An approach for developing Landsat-5 TM-based retrieval models of suspended particulate matter concentration with the assistance of MODIS

It is challenging to develop Landsat-5 TM (TM5) image-based retrieval models for estimating the suspended particulate matter concentration (C_SPM) in water when missing coincident ground C_SPM measurements. This study, with the Poyang Lake in China as a case study, proposed an approach for developing TM5-based C_SPM retrieval models with the assistance of moderate resolution imaging spectroradiometer (MODIS) images. After validation with an independent dataset, a cubic C_SPM retrieval model of 250 m MODIS red band was used to estimate the C_SPM values at 100 sampling points from the MODIS images (MODIS-based C_SPM) captured at three time periods. The MODIS-based C_SPM values at the time period with the largest C_SPM variation were combined with their coincident TM5 image reflectance for TM5-based model calibrations. The linear, quadratic, cubic, power and exponential models of MODIS-based C_SPM against TM5 single bands and their combinations were calibrated, respectively. Four best-fitting TM5-based C_SPM models were selected to retrieve the C_SPM values at 100 sampling points from the TM5 images (TM5-based C_SPM) at the other two time periods, and the coincident MODIS- and TM5-based C_SPM values were compared to assess TM5-based model performances. Model calibration results showed that the cubic and exponential models of TM5 red band (band 3) and red subtracting mid-infrared band (band 5) obtained the best fitting for estimating C_SPM from the TM5 image on 12 August 2005, and they explained 94–97% of the variation of MODIS-based C_SPM values with an estimated standard error of 6.617–8.457 mg/l. Model validations indicated that the exponential model of TM5 red band got the best result for estimating C_SPM from TM5 images when the MODIS-based C_SPM values were assumed as ground truths (correlation coefficient between MODIS- and TM5-based C_SPM values = 0.96, root mean square error = 4.60 mg/l). We concluded that the TM5-based C_SPM retrieval models could be developed with the assistance of MODIS, and the approach proposed in this study will be helpful for other researchers who also want to retrieve C_SPM from TM5 image archive but without coincident ground C_SPM measurements.