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Open AccessArticle

Decadal Spatial-Temporal Variations in the Spatial Pattern of Anomalies of Extreme Precipitation Thresholds (Case Study: Northwest Iran)

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Department of Geography, Yazd University, Yazd 8915818411, Iran
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Department of Geography, Kharazmi University, Tehran 1491115719, Iran
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Department of Geography, Zanjan University, Zanjan 3879145371, Iran
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Department of Geography, Tabriz University, Tabriz 5166616471, Iran
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Department of Physics, University of Iceland and Icelandic Meteorological Office, Bustadavegur 9, IS-150 Reykjavik, Iceland
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Authors to whom correspondence should be addressed.
Atmosphere 2017, 8(8), 135; https://doi.org/10.3390/atmos8080135
Received: 4 June 2017 / Revised: 14 July 2017 / Accepted: 22 July 2017 / Published: 3 August 2017
(This article belongs to the Special Issue Global Precipitation with Climate Change)
This study focused on decadalvariations of extreme precipitation thresholds within a 50-year period (1961–2010) for 250 stations of Iran’s northwest. The 99th percentile was used as the threshold of extreme precipitation. In order to analyze threshold cycles and spatial autocorrelation pattern dominating extreme precipitation thresholds, spectral analysis and Gi (known as HOTSPOT) were used respectively. The results revealed that the highest threshold of extreme precipitation occurred along the Ghoosheh Dagh mountain range. Additionally, in all the five studied decades, the highest positive anomalies were observed in the same region (i.e., the Ghoosheh Dagh). The findings also showed that the intensity of positive spatial autocorrelation pattern of extreme precipitation thresholds experienced a declining trend in recent decades. At the same time, extreme precipitation weighted mean center indicated that they followed an ordered pattern during the studied period. The results of harmonic analysis demonstrated that, in all decades, short-term (2–4 years) and mid-term (4–8 years) cycles of extreme precipitation thresholds were dominated. However, especially the southwest of the studied area, the return period of extreme precipitation thresholds was as long as the studied period, a phenomenon that indicates the existence of a trend in extreme precipitation thresholds of these regions. View Full-Text
Keywords: extreme precipitation threshold; anomaly; weighted mean center; Gi; harmonic analysis; northwest of Iran extreme precipitation threshold; anomaly; weighted mean center; Gi; harmonic analysis; northwest of Iran
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Rousta, I.; Nasserzadeh, M.H.; Jalali, M.; Haghighi, E.; Ólafsson, H.; Ashrafi, S.; Doostkamian, M.; Ghasemi, A. Decadal Spatial-Temporal Variations in the Spatial Pattern of Anomalies of Extreme Precipitation Thresholds (Case Study: Northwest Iran). Atmosphere 2017, 8, 135.

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