Summer land surface temperature from MODIS Aqua and Terra satellites for Houston in 2014 and Phoenix in 2003 at 1km resolution

Satellite remote-sensing is used to collect important atmospheric and geophysical data at various spatial resolutions, providing insight into spatiotemporal surface and climate variability globally. These observations are often plagued with missing spatial and temporal information of Earth’s surface due to (1) cloud cover at the time of a satellite passing and (2) infrequent passing of polar-orbiting satellites. While many methods are available to model missing data in space and time, in the case of land surface temperature (LST) from thermal infrared remote sensing, these approaches generally ignore the temporal pattern called the ‘diurnal cycle’ which physically constrains temperatures to peak in the early afternoon and reach a minimum at sunrise. In order to infill an LST dataset, we parameterize the diurnal cycle into a functional form with unknown spatiotemporal parameters. Using multiresolution spatial basis functions, we estimate these parameters from sparse satellite observations to reconstruct an LST field with continuous spatial and temporal distributions. These estimations may then be used to better inform scientists of spatiotemporal thermal patterns over relatively complex domains. The methodology is demonstrated using data collected by MODIS on NASA’s Aqua and Terra satellites over both Houston, TX and Phoenix, AZ USA.

Methods
These land surface temperature data were collected by MODIS onboard NASA's Aqua and Terra remote-sensing satellites, over Houston, TX (28 June-4 July 2014) and Phoenix, AZ (11-17 Sept 2003). Raw data are available at https://lpdaac.usgs.gov/products/mod11a1v006/ and https://lpdaac.usgs.gov/products/myd11a1v006/, for the Terra and Aqua satellite, respectively. The data were collected twice daily for each satellite, yeilding a total of four satellite overpasses each day. The Aqua satellite passes over the regions at about 02:00 and 13:00 local time, while Terra overpasses at about 11:00 and 22:00 local time. These raw data were trimmed and prepared for use by Leiqiu Hu, coauthor on the corresponding manuscripts. Data for the Houston area are in a 151x151 grid of 1km^2 pixels, while data for Phoenix are in a 100x150 grid of 1km^2 pixels. Because we were interested in land surfaces only, we removed the water pixels -- lakes and inlets -- in the Houston area, so these appear as missing for all satellite overpasses. There were no lakes or inlets in the Phoenix area. In addition, the data quality was rated as poor for some pixels on certain days, mostly due to cloud cover. These poor-quality data were also removed, leaving additional missing data. Land surface topology is included for all pixels in both regions, in two separate data files. These land cover data were originally obtained from https://lpdaac.usgs.gov/products/mcd12q1v006/, then modified to fit the grid structure of the satellite readings of land surface temperature.