کاهش اثر ناهم‌واریانسی در محاسبه‌ی میانگین بارش سالانه ایران با کمک طبقه‌بندی اقلیمی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 استادیار/ گروه مهندسی منابع طبیعی، دانشکده کشاورزی و منابع طبیعی، دانشگاه هرمزگان.

2 دانشجوی دکتری علوم و مهندسی آبخیزداری/ دانشکده کشاورزی و منابع طبیعی، دانشگاه هرمزگان.

چکیده

ناهم‌واریانسی به‌عنوان مفهومی تعیین‌کننده می‌تواند محاسبه و کارآیی میانگین بارش را در پهنه‌ی سرزمینی ایران به ‌چالش بکشد. این ناکارآیی باعث بروز خطا در برآورد آورد آب سالانه و بروز مشکل در مدیریّت منابع آبی کشور می‌شود. لذا در این پژوهش با مبنا قراردادن طبقه‌بندی اقلیمی مسعودیان و بررسی داده‌های بارش 146 ایستگاه‌ همدید، در چهار مقیاس زمانی فصل پُربارش، نیمه پُربارش، پیش‌بارش و کم بارش، اثر ناهم‌واریانسی بر میانگین بارش از طریق آزمون لوین مورد بررسی قرار گرفته است. نتایج نشان ‌داد علی‌رغم اینکه داده‌های بارش تمامی نواحی اقلیمی توزیع نرمال دارند امّا وجود بارش‌های حدّی به‌عنوان داده‌های پرت، واریانس‌های بسیار بزرگ و متفاوت‌ بودن رژیم‌های بارشی برخی از ایستگاه‌های هر ناحیه‌ی اقلیمی، باعث پذیرفته ‌‌نشدن فرضیّه‌ی صفر آزمون لوین می‌شود و بیشتر نواحی اقلیمی با ناهم‌واریانسی روبه‌رو هستند. نتیجتاً کاربرد شاخص میانگین نمی‌تواند شناخت کاملی از وضعیّت بارش و توزیع داده‌های بارش را ارائه دهد. بنابراین برای نیل به میانگینی کارآ از بارش سالانه کشور لازم است با پرهیز از محاسبه‌ی میانگین در پهنه‌ی سرزمینی، اقدام به ارتقای میانگین بارش محاسبه‌شده در پهنه‌ی اقلیمی کرد و با انجام طبقه‌بندی اقلیمی اصلاح‌شده در محدوده‌ی حوزه‌های آبخیز، شناخت بهتری از رفتار بارشی در هر پهنه‌ی اقلیمی و کلّ پهنه‌ی سرزمینی ایران به‌دست آورد.

کلیدواژه‌ها


عنوان مقاله [English]

Modifying Annual Precipitation Mean Concerning the Effects of Heteroscedasticity in Different Climatic Regions of Iran

نویسندگان [English]

  • Arashk Holisaz 1
  • Safikhany Sajedeh 2
1 Assistant Professor, Department of Natural Resources Engineering , Faculty of Agriculture and Natural Resources, University of Hormozgan, Bandar Abbas, Iran.
2 Ph.D. Student of Watershed Management Science and Engineering, Faculty of Agriculture and Natural Resources, University of Hormozgan, Bandar Abbas, Iran
چکیده [English]

Heteroscedasticity as determining concept challenges the calculation and efficiency of mean precipitation at the extent of Iran territory. This inefficiency leads to emergence of error during calculation of annual water budget and of problem in water resources of country. Accordingly, in this study, building on the Masoodian climatic classification and investigating the precipitation data from146 synoptic stations at four temporal scales- heavy rain, semi-heavy rain, pre-precipitation, and low rain- the effect of Heteroscedasticity on mean precipitation were investigated by Levene Test. The results showed that besides the precipitation data have a normal distribution across all climatic regions, but the existence of limiting precipitations as outliers data, very high-variances and the variation of precipitation regimes from some station of a climatic region, resulted in rejection of null hypothesis of Levene Test and most of climatic regions are encountered Heteroscedasticity. Consequently, use of mean index could not provide complete recognition of precipitation status and precipitation distribution. Hence, to achieve an efficient mean of annual precipitation in country, it is necessary to do practice to enhance the calculated mean precipitation in climatic extent, with avoiding calculating mean at territory extent, and by accomplishment of improved climatic classification at watershed basin scale, gains better recognition of precipitation behavior at any climatic extent, and at whole territory extent in Iran.

کلیدواژه‌ها [English]

  • Heteroscedasticity
  • Iran
  • Levene test
  • Masoodian Climatic region
  • precipitation mean
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