TVDI from OLI/TIRS and MODIS images

Abstract The aim of the study was to analyze the variability in the TVDI (Temperature-Vegetation Dryness Index) obtained from orbital sensors with distinct resolution in an agricultural region in southern Brazil. Three images of the Landsat 8 satellite OLI/TIRS (Operational Land Imager/Thermal Infrared Sensor) and 12 of Terra’s MODIS (Moderate Resolution Imaging Spectroradiometer), were used. Data collected in the field served as a basis for OLI/TIRS image classification and mapping of rice, soybean, grasslands, gallery forest and bare soil areas. The TVDI obtained by two parameterizations at different periods was evaluated, using the dispersions between Surface Temperature (TS) and NDVI (Normalized Difference Vegetation Index). The TVDI obtained for both sensors presented a similar pattern allowing differentiation of the targets. The average of all dates and classes, TVDI obtained from MODIS was 0.128 units higher than the obtained with the OLI/TIRS. When used OLI/TIRS there is a better detail in the representation of the moisture, but with less repetition throughout the crop cycle. Using TVDI-MODIS, it is possible to monitor moisture conditions on a regional scale, with less spatial detail, but in a continuous way over time. The TVDI estimated by the OLI/TIRS and MODIS can be used together, providing complementary information.

摘要 本研究旨在分析巴西南部农业区域内，不同分辨率轨道传感器获取的温度植被干旱指数(Temperature-Vegetation Dryness Index, TVDI)的变异性。本研究使用了陆地卫星8号（Landsat 8）的运行陆地成像仪/热红外传感器(Operational Land Imager/Thermal Infrared Sensor, OLI/TIRS)影像3景，以及Terra卫星的中分辨率成像光谱辐射计(Moderate Resolution Imaging Spectroradiometer, MODIS)影像12景。野外实测数据被用作OLI/TIRS影像分类以及水稻、大豆、草地、河岸林与裸土区域制图的基础依据。本研究通过地表温度(Surface Temperature, TS)与归一化植被指数(Normalized Difference Vegetation Index, NDVI)之间的离散程度，对不同时期下两种参数化方案得到的TVDI进行了评估。两款传感器获取的TVDI呈现出相似的分布模式，可实现对地物目标的有效区分。所有观测日期与地物类别的平均结果显示，MODIS反演得到的TVDI较OLI/TIRS高出0.128个单位。使用OLI/TIRS时，地表湿度的表征细节更为出色，但在作物生长周期内的观测频次较低。而采用MODIS-TVDI则可在区域尺度上开展湿度状况监测，虽空间细节稍显不足，但可实现长时间连续的动态监测。OLI/TIRS与MODIS反演得到的TVDI可结合使用，以提供互补的监测信息。