Volume 15, Issue 55 (spring 2011)
jwss 2011, 15(55): 13-26 |
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M. J. Nazemosadat, H. Ghaedamini Asadabadi. Evaluation of the Effects of Madden Julian Oscillation on the Occurrence of Dry and Wet Spells in Fars Province, Iran. jwss 2011; 15 (55) :13-26
URL: http://jstnar.iut.ac.ir/article-1-1540-en.html
URL: http://jstnar.iut.ac.ir/article-1-1540-en.html
, mjnazemosadat@yahoo.com
Abstract: (23898 Views)
The Madden Julian oscillation (MJO) is known as the primary mode of large-scale inter-seasonal variability in tropical regions, affectimg equatorial and sub-tropical climates. This study investigated the effects of the MJO on the occurrence of wet and dry spells in Fars province, central southern part of Iran, during November-April. Monthly precipitation data of nine stations spread over various parts of the province was analyzed during 1979-2005. Using two well-known MJO indices: MK and WH, the positive and negative phases of the MJO phases (enhanced and suppressed convective activity over the equatorial Indonesian region, respectively) were identified for monthly and seasonal scales. Precipitation-MJO composites were then constructed for the opposite phases. It was shown that for all the considered stations, seasonal precipitation during negative MJO phase was significantly greater (from about 2.5 to 6.0 folds) than the corresponding values during the positive phase. Moreover, the applied statistical tests proved that the frequency of wet or dry events was related to the prevalence of negative or positive MJO phase, respectively. As the positive MJO phase was engulfed, the probability of dry events varied from 60% to 84%. On the other hand, the probability of wet events was found to vary from 60% to 76% during the MJO negative phase.
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