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Daily rainfall extremes and annual totals have increased in large parts of the global land area over the last decades. These observations are consistent with theoretical considerations of a warming climate. However, until recently these global tendencies have not been shown to consistently affect land regions with limited moisture availability. A recent study, published by Donat et al. (2016, Nature Climate Change, doi:10.1038/nclimate2941), now identified rapid increases in globally aggregated dry region daily extreme rainfall and annual rainfall totals. Here, we reassess the respective analysis and find that a) statistical artifacts introduced by the choice of the reference period prior to data standardization lead to an overestimation of the reported trends by up to 40%, and also that b) the definition of `dry regions of the globe' affect the reported globally aggregated trends in extreme rainfall. Using the same observational dataset, but accounting for the statistical artifacts and using alternative, well-established dryness definitions, we find no significant increases in heavy precipitation in the world's dry regions. Adequate data pre-processing approaches and accounting for uncertainties regarding the definition of dryness are crucial to the quantification of spatially aggregated trends in the world's dry regions. In view of the high relevance of the question to many potentially affected stakeholders, we call for a cautionary consideration of specific data processing methods, including issues related to the definition of dry areas, to guarantee robustness of communicated climate change relevant findings.

The warming trend of the last decades is now so strong that it is discernible in local temperature observations. This opens the possibility to compare the trend to the warming predicted by comprehensive climate models (GCMs), which up to now could not be verified directly to observations on a local scale, because the signal-to-noise ratio was too low. The observed temperature trend in western Europe over the last decades appears much stronger than simulated by state-of-the-art GCMs. The difference is very unlikely due to random fluctuations, either in fast weather processes or in decadal climate fluctuations. In winter and spring, changes in atmospheric circulation are important; in spring and summer changes in soil moisture and cloud cover. A misrepresentation of the North Atlantic Current affects trends along the coast. Many of these processes continue to affect trends in projections for the 21st century. This implies that climate predictions for western Europe probably underestimate the effects of anthropogenic climate change., Comment: Figure 5 was the wrong file

There has been intense debate about the causes of the 1997-1998 El Nino. One side sees the obvious intense westerly wind events as the main cause for the exceptional heating in summer 1997, the other emphasizes slower oceanic processes. We present a quantitative analysis of all factors contributing to the onset of this El Nino. At six months' lead time the initial state contributes about 40% of the heating compared with an average year, and the wind about 50%. Compared with 1996, these contributions are 30% and 90% respectively. As westerly wind events are difficult to predict, this limited the predictability of the onset of this El Nino., Comment: 11 pages, incl 5 figs

In a statistical analysis of more than a century of data we find a strong connection between strong warm El Nino winter events and high spring precipitation in a band from Southern England eastwards into Asia. This relationship is an extension of the connection mentioned by Kiladis and Diaz (1989), and much stronger than the winter season teleconnection that has been the subject of other studies. Linear correlation coefficients between DJF NINO3 indices and MAM precipitation are higher than r=0.3 for individual stations, and as high as r=0.49 for an index of precipitation anomalies around 50N from 5W to 35E. The lagged correlation suggests that south-east Asian surface temperature anomalies may act as intermediate variables., Comment: latex, 14 pages, 9 figures (epsfig)

The adjoint of an ocean general circulation model is used as a tool for investigating the causes of changes in ENSO SST indices. We identify adjoint Kelvin and Rossby waves in the sensitivities to sea level and wind stress at earlier times, which can be traced back for more than a year through western and weak eastern boundary reflections. Depending on the thermocline depth the first and second baroclinic modes are excited. The sensitivities to the heat flux and SST are local and decay in about a month. The sensitivities to the fluxes are converted into the influence of SST using the adjoint of a statistical atmosphere model. Focusing on SST perturbations in the index region itself, we recover, up to a scale factor, the delayed oscillator concept., Comment: 40 pp incl figures; latex with natbib, epsfig; mpegs available at http://www.knmi.nl/~oldenbor, asaccepted by MWR (except abstract)

We investigated the effect of the light fermion masses on cross sections for e^+e^- into 4 fermions in the Fermion Loop scheme defined in hep-ph/9612260, and approximations to it. The effects are found to be very small, except of course in the collinear region of single W-boson production where the electron mass acts as the cut-off., Comment: 8 pages, latex, 3 ps figs included

