Towards a contrail climatology from NOAA—satellite images over Europe

Contrail cloudiness over Europe and the eastern part of the North Atlantic Ocean was analyzed for the two periods Sept. 1979-Dec. 1981 and Sept. 1989-Aug. 1992 by visual inspection of quicklook photographic prints of NOAA/AVHRR infrared images. The averaged contrail cover exhibits maximum values along the transat- lantic flight corridor around 50°N (of almost 2%) and over western Europe resillting in 0.5% contrail cloudiness on the average. A strong yearly cycle appears with a maximum (< 2%) in spring and summer over the Atlantic and a smaller maximum (< 1%) in winter over southwestern Europe. Comparing the two time periods of one decade separation there is a significant decrease in contrail cloudiness over west- ern Europe and a significant increase over the North Atlantic observable between March and July. Contrail cloud cover during daytime is about twice as high as dur- ing nighttime. Contrails are preferably found in larger fields of 1000 km diameter which last usually for more than one day. Causes, possible errors and consequences are discussed

Modellbasierte Analyse des Stoffumsatzes von Mageren Flachland-Mähwiesen in Baden-Württemberg im Critical-Loads-Konzept

Critical Loads für eutrophierenden Stickstoff werden anhand der Simple-Mass-Balance (SMB) Methode berechnet und dienen etwa in FFH-Verträglichkeitsprüfungen dem Schutz empfindlicher Ökosysteme (Anhang I FFH-Richtlinie). Die auf Basis der SMB ermittelten standortspezifischen Spannen für Critical Loads sind auf Grund von Unsicherheiten sowohl in den Eingangsgrößen als auch in den empirisch regelbasierten Methoden zur Berechnung der einzelnen Summanden in der SMB wenig vertrauenswürdig. Im Rahmen des von der Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg (LUBW) koordinierten Forschungsprojektes „Analyse und Bewertung des Stickstoffhaushalts Baden-Württemberg (AG Critical Loads)“ soll deshalb die Schaffung einer Datenbasis für eine Weiterentwicklung der bisherigen Ansätze für den in Baden-Württemberg weit verbreiteten FFH-Lebensraumtyp 6510 „Magere Flachland-Mähwiesen“ erfolgen. Einen möglichen Weg hin zu belastbaren Abschätzverfahren für die Summanden der SMB-Formel stellen dynamische Simulationen der am N-Umsatz beteiligten Stoffflüsse mit Hilfe prozessbasierter Modelle dar. Ziel der vorgestellten Studie ist es, mit Hilfe des Modellpakets Expert-N standortspezifisch für ausgewählte Flachland-Mähwiesen die mehrjährigen Mittelwerte der Mineralisierung, Denitrifikation, Immobilisierung und Nitratauswaschung zu berechnen. Als experimentelle Datengrundlage für die Modellierung werden Feldmessungen zur Abschätzung des N-Umsatzes in Abhängigkeit von Standortbedingungen und Erhaltungszustand der Vegetation durchgeführt. Dazu wird auf 4 extensiv genutzten Grünlandflächen in FFH-Gebieten über 2 Jahre ein intensives Monitoring der Stickstoffflüsse im Boden sowie begleitende Messungen zur Bodenfeuchte, -temperatur und N-Deposition durchgeführt. Der Fokus liegt auf der in situ Quantifizierung der Bruttoraten des N-Umsatzes (Mineralisierung, Nitrifizierung) als wichtige Parameter für die Modellierung des N-Kreislaufs. Die aus der prozessbasierten Modellierung gewonnenen Mittelwerte werden mit den nach den derzeitigen SMB-Ansatz berechneten Ergebnissen verglichen und diskutiert. Die Ergebnisse der Studie werden so zur Entwicklung zuverlässigerer Berechnungsmethoden für Critical Loads in Baden-Württemberg beitragen. Auf dem Poster werden die methodischen Ansätze sowie erste Ergebnisse des Versuchs vorgestellt

Pomeron in diffractive processes γ∗(Q2)p→ρ0p\gamma^*(Q^2)p\to\rho^0 p and γ∗(Q2)p→γ∗(Q2)p\gamma^*(Q^2)p\to\gamma^*(Q^2) p at large Q^2: the onset of pQCD

We study the reactions $\gamma^*(Q^2)p\to\rho^0 p$ and $\gamma^*(Q^2)p\to\gamma^*(Q^2) p$ at large Q^2 and $W^2/Q^2$ and small momentum transfer, $\kappa^2_\perp$, to the nucleon where the pomeron exchange dominates. At large Q^2 the virtual photon selects a hard $q\bar q$ pair, thus selecting the hard pomeron component (the BFKL pomeron). The amplitudes for both transverse and longitudinal polarizations of the initial photon and outgoing $\rho$-meson (photon) are calculated in the framework of the BFKL pomeron exchange. Our calculations show that one cannot expect the early onset of the pure perturbative regime in the discussed diffractive processes: the small interquark distances, $\rho_{q\bar q} <0.2$ fm, start to dominate not earlier than at $Q^2 \simeq 100 GeV^2, W^2/Q^2 \simeq 10^7$ in $\gamma^*(Q^2)p\to\rho^0 p$ and $Q^2 \simeq 50 GeV^2, W^2/Q^2 \simeq 10^6$ in $\gamma^*(Q^2)p\to\gamma^*(Q^2) p$.Comment: 20 pages, LaTeX, epsfig.st

Search for Doubly-Charged Higgs Boson Production at HERA

A search for the single production of doubly-charged Higgs bosons H^{\pm \pm} in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3, masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl

Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.Comment: 22 pages, 4 figures, submitted to Eur. Phys. J., error in first submission - omitted bibliograph

Searches at HERA for Squarks in R-Parity Violating Supersymmetry

A search for squarks in R-parity violating supersymmetry is performed in e^+p collisions at HERA at a centre of mass energy of 300 GeV, using H1 data corresponding to an integrated luminosity of 37 pb^(-1). The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling lambda' is considered, taking into account R-parity violating and conserving decays of the squarks. No significant deviation from the Standard Model expectation is found. The results are interpreted in terms of constraints within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM and the minimal Supergravity model, and their sensitivity to the model parameters is studied in detail. For a Yukawa coupling of electromagnetic strength, squark masses below 260 GeV are excluded at 95% confidence level in a large part of the parameter space. For a 100 times smaller coupling strength masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table

Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table