[How to write lab report]

Assignment 8 Sonic Anemometers, fast measurements of the 3D wind speed and direction.

Here is the assignment as a MSword doc.
We will obtain a time series of wind speed from the sonic anemometer and post it here, for use in the assignment.

Purpose:
a. Learn how 3D vector winds are measured.
b. Compare sonic anemometer measurements with cup anemometer measurements.
c. Learn about how 3D vector winds can be used to measure vertical fluxes of heat, water vapor, carbon dioxide, particulate matter, etc.

 Board for the sonic anemometer lab. Click on image for larger version.

Assignment 7 Operational Amplifiers, Light emitting diodes as detectors, and Arduino: An in-class assignment.

Here is the assignment, and it is repeated here. You can copy and past the questions into MSword, answer them, and turn it in through web campus.

Purpose:
a. Introduction to more sophisticated components that can solve problems.
b. Gain experience using light emitting diodes as detectors, similar to use of photodetectors in general.

We will build the circuit below. One LED will be used as a light source, using pin 13.
The other LED of the same color will be used as a light detector, using the op amp circuit below, and pin A0 for analog input.
Set up the circuit to have the LEDs face each other.
The basic circuit is similar to the one used with the photoresistor analysis, Circuit 6, page 40 of the book.
The sketch will light the LED for a time, and the abruptly turn it off.

Here's the sketch to use for the Arduino for this assignment.

Discussion of operational amplifiers.
Use of light emitting diodes as wavelength specific radiation detectors,
as they are very useful for use in simple sun photometers, among other applications.

Questions:
1.  What is an operational amplifier?

2.  List the golden rules for op amps.

3. Insert your graph of measured photo current with LED as a function of time and discuss it (does it look like you expect it to look?).

For part 3, to calculate current, first calculate voltage using Voltage=CountsFromArduino * (5 Volts / 1023 counts).
Then calculate current using Ohm's law, i=V/R, where R is the resistance used in the feedback resistor, something like 10 MegOhm.

 Board for the Op Amp lab. Click on image for larger version. Photograph of the Arduino set up for this lab. Click on image for larger version.

Assignment 6 Arduino and Atmospheric Measurements:

## You will need to acquire data in class, write lab notes about your measurements, and write up each section of the lab as homework as soon after the section is finished so you remember it in detail. It will be very difficult to write up the lab after all the experiments are done.

Title: You can decide on the title based on your experience with this lab.

Goals:
a. Become familiar with the Arduino microcontroller as an example of a programmable device for acquiring measurements and controlling systems.
b. Demonstrate ability to modify Arduino sketches for solving problems.
c. Learn about and use sensors with atmospheric relevance.
d. Learn how to bring measurements from the Arduino into computers (interface the Arduino) to acquire data for later analysis and display.

If possible, install the Arduino software on your own laptop (if you have one), and use it in class.
Also download CoolTerm and place it somewhere that you can get to it for ease of use. This program allows us to transfer data from the Arduino to the computer.
The code for the projects in the book and kit is here: expand the file and put the folder in your Arduino examples folder.
Here is a link to the an online version of a manual that is similar to the one we use in class. (local backup).

Measurements and Analysis
2. Do Circuit 6, pg 40 in the book to learn about the photoresistor and how to measure its output.
Then create a circuit to drive the LED at different frequencies to see if the photoresistor resistance can accurately follow the LED output for low and high frequencies.
Point the LED output directly into the photoresistor input. You can use variable delay and the 'Blink' sketch to drive the LED.

 Description of the circuit for the photoresistor test. Click on the image for a larger version.

If the LED is driven by a square wave, the photoresistance should show a crisp square wave too. Use the plot monitor on Arduino to view the photoresistor output,
and save some data with CoolTerm (including time) so that you can graph the photoresistor output from the LED drive as a function of time.
Can you estimate the time constant of the photoresistor as a sensor of light?
Here's an example sketch that may be helpful in measuring response time. You may find ways of speeding it up to get more time resolution on the LED response.
[Extra question: Does photoresistor nonlinearity play a role in its frequency response?]

3. Do Circuit 7, pg 44 in the book to be become familiar with the TMP36 temperature sensor.
What is the principle of operation of the TMP36 temperature sensor? How was its signal obtained?

 Description of the analog to digital conversion for the TMP36 sensor. Click on image for a larger version.

