Wind Velocity & Pressure Gradient

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Objective

SWBAT interpret air pressure on an isobar map and examine where wind speed is highest and lowest as a consequence of air pressure gradient

Big Idea

Students learn that air velocity can be determined on an isobar map by looking at the relative pressure gradients in this meteorology lesson

Lesson Introduction

This lesson is the continuation and summative piece of what is effectively a mini-unit on wind (other lessons found here, here, and here). In this lesson, we explore wind velocity and air pressure on weather maps and examine how we can effectively determine wind velocity as a result of the illustrated air pressure gradient. This lesson is also building the prerequisite knowledge for the next lesson's laboratory based practice, where students will actually be building both isobar and isotherm maps. There are no special materials needed for this lesson. 

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 5.12 - Wind Velocity (Whole Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 5.12 - Wind Velocity (Whole Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

Do Now & Objective(s)

10 minutes

Students come in silently and complete the (attached) Do Now. In this case, the Do Now is a review of important material from earlier in the unit. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material; 
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

Introduction & Isolines

20 minutes

The lesson starts with the first page of the Introduction & Isolines resource, where I show students the isobar map and ask if anyone has seen a map similar to the one on the page. In each class I've taught, a few students have raised their hands and said something akin to a "weather map," which provides the context to connect their personal experience to what they're learning today. 

We then annotate the map with questions: "What do you think of the 'L' on the map - what does it signify?" | "What do the numbers on the map mean?" | "What unit is the air pressure recorded in?"

On the next page of the Introduction & Isolines resource, we jump right in to isobar maps, defining both the term isobar map and isolines on the top of the page. We then read the small paragraph below the image before we do some annotations, but then jump into the annotations piece when I ask students to identify where they think the highest and lowest pressures are on the isobar map. After they check their work with a partner, I then ask them to list (in millibars) both the highest and lowest recorded air pressures on the map (1040 and 1000 mb, respectively). We then read the three key rules out loud as a class on the bottom of the second page.

After reading the facts over, I ask them to look at Figure 7-4 on the top of the third page of the Introduction & Isolines (before the practice begins). Focusing in on Principle 3, I ask them to annotate/identify the areas of highest and lowest wind speeds on the mini-isobar maps on the images. This is to reinforce the principle that the closer the isobars are together, the greater air pressure gradient is, and the faster the resulting wind speed. 

Practice

20 minutes

The Practice section in this lesson is, like the vast majority of questions found in all of my classwork and homework, is 100% Regents-based. All of the questions come from prior Regents examinations, and the majority of them deal with the three primary principles covered in the previous section. Likewise, as I try to generally do with all of my lessons, the questions are mostly organized to get increasingly more difficult and increase in complexity, which is why the harder questions tend to come toward the end. I've found that with practice, the idea of "the closer the isolines, the faster the wind speed" becomes quickly embedded in student's brains, so this is a rich opportunity for them to cement their learning. 

This lesson is particularly important given its high-priority on recent Regents examinations, so in your circulation and review, prioritize the ones in which students are asked to represent wind velocity through isobars. As I've said previously, I think the important facet here is not to give the trick, but to present the more logical conceptual understanding. The trick in this lesson is "the closer the isobars, the greater the wind velocity." The more deep conceptual understanding is "closer isobars yield greater wind velocity because there is a greater pressure gradient, leading to the atmosphere more "forcefully" equalizing the air pressure across a greater distance." Students can correctly answer the question without having deeper understanding (as they can across the course), so it's important to test that in your circulation and/or review of this material. Don't be afraid to ask "why"!

In terms of student work habits, I tend to sometimes make this decision in the moment, and as a response of what I know about the students and how they're processing the material on, but I'll either ask them to work independently, in partners, or (sometimes) give them the option. Usually, before starting practice, we tend to go over some steps for self-help ("What should you do if you're stuck?"), and I might reference a previously used multiple-choice or free response strategy in order to build their skills while simultaneously learning content (as an example - one popular one we always use - "If you aren't sure what the right answer is, see if you can eliminate some wrong answer choices"). I tend to circulate for compliance and then hone in on specific students while they're doing this. 

After about 10 minutes, we go over their responses. Students who finish early are encouraged to work on the exit ticket (resource below) and double-check their responses. We use a combination of strategies (active voting, cold calling, popsicle sticks, volunteers) to go over the responses, where students correct their work and ask any clarifying questions. 

Exit Ticket & Closing

5 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  1. Do you feel that you mastered the objective for the day?
  2. Can you reiterate one thing you learned about (in this case, information on the relationship between isobar spacing and wind velocity, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.