Browsing by Author "Trachte, Katja"

Now showing 1 - 4 of 4

Atmosphere-surface fluxes modeling for the high Andes: the case of páramo catchments of Ecuador
(2020) Carrillo Rojas, Galo José; Schulz, Hans Martin; Orellana Alvear, Johanna Marlene; Ochoa Sánchez, Ana Elizabeth; Trachte, Katja; Célleri Alvear, Rolando Enrique; Bendix, Jorg
© 2019 Elsevier B.V. Interest in atmosphere-surface flux modeling over the mountainous regions of the globe has increased recently, with a major focus on the prediction of water, carbon and other functional indicators in natural and disturbed conditions. However, less research has been centered on exploring energy fluxes (net radiation; sensible, latent and soil heat) and actual evapotranspiration (ETa) over the Neotropical Andean biome of the páramo. The present study assesses the implementation and parameterization of a state-of-art Land-Surface Model (LSM) for simulation of these fluxes over two representative páramo catchments of southern Ecuador. We evaluated the outputs of the LSM Community Land Model (CLM ver. 4.0) with (i) ground-level flux observations from the first (and highest) Eddy Covariance (EC) tower of the Northern Andean páramos; (ii) spatial ETa estimates from the energy balance-based model METRIC (based on Landsat imagery); and (iii) derived ETa from the closure of the water balance (WB). CLM's energy predictions revealed a significant underestimation on net radiation, which impacts the sensible and soil heat fluxes (underestimation), and delivers a slight overestimation on latent heat flux. Modeled CLM ETa showed acceptable goodness-of-fit (Pearson R = 0.82) comparable to ETa from METRIC (R = 0.83). Contrarily, a poor performance of ETa WB was observed (R = 0.46). These findings provide solid evidence on the CLM's accuracy for the ETa modeling, and give insights in the selection of other ETa methods. The study contributes to a better understanding of ecosystem functioning in terms of water loss through evaporative processes, and might help in the development of future LSMs’ implementations focused on climate / land use change scenarios for the páramo.
Clustering of rainfall types using micro rain radar and laser disdrometer observations in the tropical andes
(2021) Célleri Alvear, Rolando Enrique; Orellana Alvear, Johanna Marlene; Urgilés Calle, María Gabriela; Bendix, Jorg; Trachte, Katja
Lack of rainfall information at high temporal resolution in areas with a complex topography as the Tropical Andes is one of the main obstacles to study its rainfall dynamics. Furthermore, rainfall types (e.g., stratiform, convective) are usually defined by using thresholds of some rainfall characteristics such as intensity and velocity. However, these thresholds highly depend on the local climate and the study area. In consequence, these thresholds are a constraining factor for the rainfall class definitions because they cannot be generalized. Thus, this study aims to analyze rainfall-event types by using a data-driven clustering approach based on the k-means algorithm that allows accounting for the similarities of rainfall characteristics of each rainfall type. It was carried out using three years of data retrieved from a vertically pointing Micro Rain Radar (MRR) and a laser disdrometer. The results show two main rainfall types (convective and stratiform) in the area which highly differ in their rainfall features. In addition, a mixed type was found as a subgroup of the stratiform type. The stratiform type was found more frequently throughout the year. Furthermore, rainfall events of short duration (less than 70 min) were prevalent in the study area. This study will contribute to analyze the rainfall formation processes and the vertical profile.
Global climate change impacts on local climate and hydrology
(Springer, Berlin, Heidelberg, 2013) Timbe Castro, Edison Patricio
Global climate change will most likely have a severe impact on local climate and hydrological cycling in the tropical montane rainforest. We used a simple statistical downscaling technique for eight general circulation models and two IPCC AR4 emission scenarios (A1B, A2) to forecast feasible local climate conditions for the San Francisco river basin for three future time slices (2010–2039, 2040–2069, 2070–2099). These simulations were then used as forcing data for an ensemble of seven catchment scale rainfall-runoff models to investigate the effects on local hydrological fluxes. Precipitation for both emission scenarios is expected to increase, especially in the months May and June. These increases in precipitation input will lead to even more dynamic discharges as today. However, part of the increasing water input is compensated by raising evapotranspiration due to higher temperatures. Finally, we give an outlook on feasible future trends of water-related ecosystem services under climate change.
Precipitation characteristics at two locations in the tropical andes by means of vertically pointing micro-rain radar observations
(2019) Seidel, Jochen; Huggel, Christian; Célleri Alvear, Rolando Enrique; Bendix, Jorg; Fernández Rosales, Ciro Walter; Figueroa Tauquino, Rafael; Orellana Alvear, Johanna Marlene; Trachte, Katja
© 2019 by the authors. In remote areas with steep topography, such as the Tropical Andes, reliable precipitation data with a high temporal resolution are scarce. Therefore, studies focusing on the diurnal properties of precipitation are hampered. In this paper, we investigated two years of data from Micro-Rain Radars (MRR) in Cuenca, Ecuador, and Huaraz, Peru, from February 2017 to January 2019. This data allowed for a detailed study on the temporal precipitation characteristics, such as event occurrences and durations at these two locations. Our results showed that the majority of precipitation events had durations of less than 3 h. In Huaraz, precipitation has a distinct annual and diurnal cycle where precipitation in the rainy season occurred predominantly in the afternoon. These annual and diurnal cycles were less pronounced at the site in Cuenca, especially due to increased nocturnal precipitation events compared to Huaraz. Furthermore, we used a fuzzy logic classification of fall velocities and rainfall intensities to distinguish different precipitation types. This classification showed that nightly precipitation at both locations was predominantly stratiform, whereas (thermally induced) convection occurred almost exclusively during the daytime hours.