Showing 9 results for Yazd
A Ephtekhari, M Farahpour, H Arzani, J Abdolahi,
Volume 13, Issue 47 (4-2009)
Abstract
Species which were grazed by livestock and wildlife in range sites and the portion taken by each animal were the subject of this study. Two sites occupied with Scariola orientalis (Boiss.) Sojak and Artemisia sieberi Besser and another with Aellenia subaphyla (C.A.Mey.)Aellen and Artemisia sieberi were selected for the study. These sites were already established by Yazd Research Center for Agriculture and Natural Resources. Sites should be covered with similar vegetation (72% similarity), as much as possible indeed. One site, by the name of Kalmand, is a protected area and is exclusively grazed by Iranian gazelle, while the other, Jadehdehshir, by sheep and goat. Results of the study show that the selection of species is the same by these animals. Both are interested in the following species: Artemisia sieberi, Scariola orientalis, Bromus tectorum L, Stipa barbata Desf. , Noaea mucronata (Forsk.) A schers.et Schweinf, and Launaea acanthodes (Boiss.)o.Kuntze. On the contrary, species such as Acantholimon scorpiurs (Joub. &Spach) Boiss, Astragalus albispinus L were not taken by the animal for their woody stems and thorny branches. Fresh and non woody parts of the plants were grazed by both types of animal. Similarity between grazing behavior of wildlife and livestock in Yazd province shows that wildlife feed requirement should be seriously taken into account when grazing capacity of rangelands is to be evaluated.
Afkhami, Dastorani, Malekinejad , Mobin,
Volume 14, Issue 51 (4-2010)
Abstract
Drought is a natural feature of the climate condition, and its recurrence is inevitable. The main purpose of this research is to evaluate the effects of climatic factors on prediction of drought in different areas of Yazd based on artificial neural networks technique. In most of the meteorological stations located in Yazd area, precipitation is the only measured factor while generally in synoptic meteorological stations in addition to precipitation some other variables including maximum and mean temperature, relative humidity, wind speed, dominant wind direction and the amount of evaporation are also available. In this research it was tried to evaluate the role of the type and number of meteorological factor (as inputs of ANN model) on accuracy of ANN based drought prediction. Research area is a part of Yazd province containing only one synoptic and 13 non-synoptic meteorological stations. Three-year moving average of monthly precipitation was the main input of the models in all stations. The type of ANN used in this study was time lag recurrent network (TLRN), a dynamic architecture which was selected by evaluation of different types of ANN in this research. What was predicted is the three-year moving average of monthly precipitation of the next year, which is the main factor to evaluate drought condition one year before it occurs. For the Yazd synoptic meteorological station, several combinations of input variables was evaluated and tested to find the most relevant type of input variables for prediction of drought. However, for other 13 stations precipitation data was the only variable to use in ANN models for this purpose. Results in all stations were satisfactory, even where only one input (precipitation) was used to the models, although the level prediction accuracy was different from station to station. Result taken from this research, indicates high flexibility of ANN to cope with poor data condition where it is difficult to get acceptable results by most of the methods.
E. Shayegh, S. Soltani ,
Volume 15, Issue 57 (10-2011)
Abstract
In this research, 5 percent of normal Precipitation Index (PNPI),Deciles of Precipitation(DPI),Rainfall Anomaly Index (RAI), Bahlme & Mooley Drought Index (BMDI) and standardized Precipitation Index (SPI) were used in order to investigate drought in Yazd synoptic station and 31 non synoptic stations all around this province. For this purpose, the present statistical errors were reconstructed via correlation between the stations, after raining data collection from the considered stations. Then, calculation of PNPI, DPI, RAI, BMDI and SPI indexes were calculated on monthly and annual scales. Situation of drought was determined based on the obtained values from calculation of each index according to tables related to the considered indexes in different classes of drought during the statistical period. Then indexes were compared to each other, considering drought given situation for each station. The difference and similarity of each index with other 4 indexes were calculated and investigated. Also after determination of drought situation in each station, given percentage of drought different situations via each Index was determined on annual scales, in 33 study stations. After passing the above mentioned stages, it was found that there was the highest percentage value of similarity between the two indexes RAI & DPI, as both indexes indicated similar situation of hard drought in the stations. These two indexes are considered most efficient to investigate aerology drought. But considering that static indexes are faced with problem on monthly scales and in stations located in drought regions, it is recommended to use SPI & BMDI dynamic indexes whose similarity percentages are acceptable.
