Assessment of Satellite-Based Rainfall Products Using a X-Band Rain Radar Network in the Complex Terrain of the Ecuadorian Andes

Ground based rainfall information is hardly available in most high mountain areas of the world due to the remoteness and complex topography. Thus, proper understanding of spatio-temporal rainfall dynamics still remains a challenge in those areas. Satellite-based rainfall products may help if their rainfall assessment are of high quality. In this paper, microwave-based integrated multi-satellite retrieval for the Global Precipitation Measurement (GPM) (IMERG) (MW-based IMERG) was assessed along with the random-forest-based rainfall (RF-based rainfall) and infrared-only IMERG (IR-only IMERG) products against the quality-controlled rain radar network and meteorological stations of high temporal resolution over the Pacific coast and the Andes of Ecuador. The rain area delineation and rain estimation of each product were evaluated at a spatial resolution of 11 km2 and at the time of MW overpass from IMERG. The regionally calibrated RF-based rainfall at 2 km2 and 30 min was also investigated. The validation results indicate different essential aspects: (i) the best performance is provided by MW-based IMERG in the region at the time of MW overpass; (ii) RF-based rainfall shows better accuracy rather than the IR-only IMERG rainfall product. This confirms that applying multispectral IR data in retrieval can improve the estimation of rainfall compared with single-spectrum IR retrieval algorithms. (iii) All of the products are prone to low-intensity false alarms. (iv) The downscaling of higher-resolution products leads to lower product performance, despite regional calibration. The results show that more caution is needed when developing new algorithms for satellite-based, high-spatiotemporal-resolution rainfall products. The radar data validation shows better performance than meteorological stations because gauge data cannot correctly represent spatial rainfall in complex topography under convective rainfall environments.

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Can Weather Radars Be Used to Estimate Snow Accumulation on Alpine Glaciers? An Evaluation Based on Glaciological Surveys

Journal of Hydrometeorology ◽

10.1175/jhm-d-20-0112.1 ◽

2020 ◽

Vol 21 (12) ◽

pp. 2943-2962

Author(s):

Rebecca Gugerli ◽

Marco Gabella ◽

Matthias Huss ◽

Nadine Salzmann

Keyword(s):

Snow Water Equivalent ◽

Rain Gauge ◽

Snow Accumulation ◽

Swiss Alps ◽

High Temporal Resolution ◽

High Mountain ◽

Regional Variability ◽

Spatiotemporal Resolution ◽

Weather Radars ◽

Reliable Quantification

AbstractThe snow water equivalent (SWE) is a key component for understanding changes in the cryosphere in high mountain regions. Yet, a reliable quantification at a high spatiotemporal resolution remains challenging in such environments. In this study, we investigate the potential of an operational weather radar–rain gauge composite (CombiPrecip) to infer the daily evolution of SWE on seven Swiss glaciers. To this end, we validate cumulative CombiPrecip estimates with glacier-wide manual SWE observations (snow probing, snow pits) obtained around the time of the seasonal peak during four winter seasons (2015–19). CombiPrecip underestimates the end-of-season snow accumulation by factors of 2.2 up to 3.7, depending on the glacier site. These factors are consistent over the four winter seasons. The regional variability can be mainly attributed to the empirical visibility of the Swiss radar network within the Alps. To account for the underestimation, we investigate three approaches to adjust CombiPrecip for the applicability to glacier sites. Thereby, we combine the factor of underestimation with a precipitation-phase parameterization. For further comparison, we apply a rain gauge catch-efficiency function based on wind speed. We validate these approaches with 14 manual point observations of SWE obtained on two glaciers during three winter seasons. All approaches show a similar improvement of CombiPrecip estimates. We conclude that CombiPrecip has great potential to estimate SWE on glaciers at a high temporal resolution, but further investigations are necessary to understand the regional variability of the bias throughout the Swiss Alps.

