Sunday, November 25, 2007

Postponed again

It is unlikely I will write another complete discussion for this Blog until next weekend at the soonest. Briefly, the change to the USA cold regime I discussed roughly a week ago is generally on track. However, globally westerly wind flow throughout the atmosphere has increased dramatically over the last 7-10 days. Global relative AAM is currently near to slightly above average, up ~3AMUs. The eastward shift of tropical convective forcing to ~0/160E, strong positive surface torques and suspected eddy feedbacks have led to the rapid increase in westerly flow. Largest zonal mean contributions have been from the equatorial and midlatitude atmospheres of both hemispheres.

Phase 5 of the GWO best describes the global weather-climate situation. I think we are in the process of a having a large circuit of the GWO. A wind signal from the MJO is contributing. An important monitoring issue will be to see how far west the tropical convective forcing redevelops across the Eastern Hemisphere during the next few weeks. I speculate that the current extension of the East Asian jet will "break through" the eastern Pacific ridge ~week 2, followed by re-amplification of existing PNA circulation anomalies ~20-30 deg of longitude farther west weeks 3-4.

Appendix

An experimental quasi-phase space plot of the GSDM utilizing a time series of normalized relative AAM tendency anomaly (Y-axis) and normalized relative AAM anomaly time series (X-axis) can be found at



http://www.cdc.noaa.gov/map/clim/gsdm.shtml

We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous the WH2004 “convention”. In addition, the GWO plot does not have the ENSO signal removed.

Links to CPC and PSD ENSO discussions:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml


These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment composite maps, composite signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. I will try to post a complete discussion next weekend.

Ed Berry

2 comments:

Jean-Jacques Rousseau said...

Do you believe that we face a "global warming" crisis? The reason I ask is that you are obviously an objective scientist with a keen interest in meterology. I'm guessing you might have something valuable to say on the subject.

Ed Berry said...

Hi Jean,

Thank you for the comment. I apologize for my slow response. We focus our research on subseasonal atmospheric variability. However, since our work involves weather-climate linkage, the global warming trend cannot be and is not ignored by us. Examples include the expansion of the west Pacific Ocean warm pool during the last few decades as well as a warming Indian Ocean. Recent responses have included tropical convective forcing across both regions often simultaneously. In fact, this trend may have played a role in shutting down El-Nino about a year ago.

The cause of this warming is still unclear to me, understanding the latest IPCC report, etc. I cannot help but feel that this trend could quickly reverse given what I am learning about forcing-response-feedback relationships, issues with modeling, etc.

Ed Berry