Arid regions are highly vulnerable to climate change and human activity, and global warming in particular has the potential to increase the arid land area. One traditional way to evaluate the extent of climate change in dryland regions is to use the aridity index (AI), defined as the ratio of annual rainfall to annual potential evapotranspiration. However, the AI is a climatic index; it does not represent actual conditions of aridity in arid regions. In contrast, the satellite-based aridity index (SbAI), which is based on day/night land surface temperature changes, is considered to represent actual conditions of moisture availability. Arid regions during 2001–2013 were classified at global scale by comparing the SbAI with the AI, that is, within Turc space, which is based on the water balance concept. In addition, factors contributing to aridification or wetness changes detected in different global regions were examined by comparing the SbAI and AI result with the yearly maximum normalized difference vegetation index and past land use. As a result, dryland regions were newly classified into five zones. In the stable zone, land areas were classified into hyper-arid, arid, semi-arid, or dry sub-humid regions by both the SbAI and the AI. Areas in the transition zone toward dryness are moderately dry. Areas in the transition zone toward wetness include large river basins, oases, and wadis with little rainfall. In the moist zone, rainfed or irrigated farming is being successfully conducted. Many parts of the dry zone, however, are extremely dry.

干旱地区极易受到气候变化和人类活动的影响，特别是全球变暖有增加干旱土地面积的潜力。评估干旱地区气候变化程度的一种传统方法是使用干旱指数（AI），该指数定义为年降雨量与年潜在蒸散量之比。但是，AI是气候指数。它不代表干旱地区的干旱实际情况。相反，基于昼/夜陆地表面温度变化的基于卫星的干旱指数（SbAI）被认为代表了水分供应的实际状况。通过将SbAI与AI（即Turc空间内）基于水平衡概念进行比较，对2001-2013年的干旱地区进行了全球分类。此外，通过将SbAI和AI结果与年度最大归一化差异植被指数和过去土地利用进行比较，研究了在全球不同地区检测到的导致干旱或湿度变化的因素。结果，干旱地区被重新划分为五个区域。在稳定区内，SbAI和AI将陆地区域划分为高干旱，干旱，半干旱或亚湿润干燥地区。过渡区的干燥区域为中等干燥。向湿润过渡的地区包括大流域，绿洲和浅水区，降雨少。在潮湿地区，雨养或灌溉农业正在成功进行。但是，干燥区的许多部分都非常干燥。