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A high-resolution multi-phase thermo-geophysical permafrost rock model to verify long-term ERT monitoring at the Zugspitze (German/Austrian Alps)

10.5194/egusphere-egu21-15231 ◽

2021 ◽

Author(s):

Tanja Schroeder ◽

Michael Krautblatter

Keyword(s):

Electrical Resistivity ◽

Energy Balance ◽

Thermal Regime ◽

Thermal Evolution ◽

High Mountain ◽

Permafrost Degradation ◽

Complex Topography ◽

Mountain Areas ◽

Permafrost Rock

<div> In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed. </div><div> We developed a new, numerical, thermo-geophysical rock permafrost model (TGRPM) to assess spatial-temporal variations of the ground thermal regime in steep permafrost rock walls on the basis of 13-years of Electrical Resistivity Tomography (ERT) monitoring of permafrost at the Zugspitze. TGRPM is a simple to understand and workable numerical 2D MATLAB-model, which is adaptable to different topographic and sub-surface conditions, and further relies on a minimum of input-data to assess the surface energy balance and the ground thermal regime. It simulates the thermal response for permafrost rock walls, including their complex topography, to climate forcing over multiple years. It aims to assess seasonal and long-term permafrost development in steep alpine rock walls, as well as serving as a straightforward calculation routine, which is solely based on physical processes and does not require any fitting of certain parameters. </div><div> At first, the model was tested against direct temperature measurements from the LfU-borehole at the Zugspitze summit to prove its accuracy. Then, it is run against a 13-year ERT data-set from the Zugspitze Kammstollen to validate the ERT measurements. </div><div> Here, we show the first thermo-geophysical model referencing thermal evolution in a permafrost rock wall with temperature-calibrated ERT. The TGRPM successfully computes the thermal evolution within the Zugspitze mountain ridge from a 2D coupled energy balance and heat conduction scheme in complex topography. It furthermore validates the temperature-resistivity relationship by Krautblatter et al. (2010) for natural rock walls reaching a correlation of 85 to 95 % between measured, ERT-derived and modelled temperatures. </div><div>Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. & Kemna, A. (2010): Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography&#160;(Zugspitze, German/Austrian Alps). J. Geophys. Res. 115: F02003.</div>

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Transient thermal effects in Alpine permafrost

The Cryosphere Discussions ◽

10.5194/tcd-2-185-2008 ◽

2008 ◽

Vol 2 (2) ◽

pp. 185-224 ◽

Cited By ~ 1

Author(s):

J. Noetzli ◽

S. Gruber

Keyword(s):

Thermal State ◽

Ground Surface ◽

Climatic Conditions ◽

Balance Model ◽

High Mountain ◽

Complex Topography ◽

Transient Effects ◽

Mountain Areas ◽

The Past ◽

Numerical Experimentation

Abstract. In high mountain areas, permafrost is important because it influences natural hazards and construction practices, and because it is an indicator of climate change. The modeling of its distribution and evolution over time is complicated by steep and complex topography, highly variable conditions at and below the surface, and varying climatic conditions. This paper presents a systematic investigation of effects of climate variability and topography that are important for subsurface temperatures in Alpine permafrost areas. The effects of both past and projected future ground surface temperature variations on the thermal state of Alpine permafrost are studied based on numerical experimentation with simplified mountain topography. For this purpose, we use a surface energy balance model together with a subsurface heat conduction scheme. The past climate variations that essentially influence the present-day permafrost temperatures at depth are the last glacial period and the major fluctuations in the past millennium. The influence of projected future warming was assessed to cause even larger transient effects in the subsurface thermal field because warming occurs on shorter time scales. Results further demonstrate the accelerating influence of multi-lateral warming in Alpine topography for a temperature signal entering the subsurface. The effects of thermal properties, porosity, and freezing characteristics were examined in sensitivity studies. A considerable influence of latent heat due to water in low-porosity bedrock was only shown for simulations over shorter time periods (i.e., decades to centuries). Finally, as an example of a real and complex topography, the modeled transient three-dimensional temperature distribution in the Matterhorn (Switzerland) is given for today and in 200 years.

