 Subjects -> METEOROLOGY (Total: 106 journals)
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- Rising solar and thermal greenhouse radiation drive rapid warming over
continents-
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Abstract:  Rising solar and thermal greenhouse radiation drive rapid warming over continentsPhilipona, Rolf; Marty, Christoph; Duerr, Bruno; Ohmura, Atsumu
Meteorologische Zeitschrift, (2023), p. - Rising anthropogenic greenhouse gases, such as CO2, CH4, N2O and others, are known to absorb and emit terrestrial thermal radiation back to the Earth's surface, leading to radiative forcing and rising surface temperatures. Nonetheless, radiation measurements now show that the rapid increase in temperature over continents since the end of the last century, which is more than twice as large as the average global warming, is also related to a clearing of the sky over land surfaces, which leads to an increase in sunshine hours, and hence, increasing solar radiation absorbed at the Earth's surface. By contrasting rising temperatures with annual sunshine hours and solar and thermal radiation in Central Europe, the measurements show that thermal radiation steadily increases owing to the rising greenhouse effect. However, the rapidly increasing warming since the end of the last century has been reinforced by a strong increase in solar radiation at the surface, resulting from rising annual sunshine hours as a positive greenhouse warming feedback, which is larger than the increase in thermal greenhouse radiation, and hence, the strongest driver of the rapidly increasing warming over continents. The rapid temperature increase in Central Europe, of more than one degree over the last decade, is larger in lowlands than in the Alps.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Toward reliable model-based soil moisture estimates for forest managers
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Abstract:  Toward reliable model-based soil moisture estimates for forest managersThanh Thi, Luong; Vorobevskii, Ivan; Kronenberg, Rico; Jacob, Frank; Peters, Alexander; Petzold, Rainer; Andreae, Henning
Meteorologische Zeitschrift, (2023), p. - The study presents a daily water balance model with a focus on quantifying drought intensity and duration in different forest stands within the Level II monitoring sites in Saxony. The model requires climatic data input and various site and stand parameters, which mostly have physical meaning and can be measured. We estimated the van Genuchten soil parameters of the model by different pedotransfer functions. Water stress is assumed to occur when the relative extractable soil water (REW) or the ratio of real transpiration and potential transpiration or pressure head drops below a certain threshold. The model was not calibrated to test the robustness of physically based parameters but was validated with available soil moisture measurements at forest climate stations (grass vegetation) and inventory locations in various vegetation and climatic conditions with Kling-Gupta efficiencies> 0.5 at most of the sites. The model captures the dynamics of soil water depletion and recharge in a study period well. Day-to-day estimates of water balance components allow us to calculate the duration and intensity of drought events and derive stress indices. A dendro-ecological application is presented: a retrospective analysis of the effects of drought on radial tree growth. Some limitations and potential of applications of the model are discussed.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Characteristics and phenomena of the urban climate
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Abstract:  Characteristics and phenomena of the urban climateKuttler, Wilhelm; Weber, Stephan
Meteorologische Zeitschrift, (2023), p. - The urban climate is a modified boundary-layer climate that is directly and indirectly influenced by anthropogenic activity and characterized by phenomena such as urban warming, reduced evapotranspiration, and increased emission of pollutants. As more than half of the global population is urban and the impacts of climate change will increase pressure on cities, a thorough understanding of the urban climate-related processes and phenomena is of vital importance. The present contribution gives a contemporary overview of the characteristics and phenomena of the urban climate addressed to non-specialists in the field. Starting with an analysis of the general differences between large cities and their surrounding environments, important aspects such as the radiation, energy and water balance as well as the temperature distribution in cities are presented in detail. Additionally, the situation of urban air quality and human–biometeorological aspects are described and the impact of climate change are addressed. Finally effective local adaptation and mitigation measures to reduce urban warming and flooding due to heavy rainfall are discussed.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Actual versus geostrophic wind: statistics from 12‑year measurements at
the 280 m high Hamburg Weather Mast-
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Abstract:  Actual versus geostrophic wind: statistics from 12‑year measurements at the 280 m high Hamburg Weather MastBrümmer, Burghard
