Analysis of effective resistance calculation methods and their effect on modelling evapotranspiration in two different patches of vegetation in semi-arid SE Spain

International audienceEffective parameters are of major importance in modelling surface fluxes at different scales of spatial heterogeneity. Different ways to obtain these effective parameters for their use in meso-scale and GCM models have been studied. This paper deals with patch-scale heterogeneity, where effective resistances were calculated in two patches with different vegetation (Retama sphaerocarpa (L.) Boiss shrubs, and herbaceous plants) using different methods: aggregating soil and plant resistances in parallel, in series or by an average of both. Effective aerodynamic resistance was also calculated directly from patch fluxes. To assess the validity of the different methods used, the Penman-Monteith equation was used with effective resistances to estimate the total ?E for each patch. The ?E estimates found for each patch were compared to Eddy Covariance system measurements. Results showed that for effective surface resistances, parallel aggregation of soil and plant resistances led to ?E estimates closer to the measured ?E in both patches (differences of around 10%). Results for effective aerodynamic resistances differed depending on the patch considered and the method used to calculate them. The use of effective aerodynamic resistances calculated from fluxes provided less accurate estimates of ?E compared to the measured values, than the use of effective aerodynamic resistances aggregated from soil and plant resistances. The results reported in this paper show that the best way of aggregating soil and plant resistances depends on the type of resistance, and the type of vegetation in the patch

Analysis of effective resistance calculation methods and their effect on modelling evapotranspiration in two different patches of vegetation in semi-arid SE Spain

Effective parameters are of major importance in modelling surface fluxes at different scales of spatial heterogeneity. Different ways to obtain these effective parameters for their use in meso-scale and GCM models have been studied. This paper deals with patch-scale heterogeneity, where effective resistances were calculated in two patches with different vegetation (Retama sphaerocarpa (L.) Boiss shrubs, and herbaceous plants) using different methods: aggregating soil and plant resistances in parallel, in series or by an average of both. Effective aerodynamic resistance was also calculated directly from patch fluxes. To assess the validity of the different methods used, the Penman-Monteith equation was used with effective resistances to estimate the total λE for each patch. The λE estimates found for each patch were compared to Eddy Covariance system measurements. Results showed that for effective surface resistances, parallel aggregation of soil and plant resistances led to λE estimates closer to the measured λE in both patches (differences of around 10%). Results for effective aerodynamic resistances differed depending on the patch considered and the method used to calculate them. The use of effective aerodynamic resistances calculated from fluxes provided less accurate estimates of λE compared to the measured values, than the use of effective aerodynamic resistances aggregated from soil and plant resistances. The results reported in this paper show that the best way of aggregating soil and plant resistances depends on the type of resistance, and the type of vegetation in the patch.This work received financial support from several different research projects: the PROBASE (ref.: CGL2006-11619/HID) and CANOA (ref.: CGL2004-04919-C02-01/HID) projects funded by the Spanish Ministry of Education and Science; and the BACAEMA (“Balance de carbono y de agua en ecosistemas de matorral mediterráneo en Andalucía: Efecto del cambio climático”, RNM-332) and CAMBIO (“Efectos del cambio global sobre la biodiversidad y el funcionamiento ecosistémico mediante la identificación de áreas sensibles y de referencia en el SE ibérico”, RNM 1280) projects funded by the regional government Junta de Andalucía. The first author enjoyed a pre-doctoral grant from the Spanish Ministry of Science and Technology

Asimilación de fuentes de carbono en cepas de saccharomyces: resultados comparativos con tres métodos

Los métodos API, MINITEK.y BEIJERINCK fueron usados en los ensayos de asimilación de glucosa, galactosa, sacarosa, maltosa, lactosa de 8 cepas de saccharomyces, a fin de verificar y analizar la reproductibilidad e implicaciones de los resultados obtenidos con esos métodos. Los resultados de asimilación de glucosa fueron idénticos con los tres métodos, habiendo variado los demás. La mayor variación fue registrada en el método API y menor en MINITEK; en BEIJERINCK hubo mayor constancia en los resultado

Homemade rovs – make yours own

Based in handy material, available in local stores, it can be build a remote operated vehicle (ROV) fully operative as the user needs. The total cost of a homemade ROV is between 80 and 400 euros, variable according to installed accessories. The vehicle limitation will be your ability on the construction and seawater pressure. These ROVs can be used only in the first meters of the water column.Peer Reviewe

Teledetección de aerosoles Saharianos con fines sanitarios

Ponencia presentada en: 1er Encuentro sobre Meteorología y Atmósfera de Canarias, celebrado en el Puerto de la Cruz, los días 12,13 y 14 de noviembre de 2003. El encuentro estuvo organizado por el Centro Meteorológico Territorial en Canarias Occidental, con la colaboración del Observatorio Atmosférico de Izaña y del Grupo de Física de la Atmósfera de la Facultad de Física (Universidad de La Laguna)Utilizamos datos de satélite para estimar las frecuencias e intensidades de entradas de Calima en Canarias y emplear esa información como medida preventiva en los enfermos asmáticos. Para el período comprendido entre los años 1997-2000, se procesaron imágenes de satélite y se analizaron los datos de espesor óptico. Se obtuvieron valores característicos para la frecuencia y variación en magnitud de días con presencia de Calima , y su relación con los cambios meteorológicos y climáticos. Paralelamente se realizó un estudio estadístico con los casos de individuos atendidos de enfermedades alérgicas de tipo respiratorio en los servicios de urgencias del hospital Dr. Negrín de Gran Canaria . Los máximos de espesor óptico y el aumento en casos atendidos clínicamente coinciden en la época del año y ambos aumentan en el 2000 con respecto a años anteriores. Se concluye en que sería de gran utilidad el establecer y pronosticar un parámetro de riesgo ambiental en base a medidas de satélite

