Analyses of air temperature and precipitation anomalies with in the south and west coastal regions of the Caspian sea for the period 1961-2023
Authors:   A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Drygval Anna , Drygval Polina ,   A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Gorbunova Tatiana ,   A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Kerimov Ibragim ,   Millionshchikov Grozny State Oil Technical University
Published: January 2025

Introduction. The issue of climate change has been an important subject of many studies in recent decades because of its far - reaching negative consequences for the socio - economic development of regions, causing unfavourable phenomena and processes and affecting the transformation and restructuring of the functioning of landscapes in general. Materials and methods. This article deals with the issue of studying climate change trends by analysing the anomalies of air temperature and precipitation within the southern and western parts of the Caspian Sea watershed on the example of seven key areas of the selected river basins. The object of the study is the territory of the southern and western coast of the Caspian Sea catchment with the basins of medium and small rivers (in particular, the basins of the Gorgan and Heraz rivers in Iran, the Karachay and Atachay rivers in Azerbaijan, and the Sulak, Sunzha, and Ulluchay rivers in Russia). To identify and evaluate anomalies, several key areas were identified, within which statistical anomalies were calculated, using the Z-analysis method (standardized anomaly method). Two types of anomalies were calculated: for the entire territory of the southern and western coasts of the Caspian Sea, taking into account elevation zones, and for the key sections of river basins. Results. One of the main results of the study was the identification of three key time periods: 1961-1981, 1982-2004 and 2005-2023, which are characterised by multidirectional changes in the direction of trends, as well as the assessment of climate change in the study region over 63 years. Graphical material in the form of maps describing the zones of distribution of anomalies of mean multiyear temperature and precipitation anomalies within the southern and western parts of the Caspian Sea watershed area was prepared. Discussion. It was found that the higher the altitude, the more pronounced are the positive temperature anomalies, while negative anomalies are present only up to altitudes of 3000 m. Negative temperature anomalies are predominant in the Caucasus, and positive temperature anomalies are predominant in the area of the Elburs mountain system. Negative precipitation anomalies are detected only at altitudes of 2000 m and above. Negative precipitation anomalies are found only at altitudes above 2000 m (occurring in small patches on the southern border of the Caspian Sea catchment, closer to the northern slopes of the Elburs mountain system), while positive anomalies appear everywhere, but mainly on the northern slopes of the Caucasus Mountains and within the southern and south - western coast of the Caspian Sea. On average, the volume of long - term precipitation averages that correspond to anomalous values decreased by 18 mm for positive and 41 mm for negative anomalies during the period under consideration. Positive temperature anomalies are noted only in the Gorgan River basin, and negative ones - in the southern part of the Sulak River basin. The tendency of decreasing the zone of positive temperature anomalies in the river basins was revealed. Negative anomalies of mean multiyear precipitation are not found within the studied river basins, but positive anomalies are found within the Sunzha River basin, as well as slightly north of the Heraz River basin, closer to the coastal zone of the Caspian Sea. Conclusions. The most significant temperature increase on the southern and western coasts of the Caspian Sea was recorded over the last 19 years (2005-2023), where mean multiyear temperatures increased by an average of 1.1°C and mean multiyear precipitation decreased by an average of 35 mm. Suggestions for practical application and direction for future research. The results obtained in this article can serve as valuable information for further study of climate change in the Caspian region.