(no subject)

[sinjun]

Busy today. No time to write up a long post. Golf yesterday - way hot, (one of those 35C +humidity=45C days, after all) and I golfed a 59. Consistent, yup.

And after that in rp ...poor Yasmin.

Comments

I would just like to point out

[chirikoboshi.livejournal.com]

That there is no scientific basis to determing relative temperature using humidity anymore than there is using wind chill factor.

Just something that irks me.

Re: I would just like to point out

[insaint.livejournal.com]

I usually go with '35C + humidity = very bloody hot'. That's accurate enough for me. :)

Re: I would just like to point out

[damara.livejournal.com]

Okay, now I'm curious. That's as generic a statement as using the wind chill factor or the relative humidity.

So - what scientific facts, theories and other information are you using to draw the conclusion that these measurements have no scientific basis?

Where can I look to find this information?

Curiouser and Curiouser ...

Bleh

[chirikoboshi.livejournal.com]

I don't know where to research this off the top of my head. But I have a better idea.

Can you find any evidence supporting wind chill factor or heat index? Science isn't obligated to disprove any crap that comes along, but certain things should be proven.

Re: Bleh

[damara.livejournal.com]

From various weather related sites - I started at www.theweathernetwork.com and looked from there.

If it's 3°C outside with a windchill factor of -8°C, will water freeze due to the windchill factor?
No. The freezing point of pure water is, as you know, 0°C. If the air temperature is not at or below freezing there is no way that any matter in contact with the air can fall below freezing. This is the first law of thermodynamics, and applies to all objects, liquid, solid or even a gas that is contained in a way so as not to mix with the air. Water placed in a room at 3°C cannot get colder than 3°C no matter what the wind is doing. In fact, even if the wind is howling and the water is already frozen as ice, if the temperature is 3°C the ice will melt and warm to 3°C in time.
The reason people and warm blooded animals feel a windchill is that we generate heat internally as we metabolize food and fat. When the wind is blowing and the temperatures are cold enough (as opposed to a hot summer day) our bodies lose this internally generated heat as the air flowing around us carries the heat away. The stronger the wind, the faster this heat loss occurs and the more we "feel" the cold.

Heat is a form of energy which is measured in Joules. The rate at which heat is generated or lost can be measured in Joules per second, which is exactly the same as Watts. In much of Western Canada it is common to describe windchill not as an equivalent (cold) temperature but in the form of Watts per square metre.

A windchill of 2200 Watts per square metre means that every second 2200 Joules of energy is lost from an area measuring one metre by one metre. This happens to be is the rate at which the average human body loses heat to the surrounding air when it is -48°C with no wind blowing at all. If it is only -25°C outside but the wind is blowing at 40 km/hr., it will feel like -48C because the rate at which heat if being lost is also 2200 Watts per square metre. While -25°C is much warmer than -48°C, the wind increases the rate of heat loss. This wind-enhanced heat loss is what we call the windchill.

And more ...

When the temperature increases our bodies adapt by perspiring. Slight breezes are enough to evaporate this water from our bodies and cool us off. In effect, the heat energy within the perspiration is dissipated to the atmosphere within water vapor molecules. As the heat leaves our skin surface, there is a cooling effect. On hot, humid days, the atmosphere is more saturated with water vapor and fewer molecules are able to evaporate into the air. As a result, the cooling effect of heat loss is lessened. So, we try to find places where the air temperature is cooler (shade, air conditioning, etc.) or the breeze is greater (open areas, electric fans, etc.).

Forgot this bit ...

[damara.livejournal.com]

Relative humidity is always calculated at all times of the year but the humidex is usually given in the warmer months from May to September.

Relative humidity can be calculated using various methods and instruments. It is a calculation to find out how many grams of water vapour can be held at a given temperature. Usually, the warmer the air the higher it's capacity for holding water vapour. Each specific temperature has a holding limit for water and the actual amount of water held in the air at the time of measurement can be represented as a percentage.

For example, if a parcel of air at 20 C has a limit or capacity of 16 grams of water vapour and 16 grams of water vapour is measured, the air's holding capacity is at it's maximum, the relative humidity (RH) of the air is said to be 100%. Take the same air with 8 grams of water vapour and your RH is 50%. Relative humidity is a percentage of water vapour per area at a specific temperature.