Meteorology Chapter on Latent Heat and Humidity

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Questions and Answers

What is the rate of temperature change with altitude for dry air parcels?

12.0 K/km

7.2 K/km

9.75 K/km (correct)

6.5 K/km

Which of the following correctly describes the effect of latent heat during condensation?

It warms the surroundings. (correct)

It cools the surroundings.

It increases humidity.

It has no effect on temperature.

What is the correct formula for calculating latent heat of sublimation?

λE = (λv - λf)⋅ρw⋅E

λE = λv⋅ρw

λE = (λv + λf)⋅ρw⋅E (correct)

λE = λv + λf

How does the latent heat of vaporization (λv) change with temperature?

It decreases slightly with increasing temperature. (B) Signup and view all the answers

Which measure of humidity is defined as the mass of water vapor per unit mass of dry air?

Specific Humidity (D) Signup and view all the answers

What is the storage coefficient primarily used to measure?

The ratio of added or extracted water depth to the change in water table level (A) Signup and view all the answers

Which variable in the water balance formula represents the change in storage?

ΔS (D) Signup and view all the answers

Which of the following is NOT a common challenge in analyzing hydrologic variables?

Temporal consistency (A) Signup and view all the answers

What does temporal variability in hydrology refer to?

Variation in hydrological processes occurring over time (B) Signup and view all the answers

Why might classical statistical assumptions often fail in hydrology?

Spatial and temporal variability affect data representation (A) Signup and view all the answers

The measurement of seepage in hydrology is best expressed in which of the following units?

Millimeters per day (A) Signup and view all the answers

In the water balance formula, what does the variable 'I' denote?

Other inflow not specified (D) Signup and view all the answers

What is the primary significance of identifying trends and patterns in a time series within hydrology?

Managing water resources and predicting events like floods (A) Signup and view all the answers

Which hydrological process is primarily influenced by the combination of seasonal and interannual variations?

Streamflow (B) Signup and view all the answers

What is one of the specialized statistical techniques recommended for addressing challenges caused by spatial and temporal variability?

Trend analysis (D) Signup and view all the answers

What primarily defines a watershed?

A region that collects rain and snow into rivers, lakes, or oceans. (D) Signup and view all the answers

Which factor mentioned does NOT influence water quality within a watershed?

Atmospheric temperatures during precipitation. (A) Signup and view all the answers

Why is proper watershed management crucial for flood control?

It influences the movement of water through size, shape, and vegetation. (A) Signup and view all the answers

What is a watershed outlet in the context of watershed delineation?

The point where water exits the watershed, such as a river or lake. (B) Signup and view all the answers

Which characteristic of a watershed helps in understanding its hydrologic responses?

Topography, since it directs surface water movement. (B) Signup and view all the answers

What role do watersheds play in water resource management?

They define natural water flow and aid in water distribution. (D) Signup and view all the answers

Which statement about watershed characteristics is FALSE?

Soil composition has no effect on runoff rates. (B) Signup and view all the answers

Which aspect is NOT considered when selecting an outlet for watershed analysis?

Proximity to urban development. (B) Signup and view all the answers

What is the first step in the process of manual delineation?

Start at the watershed outlet (B) Signup and view all the answers

Which task is NOT part of the digital delineation process?

Drawing perpendicular lines to contour lines (A) Signup and view all the answers

Which of the following is a primary advantage of digital watershed delineation?

Rapid data processing (D) Signup and view all the answers

How is slope calculated in digital delineation?

Using the difference in elevation and distance (B) Signup and view all the answers

What is the purpose of a water balance in hydrology?

To understand equilibrium between water input, storage, and output (B) Signup and view all the answers

Which component is NOT included in the process of digital delineation from a DEM?

Data compression (B) Signup and view all the answers

In the context of a water balance, which aspect primarily affects irrigation planning?

Equilibrium of input and output (D) Signup and view all the answers

What does the term 'sinks' refer to in the digital delineation process?

Depressions in the terrain (D) Signup and view all the answers

Which tool is NOT necessary for manual delineation?

Digital Elevation Model (D) Signup and view all the answers

What hydrological insight is NOT typically derived from DEMs?

Soil composition (C) Signup and view all the answers

What does a Flow-Duration Curve primarily illustrate?

The temporal variability of streamflow and the fraction of time a flow rate is exceeded (D) Signup and view all the answers

How does atmospheric pressure change with increased altitude?