Example sketch for response time measurement. Read it and follow instructions. Pinch the temperature sensor to warm it up when the LED comes on.
Record a time series with CoolTerm as you pinch the the sensor to warm it up to a steady temperature, and let it decay to a lower temperature.
Estimate the time constant for the sensor as you are warming it up with your fingers, and the time constant as you are cooling it off by letting it sit in air.

4. Create a voltage divider circuit to measure the resistance of the thermistor sensor using a fixed resistance of 1 MegOhm (1,000,000 ohms).
Calculate the temperature that corresponds to your measured resistance using the equation given here (thanks Alex).
Record a time series using CoolTerm as you pinch the the sensor to warm it up to a steady temperature, and let it decay to a lower temperature.
Estimate the time constant for the sensor as you are warming it up with your fingers, and the time constant as you are cooling it off by letting it sit in air.
Here's an example sketch to use for the thermistor sensor evaluation. Read the sketch for instructions on what to do.
Pinch the thermistor carefully (without affecting the wires) when the LED is on.

Click on image for larger version.

5. Set up a circuit and sketch to acquire data from the pressure sensor. Do appropriate data averaging so that you can easily tell the pressure difference
between having the sensor on the desk, and having the sensor about 1 meter higher or lower. Record data with CoolTerm to demonstrate your results.
Here's an example sketch for the pressure sensor. You'll have to comment out some lines near the end to get only the pressure measurements to CoolTerm.
Do measurements with 1 second time average, holding the sensor down for 10 seconds, then up for 10 seconds.
Then modify the code to obtain 10 second time averages. Test by holding the sensor low for 100 seconds, and high for 100 seconds.
Comment on the effects of additionally time averaging the data.

Click on image for larger version.

Note: It seems the 10 bit analog to digital (a/d) converter of the Arduino would not be able to resolve a pressure difference of about 0.1 mb associated with
1 meter height difference. 1 bit change in the a/d counts corresponds to a voltage change of about 0.005 volts, and a pressure change of and about 1 mb pressure.
Dither helps: the voltage source for the Arduino is noisy enough to cause around 50 mv or so of noise so that the a/d counts fluctuate to a useful average.
The example sketch for pressure averages the measurements of the pressure sensor voltage and the voltage divider voltage about 1800 times for each measurement.
Use of the voltage divider for the power supply voltage measurement is necessary since the a/d range is 5 volts, and direct measurement might be over the measurement range.

6. Implement the infrared sensor. Interface it with Labview using the indicated code.
Demonstrate a time series of temperature from Labview by doing a screen capture. Include a discussion of how the sensor works.
Those with laptops can take the IR sensor outside to get a time series of infrared brightness temperature.

 Notes on the IR sensor: Click on image for larger version.

Very useful voltage divider circuit to use for measuring sensors that depend on resistance.

Click on image for larger view.

Assignment 5

Title: Introduction to Python programming.

This assignment should be accomplished mostly in class.

Those with laptops, bring them. You can download and install the following programs for the Python language, and for the integrated development environment (IDE).

First, here are the materials for the in-class exercise.

Python programming language It is here at https://www.continuum.io/downloads, install the Python 2.7 version. If the install fails at the last step, don't worry, just go on to the second step.
PYCHARM IDE for working with the source code It is here at https://www.jetbrains.com/pycharm/download/ . When you run it, you'll need to get it to find Python, if it doesn't do so automatically.

We will then work on the assignment together in class.

Assignment 4

Title: Vertical distribution of pressure, temperature, and dew point temperature inside and outside the Physics building: Analog for weather balloon sampling in the atmosphere.

Goals:
a. To investigate the vertical distribution of atmospheric thermodynamic properties, in analogy to balloon sampling in the atmosphere.
b. To appreciate the time constant of sensors, and how measurement strategy needs to account for it.
c. To use custom instruments to better understand the components.
d. To use a simple method for sampling near surface atmosphere properties.
e. Gain a sense of how important balloon sampling of the atmosphere is for weather prediction.

Measurements:
We have 4 'Teensy' data cards for use in this lab, and 8 microSD cards. You can work in groups of 2 to acquire data, but each person will process the data.
We get data off the cards using microSD cards. Measurements include pressure, temperature, relative humidity, and GPS latitude, longitude, and height.
GPS measurements won't be useful for this exercise.

a. We measure the time constant of the temperature, relative humidity, and pressure sensors so we know how to do the rest of the measurements.
Instrument/sensor time constant is the time it takes to respond to a changing value.
Stand on the inside of the Physics building by the 1st floor doors to the outside for 5 minutes with the instrument operating.
After 5 minutes, step outside into the cold shade, making sure the sensor doesn't get heated by the sun. Wait 5 minutes.
Come back inside after 5 minutes. Again wait 5 minutes inside for the sensor to warm up.
Then go to the lab and get the data off of the Teensy microSD card.
Make a time series plot of temperature and relative humidity.
An example of a time series for another type of sensor is below, along with a fit of the data to a model.
Is the time constant the same whether warming up or cooling down?
We will fit an exponential curve to the time series and use the fit parameters to get the time constant.
This exercise will introduce you to the 'solver' in Excel and how to use it to obtain parameters from measurements.
The basic philosophy of the solver is this: minimize the error by letting the solver change the model parameters p1, p2, and p3.
It's best to have a lot of redundancy, many more measurements with information content than model parameters.

 Time constant of thermistor measured using room temperature and freezer temperature (click on image for larger version).

b. Start at the basement level of the Physics building.
Measure the vertical distribution of T, Tdew, and pressure in the Physics building, from the basement to 4th floor deck outside.
Be sure you wait long enough on each level of the Physics building for the sensors to come to equilibrium (the time constant from part a.).
You may use the DRI station pressure to see if the pressure was actually 'constant' during the time of our measurements.
Then return to the basement rapidly so that the pressure sensor value doesn't change if the ambient pressure is changing a lot during the day.
Calculate the height of the building by using an appropriate equation and your measurements, starting with zero meters at the basement level.

c. Measure the actual height of the this distance using a ruler to measure step size, and to count the number of steps. (Is step size similar from step to step?)

d. We may also use the fishing poles to lower the sensor to the ground from outside the Physics building, or we may launch a sensor using the party balloons, to measure the value aloft. Stay tuned.

NOTES ON THEORY FOR DETERMINING THE TIME CONSTANT, AND FOR CONVERTING PRESSURE TO HEIGHT.

(click on images for larger version).

 H=scale height of atmosphere, calculated as shown. RD = 287.1 Joules/(kg K) is the gas constant for air. We'll use the simple approach to get the height from pressure, (see the circled equation on the figure to the right). Use the circled equation for converting pressure to height. Note that z=0 meters when P(z)=Po. The noise on the pressure sensor of about 0.02 mb gives a height uncertainty of about 21 cm. This general approach could be used to obtain pressure. It is more accurate when the temperature changes a lot between pressure levels. Here is the equation we used and fitted to obtain the time constant for the temperature sensor.

1. Introduction to include history of balloon sampling of the atmosphere, and importance of it.
2. Measurements section should describe sensors used, see resources below.
3. Define and discuss the time constant, showing your data and the fit to it to obtain the value. Discuss how the measurement was obtained.
4. Use the pressure measurements from the day of the temperature time constant measurements to discuss the pressure sensor noise, and the ability to see pressure fluctuations from ground level to above your head.
5. Discuss methodology and calculation of obtaining building height from the basement to the roof from pressure measurements, and uncertainty in this measurement.
6. Measure the height of a step and count the total number of steps in the building from the basement to the roof. Compare with the height obtained in question 4.
7. Evaluate the response of the pressure sensor with temperature change using the data we obtained at the end of the measurements, when we walked outside after doing the measurements in the stair well. Does the pressure sensor output change with temperature, implying that it is not properly temperature compensated?

Here's a summary of the graphs needed for your report. Click on each image to obtain a larger size.

 Here is the pressure from the UNR and DRI weather stations during our measurements on Tuesday. Note how pressure changes would affect our determination of the building height using pressure measurements.

Resources:
Pressure Sensor (Transducer) MPX 4115 APand application note on how to filter the output
Temperature and humidity sensors made by Sensirion
Schematic and board layout, and the program for the Teensy microcontroller based package, in case you are interested (It is not a requirement for this assignment to describe/understand the entire system, just become familiar with the sensors.)

Literature to help with the introduction, though you can use others as well:
National weather service upper air measurements made with balloons (complementary site).
Tethered kites used to sample in the vertical.
Smart balloons for measuring along with a moving air masses.

Assignment 3 Infrared camera laboratory: radiation in the atmosphere discussion and demonstration notes.

Assignment 3, short answer to 16 questions on radiation in the atmosphere. Copy these questions into MSWORD and answer them.
Turn in through webcampus.

We will do most of this in class.

Questions for the Infrared Camera and Solar Radiation Laboratory:
1. What wavelength range comprises solar radiation at the Earth's surface?
2. How is solar radiation affected by the Earth's atmosphere and surface?
3. What is the equivalent black body temperature of the Sun with regard to the solar spectrum we see at the top of the Earth's atmosphere?
4. How much solar radiation (irradiance) is present at the top of the Earth's atmosphere in watts per square meter units?
5. How many one square meter, 20% efficient solar panels would be needed at the top of the Earth's to run a 2000 watt hair dryer?
6. What are the primary atomic and molecular properties are involved with absorption of solar radiation at wavelengths from the UV to the near IR?
7. What is the peak wavelength of solar radiation?
8. We will do a 'high five' in class by pointing our hands towards each other and letting the infrared photons fly. Assuming human skin is a perfect blackbody emitter and absorber, and that the hand is at normal body temperature (expressed in Kelvin units), use the Stefan Boltzmann law to calculate how much radiation in watts per square meter is emitted by your hand. What fraction is this compared with the solar radiation at the top of the atmosphere?
9. Use Wien's displacement law to calculate the peak wavelength of infrared emission by your hand, using the same temperature from question 8, and the sun's equivalent blackbody temperature from question 3.
10. Suppose that one hand was dipped in water and then you waved dry air over your hand to cause it to evaporate. What does the infrared camera show for your hand show for your wet hand temperature compared with your dry hand temperature, and why?
11. When looking at a person with an infrared camera, why is the face warm while the hair, nose, glasses, and clothes look cool by comparison?
12. In the experiment with a small square of aluminum foil put on a student's forehead, it was observed that the aluminum foil looked dramatically cool, even though the aluminum foil is at the same temperature as the forehead. From this observation we can learn about how aluminum interacts with infrared radiation: describe this.
13. We were able to write a message on the wall just by vigorously rubbing it in the pattern of letters, and observing it with the infrared camera. How does this work? Could we make a cool message by putting a thin film of water on the wall and evaporating it? (try this).
14. We did a demonstration with the dinner plate that was transparent at visible wavelengths, and argued that it must be a strong absorber because we can't see the infrared radiation emitted by a hand if the plate is between the hand and the camera. Describe how the plate is like the Earth's atmosphere in its effect on visible and infrared radiation, and the 'greenhouse' effect. Which gases in the atmosphere are infrared active as 'greenhouse' gases?
15. We did a demonstration of visualizing atmospheric convection by having the camera visualize the hot air, from use of a propane torch below the camera field of view, rise into the field of view of the camera. We also did a demonstrate of thermal conduction by heating the glass rod with the propane torch. Which process is more effective at transferring heat in the atmosphere above the Earth's surface? By the way, why does the hot air rise? And why is the hot air visible -- what are the gases produced by combustion of the propane, and are they infrared active gases that can absorb and emit infrared radiation?
16. Fill a transparent container with water and use the infrared camera to view the water. Is water a strong absorber and emitter of infrared radiation? How can you figure this out? Can you observe thermally induced convection in the water using the camera? Would you expect ice to behave the same as water in its interaction with infrared radiation?

Assignment 2

Submission through webcampus is preferred. Copy these questions to MS word and work on them.
Be sure to give your sources for answers. We'll go through this in class.

Basics:
1. What diameter range are raindrops?
2. What is the shape of raindrops?
3. Why don't raindrops get arbitrarily large?

Local Rain Measurements:
4. What is the rainfall rate equation?
5. How does a simple rain gauge work?
6. How does a tipping bucket rain gauge measure rain?
7. How does a disdrometer work?

Weather Radar basic presentation; brief presentation for dbZ; animation
8. What is the name of weather radars used by the National Weather Service?
9. What wavelength range used by this radar?
10. Briefly, how does radar work to measure rain?
11. Calculate the size parameter x=2 pi * Raindrop Radius / radar wavelength.
12. What 'radiation regime' is the size parameter of equation 11? Note that it is the same radiation regime that gives rise to the blue sky on a clear day. Note.
13. What is the basic relationship for radar backscattering in terms of number of raindrops per volume, back scattering strength, droplet diameter D, and radar wavelength lambda? Note.
14. Why must the radar be empirically calibrated given question 13, and question 4?
15. How does Doppler radar work? What can be detected with it?
16. How does dual polarization radar work, and what can be detected with it?

Assignment 1

The purpose this assignment is to become familiar with instrument used to measure atmospheric:
temperature
relative humidity

atmospheric pressure.
Note that the UNR pressure sensor is not properly temperature compensated.
Here's what we use to compensate it for temperature variation
.
click on image for larger version and equation to use for pressure compensation.

