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  • 1
    Online Resource
    Online Resource
    Copernicus GmbH ; 2017
    In:  Geoscientific Model Development Vol. 10, No. 5 ( 2017-05-31), p. 2031-2055
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 10, No. 5 ( 2017-05-31), p. 2031-2055
    Abstract: Abstract. Increasing computational resources and the demands of impact modelers, stake holders, and society envision seasonal and climate simulations with the convection-permitting resolution. So far such a resolution is only achieved with a limited-area model whose results are impacted by zonal and meridional boundaries. Here, we present the setup of a latitude-belt domain that reduces disturbances originating from the western and eastern boundaries and therefore allows for studying the impact of model resolution and physical parameterization. The Weather Research and Forecasting (WRF) model coupled to the NOAH land–surface model was operated during July and August 2013 at two different horizontal resolutions, namely 0.03 (HIRES) and 0.12° (LOWRES). Both simulations were forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis data at the northern and southern domain boundaries, and the high-resolution Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) data at the sea surface.The simulations are compared to the operational ECMWF analysis for the representation of large-scale features. To analyze the simulated precipitation, the operational ECMWF forecast, the CPC MORPHing (CMORPH), and the ENSEMBLES gridded observation precipitation data set (E-OBS) were used as references.Analyzing pressure, geopotential height, wind, and temperature fields as well as precipitation revealed (1) a benefit from the higher resolution concerning the reduction of monthly biases, root mean square error, and an improved Pearson skill score, and (2) deficiencies in the physical parameterizations leading to notable biases in distinct regions like the polar Atlantic for the LOWRES simulation, the North Pacific, and Inner Mongolia for both resolutions.In summary, the application of a latitude belt on a convection-permitting resolution shows promising results that are beneficial for future seasonal forecasting.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2456725-5
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  • 2
    In: International Journal of Climatology, Wiley, Vol. 41, No. S1 ( 2021-01)
    Abstract: The new SEAS5 global ensemble forecast system was dynamically downscaled over the Horn of Africa for summer (June‐July‐August) 2018. For this purpose, a multi‐physics ensemble was designed with a grid increment of 3 km and without any intermediate nest based on the Weather Research and Forecasting model (WRF). The WRF and the SEAS5 model output were compared with each other and reference datasets to assess the biases in 4 different regions of Ethiopia. Also, the WRF ensemble variability was investigated in relation to model parameterization and lateral boundary conditions. Over the summer, the SEAS5 has a positive temperature bias of 0.17°C compared to ECMWF analysis average for the study domain, while the WRF bias is +1.14°C. Concerning precipitation, the WRF model had average accumulated values of 264 mm, compared to 248 mm for SEAS5 and 236 mm for the observations. Over south Ethiopia, however, the downscaling produced over 50% more precipitation than the other datasets. The maximum northward extension of the tropical rain belt was reduced by about 2° in both models when compared to observations. Downscaling increased reliability for precipitation, correcting the SEAS5 underdispersion: ensemble spread for precipitation was increased by about 70% in the WRF ensemble in three of the four Ethiopian sub‐regions, whereas the very dry Somali region remained unaffected. The WRF ensemble analysis revealed that the ensemble spread is mainly caused by the perturbed boundary conditions, as their effect is often 50% larger than the physics‐induced variability in the mountainous part of Ethiopia for precipitation and temperature.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 3
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 147, No. 741 ( 2021-10), p. 4163-4185
    Abstract: We discuss the analysis impact of the ensemble‐based assimilation of differential absorption lidar observed water vapour and Raman lidar observed temperature profiles into the Weather Research and Forecasting model at convection‐permitting scale. The impact of flow‐dependent background error covariance in the data assimilation (DA) system that uses the hybrid three‐dimensional variational (3DVAR) ensemble transform Kalman filter (ETKF) was compared to 3DVAR DA. The 3DVAR‐ETKF experiment resulted in a 50% lower temperature and water vapour RMSE than the 3DVAR experiment when taking the assimilated lidar data as reference and 26% (38%) lower water vapour (temperature) RMSE when comparing against independent radiosonde observations collocated with the lidar site. The planetary boundary‐layer height of the analyses compared to independent ceilometer data provided additional evidence of improvement. The 3DVAR analysis RMSE showed 140 m, whereas 3DVAR‐ETKF showed 60 m. Although limited to a single case study, we attribute these improvements to the flow‐dependent background error covariance matrix in the 3DVAR‐ETKF approach. The vertical profile measured from a single stationary lidar system established a spatial impact with a 100 km radius. This seems to indicate future assimilation of water vapour and temperature data from an operational lidar network. The assimilation impact persisted 7 hr into the forecast time compared with the ceilometer data and 4 hr with GPS observations.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    American Meteorological Society ; 2014
    In:  Journal of Applied Meteorology and Climatology Vol. 53, No. 5 ( 2014-05), p. 1143-1169
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 53, No. 5 ( 2014-05), p. 1143-1169
