scholarly journals Measuring and modelling evapotranspiration in a South African grassland: Comparison of two improved Penman-Monteith formulations

Water SA ◽  
2018 ◽  
Vol 44 (3 July) ◽  
Author(s):  
Onalenna Gwate ◽  
Sukhmani K Mantel ◽  
Anthony R Palmer ◽  
Lesley A Gibson ◽  
Zahn Munch
Keyword(s):  
South African ◽  
Climate Models ◽  
Meteorological Data ◽  
Area Index ◽  
Use Of Data ◽  
Model Predictions ◽  
The Mean ◽  
Study Sites ◽  
Atmospheric Changes

Accurately measuring evapotranspiration (ET) is important in the context of global atmospheric changes and for use with climate models. Direct ET measurement is costly to apply widely and local calibration and validation of ET models developed elsewhere improves confidence in ET derived from such models. This study sought to compare the performance of the Penman-Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) ET models, over mesic grasslands in two study sites in South Africa. The study used routine meteorological data from a scientific-grade automatic weather station (AWS) to apply the PML and PMP models. The PML model was calibrated at one site and validated in both sites. On the other hand, the PMP model does not require calibration and hence it was validated in both sites. The models were validated using ET derived from a large aperture scintillometer (LAS). The PML model performed well at both sites with root mean square error (RMSE) within 20% of the mean daily observed ET (R2 of 0.83 to 0.91). Routine meteorological data were able to reproduce fluxes calculated using micrometeorological techniques and this increased the confidence in the use of data from sparsely distributed AWSs to derive reasonable ET values. The PML model was better able to simulate observed ET compared to the PMP model, since the former models both transpiration and soil evaporation (ES), while the latter only models transpiration. Hence, the PMP model systematically underestimated ET in a context where the leaf area index (LAI) was < 2.5. Model predictions in the grasslands could be improved by incorporating the ES component in the PMP model while the PML model could be improved by careful choice of the number of days to be used in the determination of the fraction of ES.

scholarly journals Potential Fertilization Capacity of Two Grapevine Varieties: Effects on Agricultural Production in Designation of Origin Areas in the Northwestern Iberian Peninsula

Agronomy ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 961
Author(s):  
J. Antonio Cortiñas Rodríguez ◽  
María Fernández-González ◽  
Estefanía González-Fernández ◽  
Rosa A. Vázquez-Ruiz ◽  
F. Javier Rodríguez-Rajo ◽  
...  
Keyword(s):  
Airborne Pollen ◽  
Germination Rate ◽  
Pollen Viability ◽  
Weather Conditions ◽  
Triphenyl Tetrazolium Chloride ◽  
Tetrazolium Chloride ◽  
The Mean ◽  
Study Sites ◽  
Fertilization Capacity

In the present study, we analyzed the main parameters related with the potential fertilization ability of two grapevine varieties, Godello and Mencía, during the years 2017 and 2018. The research was carried out in two vineyards of the Galician winegrowing Designation of Origin areas of Ribeiro and Ribeira Sacra. Ten vines of each variety were selected for bunch and flower counting, pollen calculations, pollen viability studies by means of aceto-carmine (AC) stain and 2, 3, 5-triphenyl tetrazolium chloride (TTC) methods, and the determination of their germination rate. In all vineyards the 50% fruitset was reached, except for Godello in Cenlle during 2017. The mean coulure value was higher for Godello (40.5%) than for Mencía (31%). Analyzing the pollen production per plant and airborne pollen levels, we observed important discordances between them, which can be due to the influence of weather conditions and be related with self-pollination processes. We found important differences on pollen viability depending on the applied method and variety, with higher values for the AC method than the TTC for both varieties in all study plots, and higher values for Mencía variety than Godello. Regarding germination rates, we observed a marked reduction in 2017 with respect to 2018, in all study sites and for both varieties. The analyzed parameters were useful to explain the different productive abilities of Godello and Mencía varieties in the two studied bioclimatic regions of Ribeiro and Ribeira Sacra.

scholarly journals MODELING AND SIMULATION OF RELIEF INFLUENCE ON EUCALYPTUS FORESTS: INTERACTION BETWEEN SOLAR IRRADIANCE AND PRODUCTIVITY

2016 ◽  
Vol 40 (2) ◽  
pp. 319-327
Author(s):  
Yhasmin Paiva Rody ◽  
Aristides Ribeiro ◽  
Aline Santana de Oliveira ◽  
Fernando Palha Leite
Keyword(s):  
Solar Radiation ◽  
Meteorological Data ◽  
Geographical Location ◽  
Area Index ◽  
Model Simulations ◽  
Incident Solar Radiation ◽  
Eucalyptus Forest ◽  
Vertical Location ◽  
Weather Stations ◽  
Study Sites

