基于AVHRR和MODIS数据的全球植被物候比较分析

Comparative Analysis of Global Vegetation Phenology based on AVHRR and MODIS

AVHRR和MODIS卫星数据在全球和区域尺度植物物候对气候变化响应研究中起着重要的作用,然而两种传感器在全球尺度物候监测的一致性有待验证。首先利用时间序列谐波分析法(HA-NTS)对2005年全球GIMMS AVHRR NDVI和MODIS 13A2数据进行滤波处理;然后基于改进的动态阈值方法,提取全球植被的返青期(SOS)、枯黄期(EOS)和生长季长度(DOS);最后分区域比较和评估两种传感器提取物候参数的潜力。研究结果表明:2005年全球大部分地区植被在第100～140d开始生长,到第260～300d逐渐停止生长,生长季长度集中在130～180d,并且和区域研究结果具有一致性;两种传感器提取的植被关键物候期的空间变化趋势是一致的,随着纬度升高,返青期呈现推迟趋势,枯黄期呈现提早趋势,生长季长度呈现缩短趋势;AVHRR和MODIS提取落叶林和草地的SOS、EOS和DOS在欧亚大陆和北美洲区域的相关系数大部分达到0.9以上。

The AVHRR and MODIS satellites have played a vital role in monitoring vegetation phenology responses to climate change at a global scale. It is important to examine whether the derived phenological parameters from AVHRR are consistent with from MODIS. In this paper,a dynamic threshold method was applied to extract the phenological metrics based on GIMMS AVHRR NDVI and MODIS 13A2 NDVI data- set smoothed with HANTS in 2005 ,such as Start of Season （SOS）,End of Season （EOS）,and Duration of Season （DOS）. Then, the comparative analysis was performed on the phenological metrics between AVHRR and MODIS. The results showed the SOS appeared between 100th and 140th days, the EOS oc- curred between 260th and 300th days,the DOS mainly existed from 130th to 180th days in most regions. The phenological variation along latitude based on AVHRR was consistent with based on MODIS,a trend of later SOS,an earlier EOS and a shorter DOS with increase of latitude were observed. The SOS,EOS and DOS from AVHRR and MODIS data were quite consistent with a correlation coefficient larger than 0.9 for the deciduous forests and grasslands in Eurasia and North America.