Meteorologische Zeitschrift, (2023), p. - The geostrophic wind, representing the horizontal pressure gradient as driving force of motion, is often taken as a first guess of the actual wind. There is, however no fixed relation between them but depends on various influencing factors. How good is this first guess i.e. to which extent do these factors change the actual versus geostrophic wind relation' A 12‑year set of six-hourly (00, 06, 12, 18 UT) geostrophic ( U g $U_{\text{g}}$ ) wind data taken from the ERA-Interim model and actual ( U $U$ ) wind data measured at five levels (10, 50, 110, 175, 250 m) at the Hamburg Weather Mast, Germany, is used to statistically study the dependence of the speed ratio U ∕ U g $U/U_{\text{g}}$ and the angle difference α g - α $\alpha_{\text{g}}-\nobreak\alpha$ on various influence parameters: height z $z$ above ground, geostrophic wind speed U g $U_{\text{g}}$ , thermal wind U therm $U_{\text{therm}}$ , surface roughness z 0 $z_{0}$ , and day-night stratification differences. The actual wind has a Weibull-like frequency distribution (FD) with systematically changing parameters from lower to upper levels. In contrast, the U g $U_{\text{g}}$ ‑FD has the same constant Weibull-like shape at all levels. This does not imply that U g $U_{\text{g}}$ is constant with height, but that the various configurations of thermal wind almost balance. The U therm $U_{\text{therm}}$ ‑FD itself is Weibull-like. The all-times FDs of U ∕ U g $U/U_{\text{g}}$ ( α g - α $\alpha_{\text{g}}-\nobreak\alpha$ ) peak at 0.25 (47°) at 10 m and gradually increase (decrease) to 0.77 (17°) at 250 m. The U ∕ U g $U/U_{\text{g}}$ ratio decreases systematically with increasing U g $U_{\text{g}}$ towards height-staggered asymptotic limits for U g > 3 0 m/s $U_{\text{g}}>\nobreak 30\,\text{m/s}$ . With respect to the thermal wind influence, cold-air advection (CAA) causes on average 1–1.5 m/s larger U values accompanied with 12° less wind turning between 10 m and 250 m than warm-air advection (WAA) for the same low-level U g $U_{\text{g}}$ forcing. The z 0 $z_{0}$ values around the Hamburg Weather Mast vary between 0.3 and 1.1 m and lead to 0.1 differences in the U ∕ U g $U/U_{\text{g}}$ ratio. Vertical stratification has the largest impact on U ∕ U g $U/U_{\text{g}}$ and α g - α $\alpha_{\text{g}}-\nobreak\alpha$ . Stable stratification developing during nig...
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Coastal horizontal wind speed gradients in the North Sea based on
observations and ERA5 reanalysis data-
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Abstract:  Coastal horizontal wind speed gradients in the North Sea based on observations and ERA5 reanalysis dataCañadillas, Beatriz; Wang, Shuhan; Ahlert, Yasmin; Djath, Bughsin'; Barekzai, Mares; Foreman, Richard; Lampert, Astrid
Meteorologische Zeitschrift, (2023), p. - The transition from land to sea affects the wind field in coastal regions. From the perspective of near-coastal offshore wind farms, the coastal transition complicates the task of energy resource assessment by, for example, introducing non-homogeneity into the free wind field. To help elucidate the matter, we quantify the average horizontal wind speed gradients at progressively increasing distances from the German coast using two years of hourly ERA5 reanalysis data, and further describe the dependence of wind speed gradients on the measurement height, atmospheric stability, and season. A vertical wind lidar located on Norderney Island near the German mainland acts as our observational reference for the ERA5 data, where a good agreement ( R 2 = 0 . 9 3 $R^2 =\nobreak 0.93$ ) is found despite the relatively coarse ERA5 data resolution. Interestingly, the comparison of lidar data with the higher-resolution Weather Research and Forecasting (WRF) mesoscale model yields good but relatively weaker agreement ( R 2 = 0 . 8 5 $R^2 =\nobreak 0.85$ ). The ERA5 data reveal that, for flow over the North Sea originating from the German mainland from the south, the wind speed at 10 m (110 m) above sea level increases by 30 % (20 %) some 80 km from the coast on average, and by 5 % at larger heights. An increased stratification increases the horizontal wind speed gradient at 10 m above sea level but decreases it at 110 m. Case studies using satellite and flight measurements are first analyzed to help reveal some of the underlying mechanisms governing horizontal wind speed gradients, including cases of decreasing wind speed with increasing distance from the coast, in which stable flow of warm air over the colder sea leads to an overall deceleration of the flow. The accuracy of offshore resource assessment appears to profit from utilising the horizontal wind speed gradient information contained in ERA5 reanalysis data.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Linkages between Arctic and Mid-Latitude Weather and Climate: Unraveling
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Abstract:  Linkages between Arctic and Mid-Latitude Weather and Climate: Unraveling the Impact of Changing Sea Ice and Sea Surface Temperatures during WinterJaiser, Ralf; Akperov, M.; Timazhev, A.; Romanowsky, E.; Handorf, D.; Mokhov, I.I.
