How does grid resolution affect a forecast?

A finer grid resolves smaller features such as individual showers and improves accuracy. A halved cell size multiplies the computation many times over.

What is meant by a time step in a weather model?

A time step is the interval by which the model advances the simulated atmosphere. The state at one step is the input to the next.

Why does forecast accuracy fall as the forecast period lengthens?

Small errors in the initial data grow at every time step. The atmosphere is chaotic, so tiny differences become large ones.

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Data Structures: Arrays, Records and Hash Tables

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Boolean Logic and Simplification

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Databases, Normalisation and Entity Modelling

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Types of Software System

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Types of Software System

Computers in weather forecasting

3 things to know
Component 2

Overview

Numerical weather model, time step in a weather model and ensemble forecasting.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a numerical weather model?

Key term

Where does the input data for a weather model come from?

Key term

Why does weather forecasting need a supercomputer?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a numerical weather model?
Model answer
A numerical weather model divides the atmosphere into a three-dimensional grid of cells. Physical equations are solved for each cell to predict its state a short time ahead.
2
Where does the input data for a weather model come from?
Model answer
Input comes from ground stations, weather balloons, ships and buoys, aircraft and satellites. Radar supplies precipitation data.
3
Why does weather forecasting need a supercomputer?
Model answer
The model solves equations for millions of grid cells at every one of thousands of time steps. A forecast is worthless if it takes longer to compute than the period it predicts.
4
How does grid resolution affect a forecast?
Model answer
A finer grid resolves smaller features such as individual showers and improves accuracy. A halved cell size multiplies the computation many times over.
5
What is meant by a time step in a weather model?
Model answer
A time step is the interval by which the model advances the simulated atmosphere. The state at one step is the input to the next.
6
Why does forecast accuracy fall as the forecast period lengthens?
Model answer
Small errors in the initial data grow at every time step. The atmosphere is chaotic, so tiny differences become large ones.

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