Document Type : Research Paper

Authors

1 Asisstant Professor of University of Kurdistan

2 Graduate Master of Applied Climatology, University of Kurdistan

10.22034/gp.2020.10541

Abstract

Introduction
The consequences of climate change, changes in precipitation characters, including the amount, time and it’s duration are expected. Considering that the rain provides the water resources on the planet, change in regime, amount and duration of rainfall, caused a disturbance in the ecosystem of the Earth. It also affects the environmental conditions. Kurdistan province has an agricultural economy, thus variation in the rainfall duration can affect agricultural activity and other activities. To achieve success in the environmental management planning and efficient use of water resources over an area, it is essential to have information about rainfall variation.
An important parameter of atmospher is precipitation.It has a lot of changes over the time and space. It is a basic element in the formation of the activities and prospects of the environment. Several studies have done by researchers on the properties of precipitation in the different regions of the world and also in Iran. In general, precipitation showed a negative trend in many regions (Gorgio,2002: 675). For example, an assessment of summer rainfall in eastern China showed a positive and a negative trend in the north (Gemmer et al, 2004: 39; Gong et al, 2004: 771).Annual rainfall has decreased in southern parts of Italy and the decrease in winter precipitation was larger (Marco et al, 2004: 907). An increase in summer rainfall, especially, in June and July has been reported in the Yangtze River basin (Tong et al, 2007: 1016). A decrease in winter rainfall and an increas for other seasons has been showed in Turkey (Kahya and Partal, 2007: 43). Evaluation of maximum daily rainfall at the global scale showed an increasing trend in rainfall (Sethwestra et al. 2013: 3904). Negative anomalies of precipitation was reported for the most stations in southern west Ethiopia (Girma et al. 2016: 3037). Based on Iran's annual rainfall, positive and negative trends in annual rainfall have been showed (Asgari and Rahimzadeh, 2006: 67). A decrease in rainfall, especially in the decade of 1995-2005 revealed in Iran using annual rainfall (Asakereh and Razmi,2012: 159). Assessment of changes in seasonal patterns of rainfall in Hamedan, showed that the beginning of the rain tend to the summer and the end of winter (Movahedi et al.,2013: 23). The results of precipitation extreme indices on Iran showed a positive trend in  the west and the south west and a negative trend in the north (Masoodian and Darand, 2013: 239).
 
Methodology
For this study, the daily precipitation obseravtions obtained from synoptic stations in Kurdistan province during 01.01.1989 to 31.12.2014 were anlayzed. A database with dimensions of 9526 * 8 was created. The time was set on rows (9526 days) and the rainfall was set on columns. Homogeneous and heterogeneous monthly rainfall data were assessed by apply cumulative deviations test and Vercelli maximum of likness. Mann-Kendall approach was implemented to extraxt the trend at the significant level of 90%, 95%, and 99 %. The significant differences in the mean of time series data before and after a mutation year by Mann-Whitney test were evaluated. The statistical calculations were done in the Matlab software.
              
Results and Discussion                
The results showed that during the study period, duration of rainfall for autumn, winter and spring, in most of the stations, has been reduced. The results indicated that the rainfall duration for summer showes an increases in rainfall.Which is in line with the result of many previous studies.The reduction in the rainfall in the rainy season and an increase in rainfall in summer were obsorved. As a result the duration rainfall also has been  changed. Annual rainfall has decreased in southern Italy and decrease in precipitation in winter is more (Marco et al, 2004: 907). Movahedi et al. 2013, By studying the seasonal rainfall in Hamadan, They found that the rainfall began to ward the winter and their end to the summer have changed.

Conclusion                                 
 
   Evaluation of duration time series of rainfall over different months of the year showed that in the rainy months of autumn, winter and spring rainfall duration has decreased. For example, Baneh station showed a decline of 0.3 day in December, and Marivan showed a decline of 0.6 day in January. The average rate of decline in rainfall duration in March for the Qorveh station was 0.4 day per decade. In addition, a decline in spring rainfall duration was observed as well. Bijar station showed a decline of 0.2 day in May. However the rainfall duration in summer showed an increase. For example, Zarinah station obtained an increase of 0.2 day per decade in August.

