2011-04-30-世界卫生组织-Useful_Definitions_and_Early_Warning_Information_for_Natural_Hazards_5页_79kb

Disaster Risk Management for Health Fact Sheets: Natural Hazards Definitions and Early Warning Information Summary

Cyclones

• Definition: A tropical cyclone forms over tropical or sub-tropical waters with organized convection and a definite cyclonic surface wind circulation. WMO-defined categories range from tropical depression to hurricane based on wind speed.
• Early Warning Information: Seasonal cyclone activity can be predicted using sea temperature anomalies. Warning centers use models to forecast cyclones up to several days in advance. Lead times vary, with alerts issued for non-tropical cyclones up to 5 days ahead and warnings with 24-hour or more notice.

Hurricanes

• Definition: A type of tropical cyclone with sustained winds of 74 mph or higher, categorized by wind speed on the Beaufort scale from tropical depression (≤7) to hurricane (≥12).
• Early Warning Information: Predicted using meteorological models, with lead times up to several days for seasonal activity. Warnings are issued by designated centers with various lead times, depending on intensity and location.

Heat Waves

• Definition: Prolonged periods of unusually hot weather, which can be dry or humid, impacting health. No universal definition exists, but thresholds vary based on location and climate, often involving maximum apparent temperature above local percentiles.
• Early Warning Information: Warnings issued 2-5 days ahead based on meteorological models. Heat-health action plans often involve national or regional health authorities, with systems like the UK's Heat-Health Watch operating during summer months.

Cold Weather

• Definition: Periods of prolonged cold temperatures, often defined by daily mean temperature below zero for four or more days, associated with hazards like freezing rain or icy roads.
• Early Warning Information: Predicted at monthly scales using models. Alerts issued 5 days in advance, with warnings given 24 hours ahead. Lead times consider geological factors and potential impacts.

Snow

• Definition: Solid precipitation that occurs as ice crystals or larger snowflakes, often at temperatures below 0°C.
• Early Warning Information: Difficult to predict due to rapid weather changes. Alerts issued 5 days in advance; the UK Met Office issues severe weather warnings if snowfall exceeds 2 cm/hour for at least two hours.

Avalanches

• Definition: Rapid downslope movement of snow, ice, or rock, typically triggered by loosened material, common in mountainous areas or volcanic regions.
• Early Warning Information: Very difficult to forecast with little or no warning time. Monitoring systems exist for high-risk volcanoes, but no reliable prediction method is available for most cases.

Flooding

• Definition: Overflowing of water from rivers, streams, or increased water accumulation, categorized into surface (pluvial), groundwater, and river flooding.
• Early Warning Information: River flooding warnings based on watercourse capacity; surface flooding short-lead-time forecasts due to high-intensity rainfall; groundwater flooding possible with 5+ days advance. Coastal flooding alerts issued 5 days ahead for events from storms or high tides.

Drought

• Definition: Prolonged lack of sufficient precipitation leading to water shortages, or hydrological and agricultural conditions. Types include meteorological (low rainfall), hydrological (below-normal water flow), and agricultural (plant moisture deficit).
• Early Warning Information: Monitoring trends using seasonal and monthly predictions. Lead times up to months, with assessments indicating water availability deficiency.

Earthquakes

• Definition: Ground vibrations from seismic energy release along fault lines, measured on scales like Richter or Moment magnitude.
• Early Warning Information: No reliable long-term prediction; instead, real-time monitoring provides location and magnitude information within minutes. Alerts with 24-hour lead times may be issued for significant events.

Volcanic Eruptions

• Definition: Ejection of magma through a crust opening (vent), with types including Plinian (high ash dispersal column) or explosive bombs.
• Early Warning Information: Enhanced monitoring enables predictions of eruptions within 2-5 days for high-risk volcanoes. Volcanic Ash Advisory Centres issue forecasts for plume dispersion.

Landslides

• Definition: Sudden downslope movement of rock, earth, or debris, classified into types such as falls, topples, slides, flows, and spreads.
• Early Warning Information: Very difficult to predict; no reliable early warning for most cases due to complex triggers.

Tsunamis

• Definition: Giant waves caused by underwater earthquakes, landslides, or volcanic eruptions, particularly from shallow tectonic plate boundaries.
• Early Warning Information: Automated systems detect earthquakes within minutes, allowing models to estimate arrival time and wave height. Local warnings may have short lead times (minutes), while distant predictions provide hours for evacuation.

Wildfires

• Definition: Outdoor fires, often ignited by lightning or human activities, spreading through vegetation when cured (dry and weather-friendly conditions).
• Early Warning Information: Based on fuel (vegetation), weather, and ignition; fire behavior can be predicted days ahead with 24-hour site-specific alerts.

Space Weather

• Definition: Conditions in space influenced by solar emissions, affecting technology and human health through events like geomagnetic storms or radiation bursts.
• Early Warning Information: Solar events such as flares and CMEs are predicted with lead times from minutes to days, allowing alerts for radio blackouts, radiation storms, and geomagnetic disturbances.