Recent Climate Change Study near Lake Hovsgol
Banzragch Nandintsetseg, Clyde E. Goulden and J. Scott Greene
The purposes of this study are to examine long-term climatic changes near Lake Hövsgöl and describe short term climate conditions for the eastern shore’s six valleys. The Hövsgöl region is located in the transition zone between the Siberian taiga, the Steppe, and the Central Asian Desert. Climate change scenarios of General Circulation Models (GCMs), suggest large shifts in the distribution and the productivity of vegetation, especially those of boreal forest systems. In the boreal zone, several scenarios suggest that ambient temperature will rise more in the winter than in the summer, and precipitation is likely to increase.
The Hövsgöl Basin has a harsh continental climate with sharply defined seasons and high annual and diurnal temperature fluctuations. The average air temperature has ranges from 12°C in July to -21°C in January, with an absolute maximum of 35˚C and an absolute minimum of -49°C. Mean annual air temperature recorded at Hatgal (southern shore of Hövsgöl) is -4.5°C. The area is semi-arid, with precipitation occurring mainly in summer months with a peak of about 100 mm in July. At Hövsgöl Lake the mean annual precipitation varies from 300 to 350 mm, increasing to 550 mm in the high mountains. Wintertime precipitation is mostly snow that on south-facing slopes tends to sublimate. There appears to be a normal four-year cycle of one year’s heavy precipitation followed by three years of low precipitation. There does not appear to be a change in precipitation associated with the warming trend, the pattern of precipitation closely follows a summer monsoonal pattern, though the origin of the rains is not a result of the monsoons, i.e., the summer monsoon rains of Asia do not extend to Mongolia. We are closely monitoring meteorological conditions in the study valleys, and reviewing longer term data sets collected at three meteorological stations located at Hanh (north end of lake), Hatgal (south end of lake) and Murun, the aimag center 80 kms south of Hovsgol National Park.
During the last 43 years the annual mean air temperature has increased 1.68°C. The winter temperature has significantly (p<0.05) increased 2.7°C, the spring (p<0.05) 2.0°C, the summer (p<0.05) 1.3°C, but the autumn temperature not significantly (p=>0.05) roses 0.9°C around the Hövsgöl Basin. Winter temperatures have increased more than during the other seasons. In general all season’s temperatures have increased over the last 43 years. The coldest winters of the 11 years occurred between 1963 and 2003. The seven coldest winters of this 43-year period occurred since 1990. The hottest summer of 14 years occurred between 1991 and 2002. The 2002 were considerably hottest summer over the period 1963 to 2003.
Changes in climate variability and extremes of weather and climate events have received increased attention in the last few years. Understanding changes in climate variability and climate extremes is made difficult by interactions between the changes in the mean and variability. Specifically, since humans and the environment often respond to extremes rather than mean conditions, it is important to determine the variability or trends in a range of extreme values, rather than just mean conditions. Significant increases were detected in the annual number of hot days and warm nights in region. Associated with these changes are concomitant decreases in the annual number of cold days and cold nights.
While the annual precipitation has not significantly increased in northern Mongolia, the number of precipitation days (e.g., days with at least two mm of precipitation) has increased. On average, there was no significant decrease in the maximum number of consecutive dry days or increase in the wet days. One change that may be an important environmental impact is the upward trend in the five-day precipitation accumulations. This would suggest an enhancement of the overall hydrologic cycle in the region, which could have significant impacts (in terms of flooding, water availability, etc.) on the local environment. The five-day precipitation total is also increasing, but the trend-line is not statistically significant.
Growing degree days above 5°C has increased 18 days between 1963 and 2005. At Hatgal and Hanh stations, however, the date air temperature passed 10 degrees has actually occurred one month earlier in the spring. This suggests what may be occurring is that evaporation has actually increased. Potential evapotranspiration has been widely used in research related to dry and wet climates. Trends of annual potential and actual evapotranspiration not significantly increased near Lake Hovsgol during the past 43 years. In addition, we estimated dryness and over wetting index near Lake Hovsgol during past 1963-2005. The maximum value of the over wetting period were observed in 1971, 1983 and the years 1983-1990 in almost territory of Northern Mongolia have observed the over wetting. In the end of the last century the years 1998, 1999, 2002 are extremely dry. In 2002, the severe drought observed in Northern Mongolia. The drought index has an increasing tendency near Lake Hövsgöl.