USE OF SATELLITE IMAGERY FOR
SHORT-TERM PREDICTION OF
Introduction:
RAINFALL IN ETHIOPIA
Since more than a decade National Meteorological Agency (NMA) has been receiving and using
hard copies of satellite imagery, then starting from 1990 a system for the reception and
processing of digital data from European Meteorological satellite (MTEOSAT) has been installed
in cooperation with the UK government. This system called METEOSAT PRIMARY DATA USERS
SYSTEM (PDUS).
Then after NMA has some satellite receiver to receive satellite data till PUMA project launched,
now a day with PUMA station received satellite imageries every 15 minute (MSG) and other
meteorological products from different centers.
In Ethiopia there are three seasons based on climatological mean of rainfall and temperature
namely Bega, Belg and Kiremt.
Bega (dry season) is from October to January. It is characterized by dry and cool period.
Belg (small rainy season) is from February to May. It is characterized by varying dry and wet
days.
Kiremt (main rainy season) is from June to September.
Even though, the Belg rainfall has its own contribution for agricultural production around 35%,
Kiremt has more than 65% of annual agricultural production. Kiremt season agricultural production
harvesting takes place in the Bega season. However, in some years occasionally Bega be come wetseason therefore, unseasonal rainfall affects the standing crops on the field. To minimize the
effect of the unseasonal rainfall precise prediction and close monitoring of rainfall with the aid
of satellite imagery is very important. This paper aims to explain how to use the satellite imagery
to reduce the adverse effect of shortage of rainfall and unseasonal rainfall during the harvesting
period.
Short-term prediction:
The demand of short-term prediction from various individuals, policy makers, government and
non-government organization and others are ever increasing in Ethiopia. In particular, the
agricultural sectors give high attentions to monitor the crop performance and to protect
disastrous weather conditions. Thus, in order to meet these needs, National meteorological
Agency (NMA) has effort enabled to maximize the performance of the forecasting capabilities.
Short-term prediction, which is given by NMA prepared based on Meteorological model out put,
upper air and surface synoptic charts and prognostic charts as well as satellite imagery from
MSG, PUMA station
The rainfall and cloud imagery from the satellite can be used for forecasting in several ways:
•
•
To identify specific categories of weather phenomena especially on the
mesoscale,
To provide detailed forecasts for a few hours ahead by means of simple
extrapolation, i.e now casting,
Early warning systems:
With the help of the satellite images, meteorologists are now able to detect the existence of
disturbances for which sometimes there is no other evidence. For instance, in some year’s early
warning were given for peasants through the mass-media of the forecast of the disastrous
unseasonal rain on the harvesting activities. The warning is given based on the satellite picture
observations and the weather charts for the forecast.
Coffee harvesting
Crop harvesting
Weather discussion:
In the weather forecast office of National Meteorological Agency (NMA) of Ethiopia weather
discussions are take places for two days in a week in two sessions:
• Weather assessment session and
• Weather forecast session
In weather assessment session duty meteorologist presents actual weather charts, actual
weather conditions compared with the forecasted one which was given on last forecast day and
each forecast day’s satellite pictures at 1500 UTC.
In weather forecast session before issuing the forecast present the prognostic charts,
Precipitation model out put and current satellite imagery. Then, the participants discuss
thoroughly and give the forecast. So we can recognize that the important of the satellite
imageries for assess and issuing the forecast.
Public weather service:
In Ethiopia weather forecasts are disseminated to multi disciplinary field’s users in many ways
some of these are:
• Through television
Every day, the public weather service section prepare weather forecast on their studio for
television program. At night time after News, the daily weather forecast broadcasted to the
public and some times displayed the satellite imagery to realize the actual weather.
National weather broadcasting through Television
• Through News paper
One of the media issuing the weather forecast to the public is News paper.
It includes weather summary, rainfall and temperature data for some selected cities, satellite
imagery and weather forecast.
Satellite picture
format
for
News
Weather
papers
Forecast
Conclusion:
Satellite imagery for short-term prediction of rainfall in Ethiopia is not used potentially. How
ever, satellite imagery reception and usage in order to perform short-term prediction has a
gradual progress. Further efforts have needed to improve short-term prediction of rainfall with
the aid of satellite imagery. The recommended measures that are will taken to improve shortterm prediction with the aid of satellite imagery are:
• Satellite imagery interpretation professional training
• Satellite imagery reception equipments maintenance training
• Satellite imagery reception equipments facility