UNDEO 4 Assessment of Student Learning

The success of UNDEO-2015 and identification of opportunities for improvement were assessed using the following vehicles:

  • Anonymous survey of the students Students were asked to evaluate how well the learning objectives were met. The survey and average results are included in Table 3
  • Graded assessment in Radar Meteorology

Student learning was also measured through standard assessment tools (“lab” exercise, final exam, term paper, etc.). The “lab” exercise used appears in Table 4.

 

Table 3. Summary of the student survey. Bold values are the average scores received. [1 = too little or no benefit, 5 =  very helpful or effective]

How would you rate the length of the on-campus deployment of the DOW? 2.67 / 5
How would you rate the overall effectiveness of the DOW training, including the DOW exercise, in preparing you to operate the DOW with some assistance? 4.00 / 5
How would you rate the overall helpfulness of CSWR staff both prior to and during the field deployments of the DOW? 4.78 / 5
How would you rate the level of involvement of students in the strategic planning of the deployments for data collection? 2.56 / 5
How would you rate the level of involvement of students in the actual data collection during the field deployments? 2.78 / 5
How would you rate the benefit of the DOW research project to your understanding of radar meteorology? 4.56 / 5
How would you rate the overall benefit of the DOW activities to your understanding of radar meteorology? 4.56 / 5
How would you rate the overall benefit of the DOW activities to your career goals? 4.39 / 5
How would you rate your overall enjoyment of the activities associated with the DOW visit? 4.83 / 5

 

Table 4. DOW "lab" exercise

METR 463/863 DOW Exercise

Turn in completed assignments via Blackboard. Only single-document files will be accepted (images, analysis, discussion, etc. must be in a single document).

Questions with a * can be answered before/after going to the DOW.

Background on staggered PRFs
A staggered PRF is used to mitigate the Doppler dilemma. It is a transmission protocol in which two PRFs are used and results in a higher Nyquist velocity than would be possible with either of the individual PRFs.

The staggered-PRF approach is based on the principle that a given actual radial velocity will produce a known difference in detected velocities from two PRFs. For example, if PRF1 = 1000 Hz and PRF2 = 1250 Hz, then Vmax 1= 8 m/s and Vmax 2 = 10 m/s and the relationship between VR1, VR2, and VR would look like this:

(blue is VR1; green is VR2; broken lines are the folds) and VR1 - VR2 looks like this:

The value of VR1 - VR2 points to a unique range of VR values and therefore the number of folds that have occurred. It can be shown that VR1 - VR2 cannot discriminate the sign of VR beyond a VR in which the ratio of the number of folds at the smaller PRF (n1) to the number of folds at the larger PRF (n2) is given by

In other words, the modified Nyquist velocity for staggered PRF is given by

1. Fill in the missing elements in the following table [Note that Rmax is based on the larger PRF of stagger.]*

Config file Pulse
duration
(ns)
PRF (Hz) Rmax
(km)
Vmax
(m/s)
Pulse
length
(m)

dowdrx.400.2500.4_5.60m

400

2000/2500

     

dowdrx.800.1250.4_5.120m

800

1000/1250

     

 

2. Beamwidth*
A. The beamwidth of the DOW is approximately 0.9°. Assuming a typical antenna efficiency for a circular, parabolic reflector that is 1.8 m in diameter, calculate the
theoretical beamwidth of the DOW antenna system.

 

B. How would the theoretical beamwidth change if the wavelength was 10 cm instead?


C. How much closer to a target would the DOW need to be if sampling required a beam
diameter of 10 m?

 

3. Clear-air sensitivity to pulse duration

Data collection
As you determined in an earlier homework assignment, the returned power is very sensitive to the pulse duration. In this set of questions you will determine the practical (qualitative) impact of clear-air sensitivity to pulse duration.

Using the dowdrx.400.2500.4_5.60m configuration, find the elevation angle that yields a PPI of radar reflectivity factor with a nominal amount of ground clutter and returns above the noise level out to the farthest range possible. For this same elevation angle, collect a sweep using the dowdrx.800.1250.4_5.120m configuration.

Analysis
Using Solo3 or IDV to visualize the data, discuss any differences that you might see in the resolution and noisiness of the reflectivity field. Provide theoretical justification for any differences that you might see. Turn in representative images from these data to support your analysis.

 

4. Impact of rotation rate on clear-air return

Data collection
Using the dowdrx.800.1250.4_5.120m configuration, run a few sweeps for each of the following rotation rates

  • 10°/s
  • 30°/s
  • 50°/s

Analysis
Using Solo3 or IDV to visualize the data, discuss any differences that you might see in the resolution and noisiness of the reflectivity field. Provide theoretical justification for any differences that you might see. Turn in representative images from these data to support your analysis.