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Wednesday, 16 April 2014

Tasik Chini Fieldwork - Climatology

Assoc. Prof. Dr. Wan whom I often see when walking around in the faculty. We had just attended one lecture conducted by him.
Climate is the weather conditions of an area over a long period of time. So weather parameters measurement is important to detect change in climate and also in predicting the following weathers by analysis the data collected. During the olden days, anemometer (for wind speed), sling psychlometer (for relative humidity), altimeter (for altitude) and barometer (for atmospheric pressure) were used in measuring the weather parameters. Then, electronic precision thermohygrometer was invented for a more accurate and consistent results by automatically drawing graph. And today, we have the super cool automatic weather station which can measure the wind direction, wind speed, solar radiation, soil temperature, air temperature, relative humidity, rain fall and atmospheric pressure all in one device!

The anemometer.
Sling psychlometer. Dry bulb above while wet bulb below. It's something works like thermometer. After we swing it for 20 seconds, we will take one reading reading from each bulb, then we have to refer to a table to get the result.
The combination of altimeter (the outermost scale) and barometer (the innermost scale).
The electronic precision thermohygrometer which works using battery! You see the graph at the left hand side?
We are quite familiar with most of the weather parameters but there are a few that I would like to point out. Firstly, the relative humidity (NOT humidity, but RELATIVE one). It indicates how much more water vapour can evaporate into the air. If the relative humidity of the air is fully saturated which is 100%, the air cannot take up anymore moisture from the ground. On the other hand, if the relative humidity of the air is low, let say 40%, the air can take up more moisture from the ground (only if the moisture is available). So the relative humidity in Arctic is actually 100%! Secondly, the dew point (which truly represents the humidity of the surrounding air). The higher the dew point temperature showed, the higher the humidity of the air. It is the temperature when water condensation occurs. So, at temperature below dew point, condensation does not occur much. This means that there are a lot of water vapour suspended in the air. Dew point is dependent on the pressure and amount of moisture in the air. Thus, if we want to know about the humidity of the air, we should look for dew point temperature instead of relative humidity.

The automatic weather station. All in one.
The wind wane which always points at the direction where wind comes and the anemometer which spins faster when the velocity of wind is high. 
The Stevenson screen which contains thermometer and hygrometer (for relative humidity and dew point) inside for protection.
The sunlight radiation detector. 
The device that detects leaf wetness (what??) which shows the amount of dew or precipitation (rain) left on the surface. Of course it won't work when the sun is beating down as all the water has evaporated.
The rain gauge which measures the precipitation rate. Quite obvious, right?
The soil temperature detector which is of course, being inserted into the soil.
The black slightly-oval-shaped thing in the middle of the circuit board is actually the barometer, being hidden in the most important part of this weather station where rain and wind will not reach. All the data collected is stored and transmitted wirelessly to the screen.
Basically you can know everything you need to know about the weather using this device which has wireless connection with the automatic weather station.
About weather forecast especially the rain indicator, many aspects including cloud coverage, atmospheric pressure and wind direction are analysed using computer software. For example, if there is a sudden drop in atmospheric pressure and the wind directions are focused at one area, there might be rain soon at that particular area. But as we know, the weather forecast is not always accurate.

(Google image) This is the example of a station model constructed after analysing all the data where we will know most of the parameters in this single diagram. There are symbols representing each type of cloud coverage and current weather.
Besides that, we also calculate the thermohygrometric (THI) using the formula involving the readings for relative humidity and temperature to know about the human thermal comfort class which indicates how comfortable the surrounding situation is to human. So the classes are classified according to the THI value measured depending on the local climate (as people from temperate countries will not normally enjoy the hot tropical afternoon here). The classes ranged from Hyperglacial (extremely cold) to Torrid (extremely hot) with 8 more classes in the middle. Instead of using THI, we can also calculate the Humidex (H) but we usually use THI here. Generally there are five climate factors that influence our comfort and health: air temperature. humidity, solar radiation, wind and air pollution. We use a generalised climatic comfort chart to evaluate the urban environments to see whether the circumstances are suitable for human occupation. (sorry that I could not find an image on Google of this chart, it has 3 ranges: heat stress risk, maximum comfort and cold discomfort and risk)

So these are what we learnt during the second session of our group. Finally I understand what are relative humidity and dew point are (and found that I have made mistakes in the previous test, ugh). Just like the previous sessions, this was only the introduction for weather parameter measurement. Weather measurement might sound minor, but it contributes to the big picture of the whole climate measurement.

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