Robust assessment of future changes in extreme precipitation over the Rhine basin using a GCM

Estimates of future changes in extremes of multiday precipitation sums are critical for estimates of future discharge extremes of large river basins. Here we use a large ensemble of global climate model SRES A1b scenario simulations to estimate changes in extremes of 1–20 day precipitation sums over the Rhine basin, projected for the period 2071–2100 with reference to 1961–1990. We find that in winter, an increase of order 10%, for the 99th percentile precipitation sum, is approximately fixed across the selected range of multiday sums, whereas in summer, the changes become increasingly negative as the summation time lengthens. Explanations for these results are presented that have implications for simple scaling methods for creating time series of a future climate. We show that the dependence of quantile changes on summation time is sensitive to the ensemble size and indicate that currently available discharge estimates from previous studies are based on insufficiently long time series

Estimates of future discharges of the river Rhine using two scenario methodologies: direct versus delta approach

International audienceSimulations with a hydrological model for the river Rhine for the present (1960?1989) and a projected future (2070?2099) climate are discussed. The hydrological model (RhineFlow) is driven by meteorological data from a 90-years (ensemble of three 30-years) simulation with the HadRM3H regional climate model for both present-day and future climate (A2 emission scenario). Simulation of present-day discharges is realistic provided that (1) the HadRM3H temperature and precipitation are corrected for biases, and (2) the potential evapotranspiration is derived from temperature only. Different methods are used to simulate discharges for the future climate: one is based on the direct model output of the future climate run (direct approach), while the other is based on perturbation of the present-day HadRM3H time series (delta approach). Both methods predict a similar response in the mean annual discharge, an increase of 30% in winter and a decrease of 40% in summer. However, predictions of extreme flows differ significantly, with increases of 10% in flows with a return period of 100 years in the direct approach and approximately 30% in the delta approach. A bootstrap method is used to estimate the uncertainties related to the sample size (number of years simulated) in predicting changes in extreme flows

Super-Clausius-Clapeyron scaling of extreme hourly convective precipitation and its relation to large-scale atmospheric conditions

\ua9 2017 American Meteorological Society. Present-day precipitation-temperature scaling relations indicate that hourly precipitation extremes may have a response to warming exceeding the Clausius-Clapeyron (CC) relation; for the Netherlands the dependency on surface dewpoint temperature follows 2 times the CC relation (2CC). The authors\u27 hypothesis- as supported by a simple physical argument presented here-is that this 2CC behavior arises from the physics of convective clouds. To further investigate this, the large-scale atmospheric conditions accompanying summertime afternoon precipitation events are analyzed using surface observations combined with a regional reanalysis. Events are precipitation measurements clustered in time and space. The hourly peak intensities of these events again reveal a 2CC scaling with the surface dewpoint temperature. The temperature excess of moist updrafts initialized at the surface and the maximumcloud depth are clear functions of surface dewpoint, confirming the key role of surface humidity on convective activity. Almost no differences in relative humidity and the dry temperature lapse rate were found across the dewpoint temperature range, supporting the theory that 2CC scaling is mainly due to the response of convection to increases in near-surface humidity, while other atmospheric conditions remain similar. Additionally, hourly precipitation extremes are on average accompanied by substantial large-scale upward motions and therefore large-scale moisture convergence, which appears to accelerate with surface dewpoint. Consequently, most hourly extremes occur in precipitation events with considerable spatial extent. Importantly, this event size appears to increase rapidly at the highest dewpoint temperature range, suggesting potentially strong impacts of climatic warming

Scaling and trends of hourly precipitation extremes in two different climate zones – Hong Kong and the Netherlands

Hourly precipitation extremes in very long time series from the Hong Kong Observatory and the Netherlands are investigated. Using the 2 m dew point temperature from 4 h before the rainfall event as a measure of near surface absolute humidity, hourly precipitation extremes closely follow a 14% per degree dependency – a scaling twice as large as following from the Clausius-Clapeyron relation. However, for dew point temperatures above 23 °C no significant dependency on humidity was found. Strikingly, in spite of the large difference in climate, results are almost identical in Hong Kong and the Netherlands for the dew point temperature range where both observational sets have sufficient data. Trends in hourly precipitation extremes show substantial increases over the last century for both De Bilt (the Netherlands) and Hong Kong. For De Bilt, not only the long term trend, but also variations in hourly precipitation extremes on an inter-decadal timescale of 30 yr and longer, can be linked very well to the above scaling; there is a very close resemblance between variations in dew point temperature and precipitation intensity with an inferred dependency of hourly precipitation extremes of 10 to 14% per degree. For Hong Kong there is no connection between variations in humidity and those in precipitation intensity in the wet season, May to September. This is consistent with the found zero-dependency of precipitation intensity on humidity for dew points above 23 °C. Yet, outside the wet season humidity changes do appear to explain the positive trend in hourly precipitation extremes, again following a dependency close to twice the Clausius-Clapeyron relation

Differential effects of tissue plasminogen activator and streptokinase on infarct size and on rate of enzyme release: influence of early infarct related artery patency: The GUSTO Enzyme Substudy

