Precipitation and Hydrologic Cycle Quiz

Precipitation: Spatial Distribution

• Precipitation is water released from clouds as rain, sleet, snow, or hail.
• Precipitation begins when water vapor in the atmosphere condenses and becomes too heavy to stay in the air.
• About one-fourth of the total precipitation on continental areas goes to the seas by direct runoff and underground water flow.
• The rainfall pattern in the Philippines is affected by major air streams, the Intertropical Convergence Zone (ITCZ) movement, and cyclonic disturbances.
• The Philippines receives an average of 965 to 4,064 millimeters of rainfall yearly. However, this is not evenly distributed over time and space.
• There are about 175 rainy days annually in the Philippines.
• Eastern coastal stations have more rainy days than the average for the Philippines.
• Western coastal stations have fewer rainy days than the average.

Hydrologic Cycle

• The hydrologic cycle is a continuous water circulation system in the Earth-atmosphere system.
• It's also known as the water cycle.

The Water Cycle (Processes)

• Evaporation: Water (liquid) changes to water vapor (gas).
• Transpiration: Water evaporates from plants and trees.
• Sublimation: Ice or snow (solid) changes directly to water vapor (gas) without becoming liquid.
• Condensation: Water vapor (gas) changes to liquid water, forming clouds.
• Transportation: Movement of water vapor in the atmosphere.
• Precipitation: Water falling to Earth's surface (rain, snow, sleet, hail).
• Deposition: Water vapor (gas) changes to ice (solid) without becoming liquid.
• Infiltration: Water seeps into the ground.
• Percolation: Water moves through soil and deeper into the groundwater.
• Surface Runoff: Water flows over the ground surface into streams, rivers, and lakes.
• Groundwater Flow: Water flows underground in aquifers.
• Plant Uptake: Water is absorbed by plants.

Forms of Precipitation

• Drizzle or Mist: Tiny liquid water droplets (0.1 to 0.5 mm in diameter).
• Rain: Mostly liquid water drops larger than 0.5 mm.
• Rime: White deposit of ice granules formed by freezing water drops on exposed objects.
• Glaze: Ice coating on exposed surfaces created by freezing supercooled water.
• Snow: Composed of ice crystals in complex, branched hexagonal form.
• Sleet: Solid, transparent, globular ice grains formed by freezing of raindrops, or by refreezing of melted ice crystals.
• Hail: Precipitation in the form of balls or pieces of ice, produced in convective clouds.

Requirements for Precipitation

• Cooling of the air mass to near saturation.
• Presence of condensation nuclei (particles on which water vapor can condense).
• Growth of water droplets or ice crystals until their falling speed exceeds the ascent rate of air.

Characteristics of Raindrops

• Small raindrops are spherical.
• Larger raindrops become distorted, resembling a hamburger bun.
• Raindrop size and speed vary based on intensity and type of storm.
• Larger drops fall faster than smaller ones.

Rainfall Characteristics

• Intensity: Rainfall depth per unit time, usually measured in millimeters per hour. High intensity indicates heavy rain, and low intensity indicates light rain.
• Duration: Length of time a rainfall event lasts
• Frequency: The frequency or return period of rainfall is the average time interval between occurrences of a specific rainfall event of a given magnitude or greater. It ranges from intense short-duration storms to less frequent but longer-duration storms. The higher the frequency, the lower the risk of the event occurring.

Rainfall-measuring Instruments

• Rain Gauge: Measures rainfall in liquid form.
  • Non-recording Rain Gauge
  • Recording Rain Gauge (Automatic) – tiping bucket, weihing bucket, optical rain gauges, and acoustic rain gauges.

Analysis and Interpretation of Precipitation Data

• Correctly interpreting precipitation data is important to prevent wrong conclusions.
• Factors affecting precipitation data quality include gauge location, gauge exposure, instrumentation, and observational procedure.
• Precipitation data is used for many applications, including agriculture, engineering, and flood control.

Estimating Missing Data

• Methods for estimating missing precipitation data include arithmetic mean and normal ratio methods.
  • The arithmetic mean method averages the precipitation of nearby stations with similar conditions.
  • The normal ratio method weights the precipitation of nearby stations by the ratio of their historical normal annual precipitation to the station with the missing record.

Estimating Average Rainfall over an Area

• Thiessen Polygon Method: divides the area into polygons using perpendicular bisectors; for each gage, a polygon encompasses stations using a weighting factor.
• Isohyetal Method: A more accurate method; draws contours for equal precipitation amounts across an area using known amounts at several locations; computations use area between successive isohyets to weight areas.

Test your knowledge on precipitation patterns and the hydrologic cycle with this quiz. Explore how rainfall is distributed across different regions, focusing on the unique climate of the Philippines. Learn about the factors that influence precipitation and its impact on the environment.