This case study will especially highlight the importance of water vapor on the clear sky downwelling infrared radiation.

The theory for this parameterization is here (from 1972): see especially Eq. 6 of that paper.
This approach takes into account the contribution by water vapor, but leaves out that due to other infrared active gases.
Modern day radiative transfer code is much more sophisticated than represented by this simple approach.
However, the simple approach helps build a physical understanding, and harks back to the days of this style of research.
Here is a more modern day radiative transfer calculator based on MODTRAN.
A review paper on long wave radiation from 1984 is here, and a research paper from 2015 is here.

Lecture notes from class on this subject are in this table.
Click on the image to get a larger version.

 board 1 board 2 board 3

Notes on how to formally calculate infrared radiation transfer.
Play with this model to see how it works.

This presentation discusses how to calculate the vapor pressure of water for a given relative humidity and temperature.
This paper gives a very accurate set of equations for the vapor pressure, and is referenced in the presentation.

The goal of this research is to see how well this very simple model of atmospheric emissivity works compared with measurements.
It is an example of the interplay of measurement and modeling.
We will study the month of June 2016 in class.
In your report you will study the month of December 2016, and compare findings with the month of June 2016.

Specific Requirements:

1. Obtain the relevant data from the UNR weather station, see below. We will go through this in class for June 2016.

2. Calculate the temperature compensated pressure. Make a time series graph of the pressure. Use it to discuss times of high and low pressure.

3. Calculate the dew point temperature. Make a time series graph of the dewpoint. Use it to discuss times of dry and moist conditions.

4. Calculate the water vapor pressure in mb.

5. Calculate the effective atmospheric emissivity. Make a time series graph of the effective emissivity. Use it to describe times of abundant and scarce downwelling infrared radiation.

6. Calculate the downwelling clear sky infrared radiation in Watts per square meter. Make an overlay time series graph of the solar radiation, measured downwelling IR, and calculated downwelling IR.

7. Calculate the 'residual' downwelling IR = measured downwelling IR - model downwelling IR. Make a time series graph and use it to identify times when the model results are close and/or far from the measurements.

8. Make a scatter plot of the modeled downwelling IR versus the measured downwelling IR. Discuss the adequacy of the model.

9. Using all of the meteorological data, evaluate when the modeled downwelling IR is reasonable, and what factors affect its accuracy.

10. Conclude with a summary of your findings, and the potential use(s) of this simple model for downwelling infrared radiation.

 Note: Use of the parameterization, where subscripts K and C refer to the temperature in Kelvin and Celcius, results in a better fit of the model to the observations for June 2016. The new terms are given in red. This is one of many parameterizations that could be used. For extra credit, you could try this model for the downwelling IR and compare it against the measurements of downwelling IR, for both the June 2016 and December 2016 data sets. Having a very good model for the clear-sky downwelling IR allows for calculation the downwelling IR contributed by clouds through use of

Description of Specific Sensors Used at the UNR Weather Station:

Pressure sensor -- Vaisala PTB101B Barometer

Temperature and humidity sensor
Humidity sensor discussion.
Thermistor presentation.
Fine wire resistance temperature detectors discussion.

Solar sensor (silicon based sensor)

 Weather station images looking north. Lake Tahoe is on the lower left, Pyramid Lake on the upper right. The UNR weather station is on the valley floor. Click on image for larger version.

EXPECTATIONS IN LAB REPORTS

Lab reports will be written the same format we use for scientific papers and for student senior, MS, and PhD theses.
One goal of this class is to work on your ability as a science writer.
Let me emphasize one word here. SCIENCE SCIENCE SCIENCE SCIENCE SCIENCE SCIENCE!!!!
So often we are obsessed with the technical details of the measurements that we don't cover the science adequately.
The following elements are needed for your lab report to be complete.
Here is an example of some hints I found using a google search with the keyword "how to write a scientific paper".
Page length doesn't matter; it's all about the contents.
Make it as short as possible to get the message across in a clear manner.

Title: The title should cover the science objective and maybe mention the instrument(s) used for the measurement.

Abstract: The abstract is a brief discussion of the findings of your work. It should be well written because it is often what is read as someone makes a decision to read your work (or fund your research).
Hint on writing abstracts.

Introduction: Explain the scientific goal in more detail and maybe hint at the measurement methods used.

Measurements: Discuss the measurement methods, including uncertainties.
Discuss the instrument(s) and the pertinent information needed to convey what you measured.