Meteorological Hazards Flashcards
What is the Recurrence level in relation to floods
the probability that an event will occur in a certain period.
How do you calculate recurrence intervals
T=(n+1)/m where T is the time measure in years,n is the no. of years recorded and m is the rank of the flood level. or T= n/N where T is time measured in years, n is the no. of years recorded/ N being no. of events.
what is the Palmer Drought Severity Index.
is a formula to determine the dryness of an area of land. It can reflect excess rain with +tive no..The advantage to the PDSI is it is standardized to local climate so can be supplied to any part of the country.
Large Scale Storms
Tropical cyclones, Extra Tropical Cyclones and are greater than 100km across both are associated with storm surges.
What is the bryant table and what is the ranks
bryant table is a table of hazards and their risks. 1. Droughts, 2. floods 3. earthquakes 4. tropical cyclones and 5. volcanoes.
What is weather hazard risks
droughts, floods and tropical cyclones rank in the top 4 deadliest natural hazards. The time period considered can be crucial. all statistics must be treated with caution. underlying poverty level and interaction with other factors such as war and ease have a crucial impact.
Analysis by Munich Re. great natural catastrophes. how do the UN define catastrophes
if the affected region’s ability to help itself is clearly overstretched and supra-regional or international assistance is required. the no. of fatalities exceeds 2,000 or the no. of homeless exceeds 200,00 and/or overall losses exceed 5% of that country’s per capita GDP.and/ or the country is dependent on international aid.
Tropical Cyclones
Hurricane Katrina. A tropical cyclone is on a synoptic scale- typically 500km. low surface pressure system- convergence of air at surface, ascent and cloud formation. associated thunderstorm activity. High wind >74mph, heavy rain storm surge. Tropical cyclones are hurricanes in N/central America, Typhoons in Western N. Pacific and cyclones in Australia/Indian ocean
what is the Saffir-simpson Hurricane Intensity scale
measure the intensity of hurricanes and windspeed. on a scale of one to five with five been the most intense.
where do tropical cyclone form
they form only over oceanic regions where sea-surface temps are greater than 26.5c. they do not form within 5 degrees of the equator due to the negligible Coriolis force there. they form in regions where vertical wind shear between surface and upper troposphere is lo (less than 10m/s or 23mph)
what is the relationship with evaporation and temperature
evaporation increases rapidly as temperature increases. evaporation is energy in the form of latent hear that fuels the cyclone.
Why don’t cyclones form in certain tropical regions
cold currents. Without the Coriolis force, surface winds cannot gain sufficient rotation to converge and the low pressure of the disturbance cannot be maintained. Large values of vertical wind shear disrupt the formation of a tropical cyclone by interfering with the organization of deep convection around the cyclone center.
Tropical Cyclone dissipation
typical lifetime is less than 1 week. they weaken rapidly when they lose their heat source. when they reach more northerly locations and cooler waters. When they travel over land (energy source removed, friction at land surface, decreases surface winds causing central pressure to rise. encounter large vertical shear. e.g. in mid-latitude.
what is the cone of uncertainty
it represents the forecast track of the center of a hurricane and the likely error in the forecast track based on predictive skill of past years as well as details about the storm. Based on forecasts over the previous 5 years, the entire track of the tropical cyclone can be expected to remain within the cone 60-70%of the time. it only conveys the uncertainty in the track. usefulness to decision makers. it represents the potential area the center of the storm may travel in.
