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Just published: our recent studies

The list of last scientific papers of the Department of Physical Geography and Geoecology.

Langhammer, J., 2019. UAV Monitoring of Stream Restorations. Hydrology, 6(2), 29.

This study examines the potential and limits of the unmanned aerial vehicles (UAVs) applicability for the monitoring of stream restoration in an urban environment. UAV imaging was used for long-term post-restoration monitoring of an urban stream. The recurrent imaging campaigns in the restored segment of Hostavicky brook in Prague, The Czech Republic, were undertaken for three years since the restoration. The UAV monitoring revealed that the new stream pattern substantially differs from the proposed restoration plan. Despite this, the new channel has proved stability, supported by intense grassing of the floodplain, resulting in only marginal evolution of the restored channel. The new channel proved the ability to mitigate the course of a significant flood event without significant flood spills outside the riparian zone. The UAV monitoring also revealed intense eutrophication in newly created shallow ponds with insufficient drainage. 


Lendzioch, T., Langhammer, J., Jenicek, M.. 2019. Estimating Snow Depth and Leaf Area Index Based on UAV Digital Photogrammetry. Sensors 2019, 19(5), 1027.

This study examines the potential and limits of the unmanned aerial vehicles (UAVs) applicability for the monitoring of stream restoration in an urban environment. UAV imaging was used for long-term post-restoration monitoring of an urban stream. The recurrent imaging campaigns in the restored segment of Hostavicky brook in Prague, The Czech Republic, were undertaken for three years since the restoration. The UAV monitoring revealed that the new stream pattern substantially differs from the proposed restoration plan. Despite this, the new channel has proved stability, supported by intense grassing of the floodplain, resulting in only marginal evolution of the restored channel. The new channel proved the ability to mitigate the course of a significant flood event without significant flood spills outside the riparian zone. The UAV monitoring also revealed intense eutrophication in newly created shallow ponds with insufficient drainage. 


Margold, M., Gosse, J.C., Hidy, A.J., Woywitka, R.J., Young, J.M., Froese, D. (in press): Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka BPQuaternary Research.

The Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the ice-free corridor east of the Rocky Mountains. The ice free corridor then provided a passage between Beringia and the region south of the North American ice sheets. We used 10Be exposure dating to constrain the beginning of the ice-free corridor opening. Based on a group of 12 samples well-clustered in time, we dated the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed.


Parajka, J., Jenicek, M. et al. (2019): MODIS snowline elevation changes during snowmelt runoff events in Europe, Journal of Hydrology and Hydromechanics, 67(1), 101-109.

This study evaluates MODIS snow cover characteristics for large number of snowmelt runoff events in 145 catchments from 9 countries in Europe. Runoff events are identified by a base flow separation approach. The snowmelt events are identified by using estimated regional snowline elevation (RSLE) changes during a runoff event. The mean duration between the start and peak of snowmelt runoff events is about 3 days and the proportion of snowmelt events in all runoff events tends to increase with the maximum elevation of catchments. The mean minimum RSLE, which represents the conditions at the beginning of snowmelt events, is situated approximately at the mean catchment elevation. It means that snowmelt events do not start only during maximum snow cover conditions, but also after this maximum. The mean RSLE during snowmelt peaks is on average 170 m lower than at the start of the snowmelt events, but there is a large regional variability.


Bližňák, V., Kašpar, M., Müller, M., Zacharov, P. (2019): Sub-daily temporal reconstruction of extreme precipitation events using NWP model simulations. Atmos. Res., 224, 65–80. 

An alternative correction procedure for a posteriori improvement of quantitative precipitation re-forecast generated by a numerical weather prediction (NWP) model COSMO in a high temporal resolution is presented. The main motivation is to provide reliable precipitation re-analyses from the NWP model, which will enable a more detailed analysis of historical extreme precipitation events (EPEs). The results show that the NWP model COSMO usually well predicts the occurrence of EPEs, but its spatial localization is not always accurate. This is usually a case of more localized convective precipitation, where the impact of the applied correction procedure is the most evident. The study provides a general performance of the proposed method and indicates that the method can be applied to historical EPEs, for which no weather radar data are available, to obtain their more accurate sub-daily temporal reconstruction.


Müller, M., Bližňák, V., Kašpar, M. (2018): Analysis of rainfall time structures on a scale of hours. Atmos. Res., 211, 38-51.

The paper is motivated by the enormous variability of short-term rainfall time structures which need to be discretized into several typical variants and explained from the viewpoint of rainfall types producing them. We present six variants of the time structure of 6-h rainfalls in Czechia, distinguished by a novel methodology for designing synthetic hyetographs. The variants were distinguished by three indexes that quantify the precipitation concentration within time steps from one to six hours. Episodes with steady intensity lasting about three hours are still mainly stratiform or mixed while two variants represented by “two-humped” hyetographs are usually mixed or convective. Two variants of most concentrated episodes are mainly convective or possibly mixed; they are characterized by enhanced frequency of southwestern and eastern cyclonic types.


Zaginaev, V. (2018): Development of a Potentially Hazardous Pro-Glacial Lake in Aksay Valley, Kyrgyz Range, Northern Tien Shan. Hydrology, (1), 3.

