SAO

• SAO - sao.txt

This is related to the QBO behavior but occurs at higher altitudes and follows the semi-annual tide and not the lunar tide because of the lower atmospheric density.

As can be seen the semi-annual forcing is by far the strongest and sharpest tidal factor. The symmetry is such that the wind is positive (eastward) whenever the sun is at an equinox nodal crossing and negative (westward) whenever the sun is at a solstice extreme. There is a slight tendency for stronger westward excursions during southern hemisphere summer.

The daily data is found here:

https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-pressure-levels?tab=form

Request ID: f5e92f19-2eca-48bc-9a65-b029c1ffd75d

Product type:Reanalysis
Variable:U-component of wind
Pressure level:1 hPa
Year:1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020
Month:January, February, March, April, May, June, July, August, September, October, November, December
Day:01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31
Time:07:00
Sub-region extraction:North 1°, West -1°, South -1°, East 1°
Format:GRIB

The convention for winds is that the U-component is positive for a west to east flow (eastward wind).