[160m] Improving Topband Conditions?!
Thomas Giella KN4LF
[email protected]
Mon, 16 Feb 2004 23:27:58 -0500
On my "KN4LF MF Radio Propagation Theory Notes" website at =
http://www.kn4lf.com/kn4lf8.htm is posted the following:
..........15.) Sudden Stratospheric Warming (STRATWARM ALERT)-=20
Sudden stratospheric warming is a major temperature change of the winter =
time polar and middle atmosphere from the Tropopause (where the =
troposphere transitions into the stratosphere) to the base (D-layer) of =
the ionosphere, lasting for many days at a time and characterized by a =
warming of the stratospheric temperature by some tens of degrees =
(temperature inversion).=20
Another way to explain stratospheric warming is a major disturbance of =
the winter polar middle atmosphere from the Tropospause to D-region =
which is at the base of the Mesosphere resulting from a breakdown of the =
polar vortex into two circulation cells. Air trapped in the vortexes is =
mixed by the new meridian flow and is exposed to sunlight. Solar lyman =
alpha ionizes the nitric oxide gasses resulting in an increase in =
electron density and producing strong MF and HF absorption.=20
A little inter-related Troposphere Meteorology:=20
Interrelated with the splitting and shifting of the Arctic Circumpolar =
Vortex, is a Tropospheric level negative North Atlantic Oscillation =
(NAO) and Pacific-North America Anomaly (PNA), mid and upper air height =
anomaly pattern. This equates to a large high pressure ridge in Western =
North America extending northward all the way into the Yukon region of =
Canada and a deep trough in the Eastern North America, from the eastern =
U.S. extending down into the Yucatan region of Mexico, with a second =
ridge in the western North Atlantic Ocean. This pattern is also called a =
dual blocking ridge and taps Siberian Arctic air, sending it across the =
North Pole into the eastern 2/3's of Canada and the U.S. providing for =
very cold surface temperatures.=20
As the stratosphere lies below the ionosphere, which is at mesosphere =
and thermosphere height, you would not expect to see stratospheric =
warming effect medium frequency propagation in any way BUT medium =
frequency signals do propagate off of temperature inversions and =
moisture discontinuities and a temperature inversion is involved with =
stratospheric warming. So it's probable that a medium frequency signal =
could do any number of things when scattering off of a temperature =
inversion, at any height. Unfortunately though some otherwise very =
knowledgeable Physicists stubbornly resist this concept.=20
Also Stratospheric Warming (STRATWARM) has a negative effect on medium =
frequency propagation, due to increasing medium frequency radio wave =
absorption by the D layer, via upward propagating Internal =
Buoyancy/Gravity Waves (IBGW's).
This phenomenon also occurs in southern hemisphere winter but seems to =
be less pronounced.=20
16.) D Region Mid Winter Absorption Anomaly-=20
A period of increased MF radio wave absorption at high and mid latitudes =
occurring in mid winter and is associated with sudden stratospheric =
warming and the Quasi Biennial Oscillation (QBO). If you look in your =
radio logs for 160 meters you will notice that most of your good DX =
contacts are in the fall and spring. This is due to the D Region Mid =
Winter Absorption Anomaly. See definition #15.) Sudden Stratospheric =
Warming (STRATWARM ALERT)..........
++++++++++++++++++++
On 02/17/04 Thomas KN4LF Says:
We have had allot of stratospheric warming during the heart of this =
winter season and therefore allot of extra NIGHT TIME D layer absorption =
of MF transmitted signals. However as the global jet stream pattern has =
now changed, this phenomena is now diminishing in frequency of =
occurrence. By the way the STRATWARM's have coincided with repeated =
cross polar flow of bitter Arctic airmasses from Siberian Russia into =
Canada and the NE U.S., Great Lakes and Northern Plains regions. You can =
almost always correlate the coldest weather with poor medium frequency =
propagation conditions.
Also we are now moving out of the "D Region Mid Winter Absorption =
Anomaly" so MF Radio propagation always improves in beginning in =
February and extending into March before the QRN returns.
++++++++++++++++++++
Also on my "KN4LF MF Radio Propagation Theory Notes" website at =
http://www.kn4lf.com/kn4lf8.htm is posted the following:
Here are some general guidelines concerning correlation off propagation =
indices to actual expected propagation conditions.=20
1.) Dropping indices numbers are better.=20
2.) For medium frequencies a solar flux under 150, under 100 better, 70 =
is best for E layer multi hop.
Keep in mind though that the 10.7 cm (2800 mhz) solar flux index is not =
a "reliable" gauge of ionization in our atmosphere, as the energy of =
photons at this frequency is to low on the order of one million times. =
However most are used to solar flux and sunspot number and it's a hard =
habit to break. A better indicator is the background x-ray flux. See #7 =
below.
