| |
Satellite Applications
|
 |
| Introduction to weather satellites |
|
Weather forecast models use a rich variety of
observations
from which to analyse the current state of the atmosphere. Since the
launch of the
first weather satellite in 1960 global observations have been
possible, even in the remotest areas. It was not until 1969 that
the first temperature profile information estimated from satellite
measurement were introduced to an NWP model. Even in those early
days the new satellite measurements improved forecasts in the
southern hemisphere.
During the 1970s and 1980s a wide range of satellite
missions have been launched from which many different meteorological
quantities could be estimated. Some satellite instruments allowed
improved estimation of moisture, cloud and rainfall. Others allowed
estimation of wind velocity by tracking features (e.g. clouds)
visible in the imagery or surface wind vectors from microwave
backscatter.
However, it was only in the 1990s that the measurements made by the
satellite instruments began to be used by NWP models in their raw
form. Data assimilation systems for NWP models had advanced to
the point where a measurement of the earth's radiance in narrow
spectral bands could be directly assimilated just like an in situ
measurement of atmospheric temperature. This advance, alongside
other improvements in the quality and range of satellite
observations and our understanding of how to model them,
has led to a situation where satellite measurements are a vital and
integral part of the global observing system in all regions, not
just those where other observations are sparse.
|
|
The Satellite Applications Section of the Met Office improves the use
of available satellite observations and makes preparations for the use
of new measurements from space. In addition to the assimilation of satellite
data into NWP models, the Section produces: new imagery products for forecasters,
such as microwave precipitation imagery; environmental products, such
as volcanic ash monitoring); products for climate monitoring, such as
sea-surface temperature.
The Satellite Application Section conducts research of several different aspects of the
exploitation of satellite data:
|
| Satellite imagery (visible,
infrared and microwave) |
|
The most basic form of satellite imagery provides pictures of the current cloud conditions. This is a familiar sight on TV weather forecasts. However, satellite imagery can also undergo various types of quantitative processing to obtain information on important meteorological variables such as wind speed and direction, cloud height and cloud amount, surface temperature, sea ice cover, vegetation cover, precipitation, etc.
More about satellite image applications
|
| Satellite sounding of the
atmosphere (infrared and microwave) |
|
Satellite sounding instruments measure radiation at infrared or microwave
wavelengths that has been emitted by the atmosphere itself, and thus provide
information on the temperature and composition (e.g. humidity, ozone amount)
of the atmosphere over a range of altitudes. Over the last few years,
much improvement in forecast accuracy has come from use of data from the
Advanced Microwave Sounding Unit on the NOAA series of satellites. Work
continues to improve the exploitation of these data and also to make use
of data from a new generation of advanced infrared sounding instruments
(spectrometers and interferometers). In order to make best use of these
data, it has proved important to develop fast radiative transfer models
to allow the radiance data to be assimilated into the NWP models.
More
about infrared sounding
More
about microwave sounding
|
|
In active remote sensing, man-made sources of energy (e.g. microwave,radio
wave or light) from a radar, lidar or other transmitting device, and which
has interacted with the earth's surface or atmosphere is detected. From
the measurement, meteorological information may be derived for eventual
use in numerical weather prediction models. Quantities that can be derived
include near-surface wind speed and direction over the oceans, vertical
profiles of horizontal wind speed, profiles of temperature and humidity
and aerosols, vertically integrated water vapour and precipitation rates.
More about satellite active sensing
|
| Further information and links |
|
The Education section of the Met Office has prepared a leaflet
with more information on the basics of weather satellites aimed at school
aged children and information is also available on the
Metlink site.
Other useful links are:
|
|
|
|
Home
