Markaziy Osiyo tog‘laridagi yog‘inlar: izotop tarkibi va namlik manbalari

Annotatsiya

Over 900 event-based precipitation samples were collected in 2019–2021 in the Tien Shan and its foothills and analysed using cavity ring-down spectroscopy. δD and δ¹⁸O values were highest in summer and lowest in winter, and annual cycles of deuterium excess (d-excess) varied between sites, reflecting local conditions. The δ¹⁸O and δD values increased from north to south in all seasons except autumn, and latitude was a statistically significant predictor of δ¹⁸O and δD in the overall data set, along with elevation in winter and elevation and longitude in autumn. Elevation was a significant predictor of d-excess in all seasons, and local air temperature was a more important control over δ¹⁸O and δD than precipitation depth. Local meteoric water lines were derived using seven regression methods applied to non-weighted and weighted precipitation. Non-weighted ordinary least squares regression and reduced major axis regression methods are recommended overall, except for summer when the precipitation-weighted least squares regression should be used, particularly in the south. Atmospheric back-trajectory and mixing-model analyses were applied in combination to identify air mass source regions and their relative contribution to precipitation. Recycled moisture from irrigated land in the Amu Darya and Syr Darya basins and from the study catchments accounted for 29 %–71 % of precipitation, depending on the site and season. In the Chon Kyzyl-Suu catchment, local re-evaporation from Issyk-Kul accounted for up to 85 % of precipitation. These findings highlight the importance of moisture from terrestrial sources, especially irrigated land, for the formation of precipitation in the Tien Shan.

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Sodda qilib aytganda

2019–2021-yillarda Qozog‘iston, Qirg‘iziston, O‘zbekiston va Tojikistondagi Tyan-Shan, Pomir-Oloy tog‘lari va ularning etaklaridagi to‘qqizta nuqtada 915 ta yog‘in namunasi olindi. Ularning deyarli barchasi alohida yomg‘ir yoki qordan so‘ng darhol yig‘ilgan. Namunalarda kislorod va vodorodning barqaror izotoplari (δ¹⁸O va δD) o‘lchandi. Uchta nuqta O‘zbekistondagi Chirchiq havzasida joylashgan: Oyg‘aying (1 490 m), Piskom (1 255 m) va Toshkent (486 m). Bu tadqiqotgacha global GNIP bazasida O‘zbekiston yog‘inlariga oid atigi yettita izotop o‘lchovi bo‘lgan, ularning hammasi Toshkentdan.

Izotop nisbatlari yozda eng yuqori, qishda eng past bo‘lib, shimoldan janubga tomon ortib boradi. Ularga yog‘in miqdoridan ko‘ra mahalliy havo harorati kuchliroq ta’sir qiladi. Butun mintaqa uchun mahalliy meteor suv chizig‘i δD = 7,56 δ¹⁸O + 8,65 ko‘rinishida bo‘lib, global chiziqdan (δD = 8 δ¹⁸O + 10) pastroq o‘tadi. Chirchiq havzasi uchun u δD = 7,66 δ¹⁸O + 7,65 ga teng. Chiziq qiyaligi qish va bahorda kattaroq, yozda esa eng kichik: bu faslda mayda yomg‘ir tushayotganda qisman bug‘lanadi. Mualliflar ko‘p hollarda oddiy eng kichik kvadratlar yoki keltirilgan katta o‘q regressiyasini, yozda esa, ayniqsa janubda, yog‘in miqdori bilan tortilgan regressiyani tavsiya qiladi.

Havo massalarining teskari traektoriyalari va aralashish modeli shuni ko‘rsatdiki, Amudaryo va Sirdaryo havzalaridagi sug‘oriladigan yerlardan hamda tadqiqot havzalarining o‘zidan qayta bug‘langan namlik nuqta va faslga qarab yog‘inlarning 29–71% ini beradi. Oyg‘ayingda qish, bahor va kuzda yog‘inlarning 68,8–70,6% i mahalliy namlikdan hosil bo‘lgan, yozda esa 73,1% ini g‘arbiy havo massalari keltirgan. Toshkentda namunalar kam bo‘lgan va yozgi qiymatlar u yerdagi yuqori haroratga mos kelmagan. Mualliflar fikricha, buni sug‘oriladigan yerlardan qayta bug‘langan suv bilan izohlash mumkin, biroq buni tasdiqlash uchun ko‘proq namuna kerak.

Rasmlar (2)

Iqtibos namunasi

Z. Saidaliyeva, M. Shahgedanova, V. Yapiyev, A. J. Wade, F. Akbarov, M. Esenaman uulu, O. Kalashnikova, V. Kapitsa, N. Kasatkin, I. Rakhimov, R. Satylkanov, D. Sayakbaev, E. Semakova, I. Severskiy, M. Petrov, G. Umirzakov and R. Usubaliev (2024). Precipitation in the mountains of Central Asia: isotopic composition and source regions. Atmospheric Chemistry and Physics, 24(21), 12203–12224. https://doi.org/10.5194/acp-24-12203-2024