Impact of interannual variability of meteorological parameters on vegetation activity over Mongolia

This study is designed to elucidate the impact of interannual variability of meteorological parameters on vegetation activity over Mongolia using 10-day composite NDVI (Normalized Difference Vegetation Index) data set and surface meteorological data (precipitation, temperature and snow depth) for 97 meteorological stations from 1993 to 2000. The analysis is made on vegetation in two developmental stages; the rapid-growth stage (almost June to July) and the mature stage (almost July to August). Positive correlations at 99% significant level between precipitation and vegetation activity are recognized for 29% and 42% of meteorological stations in the rapid-growth stage and the mature stage, respectively. Precipitation in June and July affects vegetation activity in both stages. The impact of air temperature on vegetation activity in the mature stage differs by season. The vegetation activity is negatively correlated with summer temperature over most area. Negative correlations are found over the western part of Mongolia with respect to temperature in early winter, and positive correlations are concentrated in the northeastern part of Mongolia with respect to temperature in midwinter. Furthermore, there are five meteorological stations near the Ehenty Mountains, with high correlation coefficients between snow depth and vegetation activity in the rapid-growth stage; however, the snow depth effect is limited to a narrow region. The possibility of prediction the vegetation activity in the two stages is examined using a multiple regression method, based on the above-mentioned results. Since correlation coefficients between observed vegetation activity and estimated vegetation activity from the multiple regression equations are high satisfactorily, it is found that the prediction algorithm has a potential for the prediction of NDVI over Mongolia.