The nonhydrostatic regional climate model CCLM was used for a long-term hindcast run (2002–2016) for the Weddell Sea region with resolutions of 15 and 5 km and two different turbulence parametrizations. CCLM was nested in ERA-Interim data and used in forecast mode (suite of consecutive 30 h long simulations with 6 h spin-up). We prescribed the sea ice concentration from satellite data and used a thermodynamic sea ice model. The performance of the model was evaluated in terms of temperature and wind using data from Antarctic stations, automatic weather stations (AWSs), an operational forecast model and reanalyses data, and lidar wind profiles. For the reference run we found a warm bias for the near-surface temperature over the Antarctic Plateau. This bias was removed in the second run by adjusting the turbulence parametrization, which results in a more realistic representation of the surface inversion over the plateau but resulted in a negative bias for some coastal regions. A comparison with measurements over the sea ice of the Weddell Sea by three AWS buoys for 1 year showed small biases for temperature around ±1 K and for wind speed of 1 m s−1. Comparisons of radio soundings showed a model bias around 0 and a RMSE of 1–2 K for temperature and 3–4 m s−1 for wind speed. The comparison of CCLM simulations at resolutions down to 1 km with wind data from Doppler lidar measurements during December 2015 and January 2016 yielded almost no bias in wind speed and a RMSE of ca. 2 m s−1. Overall CCLM shows a good representation of temperature and wind for the Weddell Sea region. Based on these encouraging results, CCLM at high resolution will be used for the investigation of the regional climate in the Antarctic and atmosphere–ice–ocean interactions processes in a forthcoming study.
Niederschlagswasserbewirtschaftung dient der Wiederherstellung der natürlichen Abflussprozesse. Da die negativen Auswirkungen des anthropogenen Eingriffs durch Kanalisierung, Versiegelung, Bodenverdichtung u.a. erkannt sind, sind Maßnahmen zum Erhalt des natürlichen Wasserkreislaufs bei Neubaumaßnahmen obligatorisch. Ziel ist es, durch Speicherung, Versickerung und gedrosselte Ableitung den dämpfenden Einfluss des Bodens auf die Wasserstandsganglinie von Gewässern zu nutzen, bzw. zu näherungsweise zu imitieren. Zur Optimierung der zur Regenwasserbewirtschaftung dienenden Verfahren wurden Vorschriften, Richtwerte und Bauanleitungen durch Gesetzgebung und Wissenschaft geschaffen. Diese sollen Anleitung zum bestmöglichen Einsatz der bestehenden Retentionsmöglichkeiten geben. Für ein Neubaugebiet in Rodt in der Eifel scheinen jedoch die Vorraussetzungen zum Einsatz der standardisierten Verfahren nicht gegeben. Die notwendigen Wasser-Durchlässigkeiten wurden bestimmt und als außerhalb der vorgeschlagenen Grenzwerte liegend erkannt. Somit stellt sich die Frage nach Alternativen, die durch das Erstellen einer Modellsimulation in ihrer Wirksamkeit überprüft werden sollten. In der vorliegenden Arbeit werden sechs an die Gegebenheiten im Baugebiet angepasste Konzepte erstellt, die sich aus den möglichen Regenwasser- Retentionsmaßanlagen Retentionsteich, Kunststoffrigole, Tieflockerungsrigole und Brauchwassernutzung zusammensetzen. Die Konzepte werden mit dem Simulationsprogramm STELLA- Research 7.01 in Modelle umgesetzt und vorhandene die örtlichen Gegebenheiten kennzeichnende Daten als Grundlage der Simulation aufgenommen. Mit dem Ziel der Minimierung und Optimierung des Restüberlaufs aus dem Baugebiet in den Vorfluter werden die Simulationen auf grundlegende Schalter untersucht und diese in ihrer Wirkung beschrieben. Aus den Ergebnissen werden die optimierten Verfahren auf ihre Abwendbarkeit im Baugebiet in den Punkten Niederschlagswasser- Retention, Anpassung an natürliche Gegebenheiten und Kostenminderung überprüft und Vorschläge zur Durchführung der Arbeiten abgeleitet.
Regional climate models are a valuable tool for the study of the climate processes and climate change in polar regions, but the performance of the models has to be evaluated using experimental data. The regional climate model CCLM was used for simulations for the MOSAiC period with a horizontal resolution of 14 km (whole Arctic). CCLM was used in a forecast mode (nested in ERA5) and used a thermodynamic sea ice model. Sea ice concentration was taken from AMSR2 data (C15 run) and from a high-resolution data set (1 km) derived from MODIS data (C15MOD0 run). The model was evaluated using radiosonde data and data of different profiling systems with a focus on the winter period (November–April). The comparison with radiosonde data showed very good agreement for temperature, humidity, and wind. A cold bias was present in the ABL for November and December, which was smaller for the C15MOD0 run. In contrast, there was a warm bias for lower levels in March and April, which was smaller for the C15 run. The effects of different sea ice parameterizations were limited to heights below 300 m. High-resolution lidar and radar wind profiles as well as temperature and integrated water vapor (IWV) data from microwave radiometers were used for the comparison with CCLM for case studies, which included low-level jets. LIDAR wind profiles have many gaps, but represent a valuable data set for model evaluation. Comparisons with IWV and temperature data of microwave radiometers show very good agreement.
It is generally assumed that the temperature increase associated with global climate change will lead to increased thunderstorm intensity and associated heavy precipitation events. In the present study it is investigated whether the frequency of thunderstorm occurrences will in- or decrease and how the spatial distribution will change for the A1B scenario. The region of interest is Central Europe with a special focus on the Saar-Lor-Lux region (Saarland, Lorraine, Luxembourg) and Rhineland-Palatinate.Daily model data of the COSMO-CLM with a horizontal resolution of 4.5 km is used. The simulations were carried out for two different time slices: 1971"2000 (C20), and 2071"2100 (A1B). Thunderstorm indices are applied to detect thunderstorm-prone conditions and differences in their frequency of occurrence in the two thirty years timespans. The indices used are CAPE (Convective Available Potential Energy), SLI (Surface Lifted Index), and TSP (Thunderstorm Severity Potential).The investigation of the present and future thunderstorm conducive conditions show a significant increase of non-thunderstorm conditions. The regional averaged thunderstorm frequencies will decrease in general, but only in the Alps a potential increase in thunderstorm occurrences and intensity is found. The comparison between time slices of 10 and 30 years length show that the number of gridpoints with significant signals increases only slightly. In order to get a robust signal for severe thunderstorm, an extension to more than 75 years would be necessary.