كليدواژه :
هسته هاي امواج سرمايي , تحليل طيفي , واريانس , آماره الكساندرسون , شمال غرب ايران
چكيده لاتين :
Introduction
One of the varieties of climate change is Cyclical Cycles Gradual and calm. Spectral analysis is one of the most useful tools for searching and evaluating these types of climate fluctuations. In recent decades, the application of spectral analysis in climatic fluctuations has received a special attention on a global scale; but in our country less attention has been paid. Detection of climatic cycles, and especially temperature cycles, provides planning based on climatic-temperature data. Since temperature is one of the most important climatic elements that its various states can affect other elements, it is a good indicator for climate change, so fluctuations and temperature variability are of great scientific and practical importance. The purpose of this study was to investigate and analyze the spatial variations of northwest cooling wave nuclei in different periods. In this study, the fluctuations of cold waves were not analyzed. Therefore, in order to complete the work of previous researchers, we have tried to study the fluctuations and cycles of cold waves in recent decades.
Matherials & Methods
In fact, in time series, the trend is simply manifested by drawing a simple linear graph; Therefore, in this analysis, it is attempted to reveal these fluctuations, or in other words, the latent alternatives and, of course, of importance in the series, whether these frequencies are large and occur at small frequencies, or in small fluctuations, and in High frequencies have occurred with a short period of return. In practice, spectral analysis does not speak of time, which means that it is not said that an event occurs at a given time, rather than the probability of occurrence of the cycles that have the most variance in the time series. A tool by which the behavior of a series of cycles can be modeled by trigonometric functions; therefore, in this technique, the waveforms, extraction, and the contribution of each of them in the total variance are determined. Finally, after extraction of variance, all waves are examined statistically significant.
Discussion of Results
Since the cooling waves are directly affected by the temperature, therefore, the mutation in the cooling waves, in addition to being influenced by local systems, can lead to human error due to the recording and measurement of the data. Nonetheless, the results of the Alexander Sun model for cooling waves have shown that there has been no jump in the average frequency of cooling waves. This situation is true for other continuities. This situation is true for other continuities. However, there are other behaviors in each series that are called irregular or random variations. These changes are completely random and are the result of unpredictable factors that are in some way irregular. Such changes do not have any definite design, and their occurrence is irregular and usually short-lived. Sometimes their impact is so large that it causes periodic changes and other changes.
Conclusions
Temperature is one of the most important climatic elements whose fluctuation always causes the formation of climate processes. One of the most important temperature fluctuations is the downward movement that results in cold waves as it passes through a predetermined limit. The cold waves are always considered as having a direct impact on human activities, especially agriculture. These waves can cause irreparable damage in the event of continuity. In this study, a day was chosen as a cold wave, which, in addition to its standard score of less than 1.2, was below the 5th percentile of the same day and covers a spatial extent of 50%. The crustal nuclei were mostly concentrated in the eastern and southern regions of the study area. However, in some of the continuations of the spots of cold wave nuclei, there has been little observation in the north of the studied area. he results of the analysis of the spatial self-dependence model within the decade of this study show that the core of the cold waves was more concentrated in the central regions, especially the uneven topographic regions of the study area. However, in some of the continuations, spots of cold-wave currents have been observed insignificantly in the north of the study area. With these interpretations, over the past few years, from 2010 to 2000, North-West Wave Crystals have been more distributed and dispersed. In recent times, the spatial distribution of the cooling coils has been reduced and the intensity of these waves has been reduced to two to six days.
