Digital Diatribes

A presentation of data on climate and other stuff

Archive for the ‘Tides’ Category

Full Eclipse Coming, and The Lunar Cycle (2nd in a Series)

Posted by The Diatribe Guy on February 17, 2008

As I was taking a look at the weather site this evening with my 6-year old (trying to find out whether the 8 inches of snow we’d already received today was going to stop sometime before our house was buried) he saw a little video box that he asked me to play. Of course, as soon as I did, he lost interest and fled away to his next pursuit, but I was glad he had drawn my attention to it. Little did I know that this coming Wednesday, February 20, there will be a full lunar eclipse! This doesn’t come around all that often, and as luck would have it it’s supposed to be below zero degrees Fahrenheit when it happens, but you can bet I’m going to be checking that out.

Well, this got me thinking about something I had put together some time ago. Almost a year ago, when I was on one of my Global Warming/Climate Change kicks, I started doing research into the concept of cycles. I had intended to post a series about my research, but soon life took me in another direction and I failed to follow through. As a concept, it is my contention that Climate Change is effectively driven by a complex array of cycles. These cycles range from the daily cycle of a rotation of the earth, to monthly cycles relating to the moon, to the annual revolution of the earth, and so on and so forth. There are earthly cycles, solar cycles, axis oscillation cycles, and even cycles in our solar system and galaxy that can impact our planet. The contention I had was that everyone understands and expects the short cycles. By simple experience, we observe them, and while there are scientific explanations to everything, we don’t need a climatologist to explain to us that earth is warmer during the day and cooler at night, or that summer is hotter than winter. But I think we too easily dismiss other cycles that we do not understand as well, or those that go on for centuries or millennia, since we do not ever observe a full cycle. Instead, we convince ourselves that there is something unusual about changes we see going on today because it is different from a few decades ago, and the conclusion is that we are somehow causing it. I think we give ourselves too much credit.

Well, anyway, My “first in a series” post (almost a year ago) is here. It deals with the “one day cycle.” Read the rest of this entry »


Posted in Astronomy, Climate Change, Cycles, Earth, Eclipse, Global Warming, Lunar Cycles, Moon, Science, Tides, Weather | 1 Comment »

The One Day Cycle: First in a Series (I Think)

Posted by The Diatribe Guy on March 23, 2007

OK, so this may be the “first in a series” but each post requires a little more research and thought than my normal meandering thoughts going from brain to synapse to hand to keyboard to computer to blog.

But I feel compelled to present a series on the cycles of the earth, sun, solar system, etc.   The thing is, when I started digging into this, I finally realized how many such cycles there are.   Understanding the cycles of the earth has been central in my attempt to understand the global warming/climate change debate.  I have made it clear that I don’t really buy into the global warming alarmism we are hearing so often these days.  I won’t deny that there may be some truth in aspects of theory.   But rather than debate who is right and who is wrong and all that stuff, and whether or not people contribute to it, I’d like to start with some very basic and observable aspects of the cycles of things that we know are caused by cycles, leaving man out of the equation for the time being.   My plan is to start with the short cycles and get into what observable effects these short cycles have.  My hope is that it can at least present a common sense element that acknowledges that cycles matter. 

So, let’s start with cycle #1.  This is a cycle we are all familiar with and observe every day: one rotation of the earth every 24 hours.

Let’s start with light vs. dark.   Everyone knows that because of this 24-hour cycle, there is a predictable pattern of light versus dark, based on the relative position of the Sun to our Earth.  It’s hardly worth discussing, other than to lay the groundwork for future discussions.  Clearly, there are other elements that impact light versus dark.   Some days it’s cloudy and other days it isn’t, affecting how light it is on those days.  This introduces the element of “random noise” into our equation.  By this, I mean that the earth is dynamic in so many ways that there are many contributors to what occurs during a given cycle.  This random noise needs to be filtered as best we can filter it so we can get to the general answer.   On a daily basis, this is fairly simple to do because we have a new data point each day, and over time we can determine what the actual baseline of the cycle itself is.  This proves more difficult over longer cycles, which is why it is important to realize that longer cycles will have these random elements associated with them just as shorter cycles will.  But I digress.  