Keywords

Main Subjects

 - جهانبخش اصل، سعید، خورشید دوست، علی محمد، دین پژوه، یعقوب و سرافروزه، فاطمه(1393)، تحلیل روند و تخمین دوره­های بازگشت دما و بارش­های حدی در تبریز«، جغرافیا و برنامه‌ریزی، سال 18،شماره50، صص 133-107.
- حجام، سهراب، خوشخو، یونس و شمس الدین وندی، رضا (1387)، » تحلیل روند تغییر بارندگی­های فصلی و سالانه چند ایستگاه منتخب در حوزه­ی مرکزی ایران با روش­های نا پارامتری«، پژوهش­های جغرافیایی، شماره 64، 168-157.
- عساکره، حسین (1386)، »تغییرات زمانی-مکانی بارش ایران‌زمین طی دهه­های اخیر«، جغرافیا و توسعه، شماره10، صص 164-145.
- عساکره، حسین و دوستکامیان، مهدی (1395)، » ناحیه بندی اقلیمی آب قابل بارش جو ایران‌زمین«، جغرافیا و برنامه­ریزی، سال 20، شماره 58، صص 202-181.
- عساکره، حسین و رزمی، رباب (1391)، » تحلیل تغییرات بارش سالانه­ی شمال غرب ایران«، جغرافیا و برنامه­ریزی محیطی، شماره 47، صص 162-147.
- عسگری، احمد و رحیم زاده، فاطمه (1385)، »مطالعه­ی تغییرپذیری بارش دهه­های اخیر ایران«، پژوهش­های جغرافیایی، شماره 58، صص80-67.
- کریمی، مصطفی و قاسمی، الهه (1396)، »بررسی پدیده­ی تغییر اقلیم با رویکرد تصمیم­گیری چند معیاره«، جغرافیا و برنامه­ریزی، سال21، شماره 61، صص 361-341.
- محمدی، بختیار (1392)، »تحلیل روند سالانه­ی آستانه بارش­های سنگین ایران«، تحقیقات جغرافیایی، شماره 28، صص 176-163.
- مسعودیان، سید ابوالفضل و دارند، محمد (1392)، »شناسایی و بررسی تغییرات نمایه­های بارش فرین ایران طی دهه­های اخیر«، جغرافیا و توسعه ناحیه‌ای، شماره 20، صص257-239.
- مفیدی، عباس، زرین، آذر و جانبازقبادی، غلامرضا (1391)، »تبیین علل کاهش یافتن مقدار و شدت بارش­های زمستانه در قیاس با بارش­های پاییزه در سواحل جنوبی دریای خزر«، فیزیک زمین و فضا، دوره 38، شماره 1، صص 203-177.
- موحدی، سعید، عساکره، حسین، سبزی پرور، علی اکبر، مسعودیان، ابوالفضل و مریانجی، زهره (1392)، »بررسی تغییر الگوی فصلی بارندگی در استان همدان«، تحقیقات جغرافیایی، شماره 28، صص 48-33.
- نظری پور، حمید، مسعودیان، سید ابوالفضل و کریمی، زهرا (1391)، »بررسی تغییرات فضایی سهم بارش­های یک‌روزه در تأمین روزهای بارشی و مقدار بارش ایران«، فیزیک زمین و فضا، دوره 38، شماره 4 صص،258-241.
- نگارش، حسین، ساری صراف، بهروز و دارایی، محمد (1391)، »بررسی آماری تغییرات بارش سقز«، جغرافیا و برنامه‌ریزی، شماره 42، صص 259-239.
- Bodri. L., Cermak, V. & Kresl. M. (2005). Trend in precipitation variability: Progue (the Czech Repblic). Climatic Change, 72, 151-170.
- Fujibe, F. (2008). Long-term changes in precipitation in Japan. Journal of Disaster Research, 3(1), 51-55.
- Germe, M. (2008). Seasonal precipitation changes in the wet season and their influence on flood/drought hazards in the Yangtze River basin, China. Quaternary International, 186, 12- 21.
- Girma, E, Tino, J & Wayessa, G. (2016). Rainfall trend and variability analysis in Setema-Gatira area of Jimma, Southwestern Ethiopia. Africa Journal of Agricultural Research, 11, 3037-3045.
- Gmmer, M, Becker, S & Jiang, T. (2004). Observed monthly precipitation trends in China, Theoretical and Applied Climatology. 77, 39–45.
- Gong, D.Y, Shi, P. J & Wang, J. A. (2004). Daily precipitation changes in the semi-arid region over northern China. JournalofArid Environments, 59,771-784.
- Gorgio, F. (2002). Variability and trends of sub-continental scale surface climate in the twentieth century. Part I: observations. Climate dynamics, 18, 675-691.
- ­­Kahya, E & Partal, T. (2007). Is seasonal precipitation decreasing or increasing in turkey. Journal of Earth Science, 1, 43-46.
- Kendall, M.G. 1975. Rank Correlation Methods, 4th edition, Charles Griffin, London.
- Mann, H.B. 1945. Non-parametric tests against trend, Econometrica 13:163-171.
- Marco, P., Domenico, C & Federico, B. (2004). Trend analysis of precipitation and drought in Basilicata in southern Italy context. International Journal of Climatology, 24, 907–922.
- Rodrigo, F. S., Ricardo, M & Trigob, C. (2007). Trends in daily rainfall in the Iberian Peninsula from 1951to 2002. International Journal of Climatology, 27, 513–529.
- Serrano, A., Mateos, V. L & Garcia, J. A. (1999). Trend analysis of monthly Precipitation over the Iberian Peninsula. Physics and Chemistry of Earth, 24, 85-90.
- Sethwestra, L., Alexander, V & Francis, W. (2013). Global increasing trends in annual maximum daily precipitation. Journal of Climate, 26, 3904-3918.
-Thomas, R & Richard, W. (1998). Secular Trends of Precipitation amount, frequency and Intensity in the United States. Theoretical and Applied Climatology, 79, 231-241.
- Tong, J. Buda, Su & Heike, H. (2007). Temporal and spatial trends of precipitation and river flow in the Yangtze River Basin. Geomorphology, 85, 143-154.
- Wang, Y & Zhou, Li. (2005). Observed trends in extreme precipitation events in China and the associated changes in large scale­­­ circulation. Geophysical Research. Letters, 32, L09707, doi: 10.1029- GL022574.