Analysis of Different Types of Droughts and Their Characteristics in Iran Using the Standardized Precipitation Evapotranspiration Index (SPEI)

Introduction Drought is a costly natural hazard with wide-ranging consequences for agriculture, ecosystems, and water resources. The purpose of this research is to determine the characteristics of drought and its types in Iran during the last four decades. Drought turns into different types in the water cycle and imposes many negative consequences on natural ecosystems and different socio-economic sectors. According to International Disaster Database (EM-DAT), drought accounts for 59% of the economic losses caused by climate change. Many parts of the world have experienced extensive and severe droughts in recent decades. In Iran, droughts have occurred frequently during the last four decades and have become more severe in the last decade. Materials and Methods In this research, we used precipitation, temperature, wind speed, and sunshine hours of 49 synoptic meteorological stations during 1981-2020. Drought has been investigated with The Standardized Precipitation-Evapotranspiration Index (SPEI) in four scales of 3, 6, 12, and 24 months, which represent meteorological, agricultural, hydrological, and socio-economic droughts. To calculate the SPEI, the precipitation variable (P) is analyzed with the cumulative difference between P and potential evapotranspiration (PET). In other words, surplus/deficit climate water balance (CWB) is considered. The FAO Penman-Monteith method was used to calculate PET. Then, using the RUN theory, the characteristics of drought, including its magnitude, duration, intensity, and frequency, were determined for all four investigated scales. Results and Discussion The results showed that the frequency of drought events fluctuates from a minimum of 12.13% to a maximum of 18.13% in different regions of the country during 1981-2020. The climatological study of drought characteristics shows that the most frequent drought events occurred in the west, southwest, and southern coasts of the Persian Gulf and northwest of Iran compare to other regions of the country. This is while the duration of the drought period is longer in the eastern and interior regions of Iran. Examining the types of droughts shows that more than 60% of the droughts occurring in Iran are moderate droughts. Moderate and severe droughts are mostly seen in the west, southwest, and northwest of Iran. The duration of Iran's drought varies from at least 3 months in meteorological drought to more than 8 months in socio-economic drought. Therefore, droughts are more frequent in the western regions and longer in the eastern regions. The intensity of drought is also higher in the eastern and interior regions than in the western and northwestern regions of Iran. The decadal changes of drought show that the duration and magnitude of drought in Iran have increased and the severity of the drought has decreased during recent decades. Conclusion The intensity, magnitude, and duration of the drought period in Iran increased with the increase of the investigated scales from 3 months to 24 months. Examining the average frequency of drought showed that as we move from meteorological drought to socio-economic drought, the frequency of drought increases, which confirms the previous findings. The eastern and southeastern parts of Iran have experienced a longer duration and larger magnitude of drought than the western and northwestern Iran, which can be caused by the climate conditions of this region, i.e., high temperature and evapotranspiration and less precipitation, and seasonality. The maximum magnitude of drought in Iran is related to socio-economic drought (SPEI-24) followed by hydrological drought (SPEI-12). This characteristic has increased especially in the last two decades (2001-2020) compared to the previous decades (1981-2000). This is while the magnitude of meteorological (SPEI-3) and agricultural (SPEI-12) droughts do not increase much in the last two decades compared to the previous decades. Anthropogenic activities play a more prominent role in increasing the magnitude of socio-economic (SPEI-24) and hydrological (SPEI-12) droughts than natural forcing. With the construction of many dams and the digging of countless deep wells, as well as changing the direction of rivers, the water cycle has been completely affected by human activities during the last four decades in Iran. Obviously, anthropogenic activities play an important role in increasing the magnitude of hydrological and socio-economic droughts. In contrast, meteorological and agricultural droughts have not shown many changes in Iran. The results of the decadal average of drought intensity showed that this characteristic of drought in the last decade (2011-2020) has decreased compared to previous decades (1981-2010). On the other hand, as mentioned earlier, the magnitude and duration of drought, especially for hydrological and socio-economic droughts, have increased in the last two decades (2001-2020). Therefore, the reason for the decrease in the severity of the drought has a statistical explanation before it has a climatic reason because the severity of the drought is calculated by dividing the magnitude of the drought by its duration

Temporal characteristics of nasalization in Persian speaker children with and without cleft palate

Objectives: The purpose of this study was to measure and compare temporal patterns of nasalization in Persian children with and without cleft palate in three vowel contexts. Methods: A Sample of 14 children with repaired cleft palates with or without cleft lip with moderate to severe hyper nasality and 14 children without cleft palate was chosen as subjects. The subjects were chosen from the ages of 4 to 12 years. The nasal onset interval, nasal offset interval and total nasalization duration were obtained from acoustic waveforms and spectrograms in three vowel contexts using Praat Software. For eliminating the effect of different speed of speech in the cleft palate group and control group, the ratio of nasalization duration was calculated. Results: Total nasalization duration are demonstrated by acoustic signals which shows the total significant different temporal patterns in children with cleft palate and without cleft palate and across the vowel contexts (. P<. 0.000). Conclusions: Longer nasalization durations in children with cleft palate in comparison to children without cleft palate show the delayed or deviant temporal patterns in children with cleft palate. The duration of nasalization reflecting temporal patterns of the oral-nasal acoustic impedance in children with cleft palate may have an influence on the perception of hyper nasality. © 2015 Elsevier Ireland Ltd

A Comparison of Persian Vowel Production in Hearing-Impaired Children Using a Cochlear Implant and Normal-Hearing Children

Objective Normal-hearing (NH) acuity and auditory feedback control are crucial for human voice production and articulation. The lack of auditory feedback in individuals with profound hearing impairment changes their vowel production. The purpose of this study was to compare Persian vowel production in deaf children with cochlear implants (CIs) and that in NH children. Methods The participants were 20 children (12 girls and 8 boys) with age range of 5 years; 1 month to 9 years. All patients had congenital hearing loss and received a multichannel CI at an average age of 3 years. They had at least 6 months experience of their current device (CI). The control group consisted of 20 NH children (12 girls and 8 boys) with age range of 5 to 9 years old. The two groups were matched by age. Participants were native Persian speakers who were asked to produce the vowels /i/, /e/, /æ/, /u/, /o/, and /a/. The averages for first formant frequency (F1) and second formant frequency (F2) of six vowels were measured using Praat software (Version 5.1.44, Boersma &amp; Weenink, 2012). The independent samples t test was conducted to assess the differences in F1 and F2 values and the area of the vowel space between the two groups. Results Mean values of F1 were increased in CI children; the mean values of F1 for vowel /i/ and /a/, F2 for vowel /a/ and /o/ were significantly different (P &lt; 0.05). The changes in F1 and F2 showed a centralized vowel space for CI children. Conclusions F1 is increased in CI children, probably because CI children tend to overarticulate. We hypothesis this is due to a lack of auditory feedback; there is an attempt by hearing-impaired children to compensate via proprioceptive feedback during articulatory process. © 2016 The Voice Foundation