How accurate are today’s weather predictions? At a time when our environment is changing so rapidly, forecasts are now primarily driven by the requirements of agricultural and aviation community, and as such the need for better and longer days weather predictions have become very urgent. In reality, the weather science is improving so fast today that expert meteorologist now forecast that we can expect increased accuracy of forecast over periods of up to several weeks, sufficient to be useful for economic planning and for weather hazard warning.
Today, the cost of covering the entire globe with ships and other conventional weather stations’ would be prohibitive, so weather forecasts depend heavily on satellite soundings with infrared sensors. Globally, over 100 weather satellites are currently circling in earth orbit, passing through the pole to the equator. Within minutes, a combination of ten weather satellites can made a complete circuit of the globe, passing near the North Pole and then sweeping south over Arabia, the Atlantic and Indian Ocean to Antarctica and back north again. The multiple eyes in the spacecraft scanned the swift moving panorama 900 miles below. The camera systems onboard the satellites caught the glint of oceans and ice fields, the white expanse of clouds, the familiar outlines of continents and islands. More important, instruments known as radiometers detected heat and light radiation from earth, cloud and sea.
Atmospheric motion vectors
It is always impressive to watch cloud pictures at the weather forecasting stations, as it come in as a wide sheet of paper slides slowly from the machine, an electric needle moves rapidly back and forth, burning a pattern of light and dark. The needle makes 600 passes in two and a half minutes to complete each picture – each pass corresponding to a scan made by the camera. The individual lines blend to form a continuous picture, just as on a TV screen.
The cloud cover pictures are generated regularly. More frequent pictures are taken whenever the weather situation so demands. They are produced in visible and infrared during the day and in infrared at night. The images are used in conjunction with interactive facilities available at the Data Processing System for the interpretation of cloud features. These images are particularly useful in identifying cloud systems over the ocean, for rainfall tracking, intensity assessment and prediction of storm surges, among other uses. Cloud vector winds are derived from consecutive pictures by observing the movement of cloud clusters, via a fully automated, computer-based, pattern matching technique. Wind data are being transmitted over the Global Telecommunications System (GTS) of WMO for operational use.
Meteorological satellite receiving facilities
As the atmospheric weather passed beneath a weather satellite, a radio command came up from an antenna at the ground station, requesting for its picture. Like a robotic machine, the satellite turned on magnetic tape recorders that had stored pictures from one of its cameras. Then electronic impulses that encode patterns of light and dark went by radio from the spacecraft to the ground station, from which they were relayed to weather stations. In hours, forecaster had the pictures on their desks, showing storm pattern that would affect the aviation industry, agriculture, marine ecology and everything under the planet the following day.
A satellite can made such a picture every 260 seconds. Each covered a square some 2,000 miles on a scale, an area of four million square miles. From this pictures, cloud patterns as small as two miles across could be distinguished. It scanned every spot on earth at least twice each day.
While relying on this resources, NIMET provide stakeholders with round-the-clock, regular, timely synoptic images of weather systems, including severe weather, sea-surface and cloud-top temperatures, water bodies, storms, and more, over the entire country as well as adjoining land and sea areas and the timely warnings of impending natural disasters such as storms and floods.
More so, the secondary data utilization centres located at various zonal offices manages the weather forecasting services of the agency, and function by receiving processed cloud pictures, facsimile charts and conventional meteorological data transmitted directly from satellites. Other institutions interested in meteorological information, such as the agro-meteorological departments of agricultural universities, River Basin Authority, equally receive this signal and obtain meteorological information in near real time.
The climatic services division of the agency is responsible for data processing, management and archiving of all meteorological data, publication of climatological maps, maintenance of data bank and other activities relating to world climate programs.
Hydrological and Oceanic Research
In weather research, pictures from space when combine with information from scanning radiometers, detect and measure radiation not only in the form of light, but also in the form of heat – the energy of long wave infrared radiation. The heat is what drives the great engines of the ocean and atmosphere to produce our weather. Radiometer scanning can be converted to images similar to those made by cameras. And since the radiometers work with both infrared and visible light, they produce excellent pictures on the night side of earth as well as the daylight side, making 24 hour global coverage possible.
Nigeria’s land mass is covered by a gigantic expanse of the oceans, which are constantly changing. In order to effectively understand and manage the oceans, they need to be monitored as one large sea area. Therefore, the application of satellite imagery data that can be observed periodically in this manner is necessary.
“In addition to images, infrared sensing from satellites gives us the temperatures of earth, sea, and clouds, to accuracy less than 3 degree F. It helps us estimate how high the clouds we are seeing. Moreover, we can interprete the readings to give us a profile of temperature at various levels in the atmosphere. This information is absolutely essential for making longer range forecasts than those now possible.
The Ocean Research Centre applies these satellite image data for each type of ocean-related industry, for the operational and research study including ocean climate change, ocean resources, coastal environment conservation, and marine safety.
“Finally, some of the new devices will even measure water vapour at different heights, and other may report on the total levels of such pollutants as dust, carbon dioxide, and sulphur dioxide. “These infrared sensors represent a truly great leap ahead.
In Nigeria, the responsibility of marine meteorological unit of the agency is to make available to marine users at sea on the coast, marine meteorological and related geophysical information which they require, for safety operation and to generate revenue for the agency. In this sphere, potential users include shipping industry, Oil, fishing, insurance industries. Others include Universities, coastal dwellers, engineering and construction companies as well as tourists.
Conversely, rain and river gauges, drifting buoys, ships, and perhaps aircraft will, on command from orbiting spacecraft, radio their findings directly to the satellite, which will relay them to the computer in weather forecasting laboratory. With these ground devices, the satellite helps in collecting weather information from remote stations anywhere in its fields of view.
In fact the satellite could interrogate as many as 10,000 remote stations every six hours, and send back to earth pictures containing a maximum of a hundreds billions bits of information each 24 hours. Handling the mathematics involved in digesting such a torrent of information challenges even the fastest modern computers. “The hydrodynamics of meteorology,” according to scientists, “presents without doubt the most complicated series of interrelated problems not only that we know of but that we can imagine.
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