  Submillimeter emission lines of carbon monoxide (CO) in Titan's atmosphere
provide excellent probes of atmospheric temperature due to the molecule's long
chemical lifetime and stable, well constrained volume mixing ratio. Here we
present the analysis of 4 datasets obtained with the Atacama Large
Millimeter/Submillimeter Array (ALMA) from 2012 to 2015 that contain strong CO
rotational transitions. Utilizing ALMA's high spatial resolution in the 2012,
2014, and 2015 observations, we extract spectra from 3 separate regions on
Titan's disk using datasets with beam sizes of ~0.3''. Temperature profiles
retrieved by the NEMESIS radiative transfer code are compared to Cassini
Composite Infrared Spectrometer (CIRS) and radio occultation science results
from similar latitude regions. Small seasonal variations in atmospheric
temperature are present from 2012 to 2015 in the stratosphere and mesosphere
(~100-500 km) of spatially resolved regions. We measure the stratopause (320
km) to increase in temperature by 5 K in northern latitudes from 2012-2015,
while temperatures rise throughout the stratosphere at lower latitudes. While
retrieved temperature profiles cover a range of latitudes in these
observations, deviations from CIRS nadir maps and radio occultation
measurements convolved with the ALMA beam-footprint are not found to be
statistically significant, and discrepancies are often found to be less than 5
K throughout the atmosphere. ALMA's excellent sensitivity in the lower
stratosphere (60-300 km) provides a highly complementary dataset to
contemporary CIRS and radio science observations. The demonstrated utility of
CO emission lines in the submillimeter as a tracer of Titan's atmospheric
temperature lays the groundwork for future studies of other molecular species,
as temperature profiles are found to consistently vary with latitude in all
three years by up to 15 K.
