In Situ Trace Gas and Particle Measurements in the Summer Lower Stratosphere during STREAM II: Implications for O3 Production

In situ aircraft measurements of O₃, CO,HNO₃, and aerosol particles are presented,performed over the North Sea region in the summerlower stratosphere during the STREAM II campaign(Stratosphere Troposphere Experiments by AircraftMeasurements) in July 1994. Occasionally, high COconcentrations of 200-300 pbbv were measured in thelowermost stratosphere, together with relatively highHNO₃ concentrations up to 1.6 ppbv. The particlenumber concentration (at standard pressure andtemperature) between 0.018-1 m decreased acrossthe tropopause, from >1000 cm^-3 in the uppertroposphere to <500 cm^-3 in the lowermoststratosphere. Since the CO sources are found in thetroposphere, the elevated CO mixing ratios areattributed to mixing of polluted tropospheric air intothe lowermost extratropical stratosphere. Further wehave used a chemical model to illustrate that nitrogenoxide reservoir species (mainly HNO₃) determinethe availability of NO_x (=NO + NO₂) andtherefore largely control the total net O₃production in the lower kilometers of thestratosphere. Model simulations, applying additionalNO_x perturbations from aircraft, show that theO₃ production efficiency of NO_x is smallerthan previously assumed, under conditions withrelatively high HNO₃ mixing ratios, as observedduring STREAM II. The model simulations furthersuggest a relatively high O₃ productionefficiency from CO oxidation, as a result of therelatively high ambient HNO₃ and NO_xconcentrations, implying that upward transport of COrich air enhances O₃ production in the lowermoststratosphere. Analysis of the measurements and themodel calculations suggest that the lowermoststratosphere is a transition region in which thechemistry deviates from both the upper troposphere andlower stratosphere.     

Der Mechanismus der Blocking-Lagen über Westeuropa und deren Auswirkung auf das Wetter in Zentraleuropa

Zusammenfassung An Hand einer 16tägigen Frühjahrblockingsituation (2. 3. bis 18. 3. 1955) wurden die dynamischen Vorgänge bei der Bildung und Aufrechterhaltung der Blockinglage studiert. Während in der Vorperiode des Blockings ein Nordwärtstransport von absolutem Rotationsmoment der Geschwindigkeit der Luft stattfindet, wird während der Blockingsituation selbst das absolute Rotationsmoment nach Süden verfrachtet. Weiters wurden die Entwicklungsvorgänge von 25 Blockingfällen während eines Zeitraumes von acht Jahren genau analysiert und die wichtigsten Ergebnisse tabellarisch zusammengestellt.

---

Summary On the basis of a spring blocking-situation, which lasted for 16 days (March 2 to 18, 1955), the author studied the dynamic processes in building up and maintaining of a blocking-situation. Whereas during the preceding period of the blocking a northward transport of angular momentum of the air had occurred, during the blocking itself the angular momentum is transported southward. Besides, the author has analyzed thoroughly the development phases of 25 blockings, which had occurred in a period of eight years, and gives a table with the most important results.

---

Résumé On étudie ici les phénomènes dynamiques qui se produisent lors de l'établissement et du maintien d'une situation de blocage. Pour ce faire, on se sert d'une situation de printemps qui a duré 16 jours (du 2 au 18 mars 1955). Pendant la période précédent le blocage, on constate un déplacement vers le nord du moment de rotation absolu de la vitesse de l'air. Pendant la période de blocage elle-même, le moment de rotation absolu se décale au contraire vers le sud. On analyse en outre très exactement l'évolution de 25 cas de blocage répartis sur 8 ans. Les résultats les plus importants de cette analyse sont rapportés sous forme de tables.

---

---

Mit 4 Textabbildungen     

Robust estimates of climate-induced hydrological change in a temperate mountainous region

A sustainable water resources management depends on sound information about the impacts of climate change. This information is, however, not easily derived because natural runoff variability interferes with the climate change signal. This study presents a procedure that leads to robust estimates of magnitude and Time Of Emergence (TOE) of climate-induced hydrological change that also account for the natural variability contained in the time series. Firstly, natural variability of 189 mesoscale catchments in Switzerland is sampled for 10 ENSEMBLES scenarios for the control (1984–2005) and two scenario periods (near future: 2025–2046, far future: 2074–2095) applying a bootstrap procedure. Then, the sampling distributions of mean monthly runoff are tested for significant differences with the Wilcoxon-Mann–Whitney test and for effect size with Cliff’s delta d. Finally, the TOE of a climate change induced hydrological change is determined when at least eight out of the ten hydrological projections significantly differ from natural variability. The results show that the TOE occurs in the near future period except for high-elevated catchments in late summer. The significant hydrological projections in the near future correspond, however, to only minor runoff changes. In the far future, hydrological change is statistically significant and runoff changes are substantial. Temperature change is the most important factor determining hydrological change in this mountainous region. Therefore, hydrological change depends strongly on a catchment’s mean elevation. Considering that the hydrological changes are predicted to be robust in the near future highlights the importance of accounting for these changes in water resources planning.     

Large‐scale connectivity of Grapsus grapsus (Decapoda) in the Southwestern Atlantic oceanic islands: integrating genetic and morphometric data

The degree of connectivity among island populations can influence their demography and affect their level of genetic differentiation. In this study we investigated genetic and morphometric differences among four populations of Grapsus grapsus (Linnaeus 1758), in Saint Peter and Saint Paul Archipelago (0°55′ N, 29°20′ W), Fernando de Noronha Archipelago (3°50′ S, 32°24′ W), Rocas Atoll (3°50′ S, 33°49′ W) and Trindade Island (20°30′ S, 29°20′ W) from 2003 to 2011. Morphometric results indicated the existence of two distinct groups based on the morphology of their chelae (Trindade Island/Saint Peter and Saint Paul Archipelago versus Fernando de Noronha/Rocas Atoll). In addition, genetic variation in a fragment of the mitochondrial control region revealed substantial differentiation between Trindade and the other islands, with Trindade Island showing only exclusive haplotypes. The congruence of the genetic and morphologic analyses suggests the occurrence of a divergent population in Trindade Island as well as high connectivity among the three remaining equatorial islands. This is the first study to assess the level of morphologic differentiation and genetic connectivity of a species among all four Southwestern Atlantic oceanic islands. Our results provide valuable insight into understanding connectivity through surface ocean currents and suggest that the unstable current system of this area could be responsible for different dispersal patterns. We also suggest that the design of Brazilian marine protected areas should be adjusted to provide stronger protection for Trindade Island as it harbors unique genetic and morphologic variation in G. grapsus.