Assessment of stratospheric basic states in the CFS T382L64 forecast experiment

1
Assessment of stratospheric basic states in the
CFS T382L64 forecast experiment

2
Main findings

• Stratosphere is a great indicator of the general
  health of models. We find that the CFS
  stratosphere is too cold. The high resolution
  (T382) CFS made some improvement to the low
  resolution (T62) model, but the cold bias are
  still very large for longer forecast.

3
Outline

• CFS T382L64 forecast experiment
• Initial date May 15 of each year from 1981
  to 2006
• Forecast months June to October
• Observations
• Reanalysis-2
• CPC analysis (Z, T)
• Climatology (Z, T, U, ) 1981-2006 mean

4
(No Transcript)
5
Operational CFS (T62). 15-member ensemble run.
1982- 2005 climatology. (courtesy of P. Peng)
High-resolution CFS (T382). Single member run
initiated at May 15. 1981-2006 climatology.
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
Total Ozone Climatology
21
Total Ozone Climatology
22
Summary

• While the CFS forecast climatology agrees well
  with observations in the troposphere, there is
  apparently a large cold bias in the stratosphere.
• The cold bias is smaller than the T62 GFS in NH
  and tropics.
• The maximum stratospheric cold bias is found in
  the southern winter polar upper stratosphere.

23
Summary (continued)

• The cold bias grows linearly with forecast time.
• In consistence with the cold bias, the CFS
  forecast of stratospheric geopotential height is
  lower, the southern winter polar night jet stream
  is stronger.
• The CFS total ozone climatology does not show
  much low bias.