HR: 16:30h
AN: A24A-02    [Abstracts]
TI: The Role of Sea Surface Temperature in Reanalysis
AU: * Kanamitsu, M
EM: mkanamitsu@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, Mail Code 0224 CRD/SIO/UCSD 8605 La Jolla Shores Drive, La Jolla, CA 92093-0224 United States
AU: Hwang, S
EM: hwangso@kma.go.kr
AF: Korea Meteorological Administration, 460-18 Sindaebang-dong Dongjak-gu, Seoul, Korea, Republic of
AB: Aiming at understanding the role of SST in the Reanalysis for the pre-radiosonde, pre-satellite and satellite era, a number of observation system experiments were performed using the NCEP/DOE reanalysis system. Five pairs of experiments were performed using observed and climatological SSTs for cases 1) without any observation, 2) surface pressure observation only with the observation density of 1915, 3) surface pressure observation with the observation density of 1997, 4) surface observation and radiosondes and 5) all observations, including satellite retrievals. The analyses were run for 4 months in 1979 (strong El Nino) and 1993 (near normal SST). The impact of SST and the change in the observation system on the analysis of near surface parameters, upper level field and some diagnostic fields were compared against the control analysis with observed SST and all available observations. The most important finding of this study is that the impact of SST varies with the time scale of the analysis, which is most apparent in surface pressure only observation experiments. The impact of SST is largest for the low frequency (seasonal) analysis and smaller for the high frequency (daily) analyses. This is particularly apparent for near surface temperature and upper level height field analyses. In our extreme case of the strong El Nino year, the simulation with observed SST without any observations (AMIP type run) produced seasonal mean 2-meter temperature and 500 hPa height fields, agreeing better with the control analysis than the analysis with surface pressure observation only with climatological SST. On the contrary, the impact of surface pressure observation shows up more on the higher frequency analyses, and less on the low frequency analyses. Generally speaking, accurate analysis of SST is important when very little atmospheric observation is available. But even for the full atmospheric observation system, climatological SST produces inferior analysis not only over ocean but also over land. The introduction of radiosonde data to the system drastically reduces errors in all the analyses, and thus, radiosonde data are indispensable for accurate estimation of the atmospheric state both in the short and long time scales.
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 3337 Numerical modeling and data assimilation
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly