A modulation of the mechanism of the semiannual oscillation in the Southern Hemisphere.

ABSTRACT The local pressure changes associated with the twice-annual contraction/intensification and expansion/weakening of the circumpolar trough of low pressure around Antarctica, termed the semiannual oscillation (SAO), was the dominant signal in the annual cycle at mid and high southern latitudes before 1979. The mechanism, as shown by Van Loon (1967), arises from different response to the surface heat budget over the polar continent and the midlatitude ocean. It has subsequently been shown that in most years since 1979 the SAO has weakened considerably. Evidence is presented here from surface temperature data, 500 mb temperatures from a station pair and zonal mean 500 mb temperatures from the NCAR/NCEP reanalyses to show that a warming trend since 1979 has not been evenly distributed through the year at each latitude. Thus an anomalous change in the temperature gradient between 50°S and 65°S, with peaks in roughly May and November, has modulated the mechanism that produces the SAO, with its peaks in March and September. Consequently, the magnitude of the SAO has decreased in the more recent period

Regioscan zoetwatermaatregelen : Verkennen van het perspectief van kleinschalige zoetwatermaatregelen voor de regionale zoetwateropgave

De Regioscan zoetwatermaatregelen brengt de bijdrage in beeld die lokale maatregelen kunnen leveren aan het opheffen van regionale zoetwatertekorten. Dit helpt bij de ontwikkeling van een zoetwaterstrategie. Het rapport bevat meer informatie en achtergronden over het instrument, en een handleiding voor het gebruik

The effect of acute and 7-days dietary nitrate on mechanical efficiency, exercise performance and cardiac biomarkers in patients with chronic obstructive pulmonary disease

Background & aims Many COPD patients have a reduced exercise capacity and mechanical efficiency and are at increased cardiometabolic risk. This study aimed to assess acute and 7-days effects of dietary nitrate on mechanical efficiency, exercise performance and cardiac biomarkers in patients with COPD. Methods This double-blind, randomized cross-over placebo controlled trial included 20 mild-to-moderate COPD patients (66.6 ± 7.5 years) with moderate exercise impairments and decreased mechanical efficiency, normal BMI (26 ± 3 kg/m2) but high prevalence of abdominal obesity (83.3%). Subjects were randomly allocated to the treatment order of 7 days sodium nitrate ingestion (∼8 mmol/day) and 7 days placebo (NaCl solution) or vice versa, separated by a washout period. Before (Day-1) and after (Day-7) both intervention periods resting metabolic rate and the metabolic response during submaximal cycle ergometry, cycling endurance time, plasma nitrate and nitrite levels, cardiac plasma biomarkers (e.g. cardiac troponin T, Nt-proBNP and creatinine kinase) and blood pressure were measured. Subsequently, gross, net and delta mechanical efficiency were calculated. Results Plasma nitrate and nitrite concentrations increased at Day-1 and Day-7 after sodium nitrate but not after placebo ingestion. Systolic and diastolic blood pressure did not change following nitrate ingestion. Furthermore, no differences were observed in gross, net, and delta mechanical efficiency during submaximal exercise, cycling endurance time and cardiac biomarkers between nitrate and placebo on Day-1 and Day-7. Meta-analysis of all available studies in COPD also showed no beneficial effect of beetroot juice on systolic and diastolic blood pressure. Conclusion Acute as well as 7-days sodium nitrate supplementation does not modulate mechanical efficiency, blood pressure or cardiac biomarkers in mild-to-moderate COPD patients

A likely outcome of the sunspot peaks' influence on the North Atlantic Oscillation and Europe in winter

The effect on the North Atlantic Oscillation of 15 sunspot peaks depends on whether the Oscillation is in-phase or out-of-phase with the sunspot peaks. When it is in-phase the anomalies of sea-level pressure adds to the average pressure distribution, and when it is out-of-phase it subtracts from it. Consequently, the atmospheric conditions over Europe in a sunspot peak depends on whether the North Atlantic Oscillation is in- or out-of-phase with the sunspot peak

Wide Green Dikes : A sustainable adaptation option with benefits for both nature and landscape values?

