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precipitation

Precipitation. Single strongest variable driving hydrologic processesFormed water vapor in the atmosphereAs air cools its ability to

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precipitation

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    1. Precipitation Chapter 2

    4. Weather Patterns Weather (day to day) vs. climate (years-decades and patterns) What are hydrologists most concerned with? Climate and geography result in biome classification

    8. Figure 2.4-where does the moisture come from Why does ohio get steady rainfall-fronts and convection Compare to other areas in US Figure 2.4-where does the moisture come from Why does ohio get steady rainfall-fronts and convection Compare to other areas in US

    9. Figure 2.6 Have students explain differences in precip due to air masses Rainfall typeFigure 2.6 Have students explain differences in precip due to air masses Rainfall type

    10. Measurement of Precipitation Terminology (2.3) Types of devices (2.4.2) Snowfall conversions (2.4.1) Location of devices (2.4) Interpretation of data (2.3.3, 2.6)

    11. Rainfall Terminology Type-hail, rain, snow, sleet Depth Storm Duration Average rate of precipitation-Intensity Return Period or Recurrence Interval

    13. Snow Measurement Determine the water equivalent 5%-60% of snow depth may be water equivalent-- density Snow pillows use antifreeze solution and pressure measurement to measure water equivalent

    14. Location of Gages Gauges measure point rainfall True precipitation unaffected by surroundings-winds, trees, buildings Clearance distance 2 times height of object For large areas multiple gauges are needed for more accurate estimates

    16. Figure 2.9-error with gagesFigure 2.9-error with gages

    17. Interpretation of Data Time distributions Area distributions Using point data to find average rainfall Thiessen method

    19. Figure 2.15 Figure 2.15

    20. Figure 2.15 Figure 2.15

    21. Figure 2.15 Figure 2.15

    22. Figure 2.15 After summing areas and rainfall Thiessen predicts 2.08 inches, and the mean is 1.97 inches. This is because the heavier rainfall amounts in center of study area get more carry more area and weight in the calculation.Figure 2.15 After summing areas and rainfall Thiessen predicts 2.08 inches, and the mean is 1.97 inches. This is because the heavier rainfall amounts in center of study area get more carry more area and weight in the calculation.

    23. Prediction-Frequency Distributions To plan and design projects must be able to predict probability of rainfall events Duration, Intensity, Return Period Often must estimate Return Periods Use Hazen method to develop intensity-duration-frequency curve (Example 2.5).

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