Earths surface temperature at night...

semiotically

just graduated BSc Biochemistry & looking to move from Portugal coast to the tropics (coast) where I've never even visited yet...

At the moment I'm trying to find harmony within temperature; humidity; windchill; microclimates etc Would really appreciate help as very serious for me & important decision I treat with respect...

If you can post reply to some of my thoughts below would help in deciding:


1. Is thermal radiation (infrared) from earths surface keeping the temperature high at night?

2. When living on the coast would the seas convection & conduction have a significant effect too?

3. In relation to convection, conduction & radiation what are thermometers (mercury/ alcohol & digital) measuring? Just trying to navigate through the effects of different thermometer types left in shade & sunlight....

Kind regards.

willem2

1. No. If the sky is clear and you are above dry land, the surface of the earth will become colder than the air above it because it cools by radiation and the surface will then cool the air above it. High humidity or clouds will reduce the amount of cooling by blocking infrared radiation.

2. If you're near the sea it won't be so warm during the day, and it won't get so cold at night.

3. They are measuring the temperature of what's in them. If you put them in a thermometer hut that's painted white and well ventilated, this will be close to the temperature of the air around it.

klimatos

1 Except for the tropical deserts, coastal tropical temperatures do not fall much at night. This is because much of the longwave radiation that the surface emits is absorbed by the high water vapor content of the overlying air. The bulk of this absorption takes place in the first one-hundred meters. This air, in turn, radiates thermal radiation back to the earth, keeping it warmer than it would be in drier air. Clouds also intercept radiation that passes through the atmospheric longwave "windows". They, in their turn, radiate heat back to the surface. Almost any good climatology text will give you day/night temperature ranges for common rainy tropical sites.

2. The surface temperature of the coastal waters and the prevailing winds are more important than the mechanisms by which these temperatures are attained. In general, winds blow offshore at night and onshore during the day--but exceptions are numerous.

3. Unless your thermometer is in the shade in a well-ventilated location, its reading will not be useful in terms of the temperatures that you actually feel. Even then, "sensible" temperatures can be up to 10°C higher than instrumental ones in the humid tropics.

Your best bet is to either take a short visit during the "worst" season, or talk to a variety of people who know the area well.

On a personal note, if you can take Dubai in August, then you can take any other climate you are likely to encounter!

semiotically

Thanks interesting info.,

personal anecdotes great also:

by saying this it means that recorded temperature can be 10C lower than what you actually feel due to the humidity; am I right saying this? I think so because I imagine Dubai to be stifling!!

I've kind of accepted a vague idea that above ~20C humidity will make you feel warmer; below 20 it will make you feel colder; any views on this... I know it's a pretty relaxed rule so maybe can shed some light here too.


Thanks for both previous replies, these thoughts are simpy the most pressing on first reading this.

klimatos

Yes. The humidity makes you feel hotter in two ways. Firstly, it reduces your body's heat loss through perspiration and respiration. Secondly, the water vapor in the surrounding air is a source of radiant heat.

I have detailed climatic data for thousands of locations over the face of the earth. If you know specifically where you are going, let me know. I can tell you pretty much what to expect.

semiotically

Could you forward me any info. on Cairns (Queensland, Australia) up to the tip of the Cape York Peninsula - would be nice...

klimatos

Cairns lies in the wet-and-dry tropics. Cairns residents see their year as having two seasons: a very hot, very humid, and very wet season; and a warm to hot, quite humid, and somewhat dry one. The rainy season runs from the middle of December through the end of April. It features higher temperatures, higher humidities, more clouds, less sunshine. and much more rain. The dry season runs from May through early December. It has lower temperatures, more sunshine, less rain and masses of tourists--both Australians and others. Below freezing temperatures do not occur.

Sunshine is the rule on some 61% of the year's daylight hours. Cloud cover averages around 48%, and about one day in four is reasonable clear. The year's high temperature will be around 99°F some windless January afternoon; and the year's low will be around 50°F some clear July sunrise. Offshore waters range from 73°F in July to 83° in January. The weather on any particular day could just as well occur on any day of the year.

Cairns is backed by the mile-high Atherton Plateau to the west, mangrove swamps to the north and south of town, and shallow seas leading to the Great Barrier Reef offshore.

russ_watters

It's possible that this is just a language barrier issue, but in American Engineer English, "sensible temperature" has a specific definition which isn't the definition you are using. Though it is often said to be 'the temperature you feel', that's not a precise enough definition because it can imply, wrongly, that it includes humidity. "Sensible temperature" is the temperature read by a dry-bulb ('normal') thermometer. It does not include a humidity component.

Human comfort is a complicated thing and there is no single sensor that can tell you how hot/cold you're going to feel. The closest is the WBGT, which is the composite of three different temperature measurements: http://en.wikipedia.org/wiki/Wet_Bulb_Globe_Temperature

One interesting tidbit: if you're an air conditioning unit and you are cooling 100% outside air, it's hotter in Philadelphia than in Las Vegas, despite the fact that the the temperature tends to be 20F higher in Vegas. But that doesn't mean humans feel hotter in Philadelphia.

klimatos

In the field of physiological climatology, "sensible" temperature most definitely does include humidity. The term has been used in that sense for almost two centuries. When climatologists use the term "sensible temperature" we mean exactly the "temperature that you feel". This includes dry-bulb temperature, humidity, solar and terrestrial radiation, and wind effects. It also includes human physiology. It is essentially "heat in" to the human body minus "heat out".

