More On The Length Of Day Delta (LODD)

I've been doing more research trying to find what causes the length of Earth's day to change every day. This change is called the Length Of Day Delta (LODD) and it seems it's as mysterious to scientists as it is to me.

Previous Posts In This Series
More On Water Vapor, Length Of Day Delta Correlation
Stunning New Climate Correlation

What Causes The LODD?
That's question I wanted to answer as I googled around the net looking for papers or articles about the LODD. But unfortunately, it seems there are almost as many different options on what causes the LODD as there are papers and articles about the LODD. According to one web site, LODD is caused by Global Warming and will make days get shorter. According to another article on the same web site, LODD is caused by Global Warming and will make days get longer.

NASA says the annual changes in length of day are caused by the atmosphere. But someone else at NASA says its the atmosphere, oceans, and land, which narrows it down to everything on the planet. That first NASA article says decade-scale changes are due to changes in the Earth's core.

So to me, it sounds like science doesn't have a solid answer on what causes the LODD, though it may have several good candidates. I told a reader, Charles, that I would look into calculating changes in the LODD based on changes in water vapor. But I think I'm going to have to forgo that promise on the grounds that if professional scientists studying this full time can't provide a solid answer, original research by a software engineer isn't going to settle things either.

But that's ok. I still have the correlations between LODD and other climate factors. I don't need to know causes to examine correlations.

Example Of Another LODD Correlation

In a previous post I showed solar ephemeris data overlaid with LODD data. That graph is reproduced here. We can see from this graph that the monthly scale changes in LODD have a good reverse correlation to the monthly scale changes in the solar ephemeris.

Solar ephemeris data is based on the Earth orbiting the sun. And in this case I think it's safe to say this orbit is causing, directly or indirectly, the monthly changes in the LODD.

That still leaves the causes of the LODD changes over a decade as unknown, and it still leaves us with no explanation as to why there seems to be two different correlations between LODD and water vapor on the decade scale.

References:

More On Water Vapor, Length Of Day Delta Correlation

Stunning New Climate Correlation

Climate Scientist Starter Kit v2.0 Coming

LODD is caused by Global Warming and will make days get shorter

LODD is caused by Global Warming and will make days get longer
NASA: Annual changes in length of day are caused by the atmosphere
NASA: Annual changes in length of day are caused by the atmosphere, oceans, and land

More On Water Vapor, Length Of Day Delta Correlation

I downloaded The official Length of Day Delta (LODD) data so that I could do a more detailed analysis on the correlation between water vapor and the LODD I discussed here. I parsed up the data and added it to my working copy of the Climate Scientist Starter Kit Spreadsheet.

What I found is the correlation is not as good as I first thought it was. Or maybe a better way to say it is the correlation is different than I first thought it was. There seems to be two correlations in the data.

Just to be clear, I'm not suggesting that changes in the LODD are causing changes in water vapor. I'm pointing out that there are correlations between the two data sets.

What Is Length Of Day Delta (LODD)?
Let's start with an explanation of what the Length Of Day Delta (LODD) is. Simply put, the LODD is a measure of how much extra time is added to each day. A "normal" day has 86,400 seconds. However, in practice, there's no such thing as a normal day. Each day has a few more or a few less milliseconds. The extra amount of time, which can be positive or negative, is the LODD.

Water Vapor And LODD, 1983 To 2008

The graph above shows water vapor (blue lines) and LODD (green lines) data for the period of July, 1983 to June, 2008. There's a 13 month running mean added to smooth the data.

As you can see, the correlation doesn't look as nice as when I just overlaid two graphs in my previous post. Specifically, in the early years water vapor is not matching LODD. I was a bit bummed out when I saw this, thinking a correlation that looked so promising turned out to be nothing.

But I kept looking and found something else: two correlations.

Water Vapor And LODD, 1983 To 1997

The first correlation runs through the first half of the data, from July 1983 to December, 1997. In this correlation the water vapor (blue lines) and LODD (green lines) are mirror images of each other. As one goes up, the other goes down. This is true both at the monthly level and at the 13 month smoothed trend.

Water Vapor And LODD, 1998 To 2008

The second correlation runs through the second half of the data, from January, 1998 to June, 2008. In this correlation water vapor (blue lines) and LODD (green lines) follow each other in the 13 month smoothed trend, even though at the monthly level they are still have reversed trends.

What's It All Mean?
The honest answer is "I don't know". Maybe there's something to this, maybe not. But the two correlations seem pretty clear.

One thing that jumps out at me is that 1998, when the new smoothing trend starts, is when the Earth stopped warming.

I'll continue to research this to see what I find and post updates here.

References:
Earth Orientation Centre Length of Day Delta (LODD) data
Stunning New Climate Correlation
Climate Scientist Starter Kit Spreadsheet

Stunning New Climate Correlation

I just discovered this and simply had to post it. It's an amazing correlation between water vapor in the Earth's atmosphere and changes in the Earth's rotation measured in milliseconds! I know. I know. It's insane to think changes of a few milliseconds could somehow be related to the total water vapor in the air. But here's the chart:

The blue line is changes in the Earth's rotation as measured in milli-seconds. The red line is changes in the total amount of water vapor in the Earth's atmosphere. The graph covers a 24 year period from 1983 through 2007.

The information for changes in the Earth's rotation comes from the U.S. Naval Observatory. The information for changes in the Earth's water vapor comes from the International Satellite Cloud Climate Project. You can graph the cloud data using the Climate Scientist Starter Kit and your favorite spreadsheet program.

I don't know what this means yet. As I said, I only just now discovered it. But I wanted to get the information out there so people can see it.

Rest assured that future posts will look into this more deeply.

References:
U.S. Naval Observatory Leap Seconds
International Satellite Cloud Climate Project
Climate Scientist Starter Kit