, CHANGES OF ARIDITY INDICES IN MONGOLIA // BSU bulletin. Biology, geography. - 2017. №4. . - С. 83-90.

CHANGES OF ARIDITY INDICES IN MONGOLIA

This research was funded by the Science and Technology Foundation of Mongolia project number 201500053

UDK: 911.7

Aridity is one of the major indicators to delineate territories prone to desertification, thus the present paper discusses spatial and temporal variability of aridity in the past over the Mon- golia. The aridity were calculated using four temperature and precipitation based indices: 1) de Martonne aridity index (IDM); 2) Thornthwaite aridity index (AI); 3) moisture coeffi- cient by V.I. Mezentsev (MI) and 4) Hydrothermal coefficient by Selyaninov (HTC). The basic meteorological data from 70 stations in Mongolia for the period of 1961-2015 are used in present paper. The area of drylands (hyper-arid, arid, semi-arid and subhumid regions) is different depending on used index. According to the results drylands delineated by IDM, MI, AI and HTC is 64.1%, 70.7%, 85%, and 98%, respectively. Out of 4 aridity indices, AI and MI showed high correlation with NDVI derived dryland regions. According to the temporal analysis of AI and MI around 66% of a time series had a decreasing tendency during ob- served period of time. The central and northeastern regions of the country have the signifi- cant decreasing trends of the aridity indices. The relative changes of the aridity indices vary between 14%-74% for stations with significant decreasing trend.

aridity index; Mongolia; trend; relative change.