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Touristic resorts
08.09.2010 |
Mavrovo(13h)
+24.7 0C
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P.Sapka(13h)
+17.4 0C
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Krushevo(13h)
+18.7 0C
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Yesterday |
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max |
min |
| 31 (13h) |
7,7 (4h) |
| Shtip |
Berovo |
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ANNOUNCEM. |
09.09.2010 |
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Till Thursday the weather will be sunny and warm with few to scattered clouds. Variable cloudiness associated with showers and longer spells of rain and also drop of the daily air temperature will affect most of our country starting from Thursday afternoon till Sunday. On Friday and Saturday intensive rain, but on Friday unstable weather associated with thundery rain and gusting wind are expected, also isolated severe waether possible. |
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Weather modification
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Historical development
Historical day of weather modification is 13 November 1946.
This simple experiment
was the first successful demonstration that the natural super cold cloud could be changed into cloud with ñî ice crystals. Up-to-date science of cloud physics and experimental meteorology began from the time of scientist Thomas Henderson, 1994. After discovering the basic principle in weather modification that is transforming the super cold cloud drops into ice crystals after cloud seeding by cold agent (dry ice), or by artificial nucleus of crystallization, AgJ (silver iodide), great number of scientists in the field of atmospheric science and technologies made fast progress toward these discovery.
Further investigations in this field increased our knowledge on microphysical and dynamical processes and precipitation from the natural clouds and human activity impacts from the aspect of modification of these processes
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Summary
Geographical climatic characteristics of Macedonia are very specific.
They are related to the appearance of long-duration droughts,intensive convective hail clouds in the summer period of the year and frequent and dense fogs during the winter.
Such weather conditions are strongly reflected on economy and life of the people in Macedonia. Water supply in several regions becomes critical. The water level in Dojran Lake falls permanently, and represents potential danger of its ecological degradation. Agriculture suffers damage permanently damage from droughts and hail clouds. The greatest energetic industry REK-Bitola, that is mine Suvodol has great losses because of frequent and dense fogs during the winter months.
Possibilities on mitigation of these conditions.
Scientific and technological achievements and world experiences, in weather modification emphasize the possibility of mitigation to certain level, from these negative effects of adverse weather phenomena. However it is well known that experiences obtained in some fields could not be automatically transferred in others, because the same depend on geographic-climatic conditions.
Weather modification is still in development phase. Therefore two conditions are necessary for successful realization of the activities in weather modification: scientific and multidisciplinary access.
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Physical bases
for weather modification
For successful weather modification from the aspect of hail suppression, precipitation enhancement or fog dispersion it is necessary to know physical dynamical processes which occur at these weather phenomena. It is generally known that forming of hail clouds is related to some atmospheric conditions: unstable atmosphere, heating, fog presence and favorable orographic conditions All this contributes to gradual development of convective clouds, at which the vertical development is characteristic, that is transport of humidity and heat from the lower layers toward the higher layers. Formed thermals by turbulence, environmental air pulling in and mixing intensify the process, condensation of water vapor begins and also cloud base forming .
Rapid evolution of cloud appears, cooling of water vapor and process transfer in the cold part of the atmosphere. Microphysical processes of water vapor transformation into other categories of water occur, as well as super cooling of drops, forming of large raindrops, ice crystals, hail and snowflakes in the upper part of the cloud . These clouds which mostly appear in the hot part of the year, sometimes can be demonstrated as intensive storms, with severe wind, torrential rain and hail and also can be potential danger for people and property.
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basic principle
of weather modification
One of the principles in weather modification is based on use of natural energy which is found in the atmosphere. During the natural evolution of atmospheric processes, conditions of instability can be controlled by relative small disorders in the system caused by the man.
It should be also emphasized that the capability which impact the microphysical structure of clouds is demonstrated in laboratory, simulated by numerical models and verified through physical measurements in some natural systems of fogs, stratiform clouds and cumulus clouds. However direct physical recording about the capability of precipitation modification, hail, electric discharge or winds by artificial way is limited. Complexity and variability of clouds make great difficulties in understanding and discovering effects and attempts for their artificial modification.
