by tonytran2015 (Melbourne, Australia).
#finding, #comfortable, #temperature, #habitat, #daily, #annual, #seasonal, #fluctuation,
Predicting the temperature of a habitat.
When you plan to leave your house for a short walk or for a long journey or for a camping trip, it is vital to be able to predict the temperature of the habitat involved in your trip.
1. Central role of environmental temperature.
The functioning of your body and your comfort depends on the temperature of the environment. If it is too hot you may lose a lot of water through breathing and sweating, your brain may stop working. If it is too cold you will feel like having cuts on your skin, may have frozen extremities and your brain may slow down appreciately. Extremely high or low temperature may cause death.
The temperature ranges for your comfort are
Sleeping 30°C to 37°C on body skin.
Moderately active: 25°C to 37°C.
Active state: 15°C to 37°C.
Outside this range of comfortable temperatures, the body has to activate its temperature stabilizing processes:
1. Cooling by increasing evaporation of water in the body through increased breathing and perspirating.
2. Heating by trembling, uncontrolled shaking and minimizing heat loss by raising skin hairs (causing goose bumps) and decreasing blood flow through limbs and lower torso.
So to be comfortable you have to plan your activities, sleeps and cooking depending on expected environmental temperature.
For comfortable cold nights, the temperature inside your bed or your sleeping bag should remain around 25°C – 29°C with actually measurement !
You have to plan your activities, sleeps and cooking depending on expected environmental temperature.
When it is hot you need to carry more drinking water, food may spoil easily but less fuel is required for cooking and fewer clothes are needed.
When it is cold your activities, food consumption, cooking time and your requirements for fuel will increase. You also need a lot of clothes.
Your tent set up, camp fire, camp cooking, have to adapt to extreme temperature conditions.
Figure: A low cost 75mmL X 40mmW plastic compass with thermometer and relative hygrometer on its top cover.
Some people carry unbreakable, accurate portable thermometers to avoid mis-judgement on their planning. Those portable thermometers are central to the planning.
To be able to predict the temperature of a habitat, you have to know about three different types of temperature fluctuation.
Temperature has 3 main types of variation. They are superimposed on each other:
2. Yearly (seasonal).
3. Caused by Air flows.
2. Daily fluctuation of temperature.
The daily temperature is coldest at the end of the sunlight deficit period and warmest at the end of surplus period.
So codest and hottest times for any 24 hour period are before sunrise and sunset.
3. Seasonal fluctuation of temperature.
Figure: Determining solar declination using a watch face. (The lines SOLAR DECLINATION Its rough estimate is required for Fine Alignment of the watch are to be ignored.)
Solar Declination makes days longer or shorter during the year.
For Northern hemisphere from Mar 21 to Sep 23. the Sun stays up in the sky for more than 12 hours, so there is a surplus of sunlight during that 6 months and the temperature becomes hottest at the end of the period. It works similarly for the other half-year. The seasonal temperature curve looks almost like the Solar Declination curve, but may lag it by up to 3 months (The temperature of the deep layer lags by 3 month, the temperature on the surface lags by few days if not affected by the deep layer, the effect on any location can be a combination of the two types of temperature).
The seasonal temperature is hottest at the end of the sunlight surplus half-year and coldest at the end of deficit half-year.
So for the Northern temperate zone, hottest and coldest nights for the seasons can be as late as on 23rd Sep and 21st Mar. The opposite happens to the Southern hemisphere.
Daily fluctuations are strongest near the equator while seasonal fluctuations are strongest near the poles.
Adding the daily and seasonal fluctuations give the surface temperature of a windless desert under a clear sky or of a flat ground surface underneath a wide glass house. There is still the fluctuation brought by winds, evaporation and rains to be considered.
4. Fluctuation caused by movements of air masses.
Besides the easy to predict annual and daily fluctuations, there is a more profound fluctuation caused by the movements of air masses. The movements are called winds.
Winds can bring hotter or colder, drier or more moist air. The consequential variation in temperarure is added on top of daily and annually fluctuations to give the total fluctuation.
You have to obtain this fluctuation from the forecasts made by local weather bureau.
1. Besides bringing air with a different temperature, unsaturated wind can also evaporate water on your clothing and your skin. This evaporation can bring your exposed wet clothing down by about 5 degrees C.
2. Cold and dry wind can make your skin cracks.
5. Effects of nearby water masses.
Nearby mass of water may affect the temperature significantly.
Unsaturated wind blowing across a lake can cool down by about 5°C.
Daily and seasonal fluctuations of water in a large lake are small. This is due to the high specific heat of water.
In summary, near a lake, the average temperature over the whole year will be slightly lower (about 5 degree C lower) and both the daily and the seasonal fluctuations will also be less.
6. Avoiding excessively cold places.
Avoid sleeping under the open sky in a desert or on a rock. The air near the ground loses its moisture content and heat and become drier, denser and colder. This layer of air near the ground may then become too cold for your comfort.
Find a place under a cover on a ground with vegetable to avoid such coldness.
The temperature inside any cave also fluctuates less than on any nearby open ground. The same holds true for the space at the corner of two tall walls.
However, before using any such natural advantage, other risks such as rock falls, snake bites, insect bites, etc . . . must be assessed.
8. Avoiding excessively hot places.
Avoid sleeping under direct sunlight in a desert or on a rock ! This is so obvious.
Walk on paths with planted trees.
9. Plan your trip to have your prefered temperature.
Select trip time to have your prefered temperature. Also choose your route through areas with comfortable temperature. Doing that can give you a better trip than not doing any planning.
Bring your suitable clothing and gears to keep yourself warm and dry.
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