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Advances in Meteorology
Volume 2015, Article ID 817513, 11 pages
http://dx.doi.org/10.1155/2015/817513
Research Article

Controlling Factors of the Stable Isotope Composition in the Precipitation of Islamabad, Pakistan

1Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
2Department of Environmental Science, Karakoram International University, Gilgit 15100, Pakistan
3Key Laboratory of Tibetan Plateau Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Building 3, Courtyard 16, Lin Cui Road, Chaoyang District, Beijing 100101, China
4Research School of Arid Environment and Climate Change, Lanzhou University, 222 South Tianshui Road, Lanzhou, Gansu 730000, China

Received 1 May 2015; Revised 28 July 2015; Accepted 11 August 2015

Academic Editor: Rossella Ferretti

Copyright © 2015 Shakir Hussain et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Significant temporal variations in δ18O and deuterium isotopes were found in the rainfall water of Islamabad, Pakistan, over a 15-year period (1992–2006). The data were obtained from the International Atomic Energy Agency/Global Network of Isotopes in Precipitation (IAEA/GNIP) database, and statistical correlations were investigated. In particular, this study provides the first detailed analysis of GNIP data for Islamabad. Both dry (1999-2000) and wet years (1994, 1997, and 2000) were chosen to investigate the correlations between precipitation amount, vapor flux, and temperature. We observed obvious differences between the dry and wet years and among seasons as well. Long-term features in the isotope composition agreed with the global meteorological water line, whereas short-term values followed rainfall amounts; that is, a total of 72% of the precipitation’s isotopic signature was dependent on the rainfall amount, and temperature controlled 73% of the isotopic features during October to May. The lower d-excess values were attributed to conditions during the spring season and a secondary evaporation boost during dry years; precipitation originating from the Mediterranean Sea showed high d-excess values. Overall, the results of this study contribute to the understanding of precipitation variations and their association with water vapor transport over Islamabad, Pakistan.