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  • 1
    In: Monthly Weather Review, American Meteorological Society, Vol. 147, No. 4 ( 2019-04-01), p. 1077-1106
    Abstract: The extratropical transition (ET) of tropical cyclones often has an important impact on the nature and predictability of the midlatitude flow. This review synthesizes the current understanding of the dynamical and physical processes that govern this impact and highlights the relationship of downstream development during ET to high-impact weather, with a focus on downstream regions. It updates a previous review from 2003 and identifies new and emerging challenges and future research needs. First, the mechanisms through which the transitioning cyclone impacts the midlatitude flow in its immediate vicinity are discussed. This “direct impact” manifests in the formation of a jet streak and the amplification of a ridge directly downstream of the cyclone. This initial flow modification triggers or amplifies a midlatitude Rossby wave packet, which disperses the impact of ET into downstream regions (downstream impact) and may contribute to the formation of high-impact weather. Details are provided concerning the impact of ET on forecast uncertainty in downstream regions and on the impact of observations on forecast skill. The sources and characteristics of the following key features and processes that may determine the manifestation of the impact of ET on the midlatitude flow are discussed: the upper-tropospheric divergent outflow, mainly associated with latent heat release in the troposphere below, and the phasing between the transitioning cyclone and the midlatitude wave pattern. Improving the representation of diabatic processes during ET in models and a climatological assessment of the ET’s impact on downstream high-impact weather are examples for future research directions.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2019
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    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 2
    Online Resource
    Online Resource
    Osterreichische Akademie der Wissenschaften, Verlag ; 2018
    In:  GW-Unterricht Vol. 1 ( 2018), p. 1-2
    In: GW-Unterricht, Osterreichische Akademie der Wissenschaften, Verlag, Vol. 1 ( 2018), p. 1-2
    Type of Medium: Online Resource
    ISSN: 2077-1517 , 2414-4169
    URL: Issue
    RVK:
    Language: German
    Publisher: Osterreichische Akademie der Wissenschaften, Verlag
    Publication Date: 2018
    detail.hit.zdb_id: 2536195-8
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  • 3
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  International Journal of Climatology Vol. 37, No. 2 ( 2017-02), p. 928-942
    In: International Journal of Climatology, Wiley, Vol. 37, No. 2 ( 2017-02), p. 928-942
    Abstract: Climate information provided by global or regional climate models ( RCMs ) are often too coarse and prone to substantial biases for local assessments or use in impact models. Hence, statistical downscaling becomes necessary. For the Swiss National Climate Change Initiative ( CH2011 ), a delta‐change approach was used to provide daily climate scenarios at the local scale. Here, we analyse a Richardson‐type weather generator ( WG ) as an alternative method to downscale daily precipitation, minimum and maximum temperature. The WG is calibrated for 26 Swiss stations and the reference period is 1980–2009. It is perturbed with change factors derived from RCMs ( ENSEMBLES ) to represent the climate of 2070–2099 assuming the SRES A1B emission scenario. The WG can be run in multi‐site mode, making it especially attractive for impact‐modellers that rely on a realistic spatial structure in downscaled time‐series. The results from the WG are benchmarked against the original delta‐change approach that applies mean additive or multiplicative adjustments to the observations. According to both downscaling methods, the results reveal mean temperature increases and a precipitation decrease in summer, consistent with earlier studies. For the summer drying, the WG indicates primarily a decrease in wet‐day frequency and correspondingly an increase in mean dry spell length of between 18 and 40% at low‐elevation stations. By definition, these potential changes cannot be represented by a delta‐change approach. In winter, both methods project a shortening of the frost period (−30 to −60 days) and a decrease of snow days (−20 to −100%). The WG demonstrates though, that almost present‐day conditions in snow‐days could still occur in the future. As expected, both methods have difficulties in representing extremes. If users focus on changes in temporal sequences and need a large number of future realizations, it is recommended to use data from a WG instead of a delta‐change approach.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    Wiley ; 2015
