Hydrology Chapter 2 Flashcards
What is precipitation?
Any form of water (liquid or solid) that falls from the atmosphere to Earth’s surface.
What are the conditions required for precipitation to occur?
1) Moisture in the atmosphere
2) Nuclei for condensation
3) Favorable weather conditions
4) Condensed products must reach Earth’s surface.
What are the forms of precipitation?
Rain, snow, drizzle, glaze (freezing rain), sleet, and hail.
What is a tropical cyclone?
A low-pressure wind system known as a hurricane in the U.S., typhoon in Southeast Asia, and cyclone in India.
What is the difference between tropical and extratropical cyclones?
Tropical cyclones form over warm oceans, while extratropical cyclones develop outside the tropics and are associated with frontal systems.
What are the key weather systems affecting precipitation in the Philippines?
Northeast Monsoon (Amihan), Southwest Monsoon (Habagat), Easterlies, Shear Line, Localized Thunderstorms, Intertropical Convergence Zone (ITCZ).
How is precipitation measured?
Using rain gauges, which can be non-recording (manual) or recording (tipping-bucket, weighing-bucket, natural-siphon).
What is a rain gauge network?
A system of rain gauges spread across an area to measure precipitation accurately.
What are the methods for estimating missing precipitation data?
Arithmetic mean method and normal ratio method.
What is a hyetograph?
A graph showing rainfall intensity versus time, often used in flood analysis.
What is a mass curve of rainfall?
A graph displaying cumulative rainfall over time, useful for analyzing storm duration and intensity.
What are the methods for estimating mean precipitation over an area?
Arithmetic mean method, Thiessen polygon method, and Isohyetal method.
What is the depth-area-duration (DAD) relationship?
A relationship showing that rainfall depth decreases as the area increases for a given storm duration.
What is the return period (T) in rainfall frequency analysis?
The average time between occurrences of a specific rainfall event, calculated as T = 1/P.
How is the probability of extreme rainfall occurrence estimated?
Using the binomial probability formula or plotting empirical return periods on semi-log graphs.
What is the formula for the depth-area relationship?
P = P0 * e^(-KAn), where P0 is peak rainfall, A is area, and K and n are constants for the region.
What is the significance of frequency analysis in hydrology?
It helps estimate the likelihood of extreme rainfall events, crucial for flood control and infrastructure design.
