What do you know about weather instrumentation?

A common complaint mentioned by prospective employers of students that graduate from undergraduate meteorology programs is that they have little hands-on experience with instrumentation (of course, they have a bunch of other common complaints too). During the last 3 weeks of the Spring Quarter, you'll receive an intensive dose of information about instrumentation. The purpose of this assignment is to assess what you know about instrumentation and to get you to track down some answers to a few basic questions. Don't panic if you can't find out everything, but do spend some time looking for as many answers as possible. You can also come and see me if you're stumped.

We'll go over this info on May 13th. Be ready to discuss your answers at that time.

Basic Electronics: or why did you have to study electricity in physics?
Electropedia
Dictionary
Martindales

What is the difference between DC and AC power?

Direct current: current flowing in one direction. Used for most instrumentation. Source of power is a battery.
Alternating current: current that changes direction. Used for most electronics.

What is a capacitor?

Two conducting plates separated by a dielectric (nonconducting substance, insulator) that is used to store a charge.

Why might an electrical current passed through a resistor provide information on temperature?

Resistor:component that opposes the flow of electrons. Resistance for any substance is related to temperature. Cold objects resist a current more than warm objects.

What is a thermocouple?

An electrical circuit composed of two dissimilar metals, which have different resistance. If the metals are exposed to air, then the resistance can be measured based on the known propoerties of the two metals.

Pressure
What is atmospheric pressure?

Force (weight) of air column above an unit area surface.

What is the molecular weight of Mercury? of water?

Mercury: 200.59. Water: 18.

If the atmospheric pressure at Salt Lake City balances a 65 cm column of Mercury, how tall would the column of water have to be to balance the same atmospheric pressure?

200*65/(18*2.54*12)=20+ feet

From the Web links on the Meteorology web page, describe 1 pressure sensor that is available commercially.

Campbell Scientific

Temperature
What is temperature?

Bulk measure of motion of molecules

What are the boiling point and freezing points (in C) of mercury? of alcohol?

HG: -39C 357C Alcohol -117C 79C

From the Web links on the Meteorology web page, describe 1 temperature sensor that is available commercially (use a different manufacturer than previous one).

Humidity
What are the best measures of water content in the atmosphere? What is the best measure of the water content relative to that of saturated air?

Vapor pressure. mixing ratio. specific humidity
Relative humidity

Why would a human (or horse) hair be used to measure relative humidity?

Hair is hygroscopic (water attracting)

From the Web links on the Meteorology web page, describe 1 humidity sensor that is available commercially (use a different manufacturer than previously).

Precipitation
Many precipitation gauges weigh the amount of water collected in a cylinder. One that the department owns has a diameter of 12 inches. If a rain event would cover the surface an inch deep, how many milliliters of water would this be? How much would it weigh in grams? The density of water is 1000 kg/m3.

pi * (6in)**2 * (2.54cm/in)**2 * 1in *2.54cm/in*1ml/cm**3=1800 ml
1800ml 1cm**3/ml*10**-6m**3/cm**3*1000kg/m**3*1000g/kg=1800g

Tipping bucket rain gauges tip when they receive .01 inches of water. The standard diameter of a tipping bucket gauge is 8 inches. How many mililiters of water must be captured by the rain gauge in order for it to tip?

pi * (4in)**2 2.54**2 *.01 *2.54=8 ml

Why is it a bad idea to put a precipitation gauge at a windy location? Such as the top of an 8 story building?

Catching rain at angle rather than vertical

From the Web links on the Meteorology web page, describe 1 precipitation sensor that is available commercially (use a different vendor).

Jeopardy Time! I've supplied the answers, what are the questions?
Measures the total incident solar radiation

What is a pyranometer?

Is launched aloft and measures temperature, pressure, etc. as it descends

what is a dropsonde?

The span over which a weather parameter can be measured

what is range?

A temperature probe should never be exposed directly to this

What is Solar radiation?

Relies on the frequency shift between a pulse of electromagnetic radiation travelling toward an object and the return pulse after it hits the object

What is a doppler radar?

A hyetometer

What is a rain gauge?