The MODIS/Terra Land Surface Temperature and Emissivity (LST/E) products provide per-pixel temperature and emissivity values in a sequence of swath-based to grid-based global products. The MODIS/Terra LST/E Daily L3 Global 1 km SIN Grid,(Short name: MOD11A1), is a gridded version of the L2 Daily LST/E data set, whose LSTs are retrieved by the split-window algorithm.
The Collection-4 (C4) LST/E L3 MOD11A1 product inputs include the MODIS L1B calibrated and geolocated radiances, geolocation, cloud mask, atmospheric profiles, land and snow cover. The band 31 and 32 emissivities are estimated by a classification-based emissivity method, which relies on the pixel's land cover type as determined by the land and snow cover inputs. Until June 2001, the AVHRR-based IGBP land cover product was used. Following that time, MODIS-derived land cover product was used. The estimated emissivities in arid and semi-arid areas are potentially uncertain, and users are advised to exercise caution in their applications. The day/night alogorithm extracts average temperatures (in Kelvin) and applies them to a pair of MODIS daytime and nighttime observations. This method yields 1 K accuracy for materials with known emissivities. The V4 MOD11A1 product has a temporal acquisition range of February 24, 2000 (2000-055) until January 3, 2007 (200-003). The C4 collection remains consistent with C41, and users may combine the two collections in a time-series analysis.
The MODIS/Terra Collection 41 (C41) products use a modified Collection-4 (C4) LST algorithm and Collection-5 (C5) data inputs. The C41 products primarily address underestimation problems in the C5 Climate Modeling Grid (CMG) products. Recent validation activities reveal that the C5 CMG products underestimate LSTs up to 6K especially in desert and semi-arid regions. The availability of this collection starts with MODIS/Terra data acquisition on January 1, 2007 (2007-001). This date is driven by the availability of the MODIS C5 data inputs (level-1B radiance data, geolocation data, cloud mask, atmospheric profiles, and land and snow cover data).
The MODIS/Terra C5 LST/E L3 Global 5 km Grid product incorporates 1-km pixels, which are produced daily using the generalized split-window LST algorithm. This algorithm is optimally used to separate ranges of atmospheric column water vapor and lower boundary air surface temperatures into tractable sub-ranges. The surface emissivities in bands 31 and 32 are estimated from land cover types. The C5 MOD11_L2 product's acquisition range started March 5, 2000 (2000-065) and will continue until some time after the C6 reprocessing is complete.
The C41 and C5 MODIS/Terra LST/E products, including the MOD11A1, are validated to Stage-2 with well-defined uncertainties over a range of representative conditions. Further details regarding MODIS land product validation for the LST/E products are available from the MODIS land team validation site referenced under 'Val Status' section.
The C41 LST products from 2007-001 will remain consistent with similar products from C4, and hence are amenable to combine them in a time-series analysis. Users should exercise caution, and not mix the C4.x (i.e., C4 and C41) and C5 LST products in their analyses.