Probability Analysis – Another Method to Predict “Es” Activity:
Due to the fact that the United States’ distribution of population and Ham activity was not equal, a better measurement practice is to apply an equal value to one single reception (PropNET capture) within a one hour period. In other words, a single occurrence in a measured period equals the occurrence of many. The probability of an occurrence is now measured, not the actual number of captures in the period.
Therefore, every hour documented and measured in the 7 years of data was re-applied. If a capture occurred during the hour it was given a value of one (1). If no capture occurred, it was given a value of zero (0). The result is that statistical probabilities can be applied to any hour on any day that an opening could occur. The quality and quantity of the hourly opening had no bearing. Opportunity is what is being measured, not how much was being worked.
The key factor is that opportunity will always produce results. The more opportunity existed, the better the results.
The following charts data are based on these factors:
- The days prior to and after the Summer Solstice (June 21)
- All 24 hours are used in the day
- The probability measured (percent) is that on any hour of that day, we will have at least one occurrence of a 10-Meter PropNET Es capture.
The results show a very clear trend on how Es begin, increase and then decline during the season. Daily total probability is based on that on the day measured, that on any measured hour, the occurrence of a 10-Meter Es PropNET capture occurred. It was amazing to see the daily differences with 7 years of cumulative volume data. The end of the Es season was difficult to identify with probability data. For most years the “median” date for captures was on 6/22 and for probability it was 6/25 a 3 day swing, but the last year it evened up. Captures are spread evenly throughout the season, but opportunities slightly favor the second half of the season as it takes more time to drop off.
Some probabilities can increase or decrease 20% in one day. As in the total captures chart, the Probability Chart represented the dramatic increase in opportunities in early May. The best day for Es opportunities was June 18 and July 4, with 67% of the total hours on these dates having a capture. By May 22, the occurrence of an Es capture for any hour of the day increases to near 50%, and remains fairly consistent for most days until July 29. One factor that draws your attention is why there are certain days less productive than others. The right skewed and tailed appearance in probability is somewhat clearer than the capture volume statistics as the season takes about 2 more weeks after the solstice to finally end. When applying a 2nd degree trend-line to the daily data, the coefficient of determination (R squared) is closer to the data. This trend-line has been applied to annualized data for 3 years and the coefficient of determination has improved each year.
As in the capture charts, I averaged 3 continuous days of data around the day measured. As in the daily charts, it was surprising how much probabilities will decline or increase in a matter of a couple of days. Still the early seasonal increase, followed by the slow decrease the second half of the season was quite evident. Trend-lines also are very close to actual data.
This trend is also clear when 6 consecutive days of probabilities are averaged for each measured day. Note that both the beginning and end of the Es season are clearly defined.
After measuring hourly probabilities on a daily basis, I decided to measure cumulative weekly periods to further confirm trends that I had seen in the prior charts. Also, I wished to see how probabilities of a capture changed for the actual hours within a day. I again divided the Spring/Summer Es season into 16 weeks. I compiled 7 day segments of data for the 7 years and calculated the probability that at least one capture occurred at any given hour in this weekly period. In 2009, I extended the measurement period by 2 weeks and reconstructed the prior 4 years.
Probability Statistics by Hour:
I was curious to find out if the probability factors would also correlate to a higher number of captures. Probability is based on a single incident during a measured hour, not on total captures. I was very pleased to find out that the two factors did relate closely. Only during the late afternoon were there minor shifts. This might be due to the shifts of average distances (higher) experienced during this period. The shift is negligible. Therefore, quality relates to quantity.
