slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Can a reanalysis using a frozen model (fixed CO2) have an anthropogenic trend ? (Cai and Kalnay, submitted to J. of C PowerPoint Presentation
Download Presentation
Can a reanalysis using a frozen model (fixed CO2) have an anthropogenic trend ? (Cai and Kalnay, submitted to J. of C

Loading in 2 Seconds...

play fullscreen
1 / 5

Can a reanalysis using a frozen model (fixed CO2) have an anthropogenic trend ? (Cai and Kalnay, submitted to J. of C - PowerPoint PPT Presentation


  • 377 Views
  • Uploaded on

Can a reanalysis using a frozen model (fixed CO2) have an anthropogenic trend ? (Cai and Kalnay, submitted to J. of Climate) Intuition may suggest that Reanalysis would at most show only a watered down trend of greenhouse warming, but it is wrong.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Can a reanalysis using a frozen model (fixed CO2) have an anthropogenic trend ? (Cai and Kalnay, submitted to J. of C' - paul


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1
Can a reanalysis using a frozenmodel (fixed CO2) have an anthropogenic trend?(Cai and Kalnay, submitted to J. of Climate)
  • Intuition may suggest that Reanalysis would at most show only a watered down trend of greenhouse warming, but it is wrong.
  • Cai and Kalnay (2003, subm. to J of Cl) show analytically that essentially the full trend present in the observations appears in the Reanalysis after a short transient.
an analogy of our reasoning

An analogy of our reasoning

versus

Observation Model

(a constant warming) (a constant drift)

Q: What does a data assimilation system do with observations?

A: In nut shell, at each observational time, a data assimilation

system does a weighted average of the observation

with the model forecasts started from previous

analysis.

an analogy of our reasoning cont

= 50/%

< 36%

Step 1

Step 2

The bleaching glass represents the model adjustment to the imbalance

between the model physics and the assimilated temperature.

< 22%

< 2%

Step 3

Step N

Weights assigned to observation and to model = 0.5

An analogy of our reasoning (cont.)

results

Observation:

  • Model without data assimilation:

“Watered-down

effect”

  • Analysis (weight assign to model a ):

Analysis step/model adjustment time step

RESULTS

slide5

0.995

0.99

0.98

0.95

0.90

0.75

0.5

0.25

Analysis Step N

Ratio of the trend between two consecutive analysis cycles to the trendin the observation as a function of N, the analysis step starting from N = 1, and (1 – a), the weight assigned to the observation in the data assimilation procedure for Dt/t = 0.01. (Cai and Kalnay, subm. to J. of Clim., 2003)

1-a