HR: 1330h
AN: H33B-07    [Abstracts]
TI: Feedbacks of vegetatoin on summertime climate variability over North America Grasslands
AU: * Wang, W
EM: wlwang@bu.edu
AF: Boston University, Dept. of Geography, 675 Commonwealth Ave., Boston, MA 02215
AU: Anderson, B T
EM: brucea@bu.edu
AF: Boston University, Dept. of Geography, 675 Commonwealth Ave., Boston, MA 02215
AU: Phillips, N
EM: nathan@crsa.bu.edu
AF: Boston University, Dept. of Geography, 675 Commonwealth Ave., Boston, MA 02215
AU: Kaufmann, R K
EM: kaufmann@crsa.bu.edu
AF: Boston University, Dept. of Geography, 675 Commonwealth Ave., Boston, MA 02215
AU: Myneni, R B
EM: rmyneni@bu.edu
AF: Boston University, Dept. of Geography, 675 Commonwealth Ave., Boston, MA 02215
AB: This paper uses the notion of Granger causality to analyze feedbacks of vegetation on summertime climate variability over the North America Grasslands. Results indicate that NDVI anomalies early in the growing season have statistically significant Granger causal relationship with precipitation and temperature later in summer (Jul.-Oct.). The nature of the relationship indicates higher mean values from the preceding months may lead to (or Granger cause) lower rainfall but higher temperatures in July through September. These results suggest that initially enhanced vegetation may dry soil faster than normal, and thereby influence climate variability through the strong soil moisture/precipitation coupling in this region. At the same time, decreasing trends of NDVI over the season also lead decreases in precipitation. Here the decreasing NDVI is a proxy for decreases in underlying soil moisture, which through the same mechanism, will result in decreased precipitation later in the season. Also consistent with this mechanism, a negative causal relationship is identified from temperature to precipitation in summer. However, it is also found that temperature may prompt precipitation at the beginning and the end of the growing season. Such changes of the causal relationship may be related to the seasonal shifts of atmospheric circulation patterns over this region.
DE: 1833 Hydroclimatology
DE: 1851 Plant ecology
DE: 1878 Water/energy interactions
DE: 3307 Boundary layer processes
DE: 3322 Land/atmosphere interactions
SC: Hydrology [H]
MN: 2005 Joint Assembly