عنوان مقاله [English]
Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. Sunspots areas may be thousands kilometers. Sunspot populations quickly rise and more slowly fall on an irregular cycle of 11 years, although significant variations in the number of sunspots attending the 11-year period are known over longer spans of time. They move slowly and closed to the suns equator(Ajabshiri and Mehravani ,2009) . Suggestive correlations between solar activity, global temperature, and rainfall have been observed, and analysis of tree-ring data spanning centuries seems to show the presence of an 11â13 year cycle.
The energy output of the Sun varies very little over the solar cycle (i.e., by about 0.1%), and some scientists doubt whether such slight changes can really affect the troposphere (lower atmosphere) of the earth, where precipitation occurs.
The effects of sunspots on climate variability were confirmed in several regions of the world.
The aim of this paper is clarifying the relation between sunspot activities and Golestan province precipitation. Golestan province is located in the north of Iran and have favorite situation in agricultural products. The annual average precipitation is about 550mm.Precipitation variability can damage many parts of the agricultural sector that sensitive to fluctuations in rainfall.
In this study annual and monthly precipitation data for 3 climatic stations over the province were used. These stations are: Gorgan (west), Gonbad (center) and Maravehtapeh (East).The sunspot activities data were obtained from National Oceanic and Atmospheric Administration (NOAA) and transformed to seasonal and monthly periods.
Pearson correlation coefficient and Continuous Wavelet Analysis were used for showing the relationship between precipitation and solar activities.
Data were normalized between +1 and -1 therefore +1 is the maximum solar activities or precipitation and -1 represent the minimum. The wavelet analysis performed by Matlab software and Morlet wavelet selected as the parent and then other parameters were extracted.
In mathematics, the Morlet wavelet (or Gabor wavelet) is a wavelet composed of a complex exponential (carrier) multiplied by a Gaussian window (envelope).
In output model, dark and light colors represents maximum/minimum solar activities and regional precipitation .
The correlation between precipitation and sunspots activities showed that the annual precipitation of eastern region have a significant relationship. The negative coefficient indicated that by increasing solar activities the annual precipitation is reduced. In winter high precipitation western regions have significant correlation coefficients.
In warm season, western region in July, central region in August and eastern region in June have a good relation to solar activities.In total, the seasonal correlation is stronger than monthly values.
The wavelet analysis indicated that the relation between precipitation variations and solar cyclic activities in eastern dry regions is irregular and 4,5,8 and 10 years cycles can by observed in model outputs.
In central regions systematic cyclic fluctuations (5 years period) specially in winter precipitations exist. In annual scale, western regions have showed 5 and 10 years periodâs cycles.
The spring rainfall have more cycles that indicated the effects of local climate elements like Caspian Sea and Alborz mountains.
In this paper the relationship between precipitation and sunspot activities in Golestan province were investigated.
The results suggested that due to climatic variability of province, there is not a uniform relation between these phenomena. Western region have high and uniform rainfall and shown strange and direct correlation to solar activities whereas in dry eastern regions a reverse relation exist between rainfall and solar activities.
Wavelet analysis showed that precipitation cycles not identical in different areas. In west areas cycles have regular behaviors whereas eastern regions they are irregular.
The maximum precipitations of Gorgan station are coordinate with maximum solar activities but in Gonbad station these conditions does not exist.
In January the relation between rainfall and solar activities are stronger in compare to other months. In this month 11 years cycle can observe on time series.
Sequence and frequency of droughts and wet periods with the cycles of sunspot activities, confirming that the Sunspots are one of the factors that affecting Golestan province precipitation.