Analysis of near-surface diurnal temperature variations and trends in southern Mexico

We assembled daily maximum temperature, minimum temperature and precipitation records for 143 stations in southern Mexico over the period 1960-2004. We found that the average temperature for the region has increased linearly at a rate of 0.086 °C per decade with maximum temperatures increasing at twice that rate and minimum temperatures basically remaining unchanged. This results in a highly statistically significant increase in the diurnal temperature range of 0.160 °C per decade. We found that the variations and trends in maximum temperatures, minimum temperatures and the diurnal temperature range were generally unrelated to various measures of El Niño-Southern Oscillation (ENSO) or the Pacific Decadal Oscillation (PDO). Variations in regional precipitation amounts could explain 22.6% of the monthly variations in the diurnal temperature range, but not the trend over the 1960-2004 time period.