Probability by Weekly Periods:
The following charts are represented and discussed in terms of the week of the Spring/Summer Es season. When it is referenced, each week number corresponds to the following days:
Title Begins Ends
Week 1 25-Apr 1-May
Week 2 2-May 8-May
Week 3 9-May 15-May
Week 4 16-May 22-May
Week 5 23-May 29-May
Week 6 30-May 5-Jun
Week 7 6-Jun 12-Jun
Week 8 13-Jun 19-Jun
Week 9 20-Jun 26-Jun
Week 10 27-Jun 3-Jul
Week 11 4-Jul 10-Jul
Week 12 11-Jul 17-Jul
Week 13 18-Jul 24-Jul
Week 14 25-Jul 31-Jul
Week 15 1-Aug 7-Aug
Week 16 8-Aug 14-Aug
Week 17 15-Aug 21-Aug
Week 18 22-Aug 28-Aug
As shown in the Daily Probability figures, similar trends with the weekly capture computations did occur. Before 2008, the peak of the Es season was the weeks beginning May 23 and May 30 (5th and 6th week). The final 3 years of the study strongly showed the peak at and after the Summer Solstice (8th and 9th Week). On average, a slow decline begins after the 11th week. The chart reflects active hours each day rather that a percentage of the day open. For 7 weeks each season at least one half of the day has Es activity.
By the 5th week of the season, daylight period probabilities become consistent week to week and maintain the high probability levels. The evening and twilight periods (8 PM-6AM) will show higher amplitude rates of change before and after the solstice. The daytime period weekly probabilities changed little once the season was in full swing.
When the study was started, my opinion was that Es activity should form a perfectly shaped bell curve peaking at the Summer Solstice. Throughout the 5 years of this study, it was quite evident that capture totals and probability calculations once charted were showing that Es activity was somewhat right-skewed and right tailed. In other words, Es activity once the season begins rises quickly then peaks before the Summer solstice. Activity then slowing declines for the remainder of the Es season. The end of the Es season will occur further after the Summer Solstice than when it begins before.
Triple-Hour Probabilities:
To better qualify these observed trends throughout the Spring/Summer Es season, I charted probabilities into three hour increments. I first charted probabilities in 1-hour segments and found the information to be overwhelming. This approach shows the seasonal changes in Es opportunities best.
A reminder… The 9th Week is the Summer Solstice.
A reminder… The 9th Week is the Summer Solstice.
6 AM – 9 AM Local Time:
The sun rises at this QTH during this measured period. Although the right-skewed trend was evident in the earliest hour during this period, overall opportunities consistently rose and peaked at the Summer Solstice. During this weekly period one can expect a 50% chance of an Es opening. Between the 5th and 13th weeks (5/23-7/24) there is at least a one-in-three chance of an opportunity. Note the sight increase into the 16th week (8/8).
9 AM – 12 Noon Local Time:
This segment is the best time to work Es, and is best to call it “primetime”. By the 3rd Week of the season (5/09) the probabilities are greater than 50% for the entire season until the 17th week. For 3 weeks, probability is almost 90%. During the seven years of the study, specifics days and hours within this period have had a capture occur each year of the study. The obvious trend shown is that once the Es season begins in earnest, it will not end until the end of August. The 16th week of the season is just as active as the 5th. Any decline in probability as the season progresses is hardly negligible until Week 17.
12 Noon – 3PM Local Time:
The probabilities during this segment also clearly indicate and confirm that Es propagation is a daytime (diurnal) phenomenon. The probability of working 10-Meter Es is only slightly lower than the previous 3-hour period. The pattern continues until the Sun approaches due south, the Solar Noon (1:15 PM). The 6th Week again is clearly the best and we also begin to notice a slight and steady decline afterwards. The probabilities of a 10-Meter capture are at their best at the noon hour. Once the sun reaches peak elevation at solstice, a slow and steady decline occurs starting the 8th week of the season.
3 – 6 PM Local Time:
The sun is now located further west during this period. The right-skewed and right-tailed progression of the season shows up in this segment. The 6th week of the season was the best until 2009 and had me believing that Es activity was peaking prior to the summer solstice. Both the 8th and 11th week rebounded in opportunities in the later years of the study. The 11th week of the season (Independence Day 7/4) it is well known by many Es enthusiasts as an extremely active week. Much of the rise could be due to an increase in the population of participants during the holiday, although many PropNET participants vacationed.