Anyway, finishing up the discussion on light vs. dark, it may be tempting to add that other cycles affect it.  Days are longer or shorter depending on the annual cycle, for example.  But right now, the point is to focus on the small cycle.  We will discuss at a later time the impacts of longer cycles on these things.  Also, your location on earth makes a difference in the light/dark cycle, but that is really not relevant to addressing the cycle itself.

Let’s move to the tides.  We know that the rotation of the earth means that the relative positions of the moon and sun changes it’s gravitational impact on the different regions of the globe as those regions become closer in proximity to those two bodies.  Most people think of the ocean when they talk about the tides, and that’s what I’ll focus on.  However, it is interesting to note that there is also an atmospheric “tide,” meaning that our very atmosphere bubbles out towards the moon and sun.  The moon is responsible for 56% of tidal activity due to its proximity to the earth, but due to the sun’s massive size, it still exerts 44% influence. 

The ocean tidal cycle is not exactly 24 hours because while the earth is rotating, the moon is revolving around the earth.  This combines for a 24 hour, 52 minute cycle with the tides.  This tidal motion is not entirely intuitive.  The high tide occurring at the side of the earth closest to the moon is caused by the gravitational pull of the water on that side of the earth.  But there is also a high tide on the opposite side of the earth at the same time due to two things (a) inertia, and (b) a pulling of the entire earth towards the moon, while the water is trailing behind.   This means that each point on earth experiences two high tides each day.  The points on the sides of the earth experience low tide at the same time the other points experience high tide.   Each peak/trough occurs in 6 hour, 13 minute intervals.

Tide levels vary according to topography of regions and their location.  The Canadian Bay of Fundy experiences tide variations of up to 50 feet in a single day.  Typical variation is 5 to 10 feet.   Large lakes can experience tidal effects as well, but at much smaller levels (2 inches or so).  

Just like with daylight hours being affected by longer cycles, tides are also affected by longer cycles, as the sun and moon line up most directly (spring tides) twice a month and least directly (neap tides) twice a month.  Even longer cycles of apogee (furthest point away) and perigee (closest point towards) of the moon’s orbit around earth and the earth’s orbit around the sun also affect tides. 

In sum, ocean levels are dramatically impacted on a daily basis from the simple cycle of the daily earth rotation.

On to temperature…   NOAA has done studies on high versus low temperatures during the course of a day.  Unless there is a changing weather pattern occurring, in general, the high temperature occurs during the day (usually between 2:00 and 4:00 pm, depending on the time of year) and the low temperature occurs just before dawn. 

Without getting into scientific data analysis, let’s just boil this down to the unmistakeable conclusion that the temperature varies throughout the day for a number of reasons, but all other things being equal, temperature will vary simply due to the rotation of the earth and the sun’s relative position to a spot on the globe.  The difference between the high and the low will vary depending on the climate and altitude of a region, its location relative to large bodies of water, and the like.  We don’t need scientific analysis to convince us of this observation, it’s just a matter of how large the difference is.

The climate/weather itself is affected by the simple one-day rotational cycle.  According to NOAA, while severe weather can occur at any time, there are particular times during the day where severe weather is most likely to occur.  Tornadoes are most likely to occur between 3:00 – 9:00 PM, for example.  Lightning is most likely to occur in the afternoon and evening.  Other factors obviously influence severity and timing, but the cycle of heat/cold, along with associated evaporation of water during sunlight hours, and so on has a direct influence on the daily cycle of weather.  Nobody would imply that the reason it storms in the evening is because of human activities during the day.

Comparing 24 hours and how our activities affect what happens during a single day is far different from talking about long-term implications of behavior.  I accept that, but if this is the point you are focusing on, then you are missing the larger point: I can draw an initial baseline that says that the rotational cycle of the earth – all other factors held constant – directly impacts how much light we have, when we have it, temperature changes, ocean levels, and climate.   And this is just one short cycle.  Even on this short cycle with all the data we have, with all the factors involved and how it will impact temperature, climate, and the like, we still have difficulty predicting the weather with any great accuracy any more than a couple days ahead of time.  And even the next day can be a challenge! 

The longer term cycles directly affect all the things we discussed above, and more.  I will continue to demostrate how as we move out to the longer and longer cycles.   I make no promises as to when the next segment is presented.

I have kids and stuff.

Posted in Climate Change, Cycles, Earth, Global Warming, Moon, Science, Sun, Tides, Weather | 1 Comment »