scholarly journals Generation of Daily Synthetic Series of Inflow Volume to the Las Cruces Dam, Nay., Mexico, Using the Svanidze Method

10.29007/2pj3 ◽  
2018 ◽  
Author(s):  
Itzel Velazquez ◽  
Maritza Arganis ◽  
Ramón DomÍnguez Mora ◽  
Rosalva Mendoza Ramírez ◽  
Eliseo Carrizosa Elizondo

The generation of synthetic series is important for simulations of the behavior in the long term of a reservoir or systems of them. The Svanidze method is easy to use to generate periodic time series for a selected period of time (monthly, fortnightly, weekly). Compared with other methods (eg PAR, PARMA) this method does not require a normal distribution assumption for the series. In this work the Svanidze method was applied to obtain synthetic series of the daily inflow volume to the Las Cruces hydroelectric project, located in the state of Nayarit, Mexico; with this method we achieve the objective of reproducing the behavior of the historical series at least in its first moment (the mean). In addition, similar correlation coefficient are observed from one day to the next with respect to what happened historically.

2020 ◽  
Author(s):  
Sara Rubinetti ◽  
Carla Taricco ◽  
Davide Zanchettin ◽  
Enrico Arnone ◽  
Angelo Rubino

<p>The city of Venice (Northern Italy), together with its lagoon, is a historic, cultural and artistic heritage of inestimable value. One of its peculiarities consists in the recurrent storm surge phenomena, referred to as <em>acqua alta</em>. Sea level rise and local subsidence made their frequency to increase dramatically with respect to the past, causing severe damages to the lagoon and in particular to the city centre, as during the exceptional high tide verified on November 12, 2019.<br>Here we show the analysis of the historical time series of tidal maxima and minima recorded in the Venetian lagoon, covering the period 1872-2018. It is the longest and most complete historical series of the Venetian area and one of the longest records of the entire Mediterranean region. During this period, the relative sea level height has increased of about 30 cm with respect to the reference level, while the average number of <em>acqua alta</em> events – evaluated over a 40-year time interval - has passed from about 4 to 70 per year. These events usually occur during the fall season (from October to December), even if a not negligible number has been also recorded during winter. Therefore, we analyse the October-March average annual time series with advanced spectral analysis methods, like Monte Carlo Singular Spectrum Analysis (MC-SSA), to extract and reconstruct the significant variability modes characterizing the record. They are the increasing long-term trend and components with multidecadal, decadal and interannual periods. The trend results from the superposition on the global eustacy of the local subsidence affecting the Venetian lagoon, which is due to both natural causes and human activities. We also discuss the possible linkage of the other significant spectral components to large scale climatic patterns. In particular, the decadal-scale oscillation is one of the most important variability modes affecting Northern Italian hydrology.<br>Finally, we apply simple statistical methods (autoregressive models and feed-forward neural networks) to forecast the long-term evolution of sea level over the next ten years. In this contribution, we illustrate results from this state of the art two-fold statistical prediction system that provides robust predictions of sea level in the Venetian lagoon for the next decade and discuss them in the light of current longer-term projections of future sea level rise. Finally, we will test the predictive skill of the applied methods using tidal measurements recorded during 2019, to verify if our predictions are able to describe tidal variability characterizing the current year.       </p>


2008 ◽  
Vol 65 (3) ◽  
pp. 523-534 ◽  
Author(s):  
Geir Ottersen

The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series on spawners biomass by age class for Arcto-Norwegian cod (Gadus morhua) from 1913–2004, I have documented pronounced changes in the spawning stock, including a trend towards younger fish, a less diverse distribution across ages, and a declining proportion of repeat spawners. Despite the total spawning stock biomass (SSB) being at similar levels now as in 1933, the mean age in the SSB has declined from 10–12.5 years to 7–8 years during the study period, and the percentage of fish of age 10 or above in the SSB has decreased from ~97% to ~10%. Contrary to earlier theoretical and experimental studies, no clear link between age structure and recruitment was found here. Recruitment to the Arcto-Norwegian cod stock may thus be more robust towards spawner juvenation than expected, possibly because of strong recruitment compensation.


2016 ◽  
Vol 185 (2) ◽  
pp. 228-239
Author(s):  
Vladimir M. Pishchalnik ◽  
Valery A. Romanyuk ◽  
Igor G. Minervin ◽  
Alevtina S. Batuhtina

The time-series for the ice cover dynamics in the Okhotsk Sea in the period from 1882 to 2015 are reconstructed on the base of shipboard, airborne, and satellite observations and measurements of the air temperature at the coastal meteorological stations. Abnormality of the ice conditions is estimated relative to the “climate norm” determined as the mean seasonal variation for the 1961-1990. Long-term variability of the ice cover is analyzed. Its regime shift with change of trend is revealed in the late 1970s - early 1980s that corresponds to the regime shift of the air temperature variability in the northern hemisphere.