Debris flows caused by glacial lake outburst floods (GLOFs) are common hazards in mountain environments. A potentially dangerous lake has been identified adjacent to the Uchitel Glacier in Northern Tien Shan. This lake formed between 1988 and 1994 on the site of a retreated glacier in the upper part of the Aksay Valley. In this study we consider the possibility of an outburst of this pro-glacial lake in the future. The study involved bathymetry mapping of the lake, detailed profile sections of the valley, flow rate measurements on the Aksay river, and monitoring of the lake development using satellite images. The outburst of this lake could cause powerful debris flows posing a threat to permanent residents living downstream, in the Ala-Archa Valley.


Tumajer J, Treml, V. (2018): Disentangling the effects of disturbance, climate and tree age on xylem hydraulic conductivity of Betula pendula. Annals of Botany (online)

Vessel size and density is known to adjust in broadleaves after mechanical damage to stem or roots. This significantly alters hydraulic conductivity of xylem and transpiration capacity of the tree. We performed experiment with adult Silver birches, which were mechanically treated to simulate natural disturbances (e.g., landslide, windstorm, flood). Xylem conductivity abruptly dropped down after the treatment in decapitated, tilted and scarred trees.  The intensity of damage response significantly outweighed effects of climate and tree ageing on wood anatomical structure. Our results show, that increasing frequency and intensity of forest disturbances might significantly affect temperate forests.


Stryhal, J, Huth, R. (2018): Classifications of winter atmospheric circulation patterns: validation of CMIP5 GCMs over Europe and the North Atlantic. Climate Dynamics (online).

Validation of global climate model (GCM) outputs is one of key steps towards reliably predicting future climate changes. Our study, which focused on winter atmospheric circulation over Europe in 32 state-of-the-art GCMs, shows that the ensemble median overestimates the frequency of westerly circulation over the British Isles, central Europe, and the eastern Mediterranean by about 7, 21, and 70 percent, in turn, while easterly and anticyclonic circulation is typically underestimated by 30–40%. Furthermore, considerable dependence of GCM rankings was found on the choice of reference dataset (reanalysis) and circulation classification method.


Stryhal, J, Huth, R. (2018): Trends in winter circulation over the British Isles and central Europe in twenty-first century projections by 25 CMIP5 GCMs. Climate Dynamics (online).

21st-century changes in frequency, persistence, and strength of winter synoptic-scale circulation over the British Isles and central Europe are investigated in outputs of 25 global climate models. The models indicate that the zonal flow over both regions will gradually become more frequent compared to the reference (1961–2000) period, while its strength is not projected to change. On the other hand, the easterly flow is projected to become not only less frequent but also markedly weaker in central Europe, which we hypothesize might be an important factor contributing to the projected decrease of cold extremes there.


Ponocná T. et al. (2018): Deviations of treeline Norway spruce radial growth from summer temperatures in East-Central Europe. Agricultural and Forest Meteorology 253–254, 62–70.

There is increasing evidence of recent decoupling of tree-ring growth from observed temperature rise. We explored coherency of treeline radial growth and temperature trend in mountain regions of Central Europe. We found a period of low intraregional growth coherency in the 1950s reflecting warmer, less temperature-limiting conditions and land usechange. Highly coherent growth in the 1930s, 1970s and 1980s was related to the strong environmental growth-limiting signals of short growing seasons and high acid pollution loads.


Pokorná, L. et at. (2018): Annual cycle of temperature trends in Europe, 1961–2000. Global and Planetary Change 170 (2018) 146–162.

This paper introduces a new method of analysing temperature trends within a calendar year using a sifting seasons. Annual courses at 135 stations over Europe show a spatial differences of temperature trends and their variability during the calendar year. The method also demonstrates that the choice of the sliding season length and its position within the calendar year strongly affect the sign and magnitude of trends. Homogenous regions with typical annual cycle of trends were identified and some possible causes of temperature changes are mentioned.


Chandler, B.M.P. et al. (2018): Glacial geomorphological mapping: A review of approaches and frameworks for best practice. Earth-Science Reviews, 185, 806-846.

Our paper provides a review paper and assessment of glacial geomorphological methods and datasets currently available. Key challenges to accurate and robust geomorphological mapping are highlighted and the importance of combining multiple datasets and/or mapping approaches is emphasised.

 


Jenicek, M. et al. (2018): Modeling of future changes in seasonal snowpack and impacts on summer low flows in Alpine catchments, Water Resources Research, 54 (1), 538-556.

It is expected that an increasing proportion of the precipitation will fall as rain rather than snow in the future due to  increase in air temperature. Our study was focused on implications of the mentioned change on summer low flows and confirmed that 1) In snow-dominated areas, summer low flows will decrease in the future, while 2) this decrease will be caused mostly by the decrease in snow storage and the shift of snowmelt season. The study also showed that 3) low flows at higher elevations are more sensitive to the decrease in snow storage than low flows at lower elevations. This might affect water availability during summer.


 

Published: Sep 15, 2018 12:00 AM

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