Nazok Hossein Asad, Dariush Yarahmadi, Hamid Mirhashemi,
Volume 0, Issue 0 (3-1921)
Abstract
The ENSO phenomenon is considered one of the most important interannual oscillations in the Earth–atmosphere system and plays a significant role in precipitation variability across different regions of the world. In this study, to identify the multiscale relationship between different ENSO phases and monthly precipitation variability in Iraq, the monthly Niño3.4 index, the Maximum Overlap Discrete Wavelet Transform (MODWT), and the Continuous Morlet Wavelet Transform were employed. First, using multiresolution decomposition of the monthly precipitation signal from 16 stations across Iraq (1990-2020) into six (6) frequency levels (from monthly to multi-year scales), it was revealed that the precipitation signals at all stations follow a relatively similar pattern, although with different oscillation amplitudes. The amplitude of precipitation fluctuations at monthly and seasonal scales was found to be stronger at northern and foothill stations (Kirkuk, Mosul, and Khanaqin) compared to other regions of Iraq, indicating a shorter transition between wet and dry months in northern Iraq. Furthermore, the overall trend of the A6 component at all stations exhibited a decreasing pattern during 1995–2010, with this downward trend being more pronounced in the central and southern regions than in the north. The results of correlation analysis and multiscale wavelet coherence demonstrated a positive and multiscale relationship between ENSO and monthly precipitation in Iraq. Surrogate significance testing indicated that this relationship is not significant at wavelet levels 1 to 3 but becomes significant at 1.5–3-year and 2.5–5.5-year scales (wavelet levels 4 and 5). Overall, precipitation in Iraq tends to increase during El Niño (warm ENSO phase) events and decrease during La Niña (cold ENSO phase) events.
Hamed Heidari, Darush Yarahmadi, Hamid Mirhashemi,
Volume 24, Issue 75 (12-2024)
Abstract
Human interventions in natural areas as a change in land use have led to a domino effect of anomalies and then environmental hazards. These extensive and cumulative changes in land cover and land use have manifested themselves in the form of anomalies such as the formation of severe runoff, soil erosion, the spread of desertification, and salinization of the soil. The main purpose of this study is to reveal the temperature inductions of the land cover structure of Lorestan province and to analyze the effect of land use changes on the temperature structure of the province. In this regard, the data of land cover classes of MCD12Q2 composite product and ground temperature of MOD11A2 product of MODIS sensor were used. Also, in order to detect the temperature inductions of each land cover during the hot and cold seasons, cross-analysis matrix (CTM) technique was used. The results showed that in general in Lorestan province 5 cover classes including: forest lands, pastures, agricultural lands, constructed lands and barren lands could be detected. The results of cross-matrix analysis showed that in hot and cold seasons, forest cover (IGBP code 5) with a temperature of 48 ° C and urban and residential land cover (IGBP code 13) with a temperature of 16 ° C as the hottest land use, respectively. They count. In addition, it was observed that the thermal inductions of land cover in the warm season are minimized and there is no significant difference between the temperature structure of land cover classes; But in the cold season, the thermal impulses of land cover are more pronounced. The results of analysis of variance test showed that in the cold period of the year, unlike the warm period of the year, different land cover classes; Significantly (Sig = 0.026) has created different thermal impressions in the province. Scheffe's post hoc analysis indicated that this was the difference between rangeland cover classes and billet up cover.