6 – 9 PM Local Time:
During the latter time in this segment the Sun sets. The right skewed and right tailed probability trend is quite evident in this chart. Seasonal trends are clearer with only the 11th Week showing a sudden surge in probability. This time period best displays the rise and fall of the Es season and is also the secondary diurnal peak in activity. By the 3rd week, probability of an Es QSO is above 50% during the time segment and remains at least that high until the 16th week of the season.
9 PM - Midnight Local Time:
For each hour after sunset, overall probabilities continue to decline. Other than the 11th week surge (developed during the latter years), the decline is quite pronounced beginning the 8th week. The best weeks again are the 6th, through the 11th as the probabilities are greater than 50%.
Midnight – 6:00AM Local Time:
Probabilities of an Es QSO become much less into the twilight hours. The trends displayed are consistent; probability peaks near the Summer Solstice. Generally when opportunities occur at these hours, Es have been very intense. Some of the best daily openings with numerous high MUF QSOs have occurred when good conditions exist at these hours.
Over the years of the study, each peak became more pronounced. The peak during the 15th week brings up some interesting questions to why these weekly peaks occur at these early morning hours.
Hour to Hour Probabilities by Week:
The final analysis performed using probabilities was to compare the hour-to-hour trends of each week in the Spring/Summer Es season. With the volume and sampling, we should be able to identify where changes may occur from week to week of the season. Also, if the data accumulated was reliable, did it provide consistent and reasonable results?
Three Week Periods:
The following charts are probabilities of working Es in 3-week segments from the beginning to the end of the season. The chart clearly details that the 6 weeks prior to and then after the Summer Solstice (12 weeks total) are the best periods for Es. The one fact that is evident is that during this 12 week period there is not much difference between them except for a slight afternoon decline in late July.
Weeks 1 – 4:
Week 1 (4/25-5/1) starts the Es season with some limited activity in the daytime hours. In Week 2 the best opportunities are in the afternoon. Probabilities average less than 13% for Week 1 that on any hour a 10-Meter Es PropNET capture can occur. Probabilities almost double Week 2 and will favors afternoon times.
Probabilities increase near 60% the 3rd week and peak the 4th week at a total of 44%. Activity for the 3rd week of the season only favors morning Es activity and typically shows a dual-diurnal pattern to be seen for other active weeks. Most of these weekly periods showed higher probabilities in the latter years of the study.
Weeks 5 – 8:
These are the weeks approaching the Summer Solstice and historically some of the best. Probabilities between Week 4 and 8 will increase by 33% to over 58% (14 hours/day) overall. Week 6 during local 10 AM through the 12 Noon hours have probabilities of a 10-Meter PropNET capture at or above 90% (6 out of 7 days).
Despite the high activity of the 6th week of the season, the 7th week (6/06) drops off during the morning hours. Week 8 rebounds and returns to levels above Week 6 and is the most active during twilight hours and indicates that the Summer Solstice is the peak of the season.
Weeks 9 – 12:
Week 9 (6/20) is the week than contains the Summer Solstice and is the most active of all the weeks of the season. There is a noticeable decrease in Week 10 closely similar to the level of Week 7, then followed by a strong resurgence in Week 11. This is the week that contains the Independence Day (July 4th) holiday and traditionally is known to be a very active week for Es propagation. Week 12 is unusual in that it declines in afternoon and evening activity. Most week to week declines have occurred during the morning hours.
Weeks 13 – 18:
The usual “morning decline” pattern occurs again in Week 13. Although displaying a different hourly pattern, overall probability in Week 14 charges little. Week 15 and Week 16 also have steady afternoon declines in activity. The declines are slight week to week and are only down by 17%. It was a poor assumption on my part that the Es season ends by August 15. Usually the first activity-free day does occur near or around the date, but Es activity continues until the first of September. By continuing the data collection for two additional weeks, it is noted that activity returns to levels experienced at the beginning of the season and once again becomes truly sporadic in nature. The openings during this period are still good and might have some F2 influence.
Next: Conclusions and Credits
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