Maps (IMAGE) University of California - Santa Barbara Caption The top map on the left represents the current normalized difference vegetation index (NDVI) conditions (April 11-20, 2012), and the bottom left is the average for this time of year. The top right map is the difference between the top (current) and bottom (normal) on the left, and the bottom right map is the "significance" or "z-score" of that difference. Credit Joel Michaelsen Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.