Learning Hub / Bonus B2
Bonus unit B2 · practice track · no round binding
Storms and the NESIS winter
Big Northeast snowstorms are remembered for decades. NOAA's Northeast Snowfall Impact Scale (NESIS) ranks them by snow area, snow depth and how many people live underneath. Are there more big storms in El Niño winters? This unit counts real storms, and shows how the way records were kept can fool a careless counter.
美国东北部的大雪暴会被人记住几十年。NOAA 的东北降雪影响指数(NESIS)按降雪面积、雪深和受影响人口给它们排名。厄尔尼诺冬季的大风暴更多吗?本单元数真实的风暴,并展示记录方式怎样骗过粗心的统计者。
45–60 minutesReal data: NCEI NESIS ranked storms, CPC ONI
Safety. This is a statistics lesson about past storms. Never use it for safety decisions: in a real storm follow your local official weather service and the adults responsible for you.
安全提示。这是一堂关于历史风暴的统计课,不能用于安全决定:真实风暴来临时,请听从当地官方气象部门和负责你的成年人。
Goals and exit evidence
- Read an impact scale: a score turned into five named categories.
- Count storms per winter and per decade, and assign each storm to the right winter.
- Spot a record-keeping bias and choose a variable that was measured the same way throughout before comparing ENSO phases.
Exit evidence: a short table of storms per winter by ENSO phase, with one sentence on what it cannot show.
- 读懂影响指数:分数如何变成五个有名称的类别。
- 按冬季和年代计数,并把每场风暴归到正确的冬季。
- 发现记录偏差,在比较 ENSO 相位前选一个口径始终一致的变量。
出口证据:一张按 ENSO 相位统计每冬风暴数的小表,外加一句它不能说明什么。
Story hook
The top of the NESIS list is a storm from March 1993 that buried the eastern United States. The list also contains a storm from January 2026, just last winter. If you simply count storms per decade, the recent decades look stormier. Is the weather really changing, or did people start writing down smaller storms? Let us find out from the list itself.
NESIS 榜首是 1993 年 3 月一场覆盖美国东部的风暴。榜单里还有 2026 年 1 月——就在上个冬天——的一场。如果只按年代数风暴,近几十年看起来风暴更多。是天气真的变了,还是人们开始记录更小的风暴?让榜单自己回答。
Concepts
1 · What NESIS measures
NESIS combines the area that received 10 inches of snow or more, the amount of snow, and the population living in that area. Because people count, a storm over a big city scores higher than the same snow over empty land. It is an impact scale, not a pure weather scale.
NESIS 综合了降雪 10 英寸以上的面积、降雪量和该区域人口。人口计入,所以落在大城市的风暴分数高于同样的雪落在空旷地区。它是影响指数,不是纯气象指数。
2 · Winter, not calendar year
A storm in December 2025 and one in February 2026 belong to the same winter, 2025/26. Storms from July to December go to the winter that starts that year; January to June go to the winter that started the year before.
2025 年 12 月和 2026 年 2 月的风暴属于同一个冬季 2025/26。7–12 月的风暴归入当年开始的冬季;1–6 月的归入前一年开始的冬季。
3 · Same ruler over time
If small storms were rarely recorded in early decades, any count that includes them will rise over time for reasons that have nothing to do with weather. A fair comparison uses only categories that were recorded consistently.
如果早年很少记录小风暴,把它们算进去的计数会随时间上升,但原因与天气无关。公平比较只用记录口径一致的类别。
NESIS categories (NOAA NCEI)
| Category | NESIS value | Description |
|---|---|---|
| 1 | 1 – 2.499 | Notable |
| 2 | 2.5 – 3.99 | Significant |
| 3 | 4 – 5.99 | Major |
| 4 | 6 – 9.99 | Crippling |
| 5 | 10.0+ | Extreme |
Worked example: the top ten
The ranked list below is read live from our copy of the NCEI table. For each storm the page works out its winter and the ONI value of that winter's DJF season (from the CPC ONI file).
下面的排名表由页面从我们保存的 NCEI 表实时读取。页面为每场风暴算出所属冬季,以及该冬季 DJF 季的 ONI 值(来自 CPC ONI 文件)。
| Rank | Start | Winter | NESIS | Category | ONI in DJF |
|---|---|---|---|---|---|
| Loading data… | |||||
Activity A · Is the record fair over time?
Count storms per decade, split by category. Before you press the button, guess: do Notable (category 1) storms appear evenly across the decades?
按年代、分类别数风暴。按按钮前先猜:显著级(1 类)风暴是否均匀分布在各年代?
