In situ and satellite surface temperature records in Antarctica

Air-temperature records (T A ) during 1992 from five inland Antarctic automatic weather station (AWS) sites were compared with the best available infrared temperatures (T IR ) from the Advanced Very High Resolution Radiometer (AVHRR) as well as calibrated passive-microwave temperatures (T C ) from the Special Sensor Microwave/Imager (SSM/I). Daily and monthly average T A , T IR , and T C data indicate that each approach captures generally similar trends at each site but each approach also has limitations. AWS T A data are considered the most accurate but represent spatially restricted areas and may have long gaps due to sensor or transmission problems. AVHRR T IR data have daily variability similar to the T A record but have numerous small gaps due to cloud cover or observation interruptions. An offset between T A and T IR (>4 K) at the South Pole site was identified that may be due to the inclusion of data with large satellite scan angles necessary to cover this area. SSM/I T C data have the most continuity but exhibit calibration problems, a significantly damped daily response and do not cover all of Antarctica. Individual daily differences between T A and T IR as well as T A and T C can exceed 17 K, but all sites have mean daily differences of about 1 Kor better, after compensating for the offset at South Pole, and standard deviations of <6K. Monthly temperature differences are typically 5 K or better, with standard deviations generally <3K. And finally, using the available data, the 1992 average temperature differences are <1 K.