Radial Growth Decline of White Spruce (Picea glauca) During Hot Summers without Drought: Preliminary Results from a Study Site South of a Boreal Forest Border

Here we investigate the possible future response of white spruce (Picea glauca) to a warmer climate by studying trees planted 90 years ago near the southern limit of their climate tolerance in central New York, 300 km south of the boreal forest where this species is prevalent. We employed high-frequency recording dendrometers to determine radial growth phenology of six mature white spruce trees during 2013-2017. Results demonstrate significant reductions in the length of radial growth periods inversely proportional to the number of hot days with air temperature exceeding 30 oC. During years with very hot summers, the start of radial growth began about 3 days earlier than the 2013-2017 average. However, in those same years the end of radial growth was also about 17 days earlier resulting in a shorter (70 versus 100 day), radial growth season. Abundant (350-500 mm) summer precipitation, which resulted in soil moisture values of 20-30% allowed us to dismiss drought as a factor. Instead, a likely cause of reduced radial growth was mean temperature that exceeded daily average of 30^oC that lead to photoinhibition.

The Physics of Heat Waves: What Causes Extremely High Summertime Temperatures?

We analyze observations and develop a hierarchy of models to understand heat waves – long-lived, high temperature anomalies – and extremely high daily temperatures during summertime in the continental extratropics. Throughout the extratropics, the number of extremely hot days found in the three hottest months is much greater than expected from a random, single-process model. Furthermore, in many locations the temperature skewness switches from negative on daily timescales to positive on monthly timescales (or shifts from positive on daily timescales to higher positive values on monthly timescales) in ways that cannot be explained by averaging alone. These observations motivate a hierarchy of models of the surface energy and moisture budgets that we use to illuminate the physics responsible for daily and monthly averaged temperature variability. Shortwave radiation fluctuations drive much of the variance and the negative skewness found in daily temperature observations. On longer timescales, precipitation-induced soil moisture anomalies are important for temperature variability and account for the shift toward positive skewness in monthly averaged temperature. Our results demonstrate that long-lived heat waves are due to (i) the residence time of soil moisture anomalies and (ii) a nonlinear feedback between temperature and evapotranspiration via the impact of temperature on vapor pressure deficit. For most climates, these two processes give rise to infrequent, long-lived heat waves in response to randomly distributed precipitation forcing. Combined with our results concerning high-frequency variability, extremely hot days are seen to be state-independent filigree driven by shortwave variability acting on top of longer-lived, moisture driven heat waves.

Precipitation extremes over territory of Belarus under current climate change

The study presents an investigation of current and future changes in precipitation regime over territory of Belarus. An assessment of precipitation means and extremes and droughts indices was provided for period of 1948–2019 and more detailed analysis have been carried out for period of climate change in 1989–2019. The precipitation expected changes were studied for period of 2021–2099. It was established that precipitation growth up to 20–30 % in winter during 1989–2019 in comparison by 1948–1988, is connected with increase the number of days with weak precipitation and caused by growing duration of liquid precipitation falling. In summer the reducing of rain falling duration was noticed over territory of Belarus. At the same time the significant growth of precipitation maximal totals per day by 20–30 % was detected. The largest growth was found in the south of the country. Dry days number raised by 1–4 days and dry and hot days numbers raised by 1–2 days per decade. The repeatability of atmosphere droughts of different gradations increased up to 2–26 % by the majority of meteorological stations. According to climate projections based on the EURO-CORDEX-11, the growth of yearly and seasonal precipitation is expected over territory of Belarus. The precipitation increase is connected with growth of intense precipitation. At the same time, the dry periods duration is projected to rise in the warm part of the year. These tendencies are characterised the climate extremeness increase in the current century.

A Ratiometric Calcium Reporter CGf Reveals Calcium Dynamics Both in the Single Cell and Whole Plant Levels Under Heat Stress

Land plants evolved to quickly sense and adapt to temperature changes, such as hot days and cold nights. Given that calcium (Ca2+) signaling networks are implicated in most abiotic stress responses, heat-triggered changes in cytosolic Ca2+ were investigated in Arabidopsis leaves and pollen. Plants were engineered with a reporter called CGf, a ratiometric, genetically encoded Ca2+ reporter with an mCherry reference domain fused to an intensiometric Ca2+ reporter GCaMP6f. Relative changes in [Ca2+]cyt were estimated based on CGf’s apparent KD around 220 nM. The ratiometric output provided an opportunity to compare Ca2+ dynamics between different tissues, cell types, or subcellular locations. In leaves, CGf detected heat-triggered cytosolic Ca2+ signals, comprised of three different signatures showing similarly rapid rates of Ca2+ influx followed by differing rates of efflux (50% durations ranging from 5 to 19 min). These heat-triggered Ca2+ signals were approximately 1.5-fold greater in magnitude than blue light-triggered signals in the same leaves. In contrast, growing pollen tubes showed two different heat-triggered responses. Exposure to heat caused tip-focused steady growth [Ca2+]cyt oscillations to shift to a pattern characteristic of a growth arrest (22%), or an almost undetectable [Ca2+]cyt (78%). Together, these contrasting examples of heat-triggered Ca2+ responses in leaves and pollen highlight the diversity of Ca2+ signals in plants, inviting speculations about their differing kinetic features and biological functions.

