Climate change in the next 30 years : What can a convection-permitting model tell us that we did not already know?

To investigate the climate change in the next 30 years over a complex terrain in southwestern Germany, simulations performed with the regional climate model COSMO-CLM at convection-permitting resolution are compared to simulations at 7 km resolution with parameterised convection. An earlier study has shown the main benefits of convection-permitting resolution in the hourly statistics and the diurnal cycle of precipitation intensities. Here, we investigate whether the improved simulation of precipitation in the convection-permitting model is affecting future climate projections in summer. Overall, the future scenario (ECHAM5 with A1B forcing) brings weak changes in mean precipitation, but stronger hourly intensities in the morning and less frequent but more intense daily precipitation. The two model simulations produce similar changes in climate, despite differences in their physical characteristics linked to the formation of convective precipitation. A significant increase in the morning precipitation probably due to large-scale forced convection is found when considering only the most extreme events (above 50 mm/day). In this case, even the diurnal cycles of precipitation and convection-related indices are similar between resolutions, leading to the conclusion that the 7 km model sufficiently resolves the most extreme convective events. In this region and time periods, the 7 km resolution is deemed sufficient for most assessments of near future precipitation change. However, conclusions could be dependent on the characteristics of the region of investigation

Prospectus, February 25, 1991

https://spark.parkland.edu/prospectus_1991/1003/thumbnail.jp

Prospectus, January 28, 1991

https://spark.parkland.edu/prospectus_1991/1001/thumbnail.jp

Prospectus, April 1, 1991

https://spark.parkland.edu/prospectus_1991/1005/thumbnail.jp

Towards advancing scientific knowledge of climate change impacts on short-duration rainfall extremes

A large number of recent studies have aimed at understanding short-duration rainfall extremes, due to their impacts on flash floods, landslides and debris flows and potential for these to worsen with global warming. This has been led in a concerted international effort by the INTENSE Crosscutting Project of the GEWEX (Global Energy and Water Exchanges) Hydroclimatology Panel. Here, we summarize the main findings so far and suggest future directions for research, including: the benefits of convection-permitting climate modelling; towards understanding mechanisms of change; the usefulness of temperature-scaling relations; towards detecting and attributing extreme rainfall change; and the need for international coordination and collaboration. Evidence suggests that the intensity of long-duration (1 day+) heavy precipitation increases with climate warming close to the Clausius–Clapeyron (CC) rate (6–7% K−1), although large-scale circulation changes affect this response regionally. However, rare events can scale at higher rates, and localized heavy short-duration (hourly and sub-hourly) intensities can respond more strongly (e.g. 2 × CC instead of CC). Day-to-day scaling of short-duration intensities supports a higher scaling, with mechanisms proposed for this related to local-scale dynamics of convective storms, but its relevance to climate change is not clear. Uncertainty in changes to precipitation extremes remains and is influenced by many factors, including large-scale circulation, convective storm dynamics andstratification. Despite this, recent research has increased confidence in both the detectability and understanding of changes in various aspects of intense short-duration rainfall. To make further progress, the international coordination of datasets, model experiments and evaluations will be required, with consistent and standardized comparison methods and metrics, and recommendations are made for these frameworks

Climatic oscillations influence the flooding of Venice

A detailed analysis of the tidal regime in Venice, Italy, 7 during the last century shows that the frequency and 8 magnitude of high tides are correlated to interdecadal 9 climatic oscillations. The monthly high tide maxima and 10 the average elevation of all high tides are negatively 11 correlated to the North Atlantic Oscillation (NAO), to the 12 Arctic Oscillation (AO), to the East Atlantic \u2013 West Russian 13 oscillation (EA-WR), and to the Polar Eurasia 14 teleconnection (POL). The correlation is high during 15 winter months for all four indices, whereas in the fall, 16 when most of the city floods occur, the AO and the EA-WR 17 exert a stronger influence on the tidal regime. During 18 negative phases of the climate indices both the average 19 elevation of high tides and the frequency of flooding 20 increase consistently, with negative effects on the city and its 21 monuments