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COMSATS University Islamabad (2019)

Precipitation Variability and Associated Wet and Dry Spell Characterization in Pakistan

Ahmed, Nabeel

Titre : Precipitation Variability and Associated Wet and Dry Spell Characterization in Pakistan

Auteur : Ahmed, Nabeel

Université de soutenance : COMSATS University Islamabad,

Grade : Doctor of Philosophy (PhD) in Meteorology 2019

Résumé partiel
Precipitation Variability and Associated Wet and Dry Spell Characterization in Pakistan Wet (dry) spells can cause extreme climatic conditions, such as floods (droughts) which can adversely influence the natural resources. A spatio-temporal analysis of observed wet and dry spells is carried out for vulnerable and data sparse region of Pakistan (24ᴼ–38ᴼN and 61ᴼ–78ᴼE). Observed monthly precipitation datasets from 46 weather stations are used for a length of consecutive 32 years (1976−2007). Additionally, after bias adjustment, the Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) precipitation dataset, abbreviated as APH, is utilized to corroborate the findings. Decadal variability of precipitation for observed and APH datasets indicates that there is gradual decrease in wet spell length for arid and humid regimes, as compared to semi-arid regimes where there is no change in wet spell length. Monthly dry and wet slope difference (SD), on a log-log plot between number of spells and spell length, is used to classify precipitation regimes in Pakistan, for the first time. A weather station is categorized as humid if SD is less than -2.38 in units of number of spells per length of spells. If SD lies between -2.37 and -0.51, then the weather station is classified as semi-arid and if SD is greater than -0.51, then it is classified as arid. Thus, according to SD classification, 66% of area in Pakistan is arid, whereas 30% (4%) is semi-arid (humid). Comparison of precipitation regimes based upon observed and APH datasets with other climate classification schemes that involve both precipitation and temperature is presented.

Présentation (Pakistan Research Repository)

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Page publiée le 22 mai 2022