Trends in surface temperature variability over Mumbai

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Trends in surface temperature variability over Mumbai and Ratnagiri cities of coastal Maharashtra, India

Increasing urbanization and expansion of cities has led to intensification of the urban heat island (UHI). High consumption of fossil fuels and trapping of radiated heat leads to increase in surface temperature in and around city. Present research paper focuses on temperature variability over Mumbai and Ratnagiri cities, which are located in the same coastal climatic region and almost at same altitude. Trends in maximum and minimum temperature were investigated at annual and seasonal scale. The occurrences of temperature extremes were also analysed. In general, increasing trends were observed over both the stations, with high rate of increase in maximum temperature than the minimum temperatures statistically significant at 95% confidence level. Mumbai experienced significant warming with higher rates than Ratnagiri. Warm extremes have also increased significantly over Mumbai. Ratnagiri showed decrease in hot days during monsoon and hot nights during remaining seasons significant in summer.

Lengthening of summer season over the Northern Hemisphere under 1.5°C and 2.0°C global warming

Summer season has lengthened substantially across Northern Hemisphere (NH) land over the past decades, which has been attributed to anthropogenic greenhouse gas increases. This study examines additional future changes in summer season onset and withdrawal under 1.5℃ and 2.0℃ global warming conditions using multiple atmospheric global climate model (AGCM) large-ensemble simulations from the Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) project. Five AGCMs provide more than 100 runs of 10-year length for three experiments: All-Hist (current decade: 2006-2015), Plus15, and Plus20 (1.5℃ and 2.0℃ above pre-industrial condition, respectively). Results show that with 1.5℃ and 2.0℃ warmer conditions summer season will become longer by a few days to weeks over entire NH lands, with slightly larger contributions by delay in withdrawal due to stronger warming in late summer. Stronger changes are observed more in middle latitudes than high latitudes and largest expansion (up to three weeks) is found over East Asia and the Mediterranean. Associated changes in summer-like day frequency is further analyzed focusing on the extended summer edges. The hot days occur more frequently in lower latitudes including East Asia, USA and Mediterranean, in accord with largest summer season lengthening. Further, difference between Plus15 and Plus20 indicates that summer season lengthening and associated increases in hot days can be reduced significantly if warming is limited to 1.5℃. Overall, similar results are obtained from CMIP5 coupled GCM simulations (based on RCP8.5 scenario experiments), suggesting a weak influence of air-sea coupling on summer season timing changes.

Climatic conditions of the development of tourism and leisure on the Żuławy Alluvial Plain

Based on the data for the years 1981–2014 from two meteorological stations located in the central and northern part of the Żuławy Alluvial Plain, the climatic conditions for the development of tourism and recreation in this area were analyzed. The factors contributing to this type of activity are the average temperatures in the fall and winter months higher than in central Poland and lower temperatures in the summer months, a relatively small number of hot and very hot days, as well as ice and very ice days. The central part of the analyzed area is characterized by lower precipitation totals, lower relative humidity, lower number of steamy days, lower cloud cover, and a high number of days with less than 50% cloudiness than the northern part, which is favorable to tourism in this area. Due to the small number of days with snowfall and snow cover over 8 cm thick, the possibility of skiing here is limited.

275 Access to Shade Mitigate Heat Stress and Improves Growth Performance in Lambs During Summer

The objective of the present study was to investigate the effects of provision of shade on behavior, physiology, and growth of Merino lambs exposed to natural Australian summer conditions. Sixty Merino lambs were randomly allocated to either pasture with shade (n = 30;paddock with trees) or a pasture without shade (n = 30;paddock without any trees) for one month during southern-Australian summer (February-2021). Sheep were grazing on the pastures as per standard protocols followed on the farm with ad libitum access to water. Lambs were monitored twice daily between 0900-1000h and 1400-1600h to record their behavior, and physiological parameters were recorded on hot days (environmental temperature (T) &gt;30°C). Behavioral patterns were represented as the proportion of animals doing specific activities in each treatment group. Grazing was the most frequent activity observed in animals during morning measurement (&gt; 60% in both groups). However, high temperature (T &gt; 30°C) decreased grazing behavior in sheep to &lt; 5% in both treatments. Standing behavior was significantly greater (65.2 vs 21.6%; P &lt; 0.05) for animals under non-shade treatment, while lying behavior was more frequent (17.3 vs 76.3%; P &lt; 0.01) in animals having access to shade. Significantly more animals were seeking water troughs (P &lt; 0.05) in the non-shade group (33.2%) compared to the shade group (10.3%). On an average hot day (T &gt;28°C), most lambs in the shade group were seeking shade (P &lt; 0.01), and when the temperature exceeded &gt;32°C, 90% of the lambs were seeking tree shade. Sheep with access to shade exhibited lower (P &lt; 0.01) respiration rate (117breaths/min) and rectal temperature (39.7°C) than non-shade group (151breaths/min;40.2°C). Overall, access to shade improved (P &lt; 0.001) average daily gain (+0.047kg/day) in sheep compared to the non-shade group (-0.028kg/day). In conclusion, our research confirms that providing access to shade is an effective ameliorative strategy to mitigate heat-stress in sheep during summer heatwaves.