Author(s):  
G. C. Hays ◽  
A. J. Warner

The mean annual towing speed of the Continuous Plankton Recorder (CPR) varied systematically between 1946 and 1991. By mounting a pressure transducer on the CPR to record towing depth, it was shown, however, that changes in towing speed did not cause a significant change in towing depth, although the mean towing depth (6–7 m, SD=l-7 m, N=77) was shallower than the previously assumed towing depth of 10 m. Thus the observed changes in towing speed are unlikely to have caused discontinuities in the CPR time-series by affecting sampling depth.Long-term data sets play an important role in attempts to understand the causes of fluctua- tions in plankton abundance. The Continuous Plankton Recorder (CPR) survey provides multi- decadal information on plankton abundance in the North Sea and North Atlantic (McGowan, 1990), and is one of the longest standing marine plankton abundance time-series. However, while the CPR time-series has great potential, as with all other data sets spanning many years, questions may be asked regarding the consistency with which the data have been collected and hence the true continuity of the time-series.


1993 ◽  
Vol 50 (10) ◽  
pp. 2157-2165 ◽  
Author(s):  
Marc Trudel ◽  
Daniel Boisclair

We tested the hypothesis that the mean quantity food consumed by fish in situ does not vary significantly over successive days. The daily ration of minnows (Phoxinus eos × P. neogaeus) was estimated over 5–12 consecutive days (June 1–5, July 6–17, and August 3–9, 1992). Mean daily ration ranged from 0.60 to 1.32 g dry∙100 g wet−1∙d−1 and varied significantly over consecutive days in June and July, but not in August. Average day-to-day variation in food consumption rates ranged from 7.0 to 16.3%. Mean daily ration was not influenced by either water temperature or percent cloudiness. Simulated long-term consumption rates of minnows did not vary by more than 19.3% among sampling intervals ranging from 1 to 30 d. We conclude that long-term consumption rates can be accurately determined using time series of daily ration estimated at 3- to 4-wk intervals.


Neurosurgery ◽  
2012 ◽  
Vol 71 (6) ◽  
pp. 1139-1148 ◽  
Author(s):  
Lucia Schwyzer ◽  
Chun-Po Yen ◽  
Avery Evans ◽  
Sebastian Zavoian ◽  
Ladislau Steiner

ABSTRACT BACKGROUND: The effectiveness and risk of Gamma Knife surgery (GKS) in the management of partially embolized cerebral arteriovenous malformations (AVMs) remain to be elucidated. OBJECTIVE: To evaluate the long-term imaging and clinical outcomes of GKS in AVM patients who had undergone previous partial embolization and compare the results with patients treated with GKS alone. METHODS: A total of 215 embolized AVMs were analyzed. The mean patient age was 32.9 years. The mean volume of the nidus was 4.6 mL (range, 0.1-29.4 mL), and the mean prescription dose was 19.6 Gy (range, 4-28 Gy). This group was compared with 729 nonembolized AVMs. RESULTS: After embolization and GKS, angiographically confirmed total obliteration of the AVMs was significantly lower (33%) compared with patients in whom GKS was used alone (60.9%; P < .001). However, the mean nidus size was larger and the Spetzler-Martin grade was higher for the embolized AVMs compared with the nonembolized AVMs. Radiation-induced changes occurred more often in the embolized (43.4%) than the nonembolized (33.4%) AVMs (P = .028). Permanent neurological deficits associated with radiation-induced changes occurred in 2.7% of the embolized compared with 1.3% of the nonembolized patients (P = .14). CONCLUSION: In our retrospective and historical series, the long-term results suggest that the obliteration rate is significantly lower in embolized AVMs compared with nonembolized AVMs, also because of the fact that the combined treatment is applied to higher grade AVMs; the percentage of grade III-V AVMs was 58.6% and 48.8% for nonembolized AVMs.


Author(s):  
Ruby Mae Ebuna Maliberan

The study attempted to forecast the number of tourist arrival in the province of Surigao del Sur using the historical monthly tourist arrival data from 2012-2016 using three time series. Findings showed that the tourist arrival in the province is likely to be increasing. As more foreign and local tourist arrivals are expected as a result of forecast model. Furthermore, it showed that there was a long term increasing trend of the tourist arrival in the province. Results revealed that the Mean Absolute Percentage Error (MAPE) of the forecasted tourist arrival data yielded an error of 11 % which means that predicted data is closer to the actual data. Based on the findings of the study, the researcher recommends that this study can be adapted by other Tourism Office of CARAGA, Philippines. 


