fss 205.1 - describe atmospheric pressure and the associated units of measurement

Atmospheric pressure is the force per unit area exerted by ______ as a consequence of its weight, and thus is equal to the weight of a ___________, extending from the level in question to the outer limit of the atmosphere

the atmosphere, a vertical column of air of unit area

Station elevation is the vertical distance in metres _________ of the datum level to the barometer readings are corrected to give ________

above Mean Sea Level (MSL), station pressure

Mean sea level pressure is computed from ______ and reported in observations so that the ______ at stations of different elevations can be compared at a common level for ______.

the station pressure, barometric pressure, synoptic purposes

Which value is used on surface analysis charts?

Mean Sea Level pressure

What are the characteristics of the standard ICAO atmosphere are:

• Air is _______

• Pressure at the sea level is _________

• Temperature at sea level is _______

perfectly dry gas, 29.92 inHG or 1013.2 hPA, 15ºC

Altimeter setting is a computed value of mean sea level pressure expressed in _________, which is used to set the sub-scale of an altimeter so that the height scale of the altimeter indicates the height of the instrument _______. Altimeter setting is done in accordance with the ICAO Standard Atmosphere.

inches and hundredths of mercury, above mean sea level

The unit for pressure is called a _______.

hectopascal

The altimeter setting shall be reported to _______ and the sea level pressure to ________.

the nearest one hundredth of an inch, the nearest tenth of a hectopascal (hPa)

The remark PRESFR is used when the pressure trace indicates that the station pressure is falling at _______ at the time of observation.

the rate of 2.0 hPa per hour or more

The remark PRESRR is used when the pressure trace indicates that the station pressure is rising at _______ at the time of observation.

the rate of 2.0 hPa per hour or more

Pressure tendency is the characteristic and _____ during the ____ preceding the observation

the amount of change in station pressure, three hours

The pressure tendency must be included in weather reports which are taken at _________.

0000, 0300, 0600, 0900, 1200, 1500, 1800 and 2100

The tendency characteristic shall be coded as outlined in the following table; these are designed to provide a uniform basis for coding ______.

3-hour tendency characteristics.

When a trace resembles 2 codes, the observer should use the code for _________ and look to see if it is compatible with the 3-hour rise/fall.

the last portion of the trace

Which tendency characteristic codes increase, then decrease or are steady?

0, 1, 2

Which tendency characteristic codes decrease, then increase?

3, 5

Which tendency characteristic codes decrease continuously?

6, 7, 8

Which tendency characteristic codes are steady?

4

What does the height scale of the altimeter indicate?

height of the instrument above sea level