Gives Us This Day Our Daily Enthalpy

It is somewhat odd how much the place influences where the mind wanders. Not unexpected, but the degree of it was a surprise. Florida makes it very clear that we live in a water dominated world. Sometimes in things as small as dew.

So every weekday I commute to work at about 7:ish AM. Most all mornings the car is covered in dew. In the parts of California where I’ve lived, in summer there is no dew. Summers are dry. Dew is a ‘winter thing’… (or occasionally Spring / Fall). California has winter monsoons and summer dry seasons. But the “Mediterranean Climate” of California is only found in a few places in the world. It is the odd case.

Florida is completely different.

Here it is humid in summer. (Winters not so much, I’m told.) Dew forms at much higher temperatures. In fact, the daily cycle of evaporation, condensation (as rain or dew) and repeat the next day is quite striking. You can almost set your watch by it.

Yes, there are variations. Sometimes the wind is from a dry direction and the afternoon rain doesn’t happen. Sometimes the air is dry enough that dew does not form. But those are the exception, not the norm.

This morning, on the way to work, I had to repeatedly run the windshield wipers. Was it raining? Nope. It was condensation forming on the windshield from the saturated air. Usually this just happens over the cool spot from the A/C on the windshield; today it was the whole thing. Yet at lunch, while it was a bit humid, there was no condensation. This evening (about 4 pm to 5 pm) as the sun starts to set and cooling begins, but the land is still warm, we have thunderstorms. Great rolling thunder, scattered rain showers all over. Later this will end (when the heat has been redistributed and the heat engine runs out of ‘fuel’) and the cycle will begin again. Sun evaporating water, that condenses in mass as rain, or more gently as dew. Soaking up the solar heat in the middle of the day, and giving it back again as the sun sets and into the morning.

The end result is a significantly stabilized temperature range. In desert regions there is no such water moderation and temperatures range far more broadly (both higher and lower).

But this means there are “issues” with averaging temperatures from two places (or two times) that differ in their ‘entropy profile’. Florida is more south than Phoenix Arizona, so gets more sun. Yet the temperature MAX in Florida is far lower. Often the MIN can be higher in Florida as well. The range is just narrower due to the water moderation. Same or more heat input, lower range of temperatures. The difference goes into enthalpy. Heat of vaporization / condensation. (And in colder places heat of fusion). How can you make a “global average temperature” when the enthalpy varies so madly around the world? The “heat meaning” of 85 F in Florida is far different from the meaning of 85 F in Phoenix.

No amount of anomalizing, interpolation, exterpolation, nor adjusting can fix that. You simply MUST know the masses and specific heats involved along with the heats of fusion and vaporization and do a proper heat flow calculation to have any meaning to the numbers you average. Intensive vs extensive (or intrinsic vs extrinsic) properties matter.

So can we see this impact of enthalpy in temperature patterns of a place? Well, yes! In an earlier posting I showed how there was a dramatic plunge of temperature when the thunderstorms formed. (Both the cloud shading and the large quantities of cold water falling from near the stratosphere. Having risen as vapor and dumped its heat of vaporization in forming that rain.) Now we’re going to look at the small heat involved in the ‘dew cycle’. Not an inch of rain, but that mm or so of dew on the cars and ground in the morning, that turns to vapor in the heat of the sun, and gives back that heat as the dew forms.

This is a graph of temperatures and dew point in Orlando. Notice how the dew point has a daily ripple, matching, in mirror image, the daily insolation (most visible in the middle of the month when thunderstorms were minimal). Note in particular when the dew point touches the bottom of the temperature. That is when dew forms and temperatures stop dropping as the heat of vaporization is returned to the air.

Orlando, Florida, September 2011

In the middle of the month there are some days with very clear ‘counter ripples’ of the dew point ( 12 to 18). Those were sunny days with no major rain to speak of. Toward the last weeks of the month, dew point holds much more flat near the lows of the temperatures. Those were days where clouds and rain were dominant features. (20 to 27 ) Notice how on sunny days, the temperature is a neat saw tooth or triangle wave. Now look at the days with more water and a higher average dew point. Notice that the low going excursions get clipped by the dew point. With effectively constant solar input, and with hundreds or thousands of miles of water moderating temperatures on both sides of the peninsula: the daily enthalpy change can bias the imputed heat that temperatures are held to represent.

Temperature is a lousy proxy for heat flux. Surface temperatures are a worse proxy for heat flows out the top of the atmosphere. Ignoring enthalpy introduces ‘noise’ into these bad proxies. Noise which we do not measure and can not remove.

Something very similar happens in cold places. Anyone who has tried “spring skiing” can tell you that mid-day the snow is slushy with water. Then the sun sets and the ‘slush’ sets up to rock hard ice. If you spring ski, you know about hitting those ice patches and having a hard time not falling. Usually the same flattish places that were slush the prior day. The temperature cycles about the freezing point, but the heat flows in and out in much larger swings.

In the limit cases where all the water is evaporated, or frozen, and the temperature doesn’t range far enough to change that, we can exit from an enthalpy moderated regime. Alaska in winter. Phoenix in the dry season. Places known for extreme temperatures. So how can you blend a frozen extreme with an enthalpy moderated one? How can you blend a desiccated extreme with a water moderated one? If you do not measure the enthalpy change, you have a meaningless average of different things.

We don’t even have the needed data to know what the “global enthalpy change” might have been. Dew point captures a bit of it, but not enough. Precipitation a bit more, but also not enough. The data are sparse and of poor historical quality with way too little history to say anything about climate. Add in the daily cycling that isn’t captured (both in dew and in slushy ice) and the surface evaporation and plant transpiration that is substantially unknown. What can we really say about the meaning of a temperature in any one place? And if that link from temperature to heat flow and storage is broken in one place, how can it be made any better by averaging it in with temperatures from other places?

For anyone who might think that Florida, Phoenix and such are just limited extreme cases; that snow on a few mountain tops can’t mater that much: Realize that there are many other times and places where the same enthalpy problem exists. Any place that has irrigation, for example.

As a college kid, I’d ride a motorcycle in the summer. It was a hot central valley California August that I remember most. Headed out without much ‘gear’ on, as it was still a warm night. Until I reached the peach orchards. They were flood irrigating at night. Suddenly the air was quite cold and humid. Not even sprinklers involved. Just water on the ground. In winter we would get “pea soup fog”. Couldn’t see the front of the car from the driver’s seat some times. That fog would then ‘burn off’ late in the day (only to reform that night). Water changing from vapor to liquid and back. So exactly how good is the world data on irrigation and fog? Quantity of frost?

In Conclusion

There is just so much wrong with the idea that you can average temperatures from different places. Yet it makes up the core of the Global Warming mindset, and argument. It doesn’t matter if you make temperatures into anomalies or not. They simply must be adjusted for things like enthalpy change to have meaning relative to heat flow, and they are not. It is NOT sufficient to simply assume the quantity of water, and the impact of enthalpy, does not change. That it can be assumed static. We know it isn’t. Total precipitation varies dramatically from year to year and decade to decade. Fog, snow, melt dates, dew and irrigation levels too. We know that assumption is wrong; yet rests at the heart of a “Global AVERAGE Temperature”.

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