Publikationen
Es wurden 9 Publikationen gefunden
Álvarez-Estrella, J.; Muñoz, P.; Bendix, J.; Contreras, P. & Celleri, R. (2024): Enhancing Peak Runoff Forecasting through Feature Engineering Applied to X-Band Radar Data. Water 16(7), 968.
Rollenbeck, R.; Orellana-Alvear, J.; Bendix, J.; Rodriguez, R.; Pucha-Cofrep, F.; Guallpa, M.; Fries, A. & Celleri, R. (2022): The Coastal El Niño Event of 2017 in Ecuador and Peru: A Weather Radar Analysis. Remote Sensing 14(4), 824.
Orellana-Alvear, J.; Celleri, R.; Rollenbeck, R.; Muñoz, P.; Contreras, P. & Bendix, J. (2020): Assessment of Native Radar Reflectivity and Radar Rainfall Estimates for Discharge Forecasting in Mountain Catchments with a Random Forest Model. Remote Sensing 12(12), 1.
Orellana-Alvear, J.; Celleri, R.; Rollenbeck, R. & Bendix, J. (2019): Optimization of X-Band Radar Rainfall Retrieval in the Southern Andes of Ecuador Using a Random Forest Model. Remote Sensing 11(14), 1632.
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DOI: 10.3390/rs11141632
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Abstract:
Abstract:
Despite many eorts of the radar community, quantitative precipitation estimation (QPE)
from weather radar data remains a challenging topic. The high resolution of X-band radar imagery
in space and time comes with an intricate correction process of reflectivity. The steep and high
mountain topography of the Andes enhances its complexity. This study aims to optimize the rainfall
derivation of the highest X-band radar in the world (4450 m a.s.l.) by using a random forest (RF)
model and single Plan Position Indicator (PPI) scans. The performance of the RFmodel was evaluated
in comparison with the traditional step-wise approach by using both, the Marshall-Palmer and a
site-specific Z–R relationship. Since rain gauge networks are frequently unevenly distributed and
hardly available at real time in mountain regions, bias adjustment was neglected. Results showed an
improvement in the step-wise approach by using the site-specific (instead of the Marshall-Palmer)
Z–R relationship. However, both models highly underestimate the rainfall rate (correlation coecient
< 0.69; slope up to 12). Contrary, the RF model greatly outperformed the step-wise approach in
all testing locations and on dierent rainfall events (correlation coecient up to 0.83; slope = 1.04).
The results are promising and unveil a dierent approach to overcome the high attenuation issues
inherent to X-band radars.
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Keywords: |
South Ecuador |
random forest |
radar |
calibration |
Cajas National Park |
Guallpa, M.; Orellana-Alvear, J. & Bendix, J. (2019): Tropical Andes Radar Precipitation Estimates Need High Temporal and Moderate Spatial Resolution. Water 11(5), 1-22.
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DOI: 10.3390/w11051038
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Abstract:
Abstract:
Weather radar networks are an excellent tool for quantitative precipitation estimation
(QPE), due to their high resolution in space and time, particularly in remote mountain areas such as
the Tropical Andes. Nevertheless, reduction of the temporal and spatial resolution might severely
reduce the quality of QPE. Thus, the main objective of this study was to analyze the impact of spatial
and temporal resolutions of radar data on the cumulative QPE. For this, data from the world’s highest
X-band weather radar (4450 m a.s.l.), located in the Andes of Ecuador (Paute River basin), and from
a rain gauge network were used. Dierent time resolutions (1, 5, 10, 15, 20, 30, and 60 min) and
spatial resolutions (0.5, 0.25, and 0.1 km) were evaluated. An optical flow method was validated
for 11 rainfall events (with dierent features) and applied to enhance the temporal resolution of
radar data to 1-min intervals. The results show that 1-min temporal resolution images are able to
capture rain event features in detail. The radar–rain gauge correlation decreases considerably when
the time resolution increases (r from 0.69 to 0.31, time resolution from 1 to 60 min). No significant
dierence was found in the rain total volume (3%) calculated with the three spatial resolution data.
A spatial resolution of 0.5 km on radar imagery is suitable to quantify rainfall in the AndesMountains.
This study improves knowledge on rainfall spatial distribution in the Ecuadorian Andes, and it will
be the basis for future hydrometeorological studies
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Keywords: |
Cuenca |
radar |
rainfall |
Paute |
Oñate-Valdivieso, F.; Fries, A.; Mendoza, K.; Gonzales-Jaramillo, V.; Pucha Cofrep, F.; Rollenbeck, R. & Bendix, J. (2017): Temporal and spatial analysis of precipitation patterns in an Andean region of southern Ecuador using LAWR weather radar. Meteorology and Atmospheric Physics 129(295), 1-12.
