients were classified into three subgroups. The embryos obtained were frozen at the cleavage or blastocyst stage. After a warming process, the cleavage-stage embryos were divided into two subgroups: the first group of embryos was transferred (vitrification day 3-embryo transfer (ET) day 3 (D3T3)) on the warming day; for the second group, the embryo culture was extended to the blastocyst stage (vitrification day 3-ET day 5 (after the extension of the embryo culture to the blastocyst stage), (D3T5)). Frozen blastocyst-stage embryos were transferred after warming (vitrification day 5-ET day 5 (D5T5)). Hormone replacement treatment was the only endometrial preparation regimen given during the embryo transfer cycle. The main outcome of the study was live birth rates. The clinical pregnancy rate and positive pregnancy test rate were determined as the secondary outcomes of the study. The study included a total of 194 patients. The positive pregnancy test rates (PPR) and clinical pregnancy rates (CPR) of the D3T3, D3T5, and D5T5 groups were 14.0% and 59.2%; 43.8% and 9.3%; and 56.3% and 39.6%, respectively (p < 0.001 and p < 0.001). The live birth rates (LBR) of patients in the D3T3, D3T5, and D5T5 groups were 7.0%, 44.7%, and 27.1%, respectively (p < 0.001). In subgroup analysis of patients with a poor number of 2PN embryos (defined as having < = 4 2PN embryos), the D3T5 group had significantly higher PPR (10.7%, 60.6%, 42.4%; p < 0.001), CPR (7.1%, 57.6%, 39.4%; p < 0.001), and LBR (3.6%, 39.4%, 21.2%; p: 0.001). Extending the culture after warming to the blastocyst stage may be a better alternative than a cleavage-stage embryo transfer.

Flowers of a South African succulent plant predict tomorrow's weather, synchronizing flower opening with pollinator activity

Abstract Day‐to‐day synchrony between flower opening and pollinator activity is important for maximizing plant fitness. A succulent, Bulbine frutescens (L.) Willd., is an ideal model for studying synchrony in response to daily weather as it flowers year‐round. Additionally, it has self‐incompatible flowers that open for just one day, making it essential that flower opening matches pollinator activity. Observations were made on urban plants in California, USA, with validation measurements in the native range in South Africa. Independent observations indicated that flowers open primarily after favourable conditions the previous day, specifically air temperatures above 15°C. Solar radiation was experimentally shown to have limited, but significant effects. Pollinators, mostly bee species, had similar temperature thresholds to flowers. Developmental constraints on flowers were hypothesized to delay opening by a day. Flower bud growth was closely related to temperature, with warm days resulting in sufficient growth for buds to become competent to open the following day. Laboratory experiments demonstrated that competent flowers were suppressed from opening until at least 16 h was accumulated in which temperatures were above 12°C; thus, on many cool days, sufficient development to cause flower opening would only occur a day after favourable weather. Based upon regression models of pollinator and flower response to weather, fitness was estimated as a function of synchrony, over 20 years of weather from California and across the natural range in South Africa. Flowers responding to either the previous day's or current day's weather resulted in similar predicted fitness, with flower response to the current day's weather leading to a slightly higher cost, that is, flowers opened when pollinators would be absent. Multiple temperature responsive constraints on bud growth and development result in delays in flower opening, such that flower opening occurs the day after favourable weather. Given the high correlation between daily temperatures in USA and South African winter‐rainfall environments, behaviour predicting the following day's weather results in high fitness. Many pollinators share similar temperature thresholds for activity, thus diverse plants may have evolved predictive behaviour maximizing daily synchrony between pollinators and flower opening. Read the free Plain Language Summary for this article on the Journal blog.

Spatial and temporal variations of extreme climate index in the Songhua River Basin during 1961-2020.

Understanding climate change and extreme climate is of great significance for ensuring food security and socio-economic development of the Songhua River Basin. Based on the daily precipitation, maximum temperature and minimum temperature data during 1961-2020 from 69 meteorological stations in and around the Songhua River Basin, we analyzed the temporal and spatial variations of extreme temperature and precipitation in the Songhua River Basin using 27 extreme climate indices recommended by the World Meteorological Organization, and linear trend method, Mann-Kendall trend test and ordinary Kriging interpolation methodology. The results showed that, from 1961 to 2020, except for cold speel duration, the extreme cold index in the study area showed a downward trend, while the extreme warm index, extreme value index and other temperature indices showed an upward trend. The increasing trend of the minimum temperature was greater than that of the maximum temperature. Icing days, cold speel duration and warm speel duration showed an increasing trend from south to north, while the minimum value of maximum temperature and that of minimum temperature showed opposite spatial characteristics. The high value areas of summer days and tropical nights were mainly distributed in the southwestern region, while there was no obvious spatial variations of cool days, warm nights, and warm days. Overall, except for cold speel duration, other extreme cold indices had a rapid decreasing trend in the north and west of the Songhua River Basin. In the warm index, summer days, warm nights, warm days, and warm speel duration had a rapid upward trend in the north and west, and tropical nights had the fastest rise in the southwest. In the extreme value index, the maximum of temperature rose fastest in the northwest, while the minimum rose fastest in the northeast. Except for consecutive dry days, the rest of precipitation indices showed an increasing trend, and the fastest rising areas were mainly in the north-central part of the Nenjiang River Basin, while some areas in the south of the Nenjiang River Basin became dry. Heavy precipitation days, very heavy precipitation days, heaviest precipitation days, consecutive wet days, very wet day precipitation, extremely wet day precipitation, and annual precipitation showed a gradual decreasing pattern from southeast to northwest. Overall, the Songhua River Basin was warming and wetting, but there were some differences among different regions, especially the northern and southern parts of the Nenjiang River Basin.

