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  2. Probability of precipitation - Wikipedia

    en.wikipedia.org/wiki/Probability_of_precipitation

    Environment Canada reports a chance of precipitation (COP) that is defined as "The chance that measurable precipitation (0.2 mm of rain or 0.2 cm of snow) will fall on any random point of the forecast region during the forecast period." [7] The values are rounded to 10% increments, but are never rounded to 50%. [8]

  3. Water balance - Wikipedia

    en.wikipedia.org/wiki/Water_balance

    Water balance in a basin. A general water balance equation is: [5] P = Q + ET + ΔS. where P is precipitation Q is streamflow ET is evapotranspiration ΔS is the change in storage (in soil or the bedrock / groundwater)

  4. Runoff curve number - Wikipedia

    en.wikipedia.org/wiki/Runoff_curve_number

    Runoff is affected by the soil moisture before a precipitation event, the antecedent moisture condition (AMC). A curve number, as calculated above, may also be termed AMC II or C N I I {\displaystyle CN_{II}} , or average soil moisture.

  5. Intensity-duration-frequency curve - Wikipedia

    en.wikipedia.org/wiki/Intensity-duration...

    An intensity-duration-frequency curve (IDF curve) is a mathematical function that relates the intensity of an event (e.g. rainfall) with its duration and frequency of occurrence. [1] Frequency is the inverse of the probability of occurrence. These curves are commonly used in hydrology for flood forecasting and civil engineering for urban ...

  6. Return period - Wikipedia

    en.wikipedia.org/wiki/Return_period

    The theoretical return period between occurrences is the inverse of the average frequency of occurrence. For example, a 10-year flood has a 1/10 = 0.1 or 10% chance of being exceeded in any one year and a 50-year flood has a 0.02 or 2% chance of being exceeded in any one year.

  7. Earth rainfall climatology - Wikipedia

    en.wikipedia.org/wiki/Earth_rainfall_climatology

    Earth rainfall climatology Is the study of rainfall, a sub-field of meteorology. Formally, a wider study includes water falling as ice crystals, i.e. hail, sleet, snow (parts of the hydrological cycle known as precipitation ).

  8. Log-normal distribution - Wikipedia

    en.wikipedia.org/wiki/Log-normal_distribution

    In hydrology, the log-normal distribution is used to analyze extreme values of such variables as monthly and annual maximum values of daily rainfall and river discharge volumes. [ 71 ] The image on the right, made with CumFreq , illustrates an example of fitting the log-normal distribution to ranked annually maximum one-day rainfalls showing ...

  9. Numerical weather prediction - Wikipedia

    en.wikipedia.org/wiki/Numerical_weather_prediction

    Weather reconnaissance aircraft, such as this WP-3D Orion, provide data that is then used in numerical weather forecasts.. The atmosphere is a fluid.As such, the idea of numerical weather prediction is to sample the state of the fluid at a given time and use the equations of fluid dynamics and thermodynamics to estimate the state of the fluid at some time in the future.