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DOI: 10.1007/s00703-017-0535-8
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Abstract:
Abstract:
This paper focuses on the analysis of precipitation patterns, using a Local Area Weather Radar to collect information about the precipitation distribution in an Andean region of southern Ecuador (cities of Loja, Zamora and Catamayo). 54 representative events were selected to develop daily precipitation maps and to obtain their relevant characteristics, which were related to the topography and the season. The results showed that a strong correlation between the areas covered by precipitation (RA coefficient) and the season exists. In general, humid air masses come from the east (Amazon Basin), but during the main rainy season (December to April), humidity also frequently enters the study region from the west (Pacific Ocean). The rainy season is characterized by convective precipitation, associated with higher evaporation rates during austral summer. The relatively dry season is formed between May and November, but considerable precipitation amounts are registered, too, due to advective moisture transport from the Amazon Basin, a result of the predominant tropical easterlies carrying the humidity up the eastern escarpment of the Andes, generally following the natural course of the drainage systems.
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Keywords: |
Ecuador |
precipitation |
radar |
Bendix, J.; Fries, A.; Zárate, J.; Trachte, K.; Rollenbeck, R.; Pucha Cofrep, F.; Paladines, R.; Palacios, I.; Orellana Alvear, J.; Oñate-Valdivieso, F.; Naranjo, C.; Mendoza, L.; Mejia, D.; Guallpa, M.; Gordillo, F.; Gonzales-Jaramillo, V.; Dobbermann, M.; Celleri, R.; Carrillo, C.; Araque, A. & Achilles, S. (2017): Radarnet Sur – first weather radar network in tropical high mountains. Bulletin of the American Meteorological Society 98(6), 1235-1254.
Rollenbeck, R.; Bendix, J. & Fabian, P. (2011): Spatial and temporal dynamics of atmospheric water inputs in tropical mountain forests of South Ecuador. . Hydrological Processes 25, 344 - 352.
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DOI: 10.1002/hyp.7799
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Abstract:
Abstract:
As part of an interdisciplinary research programme, the spatial and temporal variability of precipitation in southern Ecuador
has been investigated since January 2002. The study site is located at the northern margin of the Podocarpus National Park in
the vicinity of Loja, about 500 km south of Quito, at altitudes ranging from 1800 to 3200 m.a.s.l. Due to its low density, the
conventional rainfall station network fails to register the highly variable spatial distribution of rain, whereas contributions by
fog are not accounted at all. Hence, for the first time in a tropical montane forest setting, a weather radar was used, covering a
radius of 60 km and reaching from the Amazon Basin to the coastal plains of the region. Furthermore, a network of sampling
stations supplies data about the altitudinal gradient of fog and rainwater inputs. The precipitation distribution in the study
area proves to be far more variable than previously thought and is strongly coupled to the orographic characteristics and
the special topographical setting of the landscape. Maxima in precipitation occur especially in the eastern parts of the radar
range on slopes exposed to advected moisture from the Amazon Basin, whereas the highest crests of the Andes receive less
precipitation. The study area has two cloud condensation levels, occurring at 1500?2000 and 2500?3500 m.a.s.l., respectively.
At 1800?2000 m.a.s.l., fog is estimated to contribute an additional input of 5% of conventionally measured rainfall, increasing
to about 35% at the highest measurement station (3200 m.a.s.l.). In contrast to some other tropical mountains, there seems to be
no maximum zone of water input, although the gradient remains positive up to the highest altitudes. The unusual precipitation
distribution is thought to reflect the contrasting climatological influences operating in the study area.
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Keywords: |
tropical montane forest |
rain |
fog |
radar |
Rollenbeck, R. & Bendix, J. (2011): Rainfall distribution in the Andes of southern Ecuador derived from blending weather radar data and meteorological field observations. . Atmos. Res. 99, 277?289.
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DOI: 10.1016/j.atmosres.2010.10.018
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Abstract:
Abstract:
The Andes of Ecuador show an extreme heterogeneity of spatial and temporal distribution of precipitation. The existing operational network of the national weather service is not capable of reproducing these complex patterns. By using a cost-efficient rain radar and a network of high-resolution rain gauges, the real complexity of the rainfall distribution and the meteorological processes of rainfall formation can be assessed. A blendingmethod encompassing geostatistical
tools allows to derive a comprehensive rainfall climatology for the study area. Precipitation is predominantly of the advective type, associated with humid air masses from the Amazon basin transported by the tropical easterlies. The typical form is light to heavy drizzle with long duration but lower rain rates. However, in contrast to former knowledge there is no single mechanism of rain formation for any given place. Several processes interact like small and large-scale convective cloud systems, local and regional valley/mountain breeze systems and terrain-lines of preferred moisture transport interact on various time scale. This leads to complex patterns of rainfall in space and
time. Several types of characteristic weather situations are revealed by the study. They are characterized by specific combinations of local and regional atmospheric processes and interactions with the topographical configuration. They are modified by mesoscale and continental circulation patterns as the annual shift of pressure cells, the east Andean low-level Jet and katabatic flows.
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Keywords: |
precipitation |
Andes |
radar |
calibration |
climatology |