A Statistical Analysis of Extreme Hot Characteristics and their Relationships with Urbanization in Southern China during 1971–2020

In this study, the total days, mean duration, and intensity of extreme hot events over southern China during the 1971–2020 warm seasons are analyzed, based on daily maximum and minimum temperatures, by comparing the newly proposed independent hot day (IHD), independent warm night (IWN), and compound extreme (CMPD, i.e., the continuous occurrences of hot days and hot nights) to the traditionally defined hot day and warm night. Relationships between the hot extremes and urbanization are explored with 1-km resolution population density data. Results show obvious differences in the spatial distributions between IHD, IWN, and CMPD over southern China. Positive correlations of 0.43, 0.41 and 0.37 are found between the population density and the total days, mean duration and mean intensity of CMPD, respectively, which are qualitatively similar to those using the traditional hot days and warm nights. In contrast, negative correlations between the IHD and IWN indices and the population density are found, as those indices are more apparent over rural areas. Moreover, total days, mean duration and mean intensity of CMPD increase significantly with trends of about 103% decade-1, 21% decade-1 and 38% decade-1, respectively, during the rapid urbanization period from mid-1990s to 2020, which are about 4.9, 2.1 and 2.4 times of their counterparts from 1970 to mid-1990s, while less significant and smaller differences between the two eras are found in IHD and IWN. These results will provide a new scientific basis for evaluating climate models of hot extremes in southern China and have important implications for the other urbanized regions as well.

Occurrence of Physiological Browning Disorders in Stored ‘Braeburn’ Apples as Influenced by Orchard and Weather Conditions

Physiological storage disorders continue to cause sizable economic losses in a range of commercially important pomefruit cultivars. Given similar storage regimes, the incidence and severity of browning disorders in the apple cultivar ‘Braeburn’ can vary in different years in a way that can be explained by the interaction of preharvest seasonal and orchard factors. Over a three-year period (2016 to 2019) at the Kompetenzzentrum Obstbau-Bodensee (KOB) in Southwest Germany a range of orchard and storage treatments were conducted for: air temperature during cell division for three weeks post petalfall or during four weeks preharvest, calcium orchard sprays, crop load and harvest timings. Following controlled atmosphere (CA) storage, the disorder incidence for internal browning and cavity formation varied markedly over the three different growing seasons. Crop load treatments strongly influenced the expression of browning disorders in all years. Differences in air temperatures (△ +/- 2 °C compared to ambient) during the cell division period showed little effect on browning incidence. Warm night temperatures (>10 °C) prior to harvest can reduce internal browning in ‘Braeburn’ apples during CA storage and shelf-life.

Variability of hydroxyl radical (OH) reactivity in the Landes maritime pine forest: results from the LANDEX campaign 2017

Total hydroxyl radical (OH) reactivity measurements were conducted during the LANDEX intensive field campaign in a coniferous temperate forest located in the Landes area, southwestern France, during July 2017. In order to investigate inter-canopy and intra-canopy variability, measurements were performed inside (6 m) and above the canopy level (12 m), as well as at two different locations within the canopy, using a comparative reactivity method (CRM) and a laser photolysis–laser-induced fluorescence (LP-LIF) instrument. The two techniques were intercompared at the end of the campaign by performing measurements at the same location. Volatile organic compounds were also monitored at both levels with a proton transfer time-of-flight mass spectrometer and online gas chromatography instruments to evaluate their contribution to total OH reactivity, with monoterpenes being the main reactive species emitted in this forest dominated by Pinus pinaster Aiton. Total OH reactivity varied diurnally, following the trend of biogenic volatile organic compounds (BVOCs), the emissions and concentrations of which were dependent on meteorological parameters. Average OH reactivity was around 19.2 and 16.5 s−1 inside and above the canopy, respectively. The highest levels of total OH reactivity were observed during nights with a low turbulence (u*≤0.2 m s−1), leading to lower mixing of emitted species within the canopy and thus an important vertical stratification characterized by a strong concentration gradient. Comparing the measured and the calculated OH reactivity highlighted an average missing OH reactivity of 22 % and 33 % inside and above the canopy, respectively. A day–night variability was observed on missing OH reactivity at both heights. Investigations showed that during daytime, missing OH sinks could be due to primary emissions and secondary products linked to a temperature-enhanced photochemistry. Regarding nighttime missing OH reactivity, higher levels were seen for the stable and warm night of 4–5 July, showing that these conditions could have been favorable for the accumulation of long-lived species (primary and secondary species) during the transport of the air mass from nearby forests.

The Penn Cove Roundup

Ted griffin awoke with a start, but he wasn’t sure why. It was a warm night in August 1970, and all seemed calm and quiet. Water lapped against the boat’s hull as the lights of Coupeville flickered a mile and a half away. Yet something wasn’t right. The breathing of the whales behind the capture nets sounded clipped and nervous. “How long have they been blowing that way?” he asked the two men on watch. “Blowing? What way?” they answered. “All night I guess.” Straining his eyes in the dark, Griffin scanned the enormous pen, anchored just off the old Standard Oil dock. Everything seemed to be in order—except on the north side. The marker lights there were too far apart. He roused Goldsberry, and the partners jumped into a skiff to investigate. When they reached the floating lights, Griffin stared down at a loose cork line, puzzled. The net looked split. “Not split—cut!” yelled Goldsberry. “And in more than one place.” Griffin couldn’t believe it. Suddenly the orcas’ anxious breathing made sense. During the night, someone had slashed a section of the net. Large portions of loose mesh now drifted in the current, threatening to drown any whales nearby. Griffin and Goldsberry shouted for their crew, and in the following hours everyone worked feverishly in the dark—reattaching lines, mending mesh, anchoring nets. Had they reacted in time? Had the animals managed to avoid danger? Griffin needed to find out. Donning his wetsuit, he slipped over the cork line and into Penn Cove’s murky waters. At first, he was hopeful. All the whales seemed to be swimming near the surface. But a moment later, his eye caught a shimmer of white—perhaps a shark caught in the net? No, it was a tiny orca calf, no more than eight feet long. Ensnared in a floating portion of mesh, the little whale hung lifeless, head down. Other divers found two more, also calves. Initially, Griffin felt only nausea, but that soon gave way to rage. He wanted to lash out at those responsible.

Photosynthesis and Rubber Production in Transgenic Guayule (Parthenium argentatum, Gray) in Response to Cold Night Temperatures

Rubber production in guayule (Parthenium argentatum, Gray) is highest in the winter months. It has been suggested that lower nighttime temperatures stimulate rubber production. Higher rubber production could be the result of up regulation of the enzymes involved in rubber synthesis, or acclimation of the photosynthetic apparatus to cold temperatures, making photosynthates available for rubber production when the plants are not actively growing, or a combination of the two factors. The effect of low night temperatures on photosynthesis and rubber production was examined in greenhouse grown plants. The experiment was set up as a split plot with different sub plots enclosed in heated or non-heated containers during the night. Those placed in non-heated containers were exposed to the ambient night temperatures of the greenhouse. During the growing season, growth was measured as change in height, and midday and diurnal photosynthetic measurements were collected. At harvest fresh and dry weight of both roots and shoots were taken. Resin and rubber were then extracted with acetone and cyclohexane respectively. Midday photosynthesis was as high or higher in cold night plants than in the warm night plants. In addition, the cold night treatment had lower growth than the warm night treatment. Percent resin and rubber were significantly higher in both shoots and roots of cold night plants, as was the overall yield of rubber. An increase in photosynthetic rate in the cold night treatment, without the concomitant increase in growth seen in the warm night treatment, could account for the increase in rubber production during the winter months.