Extended Abstract (2.3M)J6.5
Recent climate variability in Antarctica from satellite-derived temperature data
David P. Schneider, University of Washington, Seattle, WA; and E. J. Steig and J. Comiso
Considerable interest has been shown in documenting and explaining recent climate changes in the Antarctic. Because Antarctic meteorological observations are short and sparsely distributed, questions remain about both the sign and magnitude of trends across most of the continent. Furthermore, relatively little is known about Antarctica’s background climate variability. Such knowledge is needed both to place recent climate changes into context and to understand what is recorded in “proxy” ice core records from the continent. We investigate Antarctica’s climate variability on monthly to interannual time scales for the most recent two decades through a joint analysis of surface temperatures from satellite thermal infrared observations (TIR) and passive microwave brightness temperatures (TB). Although TIR data are limited to clear-sky conditions and TB data are not simply the surface temperature, but reflect the thermal diffusivity and microwave absorption and scattering physics of the upper ~ 1m of snow, the two data sets share significant covariance. This covariance is largely explained by three empirical modes, which illustrate the spatial and temporal variability of Antarctic surface temperatures. Comparison of the temperature modes with Southern Hemisphere (SH) 500-hPa geopotential height anomalies demonstrates that Antarctic temperature anomalies are predominantly controlled by the principal patterns of SH atmospheric circulation. The leading surface temperature mode strongly correlates with the Southern Annular Mode (SAM) in geopotential height. The second temperature mode reflects the combined influences of the zonal wavenumber-3 and Pacific South American (PSA) patterns in 500-hPa height on month-to-month timescales. The third temperature mode explains winter warming trends, which may be caused by blocking events, over a large region of the East Antarctic plateau. By relating the spatially-detailed satellite observations to Antarctic station records, we make a preliminary EOF-based reconstruction of temperature variations across Antarctica back to 1960.
Joint Session 6, Observed Climate Variability (JOINT with THE 15TH SYMPOSIUM ON GLOBAL CHANGE AND CLIMATE VARIATIONS AND THE 14TH CONFERENCE ON APPLIED CLIMATOLOGY (Room 609/610)
Thursday, 15 January 2004, 3:30 PM-5:30 PM, Room 609/610
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