Spatiotemporal variability characteristics of extreme climate events in Xinjiang during 1960–2019

Under the global warming, it is particularly important to explore the response of extreme climate to global climate change over the arid regions. Based on daily temperature (maximum, minimum, and average) and precipitation data from meteorological stations in Xinjiang, China, we analyzed the spatiotemporal characteristics of extreme temperature and extreme precipitation events via combining thin plate smoothing spline function interpolation, Sen's slope, and Mann-Kendall test. Our results showed that during 1960-2019, the extreme low temperature index of frost days (FD), icing days (ID), cold days (TX10p), cold nights (TN10p), and cold speel duration index (CSDI) all showed the downward trend to varying degrees, and the extreme high temperature index of summer days (SD25), warm days (TX90p), warm night (TN90p), and warm speel duration index (WSDI) all showed an upward trend to varying degrees, and the extreme low temperature index of high altitude mountains decreases more than that of the basin and plains. In addition, all the extreme temperature indices are closely related to the annual average temperature in Xinjiang (R > 0.6). Among the extreme precipitation indices, except for the consecutive dry days (CDD), the other extreme precipitation indices showed increasing trends to different degrees, but the changes in extreme precipitation in Xinjiang were mainly manifested by the increase of heavy precipitation in a short period (the increase of heavy precipitation and extreme heavy precipitation was the largest, 44.8mm/10a and 17.6mm/10a, respectively) and spatially concentrated in the Ili River and Altai Mountains in northern Xinjiang. Meanwhile, annual precipitation was positively correlated with the extreme precipitation index (R > 0.4), except for the CDD. This study provides theoretical support for the prevention and control of natural disasters in the dry zone.

Critical climate thresholds for fire in wet, temperate forests

Climate models predict more frequent droughts and more severe fire weather. Wildfires in wet forests, while historically uncommon, can have catastrophic impacts on forest values and services. Therefore, it is important to ask whether climate change is increasing the frequency of fires in wet forests. Long-term fire histories and weather records were compared in wet Eucalyptus forests supplying water to Melbourne, Australia, to identify the combination of dryness and fire weather under which stand-replacing fires occur. The effect of climate change on stand replacement frequency was predicted using down-scaled regional climate change projections for RCP4.5 and RCP8.5.An index of surface soil dryness (SSD), which is a proxy for live and dead fuel moisture, and daily maximum vapor pressure deficit (Dmax), which is a proxy for daily fire weather, were used to rank each day of each fire season from 1900/01 to 2019/20, within 898 km2 of water supply catchments. The two indices were compared for days with and without stand-replacing fire activity within the study area. Threshold values for the combination of both indices were identified. Damaging fires occurred on about 10 % of days falling above this threshold. The two worst fires, between them burning 86 % of the wet forest in the study area, occurred on days with moderate rather than severe SSD (within the top 2 % of days but only about half of the maximum SSD) but with the most extreme Dmax (highest and second highest ranked out of 43,920 days).The frequency of long fire seasons (SSD > 65 mm for 30 or more days) increased from 1 in ∼30 years during the 20th century to 1 in 4 years in the past 15 years, due to a doubling in the number of warm dry days (Dmax > 2.0 kPa) per fire season. The frequency of extreme fire weather days (Dmax > 5.5 kPa) was also higher in the past 15 years than for most of the previous century. These observations suggest that fire frequency and severity are likely to increase in these wet forests, potentially threatening a suite of ecosystem services. Based on regional climate change projections, increases in the frequency of stand replacing fire will be driven more by increases in maximum temperature than by reductions in rainfall. Under RCP4.5, stand replacing fire frequency in the study area could increase from 1 in ∼140 years historically to 1 in ∼40 years by 2050 and 1 in ∼22 years by 2090 (1 in ∼6 years under RCP8.5), which would result in widespread loss of these iconic forests, including Eucalyptus regnans, the world’s tallest Angiosperm.

Planning Queen Elizabeth II’s Visit to Bondi Beach in 1954

Planning Queen Elizabeth II’s Visit to Bondi Beach in 1954