H. Azimzadeh, F. Fotoohi, M. R. Ekhtesasi,
Volume 18, Issue 68 (9-2014)
Abstract
Soil surface roughness (SSR) is one of the important factors in wind and water erosion studies and control. Several parameters such as surface rock fragments influence SSR. Main objectives of this paper are to study and compare (Allmarass) random roughness (RR) and tortuosity (Tb) indices in coarse, medium and fine grain plains of Yazd-Ardakan and investigate the relationship between indices and desert pavement coverage. Roughness data were obtained by pin roghness-meter and roller chain in the three mentioned plains. RR and Tb were measured in 90cm transect length with systematic sampling pattern after determining the boundary of three kinds of plains. In each plain, 30 transects were randomly sampled and the height of soil surface roughness fractions was recorded. Distance of pins in the applied roughness meter is about 2cm. Therefore, in each 90 cm transect the height of 46 points was measured. Desert pavement coverage was measured in 20×20cm2 plots. The result showed that desert pavement coverage in coarse, medium and fine grain plains were in the range of 55-100, 40-85 and less than 5%, respectively. The relationship between RR and desert pavement was significant. The result of ANOVA (Duncan) showed, RR and Tb were significantly different in coarse, medium and fine grain plains (p-value<0.01). In addition, by increasing desert pavement percentage RR and Tb increased exponentially in base of Neper number. The relation between RR and desert pavement coverage is stronger than Tb and desert pavement coverage. Correlation between the two measured indices was calculated and compared in different plains. The result revealed that about 54, 33 and 14% of the arability in Tb could be explained by RR in coarse and medium grain plains, respectively. The correlations of two indices were significant in coarse and medium plain and insignificant in fine grain plain. The trend of RR and Tb decreased from mountain to plain center. Although RR increased slightly in fine grain plain, the difference was not significant.
D. Khosraviani, A. R. Davoudian Dehkordi, J. Givi, M. Sheibi,
Volume 19, Issue 74 (1-2016)
Abstract
The concentrations of rare-earth elements (REEs) were determined with the aim of investigating the behavior of these elements in granitic rock, granitic soils and soils between rock and lichen in Shir-kuh of Yazd province. Rare earth element patterns of the P-rich granite were determined by the mixture of Eu-enriched feldspars, middle REEs to heavy REEs-enriched apatite and Light REEs-enriched monazite. Granite-normalized REEs patterns for soils and soil lichen-granite interface represented the same signatures and similar to parent rocks. The REEs levels of the soils lichen-granite interface were similar to the concentrations of the elements in the natural compositions (Upper Continental Crust and Post-Archean Australian Shale). PAAS-normalized Rare earth element patterns for three soils’ lichen-granite interface were identical to each other and PAAS and close to the reference axis (PAAS). The same signatures of REEs in granitic rock, granitic soils and soils lichen-granite interface in arid and semi-arid mountainous areas indicate that the elements are immobile and therefore, they can be used as a suitable tracer in soil provenance studies.
F. Jahanbakhshi, M. R. Ekhtesasi, A. Talebi, M. Piri,
Volume 22, Issue 2 (9-2018)
Abstract
One of the main sources of runoff in arid and semi-arid mountainous highlands is typically composed of before Quaternary formations. Since the structure and lithology of formations are different, varying formations can have different significance in terms of runoff and sediment. The present study aimed to investigate the sediment production potential and the runoff generation threshold on three formations (Shirkooh Granite, Shale, Sandstone and Conglomerate of Sangestan and Taft Limestone) in Shirkooh mountain slopes. The 60 mm/h rainfall intensity with the 40 minute continuity, according to region rainfall records, and the ability of the rainfall simulator were selected as the basis for the study. Field experiments were conducted in dry conditions based on one square meter plot on rocky slopes with a gradient of 20 to 22 percent and a maximum thickness of 30 cm of soil. The results showed that in 60 mm/h rainfall intensity, the minimum rainfall to produce runoff on Sangestan, Shirkooh and, Taft, was 10, 10.7 and 16.7 mm, respectively. The maximum amount of the sediment was measured on Sangestan, Taft and Shirkooh, respectively. Statistical tests related to runoff and sediment production on all three formations confirmed a significant difference at the 5 % level. In terms of the time required to start runoff, the minimum time was for Sangestan, Shirkooh and Taft, respectively. According to the results, in terms of the potential for runoff generation and sediment production, Sangestan, Shirkooh and Taft can be ranked from high to low levels.