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Formation Patterns of Mediterranean High-Mountain Water-Bodies in Sierra-Nevada, SE Spain

Water ◽

10.3390/w13040438 ◽

2021 ◽

Vol 13 (4) ◽

pp. 438

Author(s):

Jose Luis Diaz-Hernandez ◽

Antonio Jose Herrera-Martinez

Keyword(s):

Sierra Nevada ◽

Unknown Origin ◽

Slope Instability ◽

Water Bodies ◽

High Mountain ◽

Mountain Areas ◽

Glacial Processes ◽

The Mediterranean ◽

Water Volumes

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy this situation to some extent, we studied the water-bodies of the western sector of the Sierra Nevada massif (Spain). Since thaw is a necessary but not sufficient contributor to the formation of these fragile water-bodies, we carried out field visits to identify their number, size and spatial distribution as well as their different modelling processes. The best-defined water-bodies were the result of glacial processes, such as overdeepening and moraine dams. These water-bodies are the highest in the massif (2918 m mean altitude), the largest and the deepest, making up 72% of the total. Another group is formed by hillside instability phenomena, which are very dynamic and are related to a variety of processes. The resulting water-bodies are irregular and located at lower altitudes (2842 m mean altitude), representing 25% of the total. The third group is the smallest (3%), with one subgroup formed by anthropic causes and another formed from unknown origin. It has recently been found that the Mediterranean and Atlantic watersheds of this massif are somewhat paradoxical in behaviour, since, despite its higher xericity, the Mediterranean watershed generally has higher water contents than the Atlantic. The overall cause of these discrepancies between watersheds is not connected to their formation processes. However, we found that the classification of water volumes by the manners of formation of their water-bodies is not coherent with the associated green fringes because of the anomalous behaviour of the water-bodies formed by moraine dams. This discrepancy is largely due to the passive role of the water retained in this type of water-body as it depends on the characteristics of its hollows. The water-bodies of Sierra Nevada close to the peak line (2918 m mean altitude) are therefore highly dependent on the glacial processes that created the hollows in which they are located. Slope instability created water-bodies mainly located at lower altitudes (2842 m mean altitude), representing tectonic weak zones or accumulation of debris, which are influenced by intense slope dynamics. These water-bodies are therefore more fragile, and their existence is probably more short-lived than that of bodies created under glacial conditions.

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Interpretation of Atmospheric CO2 Measurements in Mexico City

10.5194/egusphere-egu21-15117 ◽

2021 ◽

Author(s):

Yang Xu ◽

Michel Ramonet ◽

Thomas Lauvaux ◽

Jinghui Lian ◽

Francois-Marie Bréon ◽

...

Keyword(s):

Mexico City ◽

Rural Areas ◽

Ghg Emissions ◽

Single Layer ◽

Urban Canopy ◽

Horizontal Resolution ◽

Complex Topography ◽

Urban Station ◽

Mountain Areas ◽

Mixing Ratios

The French-Mexican project Mexico City&#8217;s Regional Carbon Impacts (MERCI-CO2) is building a CO2 observation network in the Metropolitan Zone of the Valley of Mexico (ZMVM). The project investigates the atmospheric signals generated by the city's emissions on total column and surface measurements, aiming at reducing the uncertainties of CO2 emissions in ZMVM and evaluating the effects of policies that had been implemented by the city authorities.&#160;A nested high-resolution atmospheric transport simulation based on the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is performed to analyze the observed CO2 mixing ratios during dry and wet seasons over Mexico City and its vicinity. Both anthropogenic emissions (UNAM 1-km fossil fuel emissions) and biogenic fluxes (CASA 5-km simulations) are taken into account. The model configuration, with a horizontal resolution of 1km and using the Single-Layer urban canopy Model (SLUCM), has been evaluated over two weeks in January 2018 using meteorological measurements from 26 stations set by the Air Quality Agency of Mexico City (Secretary of the Environment of Mexico City - SEDEMA). The reconstruction of meteorological conditions in the urban area shows better performances than suburban and mountainous areas. Due to the complex topography, wind speeds in mountain areas are 2-3 m/s over estimated and wind direction simulations in some stations are 90&#176; deflected, especially in southern mountains.&#160;Two high-precision CO2 analyzers deployed in urban and rural areas of Mexico City are used to evaluate the WRF CO2 1-km simulations. The model reproduced the diurnal cycle of CO2 mixing ratios at the background station but under-estimates the nighttime accumulation at the urban station. Mean absolute errors of CO2 concentrations range from 6.5 ppm (background station) to 27.1 ppm (urban station), mostly driven by the elevated nocturnal enhancements (up to 500 ppm at UNAM station). Based on this analysis, we demonstrate the challenges and potential of mesoscale modeling over complex topography, and the potential use of mid-cost sensors to constrain the urban GHG emissions of Mexico City.

