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Declining rainfall and regional variability changes in Jordan
Author(s) -
Rahman Kazi,
Gorelick Steven M.,
DennedyFrank P. James,
Yoon Jim,
Rajaratnam Bala
Publication year - 2015
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2015wr017153
Subject(s) - environmental science , spatial variability , precipitation , principal component analysis , climatology , physical geography , trend analysis , variance (accounting) , geography , statistics , mathematics , meteorology , geology , accounting , business
Jordan, with limited rainfall, has per capita water availability of 135 m 3 /yr making it one of the water‐poorest countries in the world. We analyzed the most comprehensive modern rainfall data set to date, consisting of 44 years of daily measurements from 58 stations primarily in the western, populated and agricultural portion of Jordan over the period 1970–2013 to assess temporal trends, variability, and spatial patterns. From 1995 to 2013, 13 of 19 years showed rainfall less than the mean, which has a probability <8.35% of chance occurrence. We used nonparametric statistical analysis and found 38 of 58 stations experienced an annual rainfall decrease at an average rate of 1.2 mm/yr. Over all 58 stations, the average decrease was 0.41 mm/yr. The annual coefficient of variation of daily rainfall showed a long‐term increase of ∼2–3% at 90% of stations. Analysis of annual variance of daily rainfall suggests decreasing variance in the low rainfall areas to the southwest and east and increasing variance in the high rainfall areas to the northwest, a pattern consistent with principal component analysis. Strict multiple hypothesis testing procedures using the k‐familywise error rate approach reinforced and confirmed the statistically significant regional rainfall decline as well as the spatial patterns of increasing and decreasing rainfall variability.