Monitoring California Drought And Its Impact On Ecosystems Using GRACE And MODIS Data.
Tuesday, April 21, 2015
Meng Zhao1, Isabella Velicogna1, Geruo A2 and John S Kimball3, (1)University of California Irvine, Irvine, CA, United States, (2)University of California Irvine, Department of Earth System Science, Irvine, CA, United States, (3)University of Montana, Missoula, MT, United States
Abstract:
We use GRACE (Gravity Recovery and Climate Experiment) terrestrial water storage estimates, Evapotranspiration (ET) and Normalized Difference Vegetation Index (NDVI) from MODIS (Moderate-Resolution Imaging Spectroradiometer) together with reanalysis global climate model output to monitor drought impact on vegetation growth in California during 2003-2014. We use a GRACE based drought severity index (GRACE-DSI) together with a MODIS based drought severity index (MODIS/re-analysis-DSI, Mu et al., 2013) to characterize the California drought events during the past decade and their impact on ecosystems. GRACE-DSI provides information about water storage availability to vegetation, whereas the MODIS-DSI allows monitoring of vegetation response to water stress. In general, we find a good agreement between the two indices, except during severe drought events. In that latter case, the combined analysis of GRACE-DSI and MODIS-DSI provides new insights about the response of ecosystems to severe drought events, in particular about the time scale of the response. In the absence of severe droughts, the GRACE-DSI presents the advantage of being based on direct, monthly observations instead of re-analysis data.