It decreases due to less air overhead (C) Signup and view all the answers

What does the Ideal Gas Law equation P=ρRT relate?

Pressure, temperature, and density of a gas (D) Signup and view all the answers

Which statement about vapor pressure is accurate?

Saturation vapor pressure increases with temperature (B) Signup and view all the answers

Which molecular weight is lighter than both nitrogen and oxygen?

Water vapor (H2O) (B) Signup and view all the answers

What does Dalton's Law of Partial Pressures state?

Total pressure is the sum of the partial pressures of dry air and vapor pressure (B) Signup and view all the answers

Which of the following describes adiabatic cooling?

Temperature decrease of rising air with no heat exchange (B) Signup and view all the answers

What is the typical maximum to minimum daily flow ratio observed in rivers, according to examples provided?

1,270 (C) Signup and view all the answers

What happens at saturation vapor pressure when additional water vapor is introduced?

Condensation occurs, leading to fog or clouds (B) Signup and view all the answers

Study Notes

Watershed Concepts

A watershed is an area of land where all precipitation drains into a common outlet, such as a river, lake, or ocean.
Also known as a drainage basin.
It collects surface runoff, rainwater, and groundwater, channeling it into a main water body.

Importance of Watersheds

Key unit for studying hydrology and water resources.
Most water in streams originates as precipitation within the watershed.
Watershed characteristics control water movement.
Watersheds are a key part of the hydrologic cycle.

Factors Influencing Watersheds

Geology: Determines underground flow paths.
Soils: Affect infiltration and runoff rates.
Topography: Controls surface flow direction and speed.
Land Use: Impacts water quality and timing.

Watersheds and Water Resource Management

Define the natural flow of water within a region.
Help manage water distribution for agriculture, drinking, and industrial use.
Act as a framework for sustainable water use.

Watersheds and Water Quality

Activities within watersheds impact water quality.
Pollutants from farms, factories, or urban areas flow into rivers and lakes.
Proper management reduces pollution and protects water quality.

Role of Watersheds in Flood Control

Predict flooding during heavy rainfall or snowmelt.
Size, shape, and vegetation influence water flow.
Manage runoff to reduce flood risks.

Watershed Delineation

Process of identifying the boundaries of a watershed.
Begins with selecting the watershed outlet.
Outlets define the area contributing water to a specific location.

Watershed Outlets Selection

The location depends on the purpose of the analysis.
Streamflow Analysis: Outlets at gauging stations for water budgets.
Geomorphic Studies: Outlets at stream junctions or where streams meet larger water bodies.
Water Resource Management: Outlets at reservoirs, hydroelectric plants, or waste-discharge sites.
Flood Management: Outlets in flood-prone areas to assess damage risk.

Importance of Manual Delineation

Valuable Insights: Manual delineation provides valuable insight into the watershed concept.
Essential for Validation: Digital methods often contain errors, requiring manual verification.

Tools Needed for Manual Delineation

Topographic maps.
Stereoscopically viewed aerial photographs.

The Process of Manual Delineation

Step 1: Start at the watershed outlet (lowest point).
Step 2: Draw a line perpendicular to contour lines, away from the stream bank.
Step 3: Mark the location of the topographic high points around the stream, inspecting contour patterns frequently to ensure accuracy.
Step 4: Trace the divide until it encloses the headwaters and connects back.

Digital Delineation

Based on Digital Elevation Models (DEMs).
DEMs provide elevation data at grid points, derived from satellite radar reflections.

Advantages of Digital Delineation

Rapid data processing.
Accessibility of hydrological insights (e.g., elevation, slope).
Elimination of tedious manual efforts.

Digital Delineation Process

Input Digital Elevation Model (DEM).
Fill Sinks (Depressions).
Flow Direction.
Flow Accumulation.
Stream Network.
Stream Links.

Water Balance

Equilibrium between input, storage, and output of water in a particular system.
Essential for understanding water availability, irrigation planning, hydrological studies, and climate change impacts.

Example of Water Balance

A polder, a low-lying area below sea level, has an area of 5 km².

Water Balance Equation

P = E + T + R + AS
P - (R + G + E + T) = AS

Hydrological Modeling

To estimate available water (Reservoirs, Lakes, Groundwater).
Application of the Water Balance Formula.

Agricultural Planning

To manage irrigation based on precipitation and evapotranspiration.

