عنوان مقاله [English]
Clouds are one of the most complex elements in the climate system which not only change the energy budget but also affect the temporal and spatial distribution of climate elements. Ffluctuations of pressure in distant oceans may lead to variations of climatic elements in Iran. This study aims at indicating the impact of North Atlantic and Mediterranean oscillation teleconnection patterns on variations of cloudiness during winter season in Iran.
in this study, initially for 53 points in Iran the monthly cloudiness reanalysis data from NCEP for a 35-year period (1979-2013) with a resolution of 1.86 degree was obtained. Thereafter, the correlation between cloud covering was calculated for December to March, with Mediterranean oscillation (1979-2000) and the North Atlantic Oscillation data (1979-2013). in the figure below gridded point is represented by a map.
Data of percent cloudiness in Iran figure 1) The distribution of gridded point for
The obtained results show that under the best of circumstances in northwestern of Iran, the highest correlation between Mediterranean and the North Atlantic Oscillation index with cloudiness is -0.62 and -0.59 for January and February, respectively. Also, in all of the winter months, there is a significant negative correlation between teleconnection patterns and cloudiness at least for one area of Iran. Effect of the teleconnection patterns on the cloudiness, in terms of spatial was more uniform compared to precipitation. As a result, in the negative phase, cloudiness was steadily increased at Iran but as shown in previous investigations and also current study this was less evident regarding the precipitation.