We call dry-bulb temperature "dry-bulb temperature", or sometimes "ambient" temperature or "environmental" temperature.

Disciplines often hi-jack a favorite term and give it a special meaning in their own fields. This does not oblige anyone to use that term in that way--unless they are publishing in those disciplines.

semiotically

Yes this coincides with my own thoughts, trying to keep out of the direct sunlight though (solar radiation component)

Being from UK Australian move would be ideal culture-wise; just I want temperature a little more consistent year-round so think have to bridge that little extra distance closer to equator.

When I mentioned Cairns was kind of ruling it out (Australia). In this way maybe you have data on Panama?

*****************************

Also wanting a little insight into current state of magnetosphere if this interests too
(mostly with regards to flights across the South Atlantic Anomaly)
http://www.physicsforums.com/showthr...66#post3169466

klimatos

I'm not sure why avoiding minor temperature fluctuations from season to season is so important to you, but here goes. Like Cairns, Panama has a wet-and-dry tropical climate, but is much less pleasant.

The climate with the least temperature variation is the Rainy Tropics. Equatorial locations, heavy cloud cover, and high humidities keep temperatures from fluctuating much from day to night or from one time of year to another. I know of nobody who considers such climates to be pleasant. In terms of human physiology, they are quite stressful.

If that's your cup of tea, however, you might consider Singapore, Nairobi, Belem, Quito, or Kiribati. Nairobi and Quito have cooler regimes because of elevation. If stress is your concern, the least stressful climates for human beings are the various versions of the Mediterranean Sub-Tropics and the odd high-altitude tropical location. In the U. S., San Diego has the least stressful climate, Honolulu is moderately stressful, and Miami is quite stressful.

semiotically

I really like your answers & in fact my current 'destinations' are Belem & the Indonesian Islands just ''under' Singapore... so you predicted my top 2...

you say they are stressful, foresight is always a winner so if you'd like say why I'm definitely listening...

klimatos

The stress is both physiological and psychological. The physiological stress is induced by the combination of high temperatures and high humidities which makes it difficult for the body to lose heat efficiently. Without air conditioning, many people find it difficult to get a good night's sleep. The same conditions encourage mildew and rot in everything around you. Clothes have to be kept in "drying closets". Tropical climates encourage disease, especially various kinds of skin fungi (i. e., "jungle rot"), not to mention the tremendous variety of insect-borne infections and parasites.

Psychological stresses include the heavy cloud cover and sparse sunshine, and the sheer monotony of the weather. The high humidity seems to make everything that you do require extra effort, while--at the same time--making you unwilling to expend that effort. Also, if you have any phobias concerning many-legged "creepy-crawlies" or snakes, lizards and other reptiles, then the tropics is definitely not your cup of tea.

Despite all this, some people find it appealing.

russ_watters

Interesting. Sounds similar to wbgt. Is there a formula for it?

Oh and I said american english but should have said american engineer english.

klimatos

I wish there were. Unfortunately, much of the physiological human response to climatic stress is subjective. A is hot when B is cold and C is comfortable. The WBGT is one of many attempts to weed out the subjective element.

Much of the early work in climatic stress was done at the U. S. Army's climate research labs in Natick, Massachusetts. This includes work in wind chill and stress temperatures. In more recent years, a lot of papers have come out of the Sports Medicine programs at major university medical schools. Obviously, both the military and sports groups have an interest in how the human body reacts to climatic stress. So far, the military seem to have a slight edge, but it is difficult to tell because many military studies are classified.

semiotically

hey thanks again regarding 1st point n quote may well get back to you... At the moment thinking I'm 25 & healthy & if there's ever a time to test my health it's now

With regard to the second point I would like to get your thoughts (or readers) on your take on these graphs: the relationship between UV & humidity:

Guayaquil, Ecuador


Quito, Ecuador



These are from the Hiperion Report.
Secondly, the report outlines that Ozone destruction at the poles reduces levels at the equator:





I'm taking it these high UV levels due to the depletion will be common at all equatorial longitudes (with this process), is this true?

klimatos

1) Go for it.

2) The graphs simply show that both relative humidity and UV radiation are diurnal in their occurrences. Correlation does not imply causation. UV radiation comes from sunshine, and its intensity is a function of the angle of incidence. Relative humidity is an inverse function of ambient temperature, it goes up when temperatures go down and vice versa. Neither graph shows a full month.

3) This short paragraph simply states that equatorial ozone depletion might be related to polar ozone depletion. Alternatively, they both could be related to global ozone depletion.

The fourth attachment has no legend and is fairly confusing. I don't get the "loops" in the lines. What is the author trying to say?