Flood and Drought Prediction

Extreme weather events.
Water availability.

Time Series

Time-ordered sequence of discrete values of a variable separated by a constant time interval (∆t).
Precipitation, Streamflow, Groundwater Levels, Temperature, Evapotranspiration

Why is Time Series Important in Hydrology?

Unveiling the power of time series in hydrology.
Identifying trends and patterns.
Predicting future behavior.
Managing water resources.
Understanding hydrological events.

Identifying Trends and Patterns

Seasonal variability of Daily Minimum Temperature.

Special Characteristics of Hydrologic Variables

Key assumptions in classical statistics.
Why these assumptions often fail in hydrology.
Spatial variability (spatial distribution issues).
Temporal variability (temporal distribution issues).
Solutions.

Spatial Variability

Differences in hydrological processes across different locations in a watershed or region.
Influenced by various physical and environmental factors (topography, soil types, vegetation, and land use).

Factors Influencing Spatial Variability

Topography (steep slopes vs. flat areas).
Vegetation (forested areas vs. urban areas).
Soil types (clayey soils vs. sandy soils).
Land Use (agriculture vs. urbanization).

Temporal Variability in Hydrology

Variation in hydrological processes over time.
Key processes: precipitation, evaporation, runoff, snowmelt.

Key Hydrological Processes

Precipitation, Evaporation, Runoff, Snowmelt

Timescales

Daily, Seasonal, Annual, Multi-Decadal

Importance

Water Resource Management, Flood Prediction, Drought Response

Temporal Variability of Streamflow

Long-term average streamflow: Indicates potential water availability.
Affected by seasonal and interannual variations in precipitation, snowmelt, evapotranspiration.
Key points: Streamflow in unregulated rivers varies widely, even in humid regions.
Typical variability spans over three or more orders of magnitude.

Flow-Duration Curves (FDCs)

Duration curves depict the temporal variability of streamflow.
Show the fraction of time a streamflow rate is exceeded.
Illustrate variability and limitations of using average streamflow as a metric.

Pressure-Temperature-Density

Hydrostatic relation: How atmospheric pressure changes with altitude.
Ideal Gas Law: Fundamental relationship between pressure, temperature, and density.

Moist Air vs. Dry Air

Dry air primarily consists of nitrogen (N2) and oxygen (O2).
Water vapor has a lower molecular weight than nitrogen and oxygen.

Vapor Pressure and Saturation Vapor Pressure

Vapor Pressure: Partial pressure exerted by water vapor in the atmosphere.
Saturation Vapor Pressure (e*): Maximum vapor pressure at a given temperature.

Partial Pressure and Adiabatic Processes

Dalton's Law: Total pressure equals the sum of partial pressures (P = Pda + e).
Adiabatic cooling: Rising air cools as pressure decreases.
Adiabatic warming: Descending air warms as pressure increases.

Comparing Moist vs. Dry Air Lapse Rates

Dry Adiabatic Lapse Rate (da): Applies to air parcels without condensation.
Observed Temperature Gradient: Near-surface lapse rate is less steep than da due to latent heat release from condensation.
Importance: Affects cloud formation, weather systems, and turbulence.

Latent Heat

Energy required to change the state of water without changing its temperature.
Example: Evaporation absorbs energy, cooling the surface.
Condensation releases energy, warming the surroundings.

Key Formula for Latent Heat

Latent Heat Transfer Formula: λE = λv * ρw * E

Latent Heat and Sublimation

Sublimation: Process where snow or ice transitions directly to vapor.
Latent Heat of Sublimation: λE = (λv + λf) * ρw * E

Temperature Dependence of Latent Heat

Latent Heat of Vaporization (λ₁) decreases slightly with increasing temperature.

Practical Importance of Latent Heat

Weather systems, energy exchanges in nature, water cycle modeling
Example: Sublimation in snowpack loss and water resource estimation.

Measures of Humidity

Absolute Humidity (pv): Mass of water vapor per unit volume of air.
Specific Humidity (q): Mass of water vapor per unit mass of dry air.
Relative Humidity (RH): Ratio of actual vapor pressure to saturation vapor pressure.

Studying That Suits You

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Description

Test your knowledge on key concepts of meteorology, focusing on the effects of temperature change with altitude and the role of latent heat during phase changes. This quiz covers essential formulas and measures related to humidity and heat transfer in the atmosphere.