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Tropopause Height Diagnostics

Tropopause Height Diagnostics. Motivation tropopause is important feature of the observed atmosphere determined by conditions in both tropo- and stratosphere position of tropopause is relevant for climate studies: e.g. cross tropopause transport

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Tropopause Height Diagnostics

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  1. Tropopause Height Diagnostics • Motivation • tropopause is important feature of the observed atmosphere • determined by conditions in both tropo- and stratosphere • position of tropopause is relevant for climate studies: • e.g. cross tropopause transport • indicator of climate change • Method • apply same criterion as for determination from radiosondes: • a. lowest level at which lapse rate decreases to 2 K/km • b. 2 km deep layer above must not exceed critical lapse rate • problem of coarse vertical resolution > vertical interpolation • limit for heights to be valid: 450-75 hPa • failure rate: overall 0.1%, mostly over Antarctica during JJA • rms: 30-40 hPa in extratropics, 10-20 hPa in tropics • Input Data • 3D temperature field: daily or monthly data • all comparisons on standard pressure levels

  2. Tropopause pressure (hPa)daily reanalysis-1: CDC vs. TJR DJF 1983-1998 JJA CDC TJR

  3. reanalysis-1 vs. reanalysis-2 DJF 1983-1998 JJA rean. 2 rean. 1

  4. reanalysis-1: daily vs. monthly data DJF 1983-1998 JJA monthly data daily data

  5. p11/exp55dan DJF 1983-1998 JJA AM2 monthly r1 monthly

  6. exp42 vs. exp55dan DJF 1983-1998 JJA exp42 - r1 exp55dan - r1

  7. p12L32_3 vs. exp55dan DJF 1983-1998 JJA p12L32_3 - r1 exp55dan - r1

  8. CAM 2.0.1 DJF 1983-1998 JJA CAM monthly r1 monthly

  9. NSIPP DJF 1983-1998 JJA NSIPP monthly r1 monthly

  10. NCEP SFM DJF 1983-1998 JJA SFM monthly r1 monthly

  11. Summary • AM2 tropopause height is generally too low (too high pressure), consistent with a too cold troposphere and too warm stratosphere • biases over northern extratropics: • +30 hPa in DJF (ca. -600 m) • +10 hPa in JJA (ca. -200 m) • tropical biases: • +8 hPa in DJF (ca. -600 m) • +3 hPa in JJA (ca. -200 m) • biases over southern extratropics: • -20 hPa in DJF • +20 hPa in JJA • global mean rms of tropopause pressure (hPa):

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