Reference Pressure for GGOS J Boehm H Schuh

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Reference Pressure for GGOS J. Boehm, H. Schuh

Reference Pressure for GGOS J. Boehm, H. Schuh

Atmosphere Loading • dh = ( p p ) r • If r =

Atmosphere Loading • dh = ( p p ) r • If r = 0. 5 mm/h. Pa, the reference pressure p has to be known with an accuracy of 2 h. Pa to get the millimeter.

Atmosphere Loading • Global atmosphere loading models already use mean pressure grids. • A

Atmosphere Loading • Global atmosphere loading models already use mean pressure grids. • A corresponding grid of heights might not be available with them. • Even if it is available, care has to be taken (Gaussian Grids vs. Cartesian Grids).

Requirements for the mean pressure • • It should be 'accurate enough' (mostly <

Requirements for the mean pressure • • It should be 'accurate enough' (mostly < 2 h. Pa). Mean pressure should refer to a height field. Easy calculation (subroutine for coordinates). Unambiguously determinable now and in future.

Example • 2. 0° x 2. 5° grid of mean surface pressure values from

Example • 2. 0° x 2. 5° grid of mean surface pressure values from 1994 to 2007 • Global Pressure and Temperature GPT (spherical harmonic expansion up to degree and order 9) • Berg (1948) (1013. 25 h. Pa at mean sea-level + height-dependent reduction)

2. 0° x 2. 5° Grid vs. Berg land + ocean land < 2

2. 0° x 2. 5° Grid vs. Berg land + ocean land < 2 h. Pa < 10 h. Pa 27 % 83 % 28 % 85 %

2. 0° x 2. 5° Grid vs. GPT land + ocean land < 2

2. 0° x 2. 5° Grid vs. GPT land + ocean land < 2 h. Pa < 10 h. Pa 71 % 98 % 56 % 96 %

Summary 2. 5° x 2. 0° Grid GPT Berg Accuracy Yes/No No Height-Relation Yes

Summary 2. 5° x 2. 0° Grid GPT Berg Accuracy Yes/No No Height-Relation Yes Yes Easy calculation Not yet Yes Unambiguous Not yet Yes

Action Items • A 1 Collect available models and compare them.

Action Items • A 1 Collect available models and compare them.