Question

How have satellites influenced modern weather forecasting?

Answer 1

Not as much as you might thing, although they are good for storm tracking.

Explanation:

Satellites provide a look at the atmosphere from the top. They can show cloud cover and temperatures and water content. However the data is not as valuable as you might think.

First off it does not show you what is happening at the surface but at the top of the cloud. That is like looking at a cake covered with chocolate icing and trying to guess what type of cake it is. It is probably chocolate but you can't know until you cut into it.

Secondly, the resolution at the sub-point is about 1 km square. That means that the smallest point that it can discriminate directly underneath it is 1 square km. So if it is measuring the temperature of that point it takes an average of everything in that point. If there is a small cloud that fits inside that the temperature of that cloud is averaged with the temperature of everything else in that point.

To make matters worse, as you move away from the sub-point the resolution goes down. For geostationary satellites (GOES) this is bad. The sub-point of a GOES satellite can be thousands of miles away from the area you are interested it. So if you are looking at something close to the arctic circle on a GOES shot you have a resolution of around 8 square km, not nearly as accurate as we would like for forecasting.

We do have polar orbiting satellite (POES) which have a moving subpoint and gives more accuracy but you are only getting 2 pictures a day, not enough to use for forecasting (we like to get at least 1 pic ever 30 mins).

For cloud and storm development the best information still comes from getting surface temperatures and pressures and from radiosonde balloons (which measure temperature and dew point up through the atmosphere over a location).

That all being said, satellites are an excellent tool for determining the motion of clouds. So while it cannot tell if a hurricane is getting worse, for example, it can give you a pretty good idea where it might go and how fast it might get there.