Analysis of the Land Surface Temperature and NDVI using MODIS Data on the Arctic Tundra during the Last Decade
Mattar, Cristian1; Durán, Claudio1; Jiménez-Muñoz, Juan Carlos2; Sobrino, J.A.2
1University of Chile, CHILE; 2University of Valencia, SPAIN

The arctic tundra is one of the most sensible biome to climate conditions which has experienced important changes in the spatial distribution of temperature and vegetation in the last decades. Previous studies used meteorological and remote sensing data to analyze the relationship between vegetation and surface temperature surface variations. In this paper we analyzed the spatio-temporal trend of the Land Surface Temperature (LST) and the Normalized Difference Vegetation Index (NDVI) over the arctic tundra biome during the last decade (2001-2012). To perform this analysis, long term data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) land products MOD11C3 (LST) and MOD13C2 (NDVI) were used. Additionally, air (Tair) and skin (Tskin) temperature extracted from ERA-Interim Reanalysis data in the period 1979 - 2011 were also used. Anomalies for each variable were analyzed at monthly level, and the magnitude and statistical significance of the trends were computed using the non-parametric tests of Sen's Slope and Mann-Kendal respectively. The results obtained from MODIS LST data showed a significant increase (p-value < 0.05) on surface temperature over the arctic tundra in the last decade. Similar results were obtained when using Reanalysis data in same time period. In the case of the NDVI, the trend was positive (increase on NDVI) but statistically not significant (p-value < 0.05). All tundra regions defined in the Circumpolar Arctic Vegetation Map have presented positive and statistically significant trends in all the NDVI, LST, Tair and Tskin variables. Values of trends obtained from MODIS data over all the tundra regions were +1.10 [°C/dec] in the case of LST and +0.005 [NDVI value/dec] in the case of NDVI. Values of trends obtained from Reanalysis data were +1.20 and +0.95 [C°/dec] with p-value < 0.05 for Tskin and Tair, respectively. Surrounding areas such Alaska presented an abrupt decrease in air and skin temperature, also evidenced in MODIS LST data. On the other hand, results obtained from Reanalysis data in the last three decades also showed positive and statistically significant trend over the whole tundra region.