Is this the end of Summer, and Summer Es?

I tend to see the harvesting of the wheat field beside GM4FVM as bringing the end of Summer Es season.

That used to happen regularly early in September. However, last year it was a month early, and this year it happened on 18 August.

So I guess this is a silly romantic idea I have, as surely the 2024 Summer season can hardly end on 18 August?

Well the schools around here have gone back from their Summer Holidays - they reckon Summer 2024 is over.

In many ways I hope the 2024 Summer Es season does end now, because hopefully Autumn will be better.

The difference between 50MHz Es this year and the same time last year is pretty stark.

50MHz contacts at GM4FVM from 19 July to 18 August in 2023 and the same period in 2024

Only around 10% on the 2024 contacts were multiple hop DX ones (that equals two contacts) compared with 32% last year (36 contacts).

Things on 70MHz were similar. On 144MHz Es openings are unusual this far north so this is harder to judge on that band. There was one big single hop opening between those dates in 2024 on 2m, on 6 August, and just one small one in the same period 2023. If I could see any pattern in the 2m openings I would be very happy because they are rare as rare things.

What can explain the significant difference this year? Well it could just be down to the random nature of Es. You cannot count on Es at any time of year, and maybe this is just natural variation. 

On the other hand I have spoken to several people who are certain it is due to the sunspot cycle peak. I do not recall this happening at the last sunspot cycle peak but then everything was much less organised on 6m then. The season was much shorter and ended about now in the year in those days, but surely that was due to lack of activity. After all it did not resolve immediately outside the peak sunspot period. Anyway, this was discussed here and after reviewing the data I cannot say that anything remarkable pops up. I need to look more closely.

Perhaps because I have read in several texts that Es is not affected by the sunspot cycle (or not noticeably anyway) then I am reluctant to accept that it might be. The upside of the sunspot peak would be F-layer propagation which I have yet to see.

I doubt if harvesting the wheat really indicates much, but it feels like it does - and may be that is as good an predictor of Es propagation as the various websites which claim to know all about it.

Harvesting under way near GM4FVM, 18 August 2024

Whatever the cause, the effect is pretty clear. For a lot of the time (days on end) I have been looking at empty waterfalls and blank "band activity" lists. Thank goodness for aurora and meteor scatter.

Yes, they call it sporadic for a reason. So therefore it could recover tomorrow.

WELL, GET ON WITH IT.

73 Jim

GM4FVM

Tracking the path of Sporadic E openings

The paths of Sporadic Es (Es) openings can often be seen to move across the Earth in regular patterns.

At one extreme, at higher frequencies we regularly get openings which only include one or two stations, and there is no movement discernible there. At other times especially at lower frequencies there is so much activity from multiple areas of Es that we cannot make out any detail out at all.

From time to time I find an opening which shows up the movement in a clear way. I have described two of these before on this blog - 

1) here, where a 50MHz opening to Japan showed an east-west pattern at the Japan end and suggested that whatever propagation method opens this path it looks very much like Es at the Japan end.

2) here, where on 144MHz the distance of the path shortened 700km over a 22 minute period.

On 6 August 2023 there was a 144MHz Es opening which showed a definite east-west transit at GM4FVM.

As luck would have it, this was a good opening with me contacting 31 stations in 103 minutes. This covered 6 countries and 18 squares, with the best DX being IK7UXW in JN80 at 2236km. On the other hand luck also dictated that I was absent from the shack for 28 minutes roughly in the middle of the event, but this did not seem to make much difference. This time the average lengths of the paths changed very little but the azimuth angle moved steadily (roughly) from "south east" to "south south east". Overall the path traced by rotator was in an arc which headed from east to west.

I have dithered a bit over how to represent this on the blog. I have plotted graphically the azimuth (my beam direction) against the time and produced a line of best fit, but somehow the graph does not show how the Es shifted very well. 

So what I have done is to show the map of the contacts with a text box showing how the front of the contacts moved across, expressed in terms of time and azimuth. The azimuth (my rotator angle) is at the top, and the time that contact occurred is below. The azimuth figures were calculated from the locators of the stations I worked.

144MHz Es contacts at GM4FVM on 6 August 2024

You will probably need to click on this image to enlarge it to see the detail.

I have listed the contacts in two different colours - red for the first phase, blue for the second phase, and I was out of the shack in between.

The leading edge of the contacts moved from 122 degrees at 09:22 to 156 degrees at 10:33, that is 34 degrees in 71 minutes or almost half a degree every minute. In reality it was not evenly spread and at times (especially at the start and end of the event) it was moving more quickly.

The "searchlight" of Es propagation shining on the ground was tracing a path which moved past stations at a surprisingly fast rate. Generally as it moved on contact was lost with those behind, with only the odd contact in the rear of the leading edge.

