Journal of Climate Research

Journal of Climate Research

Investigating changes in the heat budget of the Caspian Sea in relation to the convergence flux of water vapor

Document Type : Original Article

Authors
Elham Davari Touchahi 1
zahra hejazi zadeh 2
Hooshang Ghaemi 3
Mehdi Nadi 4
1 Ph.D. student in Climatology, Kharazmi University, Tehran
2 Faculty member and professor of Kharazmi University
3 Research Institute of Meteorology and Atmospheric Sciences
4 Associate Prof., Irrigation Dept. Sari Agricultural sciences and Natural Resources University.
10.22034/jcr.2025.207215
Abstract
The study of the effect of the atmosphere and the ocean is one of the most important topics in meteorology and climatology. In this study, in order to investigate the physical potential of the Caspian Sea in creating and enhancing precipitation, the changes in the thermal budget of the sea and its relationship with the convergence flux of water vapor in a 30-year period (1991-2020) were examined monthly. Due to the expansion of the Caspian Sea in the direction of latitude, this sea was divided into three basins: North, Central and South. The results showed that in all three ponds, energy is received in the cold seasons of the year and energy loss occurs in the hot seasons. The total heat flux in all three basins has positive changes from September to the end of February, which is the highest amount of energy output, and parallel to the increase of the total heat flux in the southern part of the sea (from October to February), a maximum core of water vapor convergence flux in the southern basin It's formed. In this situation, as the warm period of the year approaches, the intensity of the water vapor convergence core decreases and negative values of the water vapor flux are seen in the region. In terms of seasonal distribution, there are positive flows in autumn and winter, and negative flows in spring and summer. Finally, these investigations show that thermal budgeting will be an important step in seasonal precipitation forecasting in coastal areas and the investigation of these conditions will allow to determine the behavior of the total heat flux, the volume of water vapor in the atmosphere and the water vapor flow. He predicted the finding of the Caspian Sea into the air pack.

The results show that in the three basins of the Caspian Sea, the extent of the sea along the longitude and receiving different radiation energy in different latitudes, the topographic diversity of the sea floor and as a result the mixing speed of deep and shallow waters, as well as the entry of rivers with different temperatures to the sea, it will cause a change in the temperature regime and heat flux of the whole sea. In the southern basin, from the beginning of September to the end of December, the total heat flux is at its lowest value compared to the middle and northern basins; But this situation changed in January and February and the lowest amount is seen in the northern basin of the Caspian Sea. From March to May, the greatest loss of total heat flux is observed in the northern basin, but in June, July and August, these conditions occur in the central basin (with a slight difference compared to the northern basin). In terms of seasonal distribution, a climatic view of the total heat flux can be observed. In this way, the two seasons of winter and autumn have absorbed the positive flows of the total heat, and the seasons of spring and summer have allocated the negative flows.

These conditions make it possible to predict the amount of water vapor in the atmosphere and water vapor flowing from the Caspian Sea into the air package based on the behavior of the total heat flux. In this regard, it was tried to check the monthly distribution of water vapor flux in the region based on the change in the behavior of the total heat flux. The results of this study showed that with a short time delay, the water vapor fluxes have changed in parallel with the change in the total heat flux. From May to October, in most areas of the Caspian Sea, the negative flow of water vapor prevailed, and the main currents were north and northeast; At the same time as the loss of the total heat flux, the water vapor flux has also decreased. With the beginning of increasing the total heat flux and positioning itself in its positive state in the southern half of the Caspian Sea, concentrated and strong cores of positive moisture flux are formed, which have reached up to 9 g/kg. These conditions are mainly in the cold period of the year and continue from October to March. Of course, during the periods when the total heat flux values were negative in most areas of the Caspian Sea, positive water vapor fluxes can be seen in the southern coasts, especially in the southeast and southwest. As Amini (2016) and Fathi (2018) showed, the heating resulting from the transfer of water from the sea to air masses increases the flow of water vapor, and this plays an important role in the occurrence of precipitation. On the other hand, Liu et al. (2023) also showed that there will be a strong relationship between the changes in the total heat flux and the transfer of moisture to the air mass, which is also confirmed in the study area. By examining the research of Yari (2015), it was also observed that seasonal changes cause changes in the temperature budget of the Caspian Sea. In fact, the rule of a two-season system in energy transfer between the Caspian Sea and the atmosphere is in progress. This sea absorbs energy in spring and summer and loses energy in autumn and winter. The comparison of the results reported by this researcher with the results of the present study is relatively good. Finally, these investigations show that heat budgeting will be an important step in seasonal rainfall forecasts in coastal areas. On the other hand, with the assumption of knowing the atmospheric-oceanic circulation, it is possible to observe these types of events in the occurrence of precipitation events during the anomalies in the total heat flux and changes in the moisture flux.
Keywords
heat budget
water vapor flux
monthly flux distribution
Caspian Sea

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Journal of Climate Research
Volume 1403, Issue 59 - Serial Number 59
Vol. 15, No. 59,, Autumn 2024
Winter 2025
Pages 17-32