ABSTRACT This study aimed to verify the differences in radiation intensity as a function of distinct relief exposure surfaces and to quantify these effects on the leaf area index (LAI) and other variables expressing eucalyptus forest productivity for simulations in a process-based growth model. The study was carried out at two contrasting edaphoclimatic locations in the Rio Doce basin in Minas Gerais, Brazil. Two stands with 32-year-old plantations were used, allocating fixed plots in locations with northern and southern exposure surfaces. The meteorological data were obtained from two automated weather stations located near the study sites. Solar radiation was corrected for terrain inclination and exposure surfaces, as it is measured based on the plane, perpendicularly to the vertical location. The LAI values collected in the field were used. For the comparative simulations in productivity variation, the mechanistic 3PG model was used, considering the relief exposure surfaces. It was verified that during most of the year, the southern surfaces showed lower availability of incident solar radiation, resulting in up to 66% losses, compared to the same surface considered plane, probably related to its geographical location and higher declivity. Higher values were obtained for the plantings located on the northern surface for the variables LAI, volume and mean annual wood increase, with this tendency being repeated in the 3PG model simulations.

Use of satellite-based sensing in land surface climatology

1994 ◽  
Vol 18 (1) ◽  
pp. 1-15 ◽  
Author(s):  
David Greenland
Keyword(s):  
Satellite Data ◽  
Land Surface ◽  
Climate Models ◽  
Climate Model ◽  
Meteorological Data ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Climate Modelling ◽  
Area Index ◽  
Surface Climate

Common types of satellite-derived measurements are reviewed with respect to how they are used to provide information on variables important to land surface climatology. The variables considered include solar radiation, surface albedo, surface temperature, outgoing longwave radiation, cloud cover, net radiation, soil moisture, latent and sensible heat flux, surface cover and leaf area index. A selection of land surface climate modelling schemes is identified and considered with a view to their practicality for use with satellite-derived data. Issues arising from the foregoing considerations include the absence from satellite data of some variables required by land surface climate models, the importance of extreme pixel values in model parameterization, the importance of matching spatial resolution in satellite data and climate model, and the need to have concurrent, independently observed, meteorological data in order to make full use of the satellite data.

scholarly journals Determination of the interannual variability of the Bering Strait transport from satellite data

1993 ◽  
Vol 17 ◽  
pp. 207-210
Author(s):  
T.J Irwin ◽  
S. Martin ◽  
E.A. Munoz
Keyword(s):  
Interannual Variability ◽  
Chukchi Sea ◽  
Meteorological Data ◽  
Bering Strait ◽  
Volume Flux ◽  
Additional Heat ◽  
Flow Through ◽  
The Mean ◽  
The Laptev Sea

For the years 1980–88, we use satellite and meteorological data from the Chukchi and Laptev Seas to estimate the volume flux into the Chukchi Sea through the Bering Strait. We assume that the two seas have approximately the same amount of stored heat at the onset of freezing, then calculate the heat loss from both seas during the period from the onset of freezing to the formation of a solid ice cover. Because the Chukchi Sea generally takes 4–6 weeks longer to freeze over than the Laptev Sea, more heat is lost to the atmosphere from the Chukchi Sea than from the Laptev. On the assumption that the only source of this additional heat from the Chukchi is the Bering Strait inflow, and using published values for the mean temperature of the Bering Strait water, we calculate that the flow through the Bering Strait lies in the range of 0.5–1.5 Sverdrups, which is comparable to values cited in the literature. This procedure suggests a technique for determination of the interannual variability of the Bering Strait inflow.

scholarly journals On the Effective Number of Climate Models

2011 ◽  
Vol 24 (9) ◽  
pp. 2358-2367 ◽  
Author(s):  
Christopher Pennell ◽  
Thomas Reichler
Keyword(s):  
Climate Models ◽  
Future Climate Change ◽  
Effective Number ◽  
Coupled Models ◽  
Underlying Assumption ◽  
New Information ◽  
Independent Information ◽  
Model Predictions ◽  
The Mean ◽  
Multimodel Ensembles

Abstract Projections of future climate change are increasingly based on the output of many different models. Typically, the mean over all model simulations is considered as the optimal prediction, with the underlying assumption that different models provide statistically independent information evenly distributed around the true state. However, there is reason to believe that this is not the best assumption. Coupled models are of comparable complexity and are constructed in similar ways. Some models share parts of the same code and some models are even developed at the same center. Therefore, the limitations of these models tend to be fairly similar, contributing to the well-known problem of common model biases and possibly to an unrealistically small spread in the outcomes of model predictions. This study attempts to quantify the extent of this problem by asking how many models there effectively are and how to best determine this number. Quantifying the effective number of models is achieved by evaluating 24 state-of-the-art models and their ability to simulate broad aspects of twentieth-century climate. Using two different approaches, the amount of unique information in the ensemble is calculated and the effective ensemble size is found to be much smaller than the actual number of models. As more models are included in an ensemble, the amount of new information diminishes in proportion. Furthermore, this reduction is found to go beyond the problem of “same center” models and systemic similarities are seen to exist across all models. The results suggest that current methodologies for the interpretation of multimodel ensembles may lead to overly confident climate predictions.

scholarly journals Determination of the interannual variability of the Bering Strait transport from satellite data

