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Surface pressure observation - A view from Reanalysis -

Long-term historical analysis using fixed assimilation systems is crucial to maintain data quality and prevent climate change due to system alterations. This paper explores the challenges and methods of analyzing surface pressure using various observations, including winds and satellite data, while emphasizing the dynamical nature of surface pressure and the need for further research. Recommendations include freely sharing data with reanalysis communities and archiving observational data properly.

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Surface pressure observation - A view from Reanalysis -

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  1. Surface pressure observation- A view from Reanalysis - By Masao Kanamitsu Presented by Shyh-Chin Chen CRD/SIO/UCSD

  2. Reanalysis • Long series of historical analysis using fixed assimilation system (and data quality control system), to avoid climate change due to analysis system change. • Fictitious climate signal due to change in observation system is unavoidable • may require fixed observation reanalysis

  3. Reanalysis in progress • ECMWF ERA-45 • US National Reanalysis Program is now under consideration (2005?) • NOAA, NASA, NSF, DOE, DOD, …

  4. Surface pressure observation in reanalysis • Modern objective analysis utilizes a variety of observations simultaneously to analyze desired fields. • Surface pressure can be analyzed from: • Surface pressure • Surface (10m) winds • Satellite (IR and SSM/I) obs • Upper air obs. • Satellite cloud motion vectors • SST • Analysis is consistent to these observations within their observation error

  5. Objective analysis and surface pressure • Dynamical constraints in objective analysis makes surface pressure as “weak” variable, meaning easily driven by other fields (such as winds), and prone to modification by initialization process. • But this is strongly dependent on the analysis system (more true for 3-D var but probably not so for 4-D var) • It may not be easy to obtain surface pressure observation using simple dynamical balance

  6. Dynamical property of surface pressure • Strongly affected by gravity wave • Large diurnal and semi-diurnal oscillation, particularly in tropics • “Weak” variable

  7. Research required • Research on reconstruction of 3-dimensional atmospheric fields from surface pressure. • May be possible with the use of 4-D var • Surface pressure tendency observation may become important. • Research on diurnal and semi-diurnal variation of surface pressure needs to be performed to properly analyze global pressure field. • It is necessary to maintain instantaneous observation for use in data assimilation.

  8. Recommendation • Make the data freely available to Reanalysis communities. • Archive of surface pressure tendency should be considered. • Consider separate archive of instantaneous and monthly average observation. • Observational from new instruments should be properly archived. • Any consultation with Roy Jenne (NCAR)?

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