Meteorologische Zeitschrift, (2023), p. - The study addresses the question, if observed changes in terms of Arctic-midlatitude linkages during winter are driven by Arctic Sea ice decline alone or if the increase of global sea surface temperatures plays an additional role. We compare atmosphere-only model experiments with ECHAM6 to ERA-Interim Reanalysis data. The model sensitivity experiment is implemented as a set of four combinations of sea ice and sea surface temperature boundary conditions. Atmospheric circulation regimes are determined and evaluated in terms of their cyclone and blocking characteristics and changes in frequency during winter. As a prerequisite, ECHAM6 reproduces general features of circulation regimes very well. Tropospheric changes induced by the change of boundary conditions are revealed and further impacts on the large-scale circulation up into the stratosphere are investigated. In early winter, the observed increase of atmospheric blocking in the region between Scandinavia and the Urals are primarily related to the changes in sea surface temperatures. During late winter, we find a weakened polar stratospheric vortex in the reanalysis that further impacts the troposphere. In the model sensitivity study a climatologically weakened polar vortex occurs only if sea ice is reduced and sea surface temperatures are increased together. This response is delayed compared to the reanalysis. The tropospheric response during late winter is inconclusive in the model, which is potentially related to the weak and delayed response in the stratosphere. The model experiments do not reproduce the connection between early and late winter as interpreted from the reanalysis. Potentially explaining this mismatch, we identify a discrepancy of ECHAM6 to reproduce the weakening of the stratospheric polar vortex through blocking induced upward propagation of planetary waves.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- The footprint of heat waves and dry spells in the urban climate of
Würzburg, Germany, deduced from a continuous measurement campaign during
the anomalously warm years 2018–2020-
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Abstract:  The footprint of heat waves and dry spells in the urban climate of Würzburg, Germany, deduced from a continuous measurement campaign during the anomalously warm years 2018–2020Hartmann, Christian; Moser-Reischl, Astrid; Rahman, Mohammad A.; Franceschi, Eleonora; von Strachwitz, Miriam; Pauleit, Stephan; Pretzsch, Hans; Rötzer, Thomas; Paeth, Heiko
Meteorologische Zeitschrift, (2023), p. - The present study contributes to the issue of the urban heat island (UHI) effect with its possibly associated thermal stress for city dwellers and its potential mitigation during heat waves and dry spells in Central Europe. It is based on meteorological measurements along an urban transect in the city of Würzburg, Germany. Due to its topographic and structural situation, Würzburg is prone to an intense urban heat island (UHI). The measurements have started in 2018 and, hence, cover a period that was characterized by record high temperatures and long dry spells in Central Europe. Particularly on days with a maximum air temperature of more than 25 °C, an intense UHI was observed with the highest amplitude in the afternoon and, even more, during the evening hours. The highest measured difference between the densely built inner city and the outskirts was 8.2 °C. The UHI during summer is noticeably more pronounced, especially during the evening hours, when the regional background climate is anomalously warm and dry. This can be ascribed to anticyclonic weather types that prevailed over Central Europe during summertime between 2018 and 2020. The cooling effect of urban trees, in this case Tilia cordata, on near-surface air temperature amounts to partly more than 2 °C and, hence, mitigates the UHI locally, especially at noon and in the early afternoon. However, the cooling rate is only half as much when the trees suffer from water stress. Thus, an appropriate management of city's green infrastructure represents a useful strategy to mitigate the strength of the UHI and the heat stress in Central Europe.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Recent hot and dry summers in Germany in comparison to climate projections
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Abstract:  Recent hot and dry summers in Germany in comparison to climate projectionsStanley, Kelly; Leps, Nora; Hänsel, Stephanie; Klippel, Lara; Imbery, Florian; Walter, Andreas