Z. Ebrahimikhusfi,
Volume 24, Issue 1 (5-2020)
Abstract
The purpose of this study was to analyze the temporal variations of dust phenomenon and its relationship with the climatic elements in Yazd city, located near one of the critical centers of dust production in the center of Iran. For this purpose, the Dust Storm Index was first calculated. After the standardization of precipitation, temperature, maximum wind speed, average wind speed, relative humidity and, dust storm index, the co-linearity effect between variables was calculated by using inflation variance factor. Then, several regression models were prepared based on the optimal Ridge parameter. The performance of the models was evaluated based on the determination coefficient, F value and Root Mean Square Error. Finally, by using the most accurate model, the impact of climate parameters on the dust events changes was determined. The results showed that the incidence of dust events in the spring was more than the rest of the year. Based on the optimal model (Model 12), it was found that the main factor influencing the dust storm index variations in different seasons was the surface winds speed. It was also shown that 39%, 25%, 46% and 31% of dust storm index changes in winter, spring, summer, and autumn were due to the interaction of the five climatic parameters studied in this study.
H. Fathizad, M. Tavakoli, M. A. Hakimzadeh Ardakani, R. Taghizadehmehrjardi, H. Sodaiezadeh,
Volume 24, Issue 4 (2-2021)
Abstract
The purpose of this research was to investigate the trend of annual changes in Yazd station's meteorological parameters including minimum and maximum average daily temperature and average daily precipitation (1961-2005), as well as the predicted annual mean of these parameters in the three upcoming thirty years of the 2040s, 2070s and 2100s, by the SDSM model, under RCP2.6, RCP4.5, RCP8.5, A2, and B2 scenarios. Accordingly, by using the coefficient of determination and the MAE, R2, RMSE indicators, we evaluated the data generated by the SDSM model in comparison with the observed data in the base period. The lowest value of R2 based on the calibration and validation of the mean values of observed and simulated SRES was obtained for precipitation (86 and 80%). In terms of the R2 evaluation index, the accuracy of the small-scaled results of the minimum and maximum average temperature values was more than that of the average precipitation; however, in terms of the MAE and RMSE evaluation indicators, the accuracy of the small-scaled results of the average precipitation was higher than that of the minimum and maximum average temperature values. Subsequently, HadCM3 large-scale climatological data was used to predict the future periods (2010-2100). The results indicated that the temperature was raised in all months and seasons and the precipitation was decreasing in most of them, thereby confirming that the climate was changing in the studied region.
M. Zareian,
Volume 26, Issue 2 (9-2022)
Abstract
This study was conducted to investigate the effects of climate change on temperature and precipitation changes in important synoptic weather stations in Yazd province (including Yazd, Bafgh, Marvast, and Robat-e-Poshtebadam). Accordingly, a combination of the outputs of the latest AOGCM models presented in the IPCC sixth assessment report (CMIP6) were used to increase the accuracy of temperature and precipitation forecasts. A weighting method was used based on the Kling-Gupta combined index (KGE) to combine these models. After weighting the models, the monthly temperature and precipitation changes were calculated based on SSP126, SSP245, and SSP585 emission scenarios. Then, daily temperature and precipitation time series were extracted for different weather stations using the LARS-WG downscaling model. The results showed that in all the weather stations, CanESM5 and BCC-CSM2-MR models have the best ability to simulate the temperature and precipitation of the historical period, respectively. Results also showed that in all emission scenarios, the annual temperature will increase and the annual precipitation will decrease. The annual temperature of this region will increase between 0.2 to 0.6 °C, and the annual precipitation will decrease between 2.9 and 13.7% in different weather stations. Also, the maximum temperature increase and precipitation decrease in this region, will occur in spring and autumn, respectively.
