HIRS Pathfinder trends

Results of trend analysis of the intersatellite bias corrected data is given below. The analysis was carried out for three tropospheric temperature channels 4, 5 and 6. It should be noted that the intersatellite bias for channels 4 and 5 can be on the order of several K! (See diagrams in Intercalibration section), so interpretation of these trends must be handled carefully. Also, the adjustment procedure for removing intersatellite bias tends to remove long-term trends as can be seen with channel 2 in the Intercalibration section.

Global maps of HIRS 4, 5 and 6 trends were composed with the standard error of the trend, the lag-1 correlation, and the years needed for time series to reach the 95% confidence level. Channel 4 and 5 trends seem to oppose each other and correlation of the trend maps appears to be small. Channel 6 standard error map gives the largest errors in the tropical convection zones, so these errors may be related to cloud detection.

Channel 4 Global trend maps
Channel 5 Global trend maps
Channel 6 Global trend maps

Zonal mean time series for HIRS 4, 5 and 6 are given for 5 separate zonal bands. Trend lines are shown as dashed lines and the zonal time series are also smoothed with a 13-month running mean filter. As was shown with the global maps, channel 4 shows a positive temperature trend in the tropics while channel 5 shows a negative trend. Channel 6 gives very little trend for these latitude zones.

Channel 4 Global trend maps
Channel 5 Global trend maps
Channel 6 Global trend maps

Tables of trend statistics are given for the zonal times series given above. The lag-1 (T) is the lag-1 autocorrelation with the trend in the time series. Yrs Sig indicates the number of years the time series would need to extend to meet the 95% confidence level.

HIRS Channel 4 Trend Statistics

HIRS Channel 5 Trend Statistics

HIRS Channel 6 Trend Statistics