MODELING RELATIONSHIPS BETWEEN NDVI AND PRECIPITATION DURING VEGETATIVE GROWTH CYCLES

This paper describes how NDVI responds to daily precipitation for vege tation under water-limited growth conditions (e.g., in arid or semi-ar id environments). An analytical model was developed to address timing to peak NDVI response and total duration of NDVI response to a rainfal l event with the passage of time. The model also describes how effecti vely the vegetation uses precipitated water. A case study in the Sandh ills area of Nebraska, with NDVI calculated from Landsat-MSS images, s howed that the model can accurately portray NDVI time series, and then can be used to derive some useful information about relations of NDVI and precipitation. For the vegetation in the test area, we found that the peak vegetative response to a precipitation event shifts from abo ut 14 days after the rainfall event at the beginning of a growing seas on to 25 days at the late stage of the season, and then shifts back to 12 days at the end of the season. The duration of response, similar t o the peak response in behavior, is 22, 61, and 25 days, respectively.