رویکردی نوین در شناسایی میزان محل قرار گیری جبهه نسیم دریا در سواحل دریای خزر

نوع مقاله: مقاله پژوهشی

نویسندگان

استادیار، دانشگاه شهید بهشتی- دانشکده علوم زمین، گروه جغرافیا

چکیده

نسیم دریا از جمله پدیده های میان مقیاس جوی، ویژه مناطق ساحلی است. هدف این مطالعه بررسی ساعات شروع نسیم دریا در هر کدام از فصول سال، میزان پیشروی نسیم دریا به سمت خشکی و شناسایی جبهه نسیم دریا می باشد. بدین منظور ابتدا آمار ساعتی جهات باد از ایستگاه های مورد مطالعه در فاصله زمانی(2015-2011) از سازمان هواشناسی دریافت گردید، سپس روزهایی که جهت باد در ایستگاه ها از سمت ساحل به سمت خشکی بودند، استخراج گردید. برای تعیین میزان تفاوت های دمایی از خط ساحلی تا خشکی از محصول دمای سطح زمین(LST) سنجنده مادیس با توان تفکیک مکانی 1000 متر در روزهای غیر ابری استفاده گردید. نتایج بیانگر آن است که نسیم دریا پدیده بارز در سواحل جنوبی خزر می باشد، ساعات شکل گیری نسیم دریا با توجه به اختلاف دما بین خشکی و دریا در ماههای مختلف متفاوت است. از آنجائیکه بیشترین اختلاف دما بین خشکی و دریا در عصرها رخ می دهد، محیط چگال گرای قوی تر نیز در این ساعات ایجاد می شود،بگونه ای که در اکثر نمونه های مطالعاتی ساعات شروع نسیم دریا در ماههای دی، بهمن و آذر در ساعت 12 به وقت گرینویچ، در ماههای مهر، آبان، اسفند، فروردین و اردیبهشت از ساعت 9 و در ماههای خرداد، تیر، مرداد و شهریور در ساعت 6 به وقت گرینویچ می باشد. دریاچه خزر با توجه به وسعت و عمق کمتر نسبت به اقیانوس ها و تفاوت های دمای اندک نسبت به محیط های اقیانوسی، مشخصه های آب و هواشناختی روزانه آن باعث شده که حداکثر پیشروی نسیم دریا به سمت خشکی در مسافت های طولانی انجام نگیرد. حداکثر گسترش نسیم دریا در خشکی تا مسافت 13 کیلومتری مشاهده می شود و در تمامی نمونه های مطالعاتی منطقه همگرایی جبهه نسیم دریا کمتر از 13 کیلومتر در داخل خشکی پیشروی داشتند. در بیشتر نمونه های مطالعاتی، در زمان هایی که اختلاف دمایی بین ساحل و دمای جبهه نسیم دریا مشاهده نمی شود، عمق نسیم دریا و مسافت آن کمتر و در زمان هایی که اختلاف دمایی زیادتر می شود عمق نسیم دریا و پیشروی آن در داخل خشکی زیادتر می شود.

کلیدواژه‌ها


عنوان مقاله [English]

A New Approach in Determining the Location of the Sea Breeze Front on the Caspian Sea Coast

نویسندگان [English]

  • Ghasem Keykhosravi
  • Ameneh Yahyavi
چکیده [English]

Introduction:
Sea breeze is atmospheric and intermediate Ocean phenomenon that depends on the temperature difference between sea surface and drought and is generally formed under conditions of clear sky. When the sea breeze penetrates dry, its impact on temperature, humidity, clouds and rainfall can be very clear. The sea breeze is usually associated with lowering the temperature and increasing the moisture content of the atmosphere. The initiation of a sea breeze sometimes is characterized by a sudden discontinuous region, called the "sea breeze". The occurrence of this front is connected to the relatively dense, cool, and stable sea of indoor air, which makes the warm and volatile air mass rise near the sea breeze. Due to the wind's convergence near the front, the accumulated air often mixes together and forms clouds. Therefore, the presence of the sea breeze front can often be deduced from the appearance of a line of coulomb clouds parallel to the shore that is under the pressure of the sea breeze (Smith 1976; Simpson 1994).
Methodology:
In this study, in order to determine the sea breeze front in the study area, first, during the statistical period (2015-2011), using the wind directions at different hours in the days when at each of the stations, the wind direction from the coast was drought To determine the occurrence of the sea breeze. The time of the beginning of the sea breeze at each of the seasons was determined by the stations, and then the product of the Earth's surface temperature was measured on days when the satellite images were not cloudy. Afterwards, in the Envi software environment, you are plotting the cross-sectional temperature profile from the coast to the land at each station. The location of the sea breeze was determined by the sudden change of temperature in descending order, and then the amount of distance that the sea breeze was moving forward in dry times was calculated in any given day.
Discussion:
The periods of formation of the sea breeze vary according to the amount of sunshine, and the periods of warming and drying in different months. Beginning in the months of December, January and November at 12 GMT, in the months of October, November, March, April and May, at 9:00 and in June, July, August and September, from 6:00 GMT, the Sea of Aziz To be formed. The rate of advance of the sea breeze depends on various factors such as latitude, local winds, distances and proximity to heights, etc., can affect the progress of the sea breeze to land. The Caspian Sea, due to its small size and depth compared to the oceans and the small differences in temperature between oceanic and oceanic environments, its daily climatic characteristics have caused the maximum advance of the sea breeze to land over long distances. At Anzali Station, on average, in all seasons, the maximum take-off reaches 5 kilometers. At the Babolsar station, the autumn season has a further advance (4.9 km) compared to other seasons. At the KishaShahr station, the sea breeze penetrates more than other stations, reaching an average of 6.5 km in the spring, summer and autumn seasons. At the station of Noshahr, the spring season has the smallest advance to land (3.5 km). Therefore, the difference in sea water temperature and dryness in the southern margin of the Caspian Sea caused different depths and sea breeze levels in different seasons, so that the maximum pace of the sea breeze among the study samples reaches 13 km at the station of Kianeshahr.
Conclusion:
According to the studies carried out in this study, the results indicate that the sea breeze is a clear phenomenon on the southern shores of the Caspian Sea. The formation of the sea breeze is different in different months depending on the temperature difference between land and sea. As the greatest difference in temperature between land and sea occurs in the evenings, a more powerful condensation environment is created at these times, As in most of the study samples, the first days of the sea breeze in the months of December, January and November at 12:00 GMT, in the months of October, November, March, March, and May from 9:00 and in June, July, August and September It's at 6 o'clock in Greenwich. The maximum spread of the sea breeze at a distance of 13 kilometers is observed, and in all the study samples of the region, the convergence of the Sea of Breeze front was less than 13 kilometers inland. In most study samples, at a time when there is no temperature difference between the coast and the temperature of the sea breeze, the depth of the sea breeze and its distance are less, and at times when the temperature difference is greater, the depth of the sea breeze and its progression in the higher land Gets.

کلیدواژه‌ها [English]

  • Southern coast of the Caspian Sea
  • sea breeze
  • surface temperature
  • sea breeze front