    In:  International Journal of Climatology Vol. 35, No. 11 ( 2015-09), p. 3204-3219
    In: International Journal of Climatology, Wiley, Vol. 35, No. 11 ( 2015-09), p. 3204-3219
    Abstract: Fundamental changes in the hydrological cycle are to be expected in a future warmer climate. For Switzerland, recent climate change assessments based on the ENSEMBLES regional climate models project for the A1B emission scenario summer mean precipitation to significantly decrease by the end of this century, whereas winter mean precipitation tend to rise in Southern Switzerland. From an end‐user perspective, projected changes in seasonal means are often insufficient to adequately address the multifaceted challenges of climate change adaptation. In this study, we investigate the projected changes in seasonal precipitation by considering changes in frequency and intensity, precipitation type (convective vs stratiform) and temporal structure (wet and dry spells) over Switzerland. As proxies for rain‐type changes, we rely on the parameterized convective and large‐scale precipitation components simulated by the models. The study reveals that the projected summer drying over Switzerland at the end of the century is mainly driven by a widespread reduction in the number of precipitation days. Thereby, the drying evolves altitude‐specific: over low‐land regions it is associated with a decrease in both convective and large‐scale precipitation. Over elevated regions it is primarily associated with a decline in large‐scale precipitation only, whereas convective precipitation remains at current levels. As a consequence, almost all the models project an increase in convective fraction at elevated altitudes. The decrease in the number of wet days during summer is accompanied by decreases (increases) in the number of multi‐day wet (dry) spells. This future shift in multi‐day episodes also lowers down the likelihood of short dry spell occurrence in all of the models. The models further project a higher mean precipitation intensity in spring and autumn north of the Alps, whereas a similar tendency is expected for the winter season over most of Switzerland.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 5
    Online Resource
    Online Resource
    American Meteorological Society ; 2012
    In:  Monthly Weather Review Vol. 140, No. 7 ( 2012-07), p. 2044-2063
    In: Monthly Weather Review, American Meteorological Society, Vol. 140, No. 7 ( 2012-07), p. 2044-2063
    Abstract: The Ross Ice Shelf airstream (RAS) is a barrier parallel flow along the base of the Transantarctic Mountains. Previous research has hypothesized that a combination of katabatic flow, barrier winds, and mesoscale and synoptic-scale cyclones drive the RAS. Within the RAS, an area of maximum wind speed is located to the northwest of the protruding Prince Olav Mountains. In this region, the Sabrina automatic weather station (AWS) observed a September 2009 high wind event with wind speeds in excess of 20 m s −1 for nearly 35 h. The following case study uses in situ AWS observations and output from the Antarctic Mesoscale Prediction System to demonstrate that the strong wind speeds during this event were caused by a combination of various forcing mechanisms, including katabatic winds, barrier winds, a surface mesocyclone over the Ross Ice Shelf, an upper-level ridge over the southern tip of the Ross Ice Shelf, and topographic influences from the Prince Olav Mountains. These forcing mechanisms induced a barrier wind corner jet to the northwest of the Prince Olav Mountains, explaining the maximum wind speeds observed in this region. The RAS wind speeds were strong enough to induce two additional barrier wind corner jets to the northwest of the Prince Olav Mountains, resulting in a triple barrier wind corner jet along the base of the Transantarctic Mountains.