During the period I was out of the shack it did not seem to move much at all. I must go back in the log and try to work out what was happening then.

It would be easy to dismiss this as an opening into Italy and France, with one contact each in Croatia, Switzerland (with a very determined 2E0 stations adding to the fun on tropo). Looking at my normal map of an opening it just looks random. However, looking at the timings the Es path seems to be moving in an organised way.

A more conventional view of the opening on 6 August 2024

When viewed in DX Maps it is possible sometimes to see areas of high frequency refraction which appear to move between squares in a westerly direction as the day progresses. I can see a similar effect in openings such as this. What the cause is could be difficult to determine. At first it looks likely that the Sun's movement relative to the Earth might be the cause. Certainly the Sun plays a part by driving the air movements which create and organise the Es layer. Ripples in the Es layer could also be a factor. However it might be more complex that that.

I wonder if this was one event or two separate ones. The fact that the propagation did not seem to move much during around half an hour when I was not in the shack might suggest that. Also, the full picture may be hidden due to the geography. Obviously there are not many stations in the Adriatic and Tyrrhenian seas. Signals from there might have given a fuller picture. Still it looks pretty clear to me that the paths were moving steadily westwards.

Here is the summary from that first map, still with the first phase in red and the second phase in blue:-

  156        151        148         144        140        139         136        131        122       Azimuth

10:59     10:44     10:42     10:35     10:00     09:41     09:36     09:31     09:22     Time

 More research necessary.

73 Jim

GM4FVM

I saw the propagation arrive from far away

I was out on my afternoon walk when I noticed a cloud formation which suggested enhanced propagation on VHF. It was a still sunny day on 31 July with some "nuisance" cloud towards the horizon. A careful look revealed a dark grey band below the distant cloud level. I recognised this as a band of still air above the North Sea, which indicates that a temperature inversion may be underway.

I put an inch to my step, hurrying down Ayton Law, past the alpacas sunning themselves in the still air, and home where I had a look at 2m and above.

Dark grey band just above the horizon, Ayton Law, 31 July 2024

Click to enlarge images if necessary, as per.

The dark grey band can form over the North Sea when pressure is high. When it comes ashore it produces the effect known in Scotland as the "haar". When warm air passes over the sea a foggy layer of condensation forms also known as a "sea fret". The large bank of air can be very still and stable, but the entire bank can sometimes extend ashore producing very strange conditions. When the haar arrives near GM4FVM it can be seen pouring over the headland to the south, spreading down the slopes and into the valley of the Eye Water in which this station is located.

On shore the haar produces a damp fog which feels wet and yet can be surprisingly cold for something produced below warm air. On 31 July when I approached home I also noticed a cold wind which often arrives at about the same time. This feels like the output from an air conditioner, and circulates around the stable air system. The Scots word haar is derived from a Dutch word for cold. Inside the fog it can be quite dark as if enveloped in cloud as in an aircraft, and with the Sun blocked out also strangely cold. A short distance away, outside the cloud, it will be sunny, still and warm. Overall these can be a remarkable effects.

A large bank of still air over the North Sea is just what is required for tropospheric propagation. The tropo predictions had not been too hopeful for that day, showing a detached patch of enhancement north of me and then some more over on the Denmark coast. Not promising as tropo requires a continuous path.

Hepburn Tropo Chart for 18:00 on 31 July 2024.

It seemed likely that a mass of air had formed over the North Sea and this was allowing propagation. The QSOs showed two distinct paths, one to the east to to SM and OZ, and one to the south east to DL and PA.

144MHz contacts at GM4FVM on 31 July 2024

Conditions on 144MHz have been pretty awful this year, reflecting the lack of these very conditions. So it was very agreeable to be able to work 15 stations across the North Sea, and the best DX to SM7KMJ in JO66 at 947km was pretty good.

On 70cm I worked across the North Sea to OZ2ND and PA3CWS both of whom I also worked on 2m. I saw nothing  on 23cm, despite trying hard.

Haar coming ashore is fairly rare round here. This time it did not arrive on shore, well not as far inland as GM4FVM anyway. However, seeing it in the distance and feeling that cold wind on an otherwise warm day put me on alert.

Now two days later the pressure has fallen and the usual strong winds associated with a weather system coming from the West have returned. There is no possibility of still enough air over the North Sea to hold a bank of air, and the warm weather has gone. VHF conditions have returned to their usual sleep. Even the alpacas are sheltering under the trees today.

Alpacas sheltering on Ayton Law, 2 August 2024.

Most propagation enhancements arrive silently and invisibly. Actually seeing one was a bit of a surprise.

73 Jim

GM4FVM