Strengthening tropical influence on heat generating circulation over Australia through spring

Extreme maximum temperatures during Australian spring can have deleterious impacts on a range of sectors from health to wine grapes to planning for wildfires, but are relatively understudied compared to spring rainfall. Spring maximum temperatures in Australia have been rising over recent decades, and, as such, it is important to understand how Australian spring maximum temperatures develop. Australia’s climate is influenced by variability in the tropics and extratropics, but some of this influence impacts Australia differently from winter to summer, and, consequently, may have different impacts on Australia as spring evolves. Using linear regression analysis, this paper explores the atmospheric dynamics and remote drivers of high maximum temperatures over the individual months of spring. We find that the drivers of early spring maximum temperatures in Australia are more closely related to low-level wind changes, which in turn are more related to the Southern Annular Mode than variability in the tropics. By late spring, Australia’s maximum temperatures are proportionally more related to warming through subsidence than low-level wind changes, and more closely related to tropical variability. This increased relationship with the tropical variability is linked with the breakdown of the subtropical jet through spring and an associated change in tropically-forced Rossby wave teleconnections. However, much of the maximum temperature variability cannot be explained by either tropical or extratropical variability. An improved understanding of how the extratropics and tropics projects onto the mechanisms that drive high maximum temperatures through spring may lead to improved sub-seasonal prediction of high temperatures in the future.

The impact of climate change in wheat and barley yields in the Iberian Peninsula

The impact of climate change on wheat and barley yields in two regions of the Iberian Peninsula is here examined. Regression models are developed by using EURO-CORDEX regional climate model (RCM) simulations, forced by ERA-Interim, with monthly maximum and minimum air temperatures and monthly accumulated precipitation as predictors. Additionally, RCM simulations forced by different global climate models for the historical period (1972–2000) and mid-of-century (2042–2070; under the two emission scenarios RCP4.5 and RCP8.5) are analysed. Results point to different regional responses of wheat and barley. In the southernmost regions, results indicate that the main yield driver is spring maximum temperature, while further north a larger dependence on spring precipitation and early winter maximum temperature is observed. Climate change seems to induce severe yield losses in the southern region, mainly due to an increase in spring maximum temperature. On the contrary, a yield increase is projected in the northern regions, with the main driver being early winter warming that stimulates earlier growth. These results warn on the need to implement sustainable agriculture policies, and on the necessity of regional adaptation strategies.

Interannual dynamics in intensity of mesoscale hydroxyl nightglow variations over Almaty

The method of digital difference filters is applied to the data analysis of SATI observations of hydroxyl nightglow intensity and rotational temperature at altitudes 85–90 km over Almaty (43°03' N, 76°58' E), Kazakhstan, in 2010–2017. We examine seasonal and interannual variations in average monthly values and standard deviations of variations with periods 0.4–5.4 hrs, which may be associated with internal gravity waves in the mesopause region. The average monthly temperature near the mesopause has a maximum in winter and a minimum in June. The average monthly intensity has an additional maximum in June. Standard deviation of mesoscale rotational temperature variations and characteristics of internal gravity waves are maximum in spring and autumn. The spring maximum of mesoscale OH emission intensity variations is shifted to June. Interannual variations and multi-year trends of OH rotational temperature and emission intensity may differ in detail. This may be connected with seasonal and long-term variations in the complex system of the photochemical processes, which produce the OH nightglow.

Observations of Phαceliα tαnαcetifoliα as a Food Plant for Honey Bees and other insects

Three consecutive sowings of Phacelia tanacetifolia Bentham (Hydrophyllaceae) were examined for plant growth and attractiveness to bees and other insect-visitors over a three years’ study. Plants that were sown in March flowered uniformly for periods of 24 to 40 days, while those sown in June and July had a non-uniform anthesis that was impossible to estimate. Plants sown in early August, remained vegetative throughout winter and flowered the following spring. Maximum visits of honey bees were observed between 10:00 h and 17:00 h. Most honey bees (>70%) collected nectar. Seasonal differences in the ratio nectar/pollen gatherers were noted. Two species of bumble bee (B. terrestris and B. lucorum) and 9 species of solitary bee visited Phacelia.

Long-term changes of phytoplankton in the lake, not affected by anthropogenic impact (Lake Krivoe, North Karelia)

First studies of the lake ecosystem were performed in 1968–1969 in framework of the International Biological Program, as on a model lake for the observations on the natural dynamic processes. Further work had continued in 1972 and annually from 2002 to 2014. During all study period Cyanobacteria and Chrysophyta have been permanent representatives in phytoplankton. Cyanobacteria were mostly represented by small-cell species from Chroococcales, so their share in the total biomass was low, despite the high abundance. Algae from genera Dinobryon and Uroglena, had dominated in Spring and remained in the plankton during entire season. A distinctive feature of the lake plankton was a low development of diatoms (less than 10% in abundance and biomass) and the absence of the spring outbreak of diatoms in both: under ice and in open water. Cryptomonads (Cryptopyta), which also had been represented throughout of season, became practically new, fairly widespread group in lake phytoplankton. Detailed studies carried out in 2002–2014, have shown that the spring maximum of phytoplankton rarely exceeded the summer one and reached in average 0.46 mg/L. The percentage of each size class of algae in the total biomass of the plankton was determined. Algae with size to 40 microns, which are the most consumed ones by filter feeding zooplankton, constituted a significant share in the Spring time. However the most favorable trophic conditions for zooplankton were during the summer. The development of single-celled Cryptomonad, which reached about 30% of the total biomass, has increased the trophic importance of phytoplankton. Species composition and abundance of phytoplankton in the lake may indicate a conservation of the lake as a clean oligotrophic reservoir.