    Abstract: Recent advances in technology permit the irrigation of dry, coastal areas, avoiding the use of fossil water and conflicts with other land use (e.g., for food production). Consequently, it becomes reasonable to consider large-scale plantations for mitigating increases in atmospheric concentrations by carbon sequestration and to study local modifications of weather and climate. This work investigates the impact of plantations in Oman and the Sonora Desert in Mexico assuming an area of about 100 km × 100 km. For this purpose, an advanced land surface–atmosphere model was adapted to the local changes of land cover and operated on the convection-permitting scale. Explicit simulations of the impact of the plantation on soil–vegetation–atmosphere feedback were performed for a duration of 1 yr. A strong modification of diurnal cycles of variables such as surface fluxes, temperature, and boundary layer depth was found. Over the plantations, the mean temperature decreased as a result of nonlinear changes of the diurnal cycle caused by less warming during the day than cooling during the night. Moreover, the plantations caused an increase in vertical instability and a modification of the horizontal flow leading to the development of convergence zones. During several isolated cases in summer, this process led to convection initiation and precipitation with an enhancement of about 30 mm in both areas, respectively. These convection-permitting simulations lend confidence that an increase in precipitation could be induced at the mesoscale by the introduction of vegetation in desert regions. Furthermore, this effect should be included in a quantitative assessment of climate engineering by afforestation.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 5
    In: Natural Hazards and Earth System Sciences, Copernicus GmbH, Vol. 19, No. 6 ( 2019-06-13), p. 1129-1149
    Abstract: Abstract. This study investigates an extreme weather event that impacted the United Arab Emirates (UAE) in March 2016, using the Weather Research and Forecasting (WRF) model version 3.7.1 coupled with its hydrological modeling extension package (WRF-Hydro). Six-hourly forecasted forcing records at 0.5∘ spatial resolution, obtained from the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS), are used to drive the three nested downscaling domains of both standalone WRF and coupled WRF–WRF-Hydro configurations for the recent flood-triggering storm. Ground and satellite observations over the UAE are employed to validate the model results. The model performance was assessed using precipitation from the Global Precipitation Measurement (GPM) mission (30 min, 0.1∘ product), soil moisture from the Advanced Microwave Scanning Radiometer 2 (AMSR2; daily, 0.1∘ product) and the NOAA Soil Moisture Operational Products System (SMOPS; 6-hourly, 0.25∘ product), and cloud fraction retrievals from the Moderate Resolution Imaging Spectroradiometer Atmosphere product (MODATM; daily, 5 km product). The Pearson correlation coefficient (PCC), relative bias (rBIAS), and root-mean-square error (RMSE) are used as performance measures. Results show reductions of 24 % and 13 % in RMSE and rBIAS measures, respectively, in precipitation forecasts from the coupled WRF–WRF-Hydro model configuration, when compared to standalone WRF. The coupled system also shows improvements in global radiation forecasts, with reductions of 45 % and 12 % for RMSE and rBIAS, respectively. Moreover, WRF-Hydro was able to simulate the spatial distribution of soil moisture reasonably well across the study domain when compared to AMSR2-derived soil moisture estimates, despite a noticeable dry and wet bias in areas where soil moisture is high and low. Temporal and spatial variabilities of simulated soil moisture compare well to estimates from the NOAA SMOPS product, which indicates the model's capability to simulate surface drainage. Finally, the coupled model showed a shallower planetary boundary layer (PBL) compared to the standalone WRF simulation, which is attributed to the effect of soil moisture feedback. The demonstrated improvement, at the local scale, implies that WRF-Hydro coupling may enhance hydrological and meteorological forecasts in hyper-arid environments.
    Type of Medium: Online Resource
    ISSN: 1684-9981
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2069216-X
    detail.hit.zdb_id: 2064587-9
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  • 6
    In: Natural Hazards and Earth System Sciences, Copernicus GmbH, Vol. 22, No. 11 ( 2022-11-17), p. 3701-3724
    Abstract: Abstract. Extreme precipitation is a weather phenomenon with tremendous damaging potential for property and human life. As the intensity and frequency of such events is projected to increase in a warming climate, there is an urgent need to advance the existing knowledge on extreme precipitation processes, statistics and impacts across scales. To this end, a working group within the Germany-based project, ClimXtreme, has been established to carry out multidisciplinary analyses of high-impact events. In this work, we provide a comprehensive assessment of the 29 June 2017 heavy precipitation event (HPE) affecting the Berlin metropolitan region (Germany), from the meteorological, impacts and climate perspectives, including climate change attribution. Our analysis showed that this event occurred under the influence of a mid-tropospheric trough over western Europe and two shortwave surface lows over Britain and Poland (Rasmund and Rasmund II), inducing relevant low-level wind convergence along the German–Polish border. Over 11 000 convective cells were triggered, starting early morning 29 June, displacing northwards slowly under the influence of a weak tropospheric flow (10 m s−1 at 500 hPa). The quasi-stationary situation led to totals up to 196 mm d−1, making this event the 29 June most severe in the 1951–2021 climatology, ranked by means of a precipitation-based index. Regarding impacts, it incurred the largest insured losses in the period 2002 to 2017 (EUR 60 million) in the greater Berlin area. We provide further insights on flood attributes (inundation, depth, duration) based on a unique household-level survey data set. The major moisture source for this event was the Alpine–Slovenian region (63 % of identified sources) due to recycling of precipitation falling over that region 1 d earlier. Implementing three different generalised extreme value (GEV) models, we quantified the return periods for this case to be above 100 years for daily aggregated precipitation, and up to 100 and 10 years for 8 and 1 h aggregations, respectively. The conditional attribution demonstrated that warming since the pre-industrial era caused a small but significant increase of 4 % in total precipitation and 10 % for extreme intensities. The possibility that not just greenhouse-gas-induced warming, but also anthropogenic aerosols affected the intensity of precipitation is investigated through aerosol sensitivity experiments. Our multi-disciplinary approach allowed us to relate interconnected aspects of extreme precipitation. For instance, the link between the unique meteorological conditions of this case and its very large return periods, or the extent to which it is attributable to already-observed anthropogenic climate change.