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Combining remote sensing and hydrological information for improving hydrological characterization of dehesas in Mediterranean mountain areas: a study case in Cardeña-Montoro Natural Park (Spain)

10.5194/egusphere-egu21-10898 ◽

2021 ◽

Author(s):

Rafael Pimentel ◽

Pedro Torralbo ◽

Javier Aparicio ◽

María José Pérez-Palazón ◽

Ana Andreu ◽

...

Keyword(s):

Remote Sensing ◽

Heat Waves ◽

A Priori ◽

Regional Government ◽

Livestock Farming ◽

Spatiotemporal Resolution ◽

Mountain Areas ◽

Natural Park ◽

Mediterranean Shrubs

Mediterranean mountain areas are especially vulnerable to changes. Climatic trends observed in the last decades point out to an increasing number of extreme events (i.e., number of heat waves and droughts) and consequently, a direct alteration of the hydrological states of their associated ecosystems. The savanna type ecosystem called dehesa is one of them. This system is the result of a long-term co-evolution of indigenous ecosystems and human settlement in a sustainable balance, with high relevance from both the environmental (biodiversity) and socioeconomic (livestock farming, including Iberian pork food industry) point of view. Dehesa systems have a complex vegetation cover structure, where isolated trees, mainly holm oak, cork oak and oak, Mediterranean shrubs, and pastures coexist. Different problems have arisen in dehesa during last years, an example of them are seca episodes, a disease of oak trees that results in drying and final death. This condition is caused by a fungus, but very likely triggered by external hydrological related conditions like air temperature and soil water content.&#160; Remote sensing techniques have been widely used as the best alternative to monitor vegetation patterns over these areas. However, the presence of clouds and the fixed spatiotemporal resolution of these sensors constitute a limitation in more local studies.This work proposes the combined use of remote sensing by both terrestrial photography and satelital sensors, and hydrometeorological information as data sources for improving the hydrological characterization of vegetation in dehesa areas. The study was carried out in the Santa Clotilde experimental area, within the Carde&#241;a-Montoro Natural Park (southern Spain). Three years of local sub-daily terrestrial photography and hydrometeorological information allowed us to define different hydrometeorological/ecohydrological indicators that are representative of key vegetation states. This local information is linked with vegetation indexes derived from high spatial resolution satellite information (i.e., Landsat TM, ETM+ and OLI (30 m x 30 m) and Sentinel-2 (10 m x 10 m) and distributed meteorological variables to extend the results from the local to the watershed scale. The promising results will be used in a short future as the basis of an advanced monitoring service where meteorological seasonal forecast information could be used to derive key indicators and help in a priori diagnosis of the system facilitating decisions making.This work has been funded by project SIERRA Seguimiento hIdrol&#243;gico de la vEgetaci&#243;n en monta&#241;a mediteRr&#225;nea mediante fusi&#243;n de sensores Remotos en Andaluc&#237;a), with the economic collaboration of the European Funding for Rural Development (FEDER) and the Office for Economy, Knowledge, Enterprises and University of the Andalusian Regional Government.

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Trapping of Organochlorine Compounds in High Mountain Lakes

The Scientific World JOURNAL ◽

10.1100/tsw.2001.320 ◽

2001 ◽

Vol 1 ◽

pp. 609-611 ◽

Cited By ~ 1

Author(s):

Joan O. Grimalt ◽

Pilar Fernandez ◽

Rosa M. Vilanova

Keyword(s):

Atmospheric Transport ◽

Mountain Lakes ◽

Organochlorine Compounds ◽

High Mountain ◽

High Latitudes ◽

High Mountain Lakes ◽

Mountain Areas ◽

Persistent Pollutants

High mountain areas have recently been observed to be polluted by organochlorine compounds (OC) despite their isolation. These persistent pollutants arrive at these remote regions through atmospheric transport. However, the mechanisms involving the accumulation of these compounds from the atmospheric pool to the lacustrine systems still need to be elucidated. These mechanisms must be related to the processes involving the transfer of these pollutant from low to high latitudes[1] as described in the global distillation effect[2].

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