The dual task of reinforcing the dikes along the Dutch coast and preparing for the effects of climate change have stimulated a search for innovative dike designs. Triggered by the presence of gently sloped grass-covered dikes that merge smoothly into the adjacent salt marshes along the German Wadden Sea coast, we assessed the potential costs and benefits of just such a ‘Wide Green Dike’ along the Dutch Wadden Sea coast, compared to the ‘Traditional Dike’, which is now used. The Traditional Dike has a steeper seaward slope and a stone or asphalt revetment along the dike toe. The assessment criteria were identified by local experts. We investigated, particularly, the spatial impact of a Wide Green Dike on the adjacent salt marshes under various climate scenarios. We also looked at the initial costs and clay demand for both dike designs. Furthermore, we conducted a quick-scan of the vegetation present halfway up the seaward slope of a Traditional Dike in the Netherlands and a Wide Green Dike nearby in Germany. Our analysis revealed four primary advantages of use of a Wide Green Dike along the Dutch part of the Dollard estuary: lower initial costs (based on standard unit prices), greater ease of doing repairs, increased adaptability and enhanced spatial quality compared to a Traditional Dike. Both types of dike were designed to withstand an extreme storm surge with an occurrence probability of 1/4000 years. Both fully met legally mandated engineering standards as well. Though the required crest height is comparable for both designs, the Wide Green Dike had a larger areal footprint, and would overlap more Natura 2000 area than a Traditional Dike. There would thus be a trade-off concerning salt-marsh area. Moreover, the vegetation examined halfway up the seaward slope of the German Wide Green Dike offered little ecological value. Nonetheless, cyclic harvesting of sediment for periodic dike reinforcement appeared to be a sustainable option for adapting to future sea level rise

The South Pacific trough: a crucial component of low-frequency pressure variations that determine ENSO development and strength

Much ENSO research and modelling has recently focussed on air-sea interactions along the equator and high-frequency wind and pressure changes. At a larger scale, van Loon (1984) proposed that the weakening of the Pacific trades between April-July prior to El Niño occurred as an enhanced surface trough in the westerlies developed in the South Pacific. This enhancement of the annual cycle (with a stronger high pressure over Australia) was proposed to: 1) direct southerly wind anomalies up into the western equatorial Pacific to the east of Australia, thereby contributing to westerly anomalies, and 2) direct south-westerly winds against the South Pacific high, thus weakening the high and the southeast trades moving back towards the western Pacific, i.e. a combined effect on the trades. Here, we explore temporal and spatial aspects of El Niño development by comparing composite anomaly sequences of sea-level pressure (SLP), surface winds and SST leading into strong, weak and late developing events. We confirm the traditional view that the Southern Oscillation is, to first order, a standing oscillation with geographically fixed nodes and antinodes. This oscillation of low pressure between south-eastern Australia and the central South Pacific is more pronounced leading into stronger El Niño events, with a resultant stronger pressure gradient between the regions early in year (0). We therefore confirm the South Pacific troughs combined effect on the Pacific trades, and find that the maximum warming in Nino 3 occurs between April-July when the trough is most influential in the annual cycle. An El Niño will not develop, or continue into a second austral summer, without a high pressure over Indo-Australia and an enhanced South Pacific trough extending low pressure up to the eastern equatorial Pacific. Composites of stronger El Niño events suggest that there is a more self sustaining propagation of low pressure and associated westerly wind anomalies from the Australian region in year (-1) into the Pacific in year (0). This progression appears to be linked to an eastward progression of warm SST anomalies along the equator that bi-furcates into the South Pacific Convergence Zone and northern Pacific subtropics early in year (0). Significant low pressure anomalies in the North and South Pacific midlatitudes appear critical in MJJ (0) to provide the large scale forcing required for significant Pacific warming. The larger spatial extent of warm SST and negative MSLP anomalies in strong events suggest that the planetary waves in the northern subtropics also become involved and compliment the southern hemisphere. In contrast, weaker El Niño events had a weaker and less distinct eastward progression of low pressure and SST anomalies and much less support from the northern midlatitudes between May-October (0). The timing of ridge strengthening in the North and South Pacific was also found to determine whether an El Niño developed into a La Niño or neutral conditions. Reference: van Loon, H., 1984: The Southern Oscillation. Part III, Associations with the trades and with the trough in the westerlies of the South Pacific Ocean. Mon. Wea. Rev., 112, 947-954..Pages: 633-63