NAO and OLR patterns

[rainbird]

Please answer another question - What are NAO and OLR patterns? Why are these patterns either negative or positive? Always learning and lurking -Thank you very much again -

[wxmann_91]

CRAP!! Somehow I got logged out and my post was deleted. Oh well, got to start over again...

The NAO (North Atlantic Oscillation) determines the amount of ridging over Greenland. A strongly negative NAO indicates a strong ridge over Greenland. This usually causes patterns upstream to shift into a trough in the east/ridge in the west pattern. Also, this is associated many times with increased pressures in the arctic regions and decreased surfaces pressures over the Tropical Atlantic, meaning a greater possibility of tropical development.

OLR (Outgoing Longwave Radiation) is a measure of the cloudiness and association convection over an area. Negative/low OLR indicates increased convection (decreased sunlight), positive/high OLR indicates more sunlight and less convection. It is most often used in the tropics in conjunction with the MJO (Madden-Julian Oscillation). There are several phases of the MJO which favor different areas of the Tropics to receive anomalously high or low amounts of convection. For example, notice the difference between the Atlantic and the WPAC right now. There is clearly less OLR over the WPAC. Sometime's you'll hear the phrase wet or dry MJO, it's really refering to OLR and the amount of convection induced by a specific phase of the MJO. But most here actually don't know that. Obviously, decreased OLR indicates more vertically ascent and instability, and that helps TC genesis.

Interestingly, google is down right now (!), so I'll stop here. But when it's back up I'll be sure to provide some links on the subject.

You're welcome.

[rainbird]

Appreciate - would be interested in your links - Thank you much -

[wxmann_91]

http://meted.ucar.edu/climate/mjo/

http://www.icess.ucsb.edu/asr/MJO_current_run.htm

http://jisao.washington.edu/data_sets/nao/

http://www.cpc.ncep.noaa.gov/data/teledoc/nao.shtml

http://www.metoffice.com/research/seaso ... ional/nao/

http://www.cpc.noaa.gov/products/precip ... _mrf.shtml

http://www.cpc.noaa.gov/products/precip ... _ensm.html

[rainbird]

Great links! - Thank you again -