Activity B · Big storms and ENSO phase
Choose which storms count, then group every winter (including winters with no listed storm) by its DJF ONI phase. The page reports storms per winter for each group.
选择计入哪些风暴,再把每个冬季(包括榜上没有风暴的冬季)按 DJF 的 ONI 相位分组。页面报告各组每冬平均风暴数。
A few very snowy winters can move a group average a lot, and each group has only a couple of dozen winters. Treat any difference as a question for more data, not as a rule. Cannot tell is not the same as does not exist.
少数几个多雪冬季就能大幅改变组平均值,而每组只有二三十个冬季。任何差异都只能当作需要更多数据的问题,而不是规律。"看不出"不等于"不存在"。
Check for understanding
1. A storm runs from 2025-12-30 to 2026-01-02. Which winter does it belong to?一场风暴从 2025-12-30 持续到 2026-01-02,属于哪个冬季?
Answer
Winter 2025/26, the same winter as a storm in February 2026.
2025/26 冬季,与 2026 年 2 月的风暴同属一个冬季。
2. Two storms drop the same snow. One covers a big city, one covers forests. Which gets the higher NESIS and why?两场风暴降雪相同,一场覆盖大城市,一场覆盖森林。哪场 NESIS 更高,为什么?
Answer
The city storm, because NESIS includes the population in the snow area. It measures impact on people, not only snow.
城市那场,因为 NESIS 计入降雪区人口。它衡量的是对人的影响,不只是雪。
3. Activity A shows most category 1 storms in recent decades. Can you conclude small storms became more common?活动 A 显示 1 类风暴大多出现在近几十年。能否得出小风暴变多了的结论?
Answer
Not from this list. Small storms were less likely to be catalogued in earlier decades, so the rise may come from record keeping. Compare only categories recorded the same way throughout.
不能仅凭这份榜单。早年小风暴较少被收录,所以上升可能来自记录方式。只比较前后口径一致的类别。
4. Why must winters with zero listed storms be included in Activity B?为什么活动 B 必须包含榜上零场风暴的冬季?
Answer
Storms per winter = storms ÷ winters. Leaving out quiet winters shrinks the denominator and inflates every group, unevenly.
每冬风暴数 = 风暴数 ÷ 冬季数。漏掉安静的冬季会缩小分母,使各组数值被不均匀地抬高。
Classroom: 20-minute version
| 0–4 | Read the category table; place three storms from the top ten in categories.读类别表;把前十名中三场风暴放入类别。 |
| 4–10 | Guess, then run Activity A; discuss the category 1 pattern.先猜,再做活动 A;讨论 1 类风暴的分布。 |
| 10–16 | Activity B with category 3 and above; then with all categories. What changes?先用 3 类及以上做活动 B,再用全部类别。有什么变化? |
| 16–20 | Exit sentence: what the table shows and what it cannot show.出口句:这张表说明了什么、不能说明什么。 |
Full 60-minute lesson plan
| 0–10 | Why an impact scale includes people; compare with a temperature reading.为什么影响指数要计入人口;与温度读数对比。 |
| 10–22 | Worked example: assign winters by hand for five storms; check with the table.例题:手工为五场风暴归属冬季;再与表对照。 |
| 22–35 | Activity A: the record-keeping trap.活动 A:记录口径陷阱。 |
| 35–50 | Activity B: three category choices; write down how the answer moves.活动 B:三种类别选择;记下结论如何变化。 |
| 50–60 | Check questions, exit sentence, five numbers.自测题、出口句、五个数。 |
Age bands
10–12
Read the category table and the top ten; tally storms per decade with tick marks.
读类别表和前十名;用画正字的方法按年代计数。
13–15
Compute storms per winter for each phase; explain why the denominator includes quiet winters.
计算各相位每冬风暴数;解释为何分母包含安静冬季。
16–17
Discuss how population growth enters NESIS and whether that biases recent scores; design a fairer comparison.
讨论人口增长如何进入 NESIS、是否让近年分数偏高;设计更公平的比较。
No-device alternative. Print the ranked list with dates and categories and a one-page ONI DJF table. Small groups each take one decade and tally.
无设备替代。打印带日期和类别的排名表,以及一页 ONI DJF 表。小组各负责一个年代计数。
Five numbers
Math map for this unit
| MD-L2-SORT | Sorting and attributes |
| SP-L2-COUNT | Counting principles |
| RP-L2-NOADD | Ratios are not directly addable |
| EE-L2-INEQ | Write an inequality |
Sources: SOURCES.json · NOAA NCEI NESIS · CPC ONI · record-keeping boundary from spec 48.