The most likely of cloud types to allow artificial rainmaking are Cumulus Clouds, a cauliflower-like type of clouds.
Some 1.2 billion people or 20 per cent of the world's 7 billion-population, are prone to diseases due to water poverty.
A segment of this number is even dubbed as "water-refugees" by some anthropologists, because they don’t only lack water for daily usage and irrigation, but they are on the move across countries’ borders as well in search for water.
The assessment comes from the London-based International Water Management Institute (IWMI) and Earthscan which produced the 2007 "Water for Food, Water for Life: An Assessment of Water Management in Agriculture".
The continuing severity of water shortage has led Fred Pearce, author of the globally-recognized book "When the Rivers Run Dry" to conclude, “The world water crisis has caught us unaware, with a series of local hydrological pinch-points rapidly escalating into a global pandemic of empty rivers, dry boreholes, and wrecked wetland.
There is very little we can do to reverse the situation."How serious is the water problem worldwide? Water scarcity, defined as humans' inability to secure and access safe and affordable water for drinking, washing, and food production that affects one fourth of the world's area, IWMI reported.
The world regions experiencing severe economic water scarcity in the following most severe to least severe order are; Sub-Saharan Africa, followed by South Asia, then East Asia, Latin America, the Near East, and North Africa.
Sandra Postel of the World Watch Institute warned there will be potential "water wars" especially in the Mekong River, Jordan River, and the Tigris-Euphrates rivers.
Using the UNFAO and UNICEF figures, the IWMI announced that in the water-starved regions, more than 1 billion people live below the one dollar a day poverty line, majority of whom are women and children. The majority of them have no access to improved sanitation. The report added that the reason behind all of these is clearly of lack of water, worsened by prolonged absence of rains.
Rainfall Absence & Biodiversity Extinction
According to IWMI, out of the world's more than 2 billion people suffering from hunger, 850 million are dependent on agriculture. Their agriculture is dependent on rain for irrigation.
In the Sub-Saharan Africa, 95 per cent of farmers rely on rain, as well as 90 per cent in Lain America, less than 70 per cent in the Near East and East Africa, in addition to 60 per cent in South Asia, while, in Southeast Asia, the picture is more mixed.
The statistics mean that some yields from crops such as tubers which is a staple crop of much of Sub-Sahara, have dropped significantly. Poverty is found in areas where the unpredictability of rainfall creates great uncertainty.
Many people dependent on rain-fed agriculture are highly vulnerable to both short-term (2 - 3 weeks) and long-term (seasonal) dry spells and drought, the IWMI report explained.
But not only are humans but also biodiversity is suffering as well. The Millennium Ecosystem Assessment reported that many ecosystems globally have been transformed because of fast diminishing water availability in many places.
It said some 500 to 1,000 vertebrate species are adversely affected mostly in tropical and sub-tropical moist broadleaf forests followed by those in grasslands and shrublands, then those in desert and xeric shrublands, followed by the ones native to tropical and sub-tropical grasslands, as well as savannas and tropical and sub-tropical coniferous forests and mangroves.
| Clouds are classified according to their appearance and height from the ground. This classification system is: 1) Cirro. 2) Alto. 3) Strato. 4) Nimbo. 5) Cumulo. |
Wanted: Magic from the Sky
The absence or shortage of rainfall has been of increasing concern since the 1970s. One of the most popular weather modification discoveries is cloud seeding, the initiation of rainfall by clouds by targeting clouds from aircraft or from the ground with substances such as silver iodide, dry ice and even salt.
But if cloud seeding works, why isn’t it implemented in many of the world's regions that are water scarce? "Simple, there aren’t enough clouds or there is unfavorable cloud formation. Cloud seeding cannot happen without clouds", a scientist from the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), said.
The Philippines, together with Thailand and Indonesia have been implementing cloud seeding activities for the past 20 years with some high degree of success.
"Artificial rainmaking, one must understand, aims to create rainfall by inducing precipitation in clouds", he said. The use of silver iodide salts or dry ice is useless without cloud presence, he added.
Scientists from the Australian Commonwealth Science and Industrial Research Organization (CSIRO) who have been involved in cloud seeding since the 1960s said cloud composition, temperature and cloud diversion also have direct relationship to the success of artificial rainmaking.
How Does It Work?
A World Meteorological Organization (WMO) primer explains that not all types of cloud favor cloud seeding. The most likely to allow artificial rainmaking are Cumulus Clouds, a cauliflower-like type of clouds.
The cloud forms from updrafts of warm, moist air into an atmosphere that is unstable. Intense daytime heating of the near-surface layer of air, or a wedge of cold air moving across the state (as a cold front), usually triggers the formation of convective clouds.
Normally, a small percentage of cumulus clouds are needed to yield an appreciable amount of rainfall. But these clouds that do produce rainwater are often inefficient. For all the moisture they incorporate from below, only a tiny fraction of that moisture (as cloud droplets) is ever used to grow large raindrops, which ultimately fall to the ground as rainfall.
Tiny cloud droplets must collide with neighboring droplets enough number of times to yield larger drops and eventually rainwater. Seeding, using silver iodide is placed in the upper portion of the growing convective cloud rich with super-cooled droplets. The silver iodide crystal can grow rapidly by tapping that vast field of available moisture.
Because the vapor pressure gradient over ice is less than that over water, the crystal such as silver iodide will more readily attract the tiny cloud droplets. In a matter of moments, the ice crystal is transformed into a large raindrop which is heavy enough to fall through the cloud mass as a rain shaft.
The silver iodide particles are released from below cloud base, using the strong updraft of the cloud to transport the "seeds" high into the core of the cloud where super-cooled cloud droplets are plentiful.
To seed clouds, pyrotechnics or flares consisting of silver iodide burn while mounted on the wings of an aircraft that maneuvers within the updraft field below the bottom of the cloud.
At times the seeding material can be dispensed below cloud base from an aircraft that is equipped with wing-tipped generators that contain a solution of acetone mixed with seeding material.
The seeding of clouds may also be achieved from above cloud top, using an aircraft equipped with a rack containing pyrotechnics. These droppable flares are ignited as they fall from the plane's belly into the upper region of seedable convective clouds.
Either way, from above cloud top or below cloud base, seeding with silver iodide is designed to give an ample number of "seeds" with which to grow rainwater: one gram of silver iodide can supply as many as ten trillion (10,000,000,000,000) artificial ice crystals!
For now, many countries continue to conduct researches and studies on more effective methods of producing artificial rain because the demand has become greater especially for agricultural and domestic use. Others, like China, in fact claim to have done the opposite; stop rains, rather than produce some, which actually happened during the Beijing 2008 Olympic Games.
But meteorological science is more concerned in producing water in light of the worsening climate changes. Water productivity policies dot many countries' national plans and these include looking at cloud seeding either as a band-aid or cure-all for their water headaches.
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