Zhang Xiaoyang, Tan Bin, Yu Yunyue
Geospatial Sciences Center of Excellence (GSCE), South Dakota State University, 1021 Medary Ave., Wecota Hall 506B, Brookings, SD, 57007-3510, USA,
Int J Biometeorol. 2014 May;58(4):547-64. doi: 10.1007/s00484-014-0802-z. Epub 2014 Mar 18.
Land surface phenology is widely retrieved from satellite observations at regional and global scales, and its long-term record has been demonstrated to be a valuable tool for reconstructing past climate variations, monitoring the dynamics of terrestrial ecosystems in response to climate impacts, and predicting biological responses to future climate scenarios. This study detected global land surface phenology from the advanced very high resolution radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) data from 1982 to 2010. Based on daily enhanced vegetation index at a spatial resolution of 0.05 degrees, we simulated the seasonal vegetative trajectory for each individual pixel using piecewise logistic models, which was then used to detect the onset of greenness increase (OGI) and the length of vegetation growing season (GSL). Further, both overall interannual variations and pixel-based trends were examined across Koeppen's climate regions for the periods of 1982-1999 and 2000-2010, respectively. The results show that OGI and GSL varied considerably during 1982-2010 across the globe. Generally, the interannual variation could be more than a month in precipitation-controlled tropical and dry climates while it was mainly less than 15 days in temperature-controlled temperate, cold, and polar climates. OGI, overall, shifted early, and GSL was prolonged from 1982 to 2010 in most climate regions in North America and Asia while the consistently significant trends only occurred in cold climate and polar climate in North America. The overall trends in Europe were generally insignificant. Over South America, late OGI was consistent (particularly from 1982 to 1999) while either positive or negative GSL trends in a climate region were mostly reversed between the periods of 1982-1999 and 2000-2010. In the Northern Hemisphere of Africa, OGI trends were mostly insignificant, but prolonged GSL was evident over individual climate regions during the last 3 decades. OGI mainly showed late trends in the Southern Hemisphere of Africa while GSL was reversed from reduced GSL trends (1982-1999) to prolonged trends (2000-2010). In Australia, GSL exhibited considerable interannual variation, but the consistent trend lacked presence in most regions. Finally, the proportion of pixels with significant trends was less than 1 % in most of climate regions although it could be as large as 10 %.
陆地表面物候学已在区域和全球尺度上广泛通过卫星观测获取，其长期记录已被证明是重建过去气候变化、监测陆地生态系统对气候影响的动态响应以及预测生物对未来气候情景响应的宝贵工具。本研究利用1982年至2010年的先进甚高分辨率辐射计（AVHRR）和中分辨率成像光谱仪（MODIS）数据检测全球陆地表面物候学。基于空间分辨率为0.05度的每日增强植被指数，我们使用分段逻辑模型为每个像素模拟季节性植被轨迹，然后用于检测绿色度增加开始时间（OGI）和植被生长季长度（GSL）。此外，分别考察了1982 - 1999年和2000 - 2010年期间柯本气候区的总体年际变化和基于像素的趋势。结果表明，1982 - 2010年期间全球OGI和GSL变化很大。一般来说，在降水控制的热带和干旱气候区，年际变化可能超过一个月，而在温度控制的温带、寒冷和极地气候区，年际变化主要小于15天。总体而言，1982年至2010年北美和亚洲大部分气候区的OGI提前，GSL延长，而持续显著的趋势仅出现在北美的寒冷气候和极地气候区。欧洲的总体趋势一般不显著。在南美洲，OGI出现较晚较为一致（特别是1982年至1999年），而在1982 - 1999年和2000 - 2010年期间，一个气候区的GSL正负趋势大多相反。在非洲的北半球，OGI趋势大多不显著，但在过去30年中个别气候区的GSL延长明显。在非洲的南半球，OGI主要呈现出现较晚的趋势，而GSL从缩短趋势（1982 - 1999年）转变为延长趋势（2000 - 2010年）。在澳大利亚，GSL表现出相当大的年际变化，但大多数地区缺乏一致趋势。最后，尽管在大多数气候区有显著趋势的像素比例可能高达10%，但在大多数气候区该比例小于1%。
