What Makes a Blizzard?

It's not snowing much in New York City right now. But later today, we're expecting a big blizzard. The plows are getting ready to shovel a lot of snow:

All this makes us wonder: What exactly is a blizzard, and how does a regular old snowfall turn into one? According to the National Weather Service, a blizzard is actually more about wind than snow. For a snowstorm to be considered a blizzard, it has to be accompanied by winds that blow at least 35 miles per hour. It also has to reduce visibility—how far you can see—to less than 1/4 of a mile (in New York City, that's about 5 regular-length city blocks) for at least 3 hours.

Here's how a blizzard forms: Temperatures in the air and on the ground turn freezing; if the temperature on the ground is too warm, then snow falling from the sky will turn to rain or freezing rain. To make snow, air has to blow across a large body of water, like the Atlantic Ocean or the Great Lakes. This causes some of that water to evaporate and escape upwards, into the air. Finally, for a storm to achieve blizzard status, warm air has to rise over cold air. This often happens when freezing winds blow down from the North Pole, and meet warm air being pushed north from the Gulf of Mexico. This is called a "front." As of 11:30 AM in New York City on Monday, the front was moving  from the midwest of the country towards the east. The temperature was 29 degrees—3 degrees below freezing—and the winds were blowing at 22 miles an hour. How long will it take before the blizzard here is raging?

Hawks in Winter

I thought Red Tail and other hawks all migrated south for the winter. So I was surprised last week when I spotted five of them on a drive up to the Adirondacks. Three of them were sitting in barren trees by the side of the highway, with their feathers puffed up for warmth. Two of them were on the fly, chasing birds that were sure to become lunch. I spotted the hawks at regular intervals, every 10 or 15 miles. And I wondered: what are they doing here?

It turns out, not all hawks and other raptors (that is, sharp-beaked, sharp-taloned birds that hunt for animals) migrate to warmer climates. Older birds prefer to stay put in their established breeding territories, sticking out the cold weather. Maybe they don't want to have to reclaim their territories in the spring. Maybe they just plain don't want to bother migrating. Unlike songbirds and water birds, hawks don't flap their wings when they fly. Rather, they soar on updrafts they catch when they are airborne. They let themselves be carried by these as long and as far as they'll take them. For this reason, they tend to migrate less far than other birds. And they also don't migrate over big bodies of water, which don't provide updrafts. Migrating, it turns out, is a big hassle. 

But what is there to eat if they stay behind? Other non-migrating birds, for starters. In New York City, where there are growing populations of Red Tails, that certainly means pigeons. But hawks also hunt for mice, rats, chipmunks, squirrels, rabbits. And, if necessary, they'll eat carrion—already-dead animals. The reason they perch in bare trees by the side of the road is that these give them a good view of the land: both of any little animals that might be scurrying out of their burrows, and also of any animals that might be lying in the road. 

Have you seen any animals you weren't expecting to see this winter? Write in and let us know!

A New (Old) Lamppost for Clinton Street

The city re-installed an iron lamppost on our street today. A while back it was taken away for refurbishment and now it was all fixed up and ready again for service. This type of lamppost is called a Bishop's Crook, because of the shape of its upper portion—the portion that curves down to the light itself.

Around 1900, the City of New York installed many of these ornamental lampposts around the five boroughs (Brooklyn, the Bronx, Manhattan, Staten Island, and Queens). Many of them were Bishop's Crooks, which actually come in a number of different styles, but there were other shapes as well. 

The lampposts on our block are reproductions. That is, they're made to look like the original old lampposts. There aren't too many of the originals left; those that still exist are landmarks—they can't be replaced or taken away or changed. Of the kind shown here, there are only 12 left in all of New York.

The bases of these lampposts are made of cast iron. They weigh about 2,000 pounds. The workers on our street put the base back into place first. It's so heavy they had to use a crane.

The top of the lamppost is lighter. Like the originals, it's made out of iron pipe and iron castings. 

Before it could be lifted by crane to its place on top of the base, workmen had to hook it up to the light. 

Here they are attaching the wires. Soon, it will be all hooked up and ready to go!

Visit this site to learn more about the history of New York City lampposts, and to see some really cool pictures. 

Ivy, Still Growing...But How?

This is the question that plagues me this morning as I contemplate the still-growing tendril of ivy in my dining room. While outside, the temperatures are well below freezing, and have been for days. How is the ivy continuing to thrive? Is this kind of ivy hearty enough to survive a northeastern winter? Is this tendril it's own separate plant, now, with roots warm enough tucked away in the warm-enough window casing? What possibilities am I missing? 

The Science (and History) of Tap Water

This is a picture of the rusty pipe under my kitchen sink. Thanks to that big hole you see, we had water pouring out all over the floor every time we turned on the sink (until we discovered that hole, that is).

This made me start thinking about water, of course. In particular, where the water we drink in New York City comes from. It's a little complicated.

Once upon a time in New York (in 1677, to be precise), people got water from a well. It was dug down at the southern tip of Manhattan, where most non-native residents lived back then. For about 100 years, it supplied plenty of water for everyone living in the city. Then, with a growing population of 22,000, in 1776 NYC was forced to build its first reservoir to meet the water needs of its people.

Today there are over 8 million people living in the city. They use 1 billion gallons of water a day. Obviously, one well and one reservoir couldn't possibly supply that much water. So what does?

It starts with a watershed. This is basically just land—in New York City's case, 1,972 square feet of land north and west of the city. Rain and snow fall on the watershed. And the watershed drains that moisture into 19 reservoirs. These reservoirs are all connected by water-moving passageways called aqueducts. (Pictured below, the inside of the Catskill Aqueduct as it was being built in 1923.) They, along with 3 lakes, supply all the water for NYC.

From the reservoirs and lakes, water runs through the aqueducts into a big reservoir called Kensico. It sits about 30 miles north of the city and it holds 30 billion gallons of water. From there, the water travels again to another, smaller reservoir called Hillview. It's right outside the city and it holds 30 million gallons of water. The water is treated with a chemical called chlorine, which kills any bacteria that might be floating around in it. And also with ultra violet light, which kills any viruses. 

From Hillview, water flows by gravity through 2 big tunnels, into the 5 boroughs of the city. Tunnel one brings it from the Bronx, into Queens, then Brooklyn, then Staten Island. Tunnel two brings it from the Bronx into Manhattan, Brooklyn, and Staten Island. From there it's pumped into pipes that snake under the entire city, into every building in town. And finally, when we open the taps in our kitchens and bathrooms, into the pipes in our apartments. Where, if we're lucky, it won't encounter any holes!

Visit here to learn more about the science and history of water in New York City!