5:15 PM - 6:30 PM
[ACG39-P05] Analysis on the long-term wintertime drying trend over the northeastern Siberia
Keywords:northeastern Siberia, drying trend, water budget equation
It is well known that, due to the global warming, annual mean precipitation over the high-latitude land areas of the Northern Hemisphere has been significantly increasing since the middle of the 20th century. On the other hand, in the northeastern Siberia which is located at the easternmost part of the Eurasian continent, precipitation has been significantly decreasing, particularly in the winter season from December to February. In this study, we investigated the reason why the wintertime precipitation has been significantly decreasing in the northeastern Siberia.
We analyzed the Japanese 55-year Reanalysis (JRA-55) dataset for the 58-winter season from 1958 to 2016, based on the atmospheric water budget equation. Prior to the analysis, we verified reproducibility of precipitation changes of the JRA-55, comparing with GPCC dataset which is the ground-based observation data by rain gauges, and found that both datasets show significant decreasing trend in winter precipitation over the northeastern Siberia. According to the vertically-integrated atmospheric water budget equation, long-term changes in precipitation, evaporation, and horizontal divergence of vertically-integrated water vapor flux are balanced, assuming that the long-term change in local time derivative of precipitable water is very small. Geographical distributions of the long-term trends for these three terms, calculated using JRA-55, show that increases in the water vapor divergence are significant in the confidence interval of 90%, in addition to the significant decreases in precipitation. Furthermore, comparing the water vapor flux vector between the first 10 years (1958 to 1968) and the last 10 years (2006 to 2016) of the analysis period, we found that the water vapor inflow from the North Pacific to the northeastern Siberia is decreasing. We will also discuss factors that caused changes in the water vapor flux.
We analyzed the Japanese 55-year Reanalysis (JRA-55) dataset for the 58-winter season from 1958 to 2016, based on the atmospheric water budget equation. Prior to the analysis, we verified reproducibility of precipitation changes of the JRA-55, comparing with GPCC dataset which is the ground-based observation data by rain gauges, and found that both datasets show significant decreasing trend in winter precipitation over the northeastern Siberia. According to the vertically-integrated atmospheric water budget equation, long-term changes in precipitation, evaporation, and horizontal divergence of vertically-integrated water vapor flux are balanced, assuming that the long-term change in local time derivative of precipitable water is very small. Geographical distributions of the long-term trends for these three terms, calculated using JRA-55, show that increases in the water vapor divergence are significant in the confidence interval of 90%, in addition to the significant decreases in precipitation. Furthermore, comparing the water vapor flux vector between the first 10 years (1958 to 1968) and the last 10 years (2006 to 2016) of the analysis period, we found that the water vapor inflow from the North Pacific to the northeastern Siberia is decreasing. We will also discuss factors that caused changes in the water vapor flux.