Meteorologische Zeitschrift, (2023), p. - This study investigates whether the recent extremely hot and dry summers (2003, 2015, 2018 and 2019) in Germany will be normal summer conditions under future climate change scenarios. Abnormally persistent high-pressure systems during these recent German summers maintained clear skies and dry conditions on the ground, resulting in record-breaking heat and drought conditions. Here, climate indices are calculated from the German Meteorological Service's (DWD) climate model reference-ensembles for periods 2031–2060 and 2071–2100 under greenhouse gas emission scenarios RCP 2.6 (11 ensemble members) and RCP 8.5 (21 ensemble members) and are compared with climate indices calculated from three DWD observational datasets (station data and gridded datasets: HYRAS and DWD Climate Monitoring Grids). The climate projections show increasing summer heat conditions for Germany throughout this century and a slight shift to dryer conditions, especially for the RCP 8.5 scenario. These recent extreme summers are often in the 15 % hottest summers for RCP 2.6 in 2031–2060, 2071–2100 and the RCP 8.5 2031–2060 scenarios, but would be considered normal or even cool summers under the RCP 8.5 scenario in 2071–2100. Due to the combination of extreme heat and strong precipitation deficits, the climatic water balance and derived meteorological drought indicator values of these recent summers are often within the top 15 % of projected extreme summer drought indices and are sometimes only matched by the most anomalous hot and dry summers in the DWD reference-ensembles, even for the high-emission RCP 8.5 scenario in 2071–2100.
PubDate: Sun, 01 Jan 2023 00:00:00 +000
- Conference Report: Fourth European Nowcasting Conference
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Abstract:  Conference Report: Fourth European Nowcasting ConferenceSchmid, Franziska; Agersten, Solfrid; Bañon, Luis; Buzzi, Matteo; Atencia, Aitor; de Coning, Estelle; Kann, Alexander; Moseley, Stephen; Reyniers, Maarten; Wang, Yong; Wapler, Kathrin
Meteorologische Zeitschrift, (2022), p. - The fourth European Nowcasting Conference took place as an online event from 21 to 24 March 2022, organized by the EUMETNET (European National Meteorological and Hydrological Services Network) Nowcasting Program (E‑NWC), and kindly supported by EUMETCAL (EUMETNET Education and Training Collaborative Network of the National Meteorological Services within Europe). More than 110 participants attended the conference. 46 conference's presentations were given within the 0) opening session, a session on 1) observation as a basis for nowcasting, 2) seamless prediction with a special focus on Artificial Intelligence (AI), 3) nowcasting systems, products, and techniques and 4) verification, impacts on society, as well as applications and aspects of users. This report summarizes the scientific contributions presented and the discussed scientific questions.
PubDate: Mon, 12 Dec 2022 00:00:00 +000
- Modelling the heterogeneity of rain in an urban neighbourhood with an
obstacle-resolving model-
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Abstract:  Modelling the heterogeneity of rain in an urban neighbourhood with an obstacle-resolving modelFerner, Karolin S.; Boettcher, Marita; Schlünzen, K. Heinke
Meteorologische Zeitschrift, (2022), p. - Building induced winds change the falling of rain, leading to heterogeneous patterns of rain on ground and on building surfaces. These rain heterogeneities also occur in small urban scales like an urban neighbourhood, which covers an area of a few km2. For the investigation of rain heterogeneities within an urban neighbourhood the micro-scale, obstacle-resolving model MITRAS is used, which employs a microphysics parameterisation for cloud and rain processes. MITRAS has been extended by boundary conditions for cloud and rain water at building surfaces. An initialisation with radar data is implemented and the model output is successfully compared with in‑situ precipitation data. Simulations for an urban area are performed using different initial wind speeds, rain amounts, wind directions, and domain configurations. For the rain heterogeneity within this urban neighbourhood, the processes between buildings are found to be of small influence for the rain already falling. However, exchange processes from the canopy to the air above are found to influence the above-canopy rain pattern. The influence of the meteorological situation and the city's geometry on the wind field within and above the buildings are relevant to realistically represent a rain event and to create high-resolution precipitation data.
PubDate: Mon, 12 Dec 2022 00:00:00 +000
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