Background The recent international GUSTO trial of 41 021 patients with acute myocardial infarction demonstrated improved 90-mm infarct related artery patency as well as reduced mortality in patients treated with an accelerated regimen of tissue plasminogen activator, compared to patients treated with streptokinase. A regimen combining tissue plasminogen activator and streptokinase yielded intermediate results. The present study investigated the effects of treatment on infarct size and enzyme release kinetics in a subgroup of these patients. Methods A total of 553 patients from 15 hospitals were enrolled in the study. Four thrombolytic strategies were compared: streptokinase with subcutaneous heparin, streptokinase with intravenous (iv.) heparin, tissue plasminogen activator with iv. heparin, and streptokinase plus tissue plasminogen activator with i.v. heparin. The activity of alpha-hydroxybutyrate dehydrogenase (HBDH) in plasma was centrally analysed and infarct size was defined as cumulative HBDH release per litre of plasma within 72 h of the first symptoms (Q(72)). Patency of the infarct-related vessel was determined by angiography in 159 patients, 90 mm after treatment. Results Infarct size was 3·72 g-eq . 1−1 in patients with adequate coronary perfusion (TIMI-3) at the 90 mm angi-ogram and larger in patients with TIMI-2 (4·35 g-eq . 1−1) or TIMI 0-1 (5·07 g-eq . 1−1)flow (P=0·024). In this subset of the GUSTO angiographic study, early coronary patency rates (TIMI 2+3) were similar in the two streptokinase groups (53 and 46%). Higher, but similar, patency rates were observed in the tissue plasminogen activator and combination therapy groups (87 and 90%). Median infarct size for the four treatment groups, expressed in gram- equivalents (g-eq) of myocardium, was 4·4, 4·5, 3·9 and 3·9 g-eq per litre of plasma (P=0·04 for streptokinase vs tissue plasminogen activator). Six hours after the first symptoms, respectively 5·3, 6·6, 14·0 and 13·6% of total HBDH release was complete (P<0·000l for streptokinase vs tissue plasminogen activator). Conclusions Rapid and complete coronary reperfusion salvages myocardial tissue, resulting in limitation of infarct size and accelerated release of proteins from the myocardium. Treatment with tissue plasminogen activator, resulting in earlier reperfusion was more effective in reducing infarct size than the streptokinase regimens, which contributes to the differences in survival between treatment groups in the GUSTO tria

Evaluation of modeled changes in extreme precipitation in Europe and the Rhine basin

In this study, we investigate the change in multi-day precipitation extremes in late winter in Europe using observations and climate models. The objectives of the analysis are to determine whether climate models can accurately reproduce observed trends and, if not, to find the causes of the difference in trends. Similarly to an earlier finding for mean precipitation trends, and despite a lower signal to noise ratio, climate models fail to reproduce the increase in extremes in much of northern Europe: the model simulations do not cover the observed trend in large parts of this area. A dipole in the sea-level pressure trend over continental Europe causes positive trends in extremes in northern Europe and negative trends in the Iberian Peninsula. Climate models have a much weaker pressure trend dipole and as a result a much weaker ( extreme) precipitation response. The inability of climate models to correctly simulate observed changes in atmospheric circulation is also primarily responsible for the underestimation of trends in the Rhine basin. When it has been adjusted for the circulation trend mismatch, the observed trend is well within the spread of the climate model simulations. Therefore, it is important that we improve our understanding of circulation changes, in particular related to the cause of the apparent mismatch between observed and modeled circulation trends over the past century

The diurnal cycle of shallow cumulus clouds over land: A single-column model intercomparison study

An intercomparison study for single-column models (SCMs) of the diurnal cycle of shallow cumulus convection is reported. The case, based on measurements at the Atmospheric Radiation Measurement program Southern Great Plains site on 21 June 1997, has been used in a large-eddy simulation intercomparison study before. Results of the SCMs reveal the following general deficiencies: too large values of cloud cover and Cloud liquid water, unrealistic thermodynamic profiles, and high amounts of numerical noise. Results are also strongly dependent on vertical resolution.These results are analysed in terms of the behaviour of the different parametrization schemes involved: the convection scheme, the turbulence scheme, and the cloud scheme. In general the behaviour of the SCMs can be grouped in two different classes: one class with too strong mixing by the turbulence scheme, the other class with too strong activity by the convection scheme. The coupling between (subcloud) turbulence and the convection scheme plays a crucial role. Finally, (in part) motivated by these results several models have been successfully updated with new parametrization schemes and/or their present schemes have been successfully modifie

Future weather

The impact of climate change will manifest itself in our future weather. In the project Future Weather we investigated a number of these impact relevant weather conditions in the (present and) future climate. We focussed primarily on changes in precipitation extremes on different scales ranging from intense showers at local scales to multi-day precipitation extremes over the Rhine catchment area. On an intermediate scale, regional differences in precipitation within the Netherlands are studied. Finally, we considered a worst case scenario of a combined wind and discharge extreme