3.) Solar flux of at least 100 for E valley-F layer ducting mechanism.=20
4.) Previous 24 hour Ap index under 10, under 7 for several days =
consecutively is best.=20
5.) Previous 3 hour Kp index under 3 for mid latitude paths, under 2 for =
high latitude paths, 0-1 for several days consecutively is best.=20
6.) Energetic protons no greater then 10 MeV (10+0) for 160/120 meters =
and no greater then (10-1) on MF broadcast band.=20
7.) Background x-ray flux levels less than C1 for several days =
consecutively for 160/120 meters and less then B9 for MF broadcast band, =
A9 or less is best.=20
8.) No current STRATWARM alert.=20
9.) IMF Bz with a (+) sign, indicates a lesser chance of high latitude =
path auroral absorption/unpredictable refraction or scattering of MF RF =
signals, when the Kp is above 3.=20
++++++++++++++++++++
On 02/17/04 Thomas KN4LF Says:
The 9 rules above can be put into practice by looking at the observed =
space weather indices below.=20
Between 01/20-01/29 2004 the daily solar flux levels were high enough to =
support the E-Valley/F Layer ducting mechanism. Also the background =
x-ray flux was in the low B range to high A range. There were very few C =
class solar flares. It all adds up to good night time MF propagation. =
Look in your logs and/or check the OH and JA 160 spots and you will see =
many more contacts occurring during this period.=20
The same holds for the 02/10-02/16 2004 period and all the other periods =
this season before it. AND on nights where the radio Aurora is =
contracted poleward (low Kp values) even high latitude propagation paths =
are open.=20
Let's face it 160 meters is to far removed from the daily MUF to be able =
to use HF propagation prediction concepts BUT openings are predictable. =
Many a day I see posts on the Topband Reflector where people grumble =
about 160 propagation being impossible to predict, "black magic" it's =
called. I rarely respond because of flaming but all it takes is reading =
and understanding the information on my website and applying it. The =
answers to the seemingly mysterious MF propagation occurrences are =
contained within.
++++++++++++++++++++
# Sunspot Stanford GOES12
# Radio SESC Area Solar X-Ray ------ Flares =
------
# Flux Sunspot 10E-6 New Mean Bkgd X-Ray =
Optical
# Date 10.7cm Number Hemis. Regions Field Flux C M X S 1 2 =
3
#------------------------------------------------------------------------=
---=20
2004 01 20 129 94 540 1 -999 B3.9 0 1 0 1 1 1 =
0
2004 01 21 130 104 560 0 -999 B3.3 2 0 0 1 0 0 =
0
2004 01 22 122 76 400 0 -999 B2.5 0 0 0 0 0 0 =
0
2004 01 23 115 62 260 0 -999 B1.9 0 0 0 0 0 0 =
0
2004 01 24 108 47 230 0 -999 B1.8 0 0 0 0 0 0 =
0
2004 01 25 102 48 130 0 -999 B1.6 1 0 0 2 0 0 =
0
2004 01 26 98 38 30 0 -999 B1.5 1 0 0 0 0 =
0 0
2004 01 27 94 00 00 0 -999 B1.2 0 0 0 0 0 =
0 0
2004 01 28 89 00 00 0 -999 A8.7 0 0 0 0 0 =
0 0
2004 01 29 87 25 70 2 -999 A7.5 0 0 0 0 0 0 =
0
2004 02 10 117 78 520 0 -999 B2.0 0 0 0 0 0 0 =
0
2004 02 11 114 91 430 1 -999 B1.9 0 0 0 0 0 0 =
0
2004 02 12 112 65 420 0 -999 B1.9 0 0 0 0 0 0 =
0
2004 02 13 108 71 270 2 -999 B1.7 0 0 0 0 0 0 =
0
2004 02 14 104 64 210 1 -999 B1.3 0 0 0 0 0 0 =
0
2004 02 15 000 75 270 2 -999 B1.1 0 0 0 0 0 0 =
0
2004 02 16 99 81 190 0 -999 A9.0 1 0 0 1 0 =
0 0
73 & GUD DX,
Thomas F. Giella, KN4LF
Retired Space & Atmospheric Weather Forecaster
SKYWARN Observer HIL-249
SWFWMD Observer #574
Plant City, FL, USA
EL87WX
Yaesu FT-840 & PSK31 Digital Mode E Group =
http://groups.yahoo.com/group/yaesu_ft840
160-10 Meter Amateur Radio Resources http://www.kn4lf.com/kn4lf.htm
Daily Solar Space Weather & Geomagnetic Data Archive =
http://www.kn4lf.com/kn4lf5.htm
Daily MF Radio Propagation Outlook http://www.kn4lf.com/kn4lf6.htm
MF Radio Propagation Theory Notes http://www.kn4lf.com/kn4lf8.htm
Florida Space & Atmospheric Weather Institute =
http://www.kn4lf.com/fsawi.htm
Florida Daily Weather Discussion http://www.kn4lf.com/sub/fmci17.htm
Friend Website Design Studio http://www.kn4lf.com
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