4.14 Other Severe Weather Phenomenon
1. Norâ€™easters â€“ Norâ€™easters, like hurricanes, centres of low pressure with winds that circulate in a counter clockwise direction around the low pressure and are extra tropical cyclonic storms as they originate outside of the tropics. Norâ€™easters originate in various locations. They are called Norâ€™easters because the cyclonic circulation causes winds to blow out of the northeast as the storms move up coast. When compared with hurricanes, Norâ€™easters usually have winds less than hurricane strength (<115 km/hr), but they last several days and can create storm surges up to 7 metres high.
2. Drought and associated Famine - In contrast to the exceptional weather conditions like cyclones, tornadoes, hurricanes which tend to bring high quantities of rainfall; a drought is a period of abnormal dryness in a region. A drought is an extended period (of months or years) when a region experiences a noticeable deficiency in water supply and this occurs when a region receives consistently below average precipitations. Droughts, as hazards, are unique in the sense that they are slow onset hazards that may lead to secondary effects like famine. Although droughts can persist for several years, even a short, intense drought can cause significant damage to the local economy and has a substantial impact on the ecosystem and agriculture of the affected region.
Factors Leading to Drought
Rainfall is related to the amount of water vapour in the atmosphere, combined with the upward forcing of the air mass containing that water vapour and if either of these is reduced, the result is a drought. These conditions can be triggered by an above average prevalence of high-pressure systems, winds carrying continental, rather than oceanic air masses, and ridges of high-pressure areas form with behaviours, which prevent or restrict the developing of thunderstorm activity or rainfall over one certain region. Oceanic and atmospheric weather cycles such as the El NiÃ±o-Southern Oscillation (ENSO) make drought a regular recurring feature of the Americas along the Pacific coast and Australia. Farming, excessive irrigation, deforestation, and erosion adversely impact the ability of the land to capture and hold water. While the above human activities tend to be relatively isolated in their scope, activities resulting in climate change are expected to trigger droughts with a substantial impact on agriculture throughout the world, and especially in developing countries.
It can have significant environmental, agricultural, health, socio-economic consequences and the effect varies according to vulnerability. For example, subsistence farmers are more likely to migrate during drought because they do not have alternative food sources. Some areas with populations that depend on subsistence farming as a major food source are more vulnerable to drought-triggered famine. Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources. Some common consequences of drought include:
1. Decreased crop growth or yield productions and decreased carrying capacity for livestock.
2. Dust bowls, themselves a sign of erosion, further erode the landscapes.
3. Dust storms, when drought hits an area suffering from desertification and erosion.
4. Famine due to lack of water for irrigation, malnutrition, dehydration and other famine related diseases.
5. Habitat and ecosystem damage, affecting both terrestrial and aquatic wildlife.
6. Mass migration resulting in internal displacement.
7. Shortage of water for industrial users.
8. Disputes over natural resources, including water and food and social unrest.
Different Stages Of Drought
Droughts undergo three critical stages before their ultimate manifestation.
1. Meteorological drought precedes the other kinds of drought and occurs when there is an extended period with less than average precipitation.
2. Agricultural droughts are droughts that affect crop production of the region. This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural practices cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation.
3. Hydrological drought occurs when the water reserves available in sources such as aquifers, lakes and other reservoirs fall below the statistical average.
Impacts of Drought
Direct impacts include reduced cropland and forest productivity; increased fire hazard; reduced water levels; increased livestock and wildlife mortality rates; and damage to wildlife and fish. Drought impacts can be grouped as economic, environmental, and social.
1. Farmers could lose money if a drought destroys their crops or stunts the crops growth, causing lower yields and investing in irrigation or finding new water sources, like wells, loses poor crop quality or money.
2. Ranchers could lose livestock, or they might have to spend more money on feed and water for their animals. People may have to pay more for food products.
3. Businesses that manufacture and sell recreational equipment, like boats and fishing equipment, may not be able to sell some of their goods because drought has dried up lakes and other water sources.