We investigate the uncertainty induced by the Higgs-boson mass on the determination of $m_W$ from the LEP-2 run near the threshold for $W$-pair production. For a light Higgs boson the Yukawa interaction between the two slowly-moving $W$ bosons gives rise to a correction of close to 1\% to the total cross-section. This corresponds to a 15 MeV shift in the deduced $W$ mass for a Higgs-boson mass of 60 GeV. We present a simple approximation for this correction and discuss its validity., Comment: 10 pages latex, elsart, axodraw, also available from http://rulgm4.LeidenUniv.nl/preprints.html

We consider the problem of a proper definition of the mass of a heavy unstable boson. It is shown how various definitions are related by the renormalization-scheme independence of the full resummed amplitude. This is made explicit for the $W$ boson in the large $N_f$ limit, where we find an upper bound on the peak position of the lineshape and on the mass, provided a sensible definition of the mass is used. In more realistic models, we conjecture that under certain conditions the mass is similarly bounded. Using this approach an upper limit of about 1 TeV on the mass of the Minimal-Standard-Model Higgs boson is found, independent of any breakdown of perturbation theory., Comment: 12 pages, elsart, also available from http://rulgm4.LeidenUniv.nl/preprints.html, added acknowledgements

We discuss theoretical and phenomenological aspects of the use of boson propagators with energy-dependent widths in predictions for high-energy scattering processes. In general, gauge invariance is violated in such calculations. We discuss several approaches to restore gauge invariance, necessary for a reliable result. The most promising method is the addition of the relevant parts of the fermionic corrections, which fulfills all Ward identities. The numerical difference between this and other approaches is studied. A number of recommendations are given for LEP2 computations., Comment: 13 pages LaTeX inc 1 figure, uses epsf, axodraw. The ps file is available as ftp://rulgm4.leidenuniv.nl/pub/preprints/stable.ps or on http://rulgm4.leidenuniv.nl/ under preprints. Added two references

The properties of hard photon radiation in $W$ pair production at LEP 2 are studied, with emphasis on the energy loss relevant to the W mass measurement. We use a combination of the exact 1-photon matrix element and leading logarithmic structure functions. Defining unobservable, observable and initial state photons in the phase space, it is shown that neither the one-photon matrix element nor the leading logarithmic structure functions alone give an adequate description of the energy loss due to observable or initial state photons. An event generator based on these calculations is available., Comment: 15 pages, latex+elsart, full ps file available at http://rulgm4.LeidenUniv.nl/preprints.html or at ftp://rulgm4.LeidenUniv.nl/pub/preprints. Added soft radiation

We study the possibility that the production and decay of light stop squarks at Tevatron can mimic top events. We show that this scenario is very unlikely to explain the anomalously high top production cross sections recently reported by the CDF collaboration., Comment: 9 pages

We describe a generator for the process $e^+e^- \to W^+W^-$ including all one-loop and leading log photonic two-loop contributions. It includes polarization of the beam and $W$ bosons, and the possibility to study the effect of anomalous couplings., Comment: 13 pages latex with 2 figures ps; also available as http://pss058.psi.ch/preprints/eewwmc.ps; PSI-PR-94-16 (added two references)

We present an efficient generator for the process e+e- to 4 fermions + gamma through off-shell W pairs. It is based on a massless matrix element with leading order(m^2) corrections. Only the resonant WW graphs are included. We have tested it against a matrix element without these approximations and found agreement to within ~1% at LEPII energies., Comment: 13 pages incl 2 figures, latex+axodraw, full ps file available as ftp://pss058.psi.ch/pub/preprints/wwf.ps, PSI-PR-94-06

We present a gauge invariant way to compute one loop corrections to processes involving the production and decay of unstable particles., Comment: 21 pages latex, ps file, PSI-PR-93-22, REVISED. (Completely rewritten due to many complaints about the unclear exposition.)