1993 ◽  
Vol 17 ◽  
pp. 207-210
Author(s):  
T.J Irwin ◽  
S. Martin ◽  
E.A. Munoz
Keyword(s):  
Interannual Variability ◽  
Chukchi Sea ◽  
Meteorological Data ◽  
Bering Strait ◽  
Volume Flux ◽  
Additional Heat ◽  
Flow Through ◽  
The Mean ◽  
The Laptev Sea

For the years 1980–88, we use satellite and meteorological data from the Chukchi and Laptev Seas to estimate the volume flux into the Chukchi Sea through the Bering Strait. We assume that the two seas have approximately the same amount of stored heat at the onset of freezing, then calculate the heat loss from both seas during the period from the onset of freezing to the formation of a solid ice cover. Because the Chukchi Sea generally takes 4–6 weeks longer to freeze over than the Laptev Sea, more heat is lost to the atmosphere from the Chukchi Sea than from the Laptev. On the assumption that the only source of this additional heat from the Chukchi is the Bering Strait inflow, and using published values for the mean temperature of the Bering Strait water, we calculate that the flow through the Bering Strait lies in the range of 0.5–1.5 Sverdrups, which is comparable to values cited in the literature. This procedure suggests a technique for determination of the interannual variability of the Bering Strait inflow.

In vitro determination of the skin anti-aging potential of eleven South African plants

Planta Medica ◽  
2013 ◽  
Vol 79 (13) ◽  
Author(s):  
GN Ndlovu ◽  
G Fouche ◽  
W Cordier ◽  
V Steenkamp ◽  
M Tselanyane
Keyword(s):  
South African ◽  
South African Plants ◽  
African Plants

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

Determination of Plasminogen in Clots and Thrombi

1966 ◽  
Vol 16 (01/02) ◽  
pp. 038-050 ◽  
Author(s):  
Ulla Hedner ◽  
Inga Marie Nilsson ◽  
B Robertson
Keyword(s):  
Mean Value ◽  
Main Mechanism ◽  
Clot Lysis ◽  
Post Mortem ◽  
Digestion Time ◽  
Normal Volunteers ◽  
Casein Solution ◽  
The Mean

SummaryThe plasminogen content was determined by a casein method in plasma and serum from 20 normal volunteers. The mean plasminogen content was found to be 10.1 ACU (the arbitrary caseinolytic unit defined in such a way that using a 3% casein solution and a digestion time of 20 min. at 37°C, 10 ACU gave an extinction of 0.300). No difference between serum and plasma regarding the plasminogen content was found.Plasminogen was determined in drained and drained plus washed clots prepared from 2 ml plasma. The highest values found in the drained clots were 0.9 ACU/clot and 0.2 ACU/clot in the drained plus washed clots.Plasminogen was also determined in drained and drained plus washed clots prepared from plasma with added purified plasminogen. The plasminogen was recovered in the washing fluid. According to these tests, then, purified added plasminogen is washed out of the clots.The plasminogen content of 20 thrombi obtained post mortem was also determined. The mean value was found to be 0.7 ACU/cm thrombus. Judging from our results, the “intrinsic clot lysis theory” is not the main mechanism of clot dissolution.

SERUM TRIIODOTHYRONINE DETERMINATION BY SATURATION ANALYSIS

1973 ◽  
Vol 72 (4) ◽  
pp. 714-726 ◽  
Author(s):  
A. Burger ◽  
B. Miller ◽  
C. Sakoloff ◽  
M. B. Vallotton
Keyword(s):  
Ionic Strength ◽  
Limit Of Detection ◽  
Improved Method ◽  
Accuracy Of Measurement ◽  
Tracer Amount ◽  
The Mean ◽  
Physiological Values ◽  
Hyperthyroid Patients ◽  
Solvent Blank

ABSTRACT An improved method for the determination of serum triiodothyronine (T3) has been developed. After addition of a tracer amount of the hormone, T3 was extracted from 1 ml serum under conditions of pH and ionic strength which favoured T3 extraction (89%) over thyroxine (T4) extraction (58%). Chromatography of the extracted material on Sephadex LH-20 separated T3 completely from residual T4. The T3 eluate was dried, then re-dissolved in 0.5 ml NaOH 0.04 n. To 0.2 ml duplicate aliquots, a standard amount of TBG was added for the competitive protein analysis. After one hour incubation at 4°C, separation of bound from free T3 was achieved on small Sephadex G-25 columns. Overall recovery was 67 ± 10.8% and correction for the loss was made. The solvent blank was 37 ± 27 (sd) ng/100 ml. Accuracy of measurement of known quantities of T3 added to serum was 98.4%. The coefficient of variation within the assay was 6.2% and between the assays it was 11.4%. The limit of detection (0.1 ng) corresponded to a concentration of 25 ng/100 ml. T4 added to serum did not interfere with T3 determination until high non-physiological values were reached. The mean ± sd serum T3 in 54 euthyroid subjects was 153 ± 58 ng/100 ml and in 24 hyperthyroid patients it was 428 ±186 ng/100 ml; 4 out of the 24 hyperthyroid values were within 2 sd of the mean euthyroid group. All the values found in the euthyroid group were well above the limit of detection of the method.

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