Morfología Fluvial.-Obtención de la conductancia de la vegetación a partir de índices espectrales y temperatura superficial para la estimación de la evapotranspiración en vegetación semiárida

This work evaluates the possibilities for estimating stomatal conductance (C) and leaf transpiration (Trf) at the ecosystem scale from radiometric indices and surface temperature. The relationships found between indices and the transpiration component of the water balance in a semiarid tussock ecosystem in SE Spain are discussed. Field data were collected from spring 2008 until winter 2009 in order to observe the annual variability of the relationships and the behaviour of spectral indices and surface temperature. The results showed that best relationships with leaf transpiration were found with the PRI index and the Red-Green ratio (r2 > 0.86 for both), and with the vegetation temperature minus the air temperature (Tc – Ta) (r2= 0.54). For stomatal conductance, several indices showed good agreement (r2 > 0.7) with measurements, TCARI/OSAVI, NDWI, SRWI, R760 / R500 and R800 / R470 indices. These results showed the applicability of remote sensing data to monitor complex ecophysiological variables at field scale

Seasonality of net carbon exchanges of Mediterranean ecosystems across an altitudinal gradient

In the present climate change context it is important to understand the carbon balance seasonality of Mediterranean areas, that will suffer important changes in precipitation according to the last climate change predictions. This work analyzed the seasonality of carbon exchanges of three Mediterranean ecosystems according to a variety of water and temperature regimes due to differences in altitude (alpine, subalpine and lowland). Results show that the timing and duration of the growing season depended on temperature at the alpine site, while the dependence on water availability increased as altitude decreased. Thus, maximum values of net carbon uptake occurred in late spring for the alpine and subalpine sites (up to 60 and 30 gC

Morfología Fluvial.-Dew contribution to the water balance in a semiarid coastal steppe ecosystem (Cabo de Gata, SE Spain)

ABSTRACT Dewfall deposition can be a significant source of moisture in arid and semiarid ecosystems, thus contributing to improve daily and annual water balances.. Occurrence, frequency and amount of dewfall were measured in the Balsa Blanca site (Cabo de Gata, Almería, Spain) from January 2007 to May 2008. This area has a sparse vegetation cover dominated by Stipa tenaccisima combined with bare soil and biological soil crusts. Wetness sensors were used to detect occurrence and frequency of dew events. The singlesource Penman—Monteith equation simplified for water condensation was used to calculate dew amount. Micro-meteorological conditions during dew formation were also measured. Dew condensation was recorded over 98% of nights during the study period. Dewfall length varied from 1 to 16 hours per day with an average of 6.3 ±0.5.hours per day. Average dew amount was 15.6±.0.34 g H2O m-2.h-1 showing a relatively small variability throughout the year. Therefore dew amount was mostly dependent on dew duration. Dew episodes were longer in late autumn and winter and decreases along spring. Annual dewfall was 30.5 mm in 2007, which represents 15% of total rainfall. 2007 was a relatively wet year with 280 mm rainfall. Comparing contribution of dew to the local water balance during a wet (January-May 2007, 120 mm rainfall) and dry period (January-May 2008, 15 mm rainfall), we have found a dew contribution of 15% in 2007 and 128% in 2008. These results highlight the relevance of dew as a relatively small but constant source of water in arid ecosystems, as well as its significant contribution to the local water balance mainly during dry periods

Ventilation of subterranean CO₂ and Eddy covariance incongruities over carbonate ecosystems

Measurements of CO₂ fluxes with Eddy Covariance (EC) systems are ongoing over different ecosystems around the world, through different measuring networks, in order to assess the carbon balance of these ecosystems. In carbonate ecosystems, characterized by the presence of subterranean pores and cavities, ventilation of the CO₂ accumulated in these cavities and pores can act as an extra source of CO₂ exchange between the ecosystem and the atmosphere. In this work we analyse the effect of the subterranean heterogeneity of a carbonate ecosystem on measurements of CO₂ fluxes by comparing measurements from two EC systems with distinct footprints. Results showed that both EC systems agreed for measurements of evapotranspiration and of CO₂ in periods when respiratory and photosynthetic processes were dominant (biological periods), with a regression slope of 0.99 and 0.97, respectively. However, in periods when the main source of CO₂ comes from the ventilation of subterranean pores and cavities (abiotic periods) agreement is not good, with a regression slope of 0.6. Ground-penetrating radar measurements of the sub-surface confirmed the existence of high sub-surface heterogeneity that, combined with different footprints, lead to differences in the measurements of the two EC systems. These results show that measurements of CO₂ fluxes with Eddy covariance systems over carbonate ecosystems must be taken carefully, as they may not be representative of the ecosystem under consideration