Lecture Precipitation posted
Page 1: Introduction to Precipitation
Definition of Precipitation
Precipitation refers to any form of water, liquid or solid, that falls from the atmosphere and reaches Earth's surface.
Includes rain, snow, sleet, hail, and drizzle.
Factors influencing precipitation include temperature, atmospheric pressure, and humidity.
Page 2: Precipitation Processes
Key Processes Involved in Precipitation
Interception - The process by which precipitation is caught and held by vegetation before reaching the ground.
Infiltration - The absorption of precipitation into the soil.
Sublimation and Evaporation - The transformation of solid water (ice) into vapor and the transition of liquid water into vapor, respectively.
Evapotranspiration - The sum of evaporation from the land and transpiration from plants.
Surface Runoff - The movement of water, from rain, melted snow, or other sources, across the ground.
Base Flow - Water that flows in rivers and streams when there is no precipitation.
Groundwater - Water stored underground in wells or aquifers.
Storm Discharge - The rapid release of large amounts of water from rain or melted snow.
Page 3: Outline of Atmospheric Water and Precipitation
Components to be Covered
Atmosphere and Atmospheric Water: The role of gases and water vapor in precipitation.
Precipitation Processes: How different types of precipitation form.
Collision and Coalescence: The processes leading to raindrop formation.
Ice-Crystal Process: Ice formation and its impact on precipitation.
Types of Precipitation: Differentiation among various forms of precipitation.
Cloud Seeding: Artificial methods to induce precipitation.
Precipitation Chemistry: The chemical composition of precipitation.
Page 4: Composition of the Atmosphere
Major Components
Stable Gases:
Nitrogen (N2): 78%;
Oxygen (O2): 21%;
Trace gases: <0.3% including water vapor.
Key Relationships
Water capacity in air is influenced by temperature, described by the Saturation Vapour Pressure Curve.
Points at this curve represent 100% relative humidity.
Page 5: Atmospheric Water Vapor and Saturation Vapour Pressure
Saturation Vapour Pressure Curve
Illustrates the relationship between air temperature and its capacity for water vapor, which increases exponentially.
There’s lower vapor pressure over ice than liquid water at temperatures below zero.
Page 6: Vapor Pressure and Humidity
Air Pressure and Humidity Relationship
Atmospheric pressure is the total sum of partial pressures of component gases.
Relative humidity (RH) is calculated using actual vapor pressure over saturation vapor pressure (e).
Rising air leads to cooling and condensation of water vapor, contributing to cloud formation.
Page 7