When computing the properties of reactions involving unstable charged particles care has to be taken to use a gauge invariant amplitude. In this talk we present methods to (automatically) obtain such an amplitude, both at the tree level and in one-loop calculations, using only a minimal number of diagrams. The numerical difference with gauge variant methods commonly used will be discussed for the case of tree level W pair production., Comment: 6 pages, 2 figures appended, needs axodraw,epsf. The whole ps file is available with anonymous ftp from pss058.psi.ch in /pub/preprints/ as unstablepart.ps[.Z]. Proceedings of the 3rd workshop for SI and AI in HEP, Oberammergau, PSI-PR-93-19

Linear collider designs are optimized for \ep\ collisions. However, from the physics point of view, \lc s may also be advantageously operated in an \ee, \eg\ or \pp\ mode. These options, which have not been available up to now, will provide unique tests of the \sm\ and of physics beyond it. As an example, we review the prospects for discovering and studying \susy\ at linear colliders in \ee, \eg\ and \pp\ collisions. In particular, we argue that \ee\ scattering is much better suited than \ep\ annihilation for discovering \sel s or \co s., Comment: 11 pages of text, contribution to the Proceedings of the Workshop on Physics with $e^+e^-$ Linear Colliders, Annecy, February 15-16, 1993, the figures and the .ps file can be obtained via anonymous ftp from 129.187.198.1 in preprints/mpi9370.ps , MPI-Ph/93-70

We consider the production and decay of selectrons and charginos in $e^-e^-$ collisions. The advantage over usual $e^+e^-$ collisions is the very low level of standard model backgrounds which should make the discovery of selectrons or charginos relatively straightforward. The use of polarized beams provides an additional powerful tool to determine the supersymmetry parameters., Comment: 18 pages including 8 figures, included as uufiled .ps files. LaTeX with axodraw.sty for Feynman graphs, epsf.sty for figures; the texfile and complete PSfile are available via ftp from pss058.psi.ch. CERN-TH.6807/93, MPI-Ph/93-28, PSI-93-11

Several schemes to introduce finite width effects to reactions involving unstable elementary particles are given and the differences between them are investigated. The effects of the different schemes is investigated numerically for $W$ pair production. In $e^+e^-\to W^+W^-$ we find that the effect of the non-resonant graphs cannot be neglected for $\sqrt{s}\geq400\GeV$. There is no difference between the various schemes to add these to the resonant graphs away from threshold, although some violate gauge invariance. On the other hand, in the reaction $\gamma\gamma\to W^+W^-$ the effect of the non-resonant graphs is large everywhere, due to the $t$-channel pole. However, even requiring that the outgoing lepton is observable ($p_\perp > .02\sqrt{s}$) reduces the contribution to about 1\%. Again, the scheme dependence is negligible here., Comment: 9 pages plus 6 with figures (.uu at end, also available with anonymous ftp from pss058.psi.ch [129.129.40.58]), LaTeX, LMU-21/92, PSI-PR-93-05, TTP92-36

We study the occurrence of final states with only an electron-positron pair and missing transverse momentum as a signal of \susy\ in photon-photon collisions. Suitable high energy photon beams may be provided at linear colliders by back-scattering laser beams on electron beams. The final states considered represent a typical signature for the production and decay of selctron and chargino pairs within the \mssm. We show that, away from the kinematical threshold, selctrons produce this signal far more abundantly than charginos. The standard model background is dominated by W-pair production. We propose a series of kinematical cuts which reduce this background to an acceptable level. With a 1 TeV collider operated in the $\gamma\gamma$-mode, we find that interesting and complementary tests of \susic\ models can be performed for selctron masses up to 350 GeV., Comment: 12 pages + 6 pages figures (included as uufile, also with anon. ftp from gluon.hep.physik.uni-muenchen.de (129.187.198.1)), LaTeX (axodraw,epsf), CERN-TH.6742/92, MPI-Ph/92-73, LMU-92/07. (forgot the bibliography file - my excuses)

Associated selectron-neutralino production in the process $e^-\gamma\to\tilde e^-\tilde\chi^0$ provides a striking supersymmetric signal: events with a single high $p_\perp$ electron and otherwise only invisible particles. For $e^-\gamma$ collisions obtained at high energy linear colliders through back-scattering of a laser beam, this reaction is shown to be complementary to selectron pair production in the processes $e^+e^-\to\tilde e^+\tilde e^-$ and $e^-e^-\to\tilde e^-\tilde e^-$, and to be a probe of heavy selectrons beyond the kinematical limit of pair production. The standard model background from $e^-\gamma\to e^-Z^0$ and $W^-\nu$ is studied and substantially reduced by rapidity and transverse momentum cuts. The minimum required integrated luminosities for observing this \susic\ signal are given as functions of several model parameters and collider energies., Comment: 15 pages