In the case of the AVHRR GAC archive, an additional source of uncertainty may impact the quality of the data: it consists of the data reduction methodology sellekchem used for transforming the 1.1 km resolution AVHRR data into the coarse resolution of the GAC archive [23,24].Depending on the different corrections applied and processing streams and algorithms used, successive efforts have produced different coarse resolution AVHRR NDVI datasets from the original GAC data. The most common and broadly used ones are, from the earliest to the foremost, Pathfinder AVHRR Land (PAL I and II) [24,25], Fourier-Adjustment, Solar zenith angle corrected, Interpolated Reconstructed (FASIR) [26], Global Monitoring and Mapping Studies (GIMMS) [27], and Land Long-Term Data Record (LTDR) [28] datasets.

Several studies have evaluated the consistency of the NDVI trends across the PAL, FASIR, and GIMMS AVHRR datasets in different regions of the world (e.g., [29,30]), and have also compared them to those derived from SPOT VEGETATION and MODIS Terra sensors (e.g., [31]). In some of these regions, the NDVI trends have been consistent across datasets and Inhibitors,Modulators,Libraries sensors, for instance, in the humid Sahel (but not in the driest; [31]), or the Chilean arid zones [4]. Contrary, in other regions, the use of different datasets has led to conflicting findings, potentially due to differences in the processing and corrections applied to the GAC data [e.g., 3,4,32,33]. Despite the LTDR dataset is the most recently produced one and incorporates much of the learning from the previous efforts, Inhibitors,Modulators,Libraries it does not still exist any published study that includes this dataset to evaluate the consistency of the NDVI trends.

This is also the case of the Iberian Peninsula (Spain and Portugal), where previous studies have calculated the NDVI trends based on AVHRR datasets at the regional [34�C37] and local [38�C40] Inhibitors,Modulators,Libraries scales, but Inhibitors,Modulators,Libraries none have evaluated their consistency across different datasets. Following up the suggestions of recent works [3,4,31], Entinostat in this article we evaluate the spatial consistency of four AVHRR NDVI datasets to detect NDVI trends in the Iberian Peninsula, with a special focus on the recently released LTDR dataset. We also evaluated the error budget of the NDVI trends from the different slopes obtained across datasets. As far as we know, this is the first evaluation of the performance of the new LTDR dataset to detect NDVI trends.

2.?Data and Methods2.1. Satellite DatasetsWe focused on the Iberian Peninsula to compare the 1982�C1999 NDVI selleck trends across four datasets derived from the GAC archive of the AVHRR sensor (NOAA-7, -9, -11, and -14 satellites; for a comparison of the datasets see Table 1 in this paper, and Table 1 in Baldi et al. [4]). We used the portion of the images located between 35�� N and 45�� N latitude, and 3.5�� E and 10.2�� W longitude. The period considered includes both extremely dry and wet periods for the Peninsula [41,42].Table 1.