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2012
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Wiley ; 2016
    In:  International Journal of Climatology Vol. 36, No. 15 ( 2016-12), p. 4929-4941
    In: International Journal of Climatology, Wiley, Vol. 36, No. 15 ( 2016-12), p. 4929-4941
    Abstract: The University of Wisconsin‐Madison Antarctic Automatic Weather Station ( AWS ) project has been making meteorological surface observations on the Ross Ice Shelf ( RIS ) for approximately 30 years. This network offers the most continuous set of routine measurements of surface meteorological variables in this region. The Ross Island area is excluded from this study. The surface climate of the RIS is described using the AWS measurements. Temperature, pressure, and wind data are analysed on daily, monthly, seasonal, and annual time periods for 13 AWS across the RIS . The AWS are separated into three representative regions – central, coastal, and the area along the Transantarctic Mountains – in order to describe specific characteristics of sections of the RIS . The climatology describes general characteristics of the region and significant changes over time. The central AWS experiences the coldest mean temperature, and the lowest resultant wind speed. These AWSs also experience the coldest potential temperatures with a minimum of 209.3 K at Gill AWS . The AWS along the Transantarctic Mountains experiences the warmest mean temperature, the highest mean sea‐level pressure, and the highest mean resultant wind speed. Finally, the coastal AWS experiences the lowest mean pressure. Climate indices ( MEI , SAM , and SAO ) are compared to temperature and pressure data of four of the AWS with the longest observation periods, and significant correlation is found for most AWS in sea‐level pressure and temperature. This climatology study highlights characteristics that influence the climate of the RIS , and the challenges of maintaining a long‐term Antarctic AWS network. Results from this effort are essential for the broader Antarctic meteorology community for future research.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 7
    Online Resource
    Online Resource
    American Meteorological Society ; 2003
    In:  Monthly Weather Review Vol. 131, No. 2 ( 2003-02), p. 371-383
    In: Monthly Weather Review, American Meteorological Society, Vol. 131, No. 2 ( 2003-02), p. 371-383
    Type of Medium: Online Resource
    ISSN: 0027-0644 , 1520-0493
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2003
    detail.hit.zdb_id: 2033056-X
    detail.hit.zdb_id: 202616-8
    SSG: 14
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  • 8
    In: International Journal of Climatology, Wiley, Vol. 39, No. 9 ( 2019-07), p. 3750-3785
    Abstract: VALUE is an open European collaboration to intercompare downscaling approaches for climate change research, focusing on different validation aspects (marginal, temporal, extremes, spatial, process‐based, etc.). Here we describe the participating methods and first results from the first experiment, using “perfect” reanalysis (and reanalysis‐driven regional climate model (RCM)) predictors to assess the intrinsic performance of the methods for downscaling precipitation and temperatures over a set of 86 stations representative of the main climatic regions in Europe. This study constitutes the largest and most comprehensive to date intercomparison of statistical downscaling methods, covering the three common downscaling approaches (perfect prognosis, model output statistics—including bias correction—and weather generators) with a total of over 50 downscaling methods representative of the most common techniques. Overall, most of the downscaling methods greatly improve (reanalysis or RCM) raw model biases and no approach or technique seems to be superior in general, because there is a large method‐to‐method variability. The main factors most influencing the results are the seasonal calibration of the methods (e.g., using a moving window) and their stochastic nature. The particular predictors used also play an important role in cases where the comparison was possible, both for the validation results and for the strength of the predictor–predictand link, indicating the local variability explained. However, the present study cannot give a conclusive assessment of the skill of the methods to simulate regional future climates, and further experiments will be soon performed in the framework of the EURO‐CORDEX initiative (where VALUE activities have merged and follow on). Finally, research transparency and reproducibility has been a major concern and substantive steps have been taken. In particular, the necessary data to run the experiments are provided at http://www.value‐cost.eu/data and data and validation results are available from the VALUE validation portal for further investigation: http://www.value‐cost.eu/validationportal .
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 9
    In: Quaternary Science Reviews, Elsevier BV, Vol. 235 ( 2020-05), p. 106221-
    Type of Medium: Online Resource
    ISSN: 0277-3791
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 780249-3
    detail.hit.zdb_id: 1495523-4
    SSG: 14
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  • 10
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 1995
    In:  Climatic Change Vol. 30, No. 4 ( 1995-8), p. 367-395
    In: Climatic Change, Springer Science and Business Media LLC, Vol. 30, No. 4 ( 1995-8), p. 367-395
    Type of Medium: Online Resource
    ISSN: 0165-0009 , 1573-1480
    RVK:
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 1995
    detail.hit.zdb_id: 751086-X
    detail.hit.zdb_id: 1477652-2
    SSG: 14
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