    Type of Medium: Online Resource
    ISSN: 1684-9981
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2069216-X
    detail.hit.zdb_id: 2064587-9
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  • 7
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 14, No. 3 ( 2021-03-19), p. 1615-1637
    Abstract: Abstract. Effective numerical weather forecasting is vital in arid regions like the United Arab Emirates (UAE) where extreme events like heat waves, flash floods, and dust storms are severe. Hence, accurate forecasting of quantities like surface temperatures and humidity is very important. To date, there have been few seasonal-to-annual scale verification studies with WRF at high spatial and temporal resolution. This study employs a convection-permitting scale (2.7 km grid scale) simulation with WRF with Noah-MP, in daily forecast mode, from 1 January to 30 November 2015. WRF was verified using measurements of 2 m air temperature (T2 m), 2 m dew point (TD2 m), and 10 m wind speed (UV10 m) from 48 UAE WMO-compliant surface weather stations. Analysis was made of seasonal and diurnal performance within the desert, marine, and mountain regions of the UAE. Results show that WRF represents temperature (T2 m) quite adequately during the daytime with biases ≤+1 ∘C. There is, however, a nocturnal cold bias (−1 to −4 ∘C), which increases during hotter months in the desert and mountain regions. The marine region has the smallest T2 m biases (≤-0.75 ∘C). WRF performs well regarding TD2 m, with mean biases mostly ≤ 1 ∘C. TD2 m over the marine region is overestimated, though (0.75–1 ∘C), and nocturnal mountain TD2 m is underestimated (∼-2 ∘C). UV10 m performance on land still needs improvement, and biases can occasionally be large (1–2 m s−1). This performance tends to worsen during the hot months, particularly inland with peak biases reaching ∼ 3 m s−1. UV10 m is better simulated in the marine region (bias ≤ 1 m s−1). There is an apparent relationship between T2 m bias and UV10 m bias, which may indicate issues in simulation of the daytime sea breeze. TD2 m biases tend to be more independent. Studies such as these are vital for accurate assessment of WRF nowcasting performance and to identify model deficiencies. By combining sensitivity tests, process, and observational studies with seasonal verification, we can further improve forecasting systems for the UAE.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2456725-5
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  • 8
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2013
    In:  Climate Dynamics Vol. 41, No. 3-4 ( 2013-8), p. 755-774
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 41, No. 3-4 ( 2013-8), p. 755-774
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2013
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2011
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 137, No. S1 ( 2011-01), p. 156-175
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 137, No. S1 ( 2011-01), p. 156-175
    Abstract: The impact of assimilating conventional and Global Positioning System (GPS) Zenith Total Delay (ZTD) data over France into the Weather Research and Forecasting (WRF) model is investigated during COPS IOP 9c. A convection‐permitting horizontal resolution of 3.6 km covering the whole of central Europe was chosen. Four different simulations were conducted to show the influence of assimilating different observation types on the forecast. Additionally, a comparison with the models COSMO‐DE and COSMO‐EU from the German Meteorological Service (DWD) was performed. The results show a clear positive impact of assimilating data into a convection‐permitting configuration of the WRF model over Europe. The additional assimilation of GPS‐ZTD data shows a further improvement of integrated water vapour (IWV) correlation, but the influence on prediction of precipitation was not necessarily clear. A comparison with radiosonde data shows a positive impact on the humidity structure after 12 hours, while an overestimation of precipitation still remains. A further comparison with the operational high‐resolution models of DWD during this COPS IOP reveals a strong dependence on the initial boundary‐layer wind field especially as the near‐surface wind field is better represented in the ECMWF analysis than in the COSMO analysis. As this is, to our knowledge, the first study applying a convection‐permitting configuration of WRF over Europe, it can be used as a guidance for further studies. Copyright © 2011 Royal Meteorological Society
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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  • 10
    In: Tellus A, Stockholm University Press, ( 2011-03)
    Type of Medium: Online Resource
    ISSN: 1600-0870 , 0280-6495
    RVK:
    RVK:
    Language: Unknown
    Publisher: Stockholm University Press
    Publication Date: 2011
    detail.hit.zdb_id: 2026987-0
    SSG: 16,13
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