Drought also causes adverse environmental impacts- air and water quality reduced because of forest fires; soil erosion; damages to plants, animals, and the ecosystem. Sometimes the damage is only temporary, and conditions return to normal when the drought is over. In some cases, the damages become irreversible if, for example, an endangered species was lost because of low stream flows. Common examples of environmental impacts include the following:
1. Destruction and loss of fish and wildlife habitat, Increase in diseases among wild animals, because of reduced food and water supplies, Migration of wild animals, leading to a loss of wildlife in some areas and too many wildlife in the areas not affected by drought, an increased stress on endangered species.
2. Lower water levels in reservoirs, lakes, and ponds, loss of wetlands.
3. Increased forest fires.
4. Wind and water erosion of soils and decreased soil quality.
They include public safety, health conflicts that arise between people when there is not enough water. Many of the impacts that we consider economic and environmental also have social impacts. Examples of social impacts include:
1. Mental and physical stress due to economic losses caused by drought. Fewer recreational activities. Reduced incomes and migration of populations from rural to urban areas for betterment.
2. Health problems related to reduced water supplies, loss of human life due to heat stress, water shortage.
3. Threat to public safety due to an increased number of forest and range fires.
The above points should be taken into account when planning for and responding to drought conditions.
Strategies for Drought Mitigation
The components of a drought preparedness and mitigation plan are the following:
â€¢ Impact assessment
1. Prediction involves the application of scientific knowledge, such as climate studies and coupled ocean/atmosphere models, survey of snow peaks, anomalous circulation patterns in the ocean and atmosphere, soil moisture, assimilation of remotely sensed data into numerical prediction models, and knowledge of stored water available for domestic, stock, and irrigation uses.
2. Monitoring involves the use of ground-based information such as rainfall, weather, crop conditions and water availability coupled with satellite observations for the provision of synoptic, wide-area coverage.
3. Impact assessment is done and carried out on the basis of land-use type, persistence of stressed conditions, demographics and existing infrastructure, intensity and areal extent, and its effect on agricultural yield, public health, water quantity and quality, and building subsidence.
4. Response includes improved drought monitoring, better water and crop management, augmentation of water supplies with groundwater, increased public awareness and education, watershed and local planning, reduction in water demand, and water conservation.
Drought preparedness and mitigation can be carried out using the following: (1) soil and water conservation, and (2) herd management. Drought mitigation measures include various techniques that induce rainfall, water conservation and better monitoring practices. Some of the strategies include like cloud seeding (an artificial technique to induce rainfall), desalination of sea water for irrigation or consumption, drought monitoring, water restrictions and usage (using sprinklers, hoses or buckets for outdoor plants, the washing of motor vehicles, cleaning up of swimming pools, and also fitting of water conservation devices), in-situ moisture-conservation practices, Farm management and sustainable strategies, Herd management, Soil and Water Conservation.
Some Case Studies: Drought In India
The Indian agriculture is dependent on the climate of India, which is a favourable southwest summer monsoon as this is critical in securing water for irrigating Indian crops. In certain parts of India, the failure of the monsoons result in water shortages, resulting in below average crop yields. This is particularly true for the major drought-prone regions such as southern and eastern Maharashtra, northern Karnataka, Andhra Pradesh, Orissa, Gujarat, and Rajasthan. In the past, droughts have periodically led to major Indian famines, including the Bengal famine of 1770, in which up to one third of the population in affected areas died; the 1876â€“1877 famine, in which over five million people died; and the 1899 famine, in which over 4.5 million died. Some of the worst historical droughts that have occurred in the world include:
â€¢ 1900 India, killing between 250,000 and 3.25 million people
â€¢ 1921-22 Soviet Union, in which over 5 million people died from starvation due to drought
â€¢ 1928-30, northwest China, resulting in over 3 million deaths due to famine
â€¢ 1936 and 1941, Sichuan Province, China, that resulted in 5 million and 2.5 million deaths
â€¢ In 2006, Sichuan Province, China, experienced its worst drought in modern times, with nearly 8 million people and around 7 million cattle facing water shortages