Weather modification in Macedonia
Weather modification activities in Macedonia had begun in 1971/72 by establishment and organization of hail suppression on a part of the territory, by two radar centres (Gjurishte and Pozar) according to the methodology developed in the former USSR. In the period 1979-1981 four radar centres more were activated, so that hail suppression covered the greater part of the territory of Macedonia, at the whole defended area of 665.000 ha, by about 320 hail suppression stations, and average season activity of about 1500 ejected hail suppression rockets. According to the statistics for the period 1971-1996 hail phenomena are most frequently appeared from April to October with the most frequency in May and June, by (52) average number of days in a year. Damaged areas by hail are different, from several kilometers to hundreds kilometers, at intensive hail processes and catastrophic events.
Numerous restrictions, clumsiness, old-fashioned system especially in the last several years were reflected to its successful operating and further realization. This is especially expressed during 2002, when the hail suppression were carried out at about 120 active hail suppression stations, by three radar centres on the territory of about 360.000 ha defended area.
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Methodology
of hail suppression
Methodology of hail suppression which is applied in our system is based on the hypothesis of “useful competition” which supposes lack of natural ice nucleuses in the clouds. By taking artificial nucleuses of silver iodide in, the total number of ice nucleuses in hail clouds is increased. In that way available supercooled water is limited to each embryo and hailstones which are formed will be of smaller dimensions and will make less damages if they reach the land surface. By other words the same volume of supercooled water drops in convective cloud, in the zone of accumulation is arranged on many artificial nucleuses of crystallization which are created by silver iodide, and in that way forming of bigger hailstones is avoided. Some words for silver iodide which is used as reagent for hail cloud seeding. The activity of AgI, as heterogenous ice nuclei source, whose activity is temperature dependent, and is the greatest in temperature interval from -4 îC to -10 îC . As an illustration one gram pyrotechnical mixture of silver iodide makes about 1012 to 1013 artificial nucleuses of crystallization.
For successful performing of hail suppression, beside the cloud identification by radar on time, where the reflection is recorded by maximum radar reflectivity, precise application of seeding methodology is necessary, according to determined criteria of action, that is maximum reflectivity greater than 45 dBz, height of reflection with maximum reflectivity must be over zero isotherm, height of the top of accumulation zone must be over 14th isotherm, the top of reflection maximum reflectivity must be over 28th isotherm and seeding of the first radar reflection should be performed when the new cell with maximum radar reflectivity under 45 dBz appears over the height of 6th isotherm in the atmosphere.
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Present status
of weather modification
The World Meteorological Organization (WMO) has expressed special interest on the possibility of weather modification at a useful way, giving essential contribution in mitigation of negative effects of droughts, hail, fog and extreme weather conditions. In this regard 13th World Meteorological Congress (Geneva, 1999) reviewed necessary new aspects of activities in weather modification and pointed out to rapid development and application of new technologies in management of water resources. This decision by the Congress had been motivated by the potential contribution of weather modification activities in clearing up the projected global climate changes and expectations that one of the essential problems up to 2025 would be lack of water, for about two third of the world population. As an answer to these issues, WMO in the programme of cloud physics and chemistry, promotes establishment of scientific foundations for weather modification and supports the exchange of information for investigation and operative activities. For that purpose one of the WMO’s activities within the programme is related to the organization of scientific conferences at every four years. The first such conference was held 1973 in Tashkent (Uzbekistan), the last was recently held in Casablanca, Morocco.
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The programme of the Conference
for weather modification in Casablanca (2003) pointed out to some priorities in regard to the last conference from more aspects:
a) Improvement of statistic access in regard to design and assessment of experiment in weather modification;
b) Repeated assessment of all experiments in weather modification was made which covered glaciogenic seeding;
c) Seeding by cloudy condensation nuclei (CCN) becomes new standard, not only for hot clouds but for cool clouds too;
d) Use of new Now-casting software for analysis and identification of the paths of storms (TITAN);
e) Improvement of numerical models and models in meso-scales, by increasing the computer capability;
f) Use of up-to-date sophisticated technical equipment, Earth instruments and equipment, use of craft and satellite platforms for creating powerful observing systems;
g) Improvement of reagents and seeding systems, especially discovering of rapid activated AgI.
About 16 countries represented their national programmes on precipitation enhancement (stimulation). Almost the same number reported on their hail suppression programmes, and about 6 country discussed on their fog dispersion activities. Insignificant group of papers were focused on negative modification by cloudy condensation nuclei, as a result of combustion of various masses if animal and plant origin, forest fires, cooking and heating with coal. This issue is expected to be the key issue at the next 9th WMO conference on weather modification. 140 scientific papers on numeric and technical nature and final discussion by the scientific committee improved our knowledge and understanding of weather modification and determined the basic objectives of its future development.
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