Agrometeorological conditions of grassland vegetation in central Mongolia and their impact for leaf area growth

The long‐term observation of surface heat and water budget and hydrometeorological elements has been carried out over a grassland site at Arvaikheer (46.23°N, 102.82°E) in central Mongolia as the framework of the GEWEX Asian Monsoon Experiment‐Asian Automatic Weather Station Network (GAME‐AAN). The purpose of this study is to clarify the relationship between vegetation and climate using long‐term data (1982–2000) of satellite‐derived leaf area index (LAI) and climatic data observed at Arvaikheer. Furthermore, we aimed to reveal physical process by comparing soil moisture and heat and water budgets in 1999 and 2000 as a case study of good and poor vegetation growth. Significant positive correlations with 99% confidence levels were found for July precipitation (P) and the LAI in July (0.538), August (0.826), and September (0.564). Composite analysis for five highest (H5) and lowest (L5) LAI years showed the significant positive anomalies of P in July and LAI in July and August for H5. In June and July 1999, soil moisture and P values were higher than values in 2000; this pattern was reversed in August and September. The mean LAI during the 1999 growing season (1.0) was about twice that of 2000 (0.6). In 1999 the ratio of evapotranspiration (ET) to P (ET/P) and change of stored soil moisture (Δ W ) to P (Δ W /P) were 0.79 and 0.15, respectively. In 2000, ET/P and Δ W /P were 0.94 and 0.0, respectively. These results suggest that the P and Δ W before July had the most influent on grass growth in central Mongolia.