The global tropospheric ammonia distribution as seen in the 13-year AIRS measurement record

Ammonia (NH3) plays an increasingly important role in the global biogeochemical cycle of reactive nitrogen as well as in aerosol formation and climate. We present extensive and nearly continuous global ammonia measurements made by the Atmospheric Infrared Sounder (AIRS) from the Aqua satellite to identify and quantify major persistent and episodic sources as well as to characterize seasonality. We examine the 13-year period from September 2002 through August 2015 with a retrieval algorithm using an optimal estimation technique with a set of three, spatially and temporally uniform a priori profiles. Vertical profiles show good agreement (∼ 5–15 %) between AIRS NH3 and the in situ profiles from the winter 2013 DISCOVER-AQ (DISCOVER-Air Quality) field campaign in central California, despite the likely biases due to spatial resolution differences between the two instruments. The AIRS instrument captures the strongest consistent NH3 concentrations due to emissions from the anthropogenic (agricultural) source regions, such as South Asia (India/Pakistan), China, the United States (US), parts of Europe, Southeast (SE) Asia (Thailand/Myanmar/Laos), the central portion of South America, as well as Western and Northern Africa. These correspond primarily to irrigated croplands, as well as regions with heavy precipitation, with extensive animal feeding operations and fertilizer applications where a summer maximum and a secondary spring maximum are reliably observable. In the Southern Hemisphere (SH) regular agricultural fires contribute to a spring maximum. Regions of strong episodic emissions include Russia and Alaska as well as parts of South America, Africa, and Indonesia. Biomass burning, especially wildfires, dominate these episodic NH3 high concentrations.

The global tropospheric ammonia distribution as seen in the 13 year AIRS measurement record

Ammonia (NH3) plays an increasingly important role in the global biogeochemical cycle of reactive nitrogen as well as in aerosol formation and climate. We present extensive and nearly continuous global ammonia measurements made by the Atmospheric Infrared Sounder (AIRS) from the Aqua satellite to identify and quantify major persistent and episodic sources as well as to characterize seasonality. We examine the 13 year period from September 2002 through August 2015 with a retrieval algorithm using an optimal estimation technique with a set of three, spatially and temporally uniform a priori profiles. Vertical profiles show good agreement (~5–15 %) between AIRS NH3 and the in situ profiles from the winter 2013 DISCOVER-AQ field campaign in central California, despite the likely biases due to spatial resolution differences between the two instruments. AIRS captures the strongest consistent NH3 emissions from the anthropogenic (agricultural) source regions, such as, South Asia (India/Pakistan), China, the US, parts of Europe, SE Asia (Thailand/Myanmar/Laos), the central portion of South America, as well as Western and Northern Africa. These correspond primarily to croplands with extensive animal feeding operations and fertilizer applications where a summer maximum and secondary spring maximum are reliably observable. In the Southern Hemisphere (SH) regular agricultural fires contribute to a spring maximum. Regions of strong episodic emissions include Russia and Alaska as well as parts of South America, Africa, and Indonesia. Biomass burning, especially wildfires, dominate these episodic NH3 emissions.

The possible relation between cytokinins and secondary xylem formation in Pinus silvestris. I. Seasonal correlations

The Seasonal dynamics of changes in the endogenous cytokinin level was investigated in the tissue of the stem cambial region, The results of the soybean test and Amaranthus test show that marked variations occur. in the course of the year in cytokinin activity in five fractions obtained from tissue of the cambial region. These variations characterized by a spring maximum and late-summer maximum may be correlated in time with changes in cambial activity and the course of annual ring differentiation in the pine stem during the vegetation season.

On the origin of the occasional springtime nitrate concentration maximum in Greenland snow

An occasional spring nitrate concentration maximum was observed in ice cores from Central Greenland but its origin is unknown. This study performs a case study on its origin by measuring concentration and isotopic composition of nitrate (δ15N, δ18O and Δ17O) in a snowpit from Summit, Greenland covering three years of snow accumulation. A nitrate concentration maximum was found in the spring of 2005. Isotopic data of nitrate combined with photochemical calculations suggest that the presence of this spring maximum was linked to a significantly weakened stratospheric ozone (O3) layer. This weakened O3 layer resulted in elevated UV-B (Ultraviolet B) radiation on the snow surface, where the productions of OH and NOx from the photolysis of their precursors were enhanced. A concentration maximum was then observed as the result of enhanced local nitrate production due primarily to the increased OH concentrations, as indicated by decreases in δ18O and Δ17O of nitrate associated with the spring maximum. We further examined the nitrate concentration record from a shallow ice core covering the period from 1772 to 2006 and compared this record to satellite observations of springtime O3 column density data from 1979 to 2006. We found 19 spring nitrate maxima after the 1950s. After 1979, all spring concentration maxima appeared with O3 column density near or below the 1979–2006 average. We hypothesize that the presence of the spring nitrate concentration maximum is largely associated with and may be determined by the interannual variability of O3 column density, under the condition of elevated local NOx abundance at Summit after the 1950s resulting from enhanced anthropogenic nitrate deposition, though other factor(s) may dominate in some years. Isotopic data covering additional years of low O3 column density are needed to further examine this hypothesis.