2012 ◽  
Vol 1 (33) ◽  
pp. 60 ◽  
Author(s):  
Haijiang Liu ◽  
Makoto Arii ◽  
Shinji Sato ◽  
Yoshimitsu Tajima

A four-year evaluation of the nearshore morphology based on video imagery was conducted in the Miyazaki coast, Japan. An automatic nearshore bathymetry mapping technique was developed based on the linear wave dispersion relationship, in which the wave phase velocity was estimated from the cross-correlation of neighboring pixels’ brightness time series. Bathymetry estimation was carried out at both low and high tide levels of each day and integrated over a 7-day period which includes both the neap and spring tides. Model validation shows the present technique reproduced the ground truth data fairly well with a bias generally less than 0.3 m in the surf zone. In total, 88 bathymetry data were obtained within the investigation period. Subsequently, a two dimensional Empirical Orthogonal Function (EOF) analysis was applied to the time series of the obtained nearshore bathymetry data in order to investigate their long-term morphological behavior. Results from the first three modes of the EOF analysis represent the bathymetry variation from the nearshore response due to the cross-shore processes. The first mode reveals the coastal erosion occurred during the study period with a net loss of sand volume in the target region. Erosion was severe before December 2008, especially in the offshore region, and mitigated afterwards resulting a relatively equilibrium stage for the mean beach profile. The second mode shows the mean beach profile rotated in an anti-clockwise direction around a cross-shore location of 50 m away from the present shoreline, which led to a milder beach slope in the study period. The third mode represents the cross-shore movement of the longshore bar. Higher modes of the EOF analysis, such as fourth, fifth and sixth modes, correspond to the bathymetry variation due to the longshore sediment movement which frequently changed its direction as indicated from a number of nodal points in the relevant temporal eigenfunction distribution. Based on the EOF analysis, it is also confirmed that the nearshore morphological process in the target area was predominant by the cross-shore sand movement.


2016 ◽  
Author(s):  
Manolis G. Grillakis ◽  
Aristeidis G. Koutroulis ◽  
Ioannis N. Daliakopoulos ◽  
Ioannis K. Tsanis

Abstract. Bias correction of climate variables has become a standard practice in Climate Change Impact (CCI) studies. While various methodologies have been developed, their majority assumes that the statistical characteristics of the biases between the modeled data and the observations remain unchanged in time. However, it is well known that this assumption of stationarity cannot stand in the context of a climate. Here, a method to overcome the assumption of stationarity and its drawbacks is presented. The method is presented as a pre-post processing procedure that can potentially be applied with different bias correction methods. The methodology separates the stationary and the non-stationary components of a time series, in order to adjust the biases only for the former and preserve intact the signal of the later. The results show that the adoption of this method prevents the distortion and allows for the preservation of the originally modeled long-term signal in the mean, the standard deviation, but also the higher and lower percentiles of the climate variable. Daily temperature time series obtained from five Euro CORDEX RCM models are used to illustrate the improvements of this method.


2008 ◽  
Vol 31 (1) ◽  
pp. 72-82
Author(s):  
T.A. Kimaro ◽  
H. Sibande

Daily rainfall data between 1966 and 2005 across all Agricultural Development Areas (ADDs) in Malawi was investigated to determine changes in selected rainfall characteristics and their impact on Maize productivity. Rainfall indices analyzed included rainfall amounts (annual and seasonal), onset, cessation, dry spells and length of rainy season. Man Kendal’s trend test was applied to the time series of these indices to detect any trends in the time series. WaterRequirement Satisfaction Index (WRSI) for maize crop was used to study the spatial-temporal variation of maize productivity and thus its linkage to rainfall. Definition of onset and cessation adopted from the Department of Meteorological Service (DMS) Malawi was used in demarcating seasons to extract seasonal rainfall amount, length and other parameters. The results of the study indicate that with the exception of Karonga ADD located at the Northern tip of the country there were no significant trends in all variables related to crop productivity including onset, cessation, rainfall amount and dry spells. The spatial and temporal variability of maize production in Malawi was captured quite well by the WRSI. The relationship between long-term average WRSI and maize yield (tonnes/ha) for different stations in Malawi had a correlation coefficient of 0.82 while the relationship of countrywide average WRSI and maize yield had a correlation coefficient of 0.75. Areas with low long term average WRSI like Shire valley also showed low productivity while those with higher WRSI like Mzimba and Salima ADD had a good yield. On average Malawi has sufficient rainfall to sustain rain-fed maize crop as most of the time (67%) rain-fall is enough to give an average yield. It was also foundout that Malawi experience droughts and hence food shortages when WRSI value is close to or below 60%.


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