Earthrise and Hydrology Overview

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Questions and Answers

What is the term used to describe the combined processes of evaporation and transpiration?

Evaporation-Transference

Atmospheric Loss

Hydrodynamics

Evapotranspiration (correct)

Which type of plant is specifically adapted to survive in aquatic environments?

Xerophytes

Phreatophytes

Hydrophytes (correct)

Mesophytes

What is a necessary condition for condensation to occur?

Presence of freezing nuclei (correct)

High relative humidity

Increased atmospheric pressure

Continuous rainfall

Which of the following is NOT a parameter required to initiate precipitation?

Saturation of soil moisture Signup and view all the answers

What role do stomata play in plants?

Facilitate gas exchange Signup and view all the answers

What is the function of a lysimeter in measuring evapotranspiration?

It holds soil and plants to assess water loss. Signup and view all the answers

What type of root system do phreatophytes possess?

Deep taproot extending to water table Signup and view all the answers

What is the primary purpose of precipitation measurements?

To evaluate water availability and risks like fire Signup and view all the answers

What is the main significance of the photo 'Earthrise' taken by Apollo 8 astronauts?

It revealed the importance of Earth as seen from space. Signup and view all the answers

What is the primary process by which water returns to the atmosphere as vapor?

Evaporation Signup and view all the answers

Which term describes the temperature at which condensation begins?

Dew Point Signup and view all the answers

In the context of humidity, what does relative humidity represent?

The ratio of absolute humidity to saturation humidity. Signup and view all the answers

What is the characteristic of a Qanat?

It is a gently sloping tunnel that transports water by gravity. Signup and view all the answers

Which statement is true regarding the hydrologic cycle?

It includes the movement of water among several Earth systems. Signup and view all the answers

How does increasing temperature affect saturation humidity?

It increases the maximum moisture capacity. Signup and view all the answers

What role do plants play in the water cycle through transpiration?

They pump water from the soil into the atmosphere. Signup and view all the answers

What is the correct method to use when rainfall measured shows little variation across the catchment area?

Arithmetic Method Signup and view all the answers

Which step is NOT part of the Isohyetal Method?

Connect rain gauge stations using perpendicular bisectors. Signup and view all the answers

What is the final step in the Isohyetal Method for finding the average rainfall in the area?

Sum the values found from the area calculations. Signup and view all the answers

What is the primary purpose of the Theissen Method?

To adjust non-uniform gauge distribution. Signup and view all the answers

What should be considered while determining the isohyetal contours in the Isohyetal Method?

Balance the number of contours for clarity and accuracy. Signup and view all the answers

What is the main reason raindrops need to be of sufficient size when leaving clouds?

To ensure they do not evaporate before reaching the ground Signup and view all the answers

In the Thiessen Method, how are polygons around each rain gauge station formed?

Connecting adjoining stations and constructing bisectors. Signup and view all the answers

What is the primary shape formed in the Thiessen Method around each rain gauge?

Polygons based on perpendicular bisectors. Signup and view all the answers

Which type of precipitation occurs due to the lifting of air associated with low pressure areas?

Cyclonic Precipitation Signup and view all the answers

What is the purpose of isohyetal lines in the Isohyetal Method?

To show contours of varying rainfall depth. Signup and view all the answers

How does orographic precipitation generally differ between windward and leeward slopes?

It is generally heavier on the windward slope. Signup and view all the answers

Which of the following is a direct method of measuring precipitation?

Rain gauges Signup and view all the answers

What is a crucial consideration for the placement of a rain gauge?

It should be away from trees and buildings to avoid wind interference. Signup and view all the answers

What mechanism triggers the data recording in a tipping-bucket rain gauge?

The tipping of one bucket when it collects enough rainfall Signup and view all the answers

What is the purpose of measuring precipitation?

To assess water availability and the risk of natural disasters Signup and view all the answers

In a tipping-bucket rain gauge, what happens when one bucket tips?

It starts the collection of rainfall in the next bucket. Signup and view all the answers

What is the purpose of using radar in the context of Earth-observing satellites?

To measure the intensity of precipitation in a specific area Signup and view all the answers

What does the effective depth of precipitation indicate?

The amount of water that infiltrates through the soil and reaches the water table Signup and view all the answers

How can missing precipitation data at a weather station be estimated?

By utilizing data from three nearby stations with full records Signup and view all the answers

Which method is NOT used to convert point rainfall values into an average over a catchment?

Geometric mean method Signup and view all the answers

What is the significance of having full records from nearby precipitation stations?

They help in estimating missing data due to equipment malfunction Signup and view all the answers

Which atmospheric characteristic is NOT typically observed by instruments on Earth-observing satellites?

Wind speed at ground level Signup and view all the answers

What equation is used to estimate missing precipitation data for a weather station?

A formula involving mean annual precipitation from surrounding stations Signup and view all the answers

For how long can the effective depth of precipitation be determined?

For the duration of individual storms or up to a year Signup and view all the answers

Study Notes

### Earthrise and The Blue Marble

The Apollo 8 mission produced a photograph of Earth rising above the lunar horizon, known as "Earthrise".
Astronaut Bill Anders, who took the photo, stated: "We came all this way to explore the Moon, and the most important thing is that we discovered the Earth."
The "Blue Marble" photograph was taken in December 1972 by the Apollo 17 crew during the last lunar mission.
This image has been widely reproduced and shows Earth as a blue sphere against a black background.
Africa and Arabia are prominent features in the photograph.

Hydrology

Qanats are underground tunnels that transport groundwater by gravity.
These tunnels can be up to 20 kilometers long but are typically less than 5 kilometers long.
Hydrology focuses on the study of water occurrence, distribution, movement, and chemical composition on Earth.
Hydrogeology studies the interplay of geological materials and processes with water.
Geohydrology is used in engineering and deals with water circulation within Earth's oceans, atmosphere, solid Earth, and biosphere.
This constant movement of Earth's water is known as the hydrologic cycle.

Evaporation and Humidity

Evaporation is the process of water changing from a liquid to a gas.
It's the primary way water returns to the atmosphere as water vapor.
Absolute humidity measures the amount of water vapor in the air (grams per cubic meter).
Saturation humidity represents the maximum water vapor the air can hold at a given temperature.
Relative humidity is expressed as a percentage, indicating the ratio of absolute humidity to saturation humidity.
As relative humidity approaches 100%, evaporation slows down.
Cooling an air mass with constant absolute humidity increases relative humidity, leading to condensation when it reaches 100%.
The dew point is the temperature at which condensation begins.

Transpiration

Plants continuously transfer water from the ground to the atmosphere through transpiration.
This process happens through root absorption, movement through plant tissues, and release through leaf stomata.
Transpiration rates are influenced by factors like the density and size of the drainage basin.

Plant Adaptations to Water Availability

Phreatophytes are plants with deep taproots that reach the water table.
Xerophytes are desert plants adapted to survive in arid conditions.
Hydrophytes are aquatic plants that live fully or partially submerged in water.

Evapotranspiration

Evapotranspiration combines evaporation and transpiration, both contributing to water transfer from land to atmosphere.
It is often measured using a lysimeter, a container holding soil and plants where changes in soil moisture indicate evapotranspiration.

Condensation

When an air mass cools without losing moisture, its relative humidity increases, eventually reaching 100%.
Condensation occurs when the air becomes saturated, often requiring a surface for condensation to start.
Examples of condensation nuclei include clay minerals, salts, and combustion products.

Precipitation

Precipitation is any form of water falling from the atmosphere, including liquid rain and solid snow.
It is the source of water for watersheds.
Precipitation formation requires the following:
- Humid air cooling to the dew point temperature.
- Presence of condensation nuclei.
- Coalescence of water droplets to form raindrops.
- Raindrops must be large enough to reach the ground without evaporating completely.
Precipitation measurements are crucial for determining water availability, streamflow, and risks like forest fires, landslides, and soil erosion.

Types of Precipitation

Cyclonic precipitation occurs when air converges towards areas of low pressure, leading to uplift and precipitation.
Convective precipitation results from rising warm air that cools and forms showers.
Orographic precipitation is caused by air lifting as it passes over mountains, with higher precipitation on the windward side.

Precipitation Measurement

Precipitation is measured directly using ground-based instruments like rain gauges.
Remote sensing techniques, like radar systems and satellites, provide indirect measurements.
Rain gauges (also known as pluviometers, ombrometers, and hyetometers) are used to measure the amount of precipitation.
The size of the gauge opening has a minimal effect on catch, except for very small openings.
High winds can reduce the catch of rain gauges.
The location of rain gauges is critical:
- Place as close to the ground as possible to avoid wind.
- Ensure an open location, away from trees and buildings.
- Place the opening parallel to the slope on steep slopes.
Tipping-bucket rain gauges are commonly used and detect precipitation changes by tilting when a certain volume accumulates.
They provide intensity information and are suitable for digitalizing output.

Satellites and Precipitation Data

Earth-observing satellites carry instruments to observe cloud temperatures and precipitation particles.
These data help fill in gaps between rain gauge readings.

Effective Depth of Precipitation

Effective depth of precipitation refers to the amount of water that infiltrates through the soil and reaches the water table, recharging aquifers.
It can be measured over various time periods, from specific storms to a full year.
Missing data from individual stations can be estimated using data from nearby stations with complete records.

Calculating Average Precipitation

Average precipitation over a catchment is calculated by converting point rainfall values from different stations.
Three methods are commonly used:
- Arithmetic mean method: Used when rainfall values show minimal variation.
- Thiessen polygon method: Used for non-uniform gauge distribution, where each gauge is assigned a weighting factor based on its area.
- Isohyetal method: Involves constructing contours of equal rainfall (isohyets) and calculating areas bounded by them.

### Thiessen Polygon Method

Thiessen polygons are constructed around rain gauge stations to indicate the effective area for each station.
They are used when the number of stations is limited compared to the size of the area.
The polygons are formed by:
- Plotting stations on a map.
- Connecting adjoining stations with lines.
- Constructing perpendicular bisectors of these lines.
- Extending these bisectors to form polygons.
This method provides weighting factors based on the area within each polygon.

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Description

This quiz explores significant photographs from space, namely 'Earthrise' and the 'Blue Marble,' alongside key concepts in hydrology. Learn about the importance of these images in understanding our planet and the fundamental principles of water distribution and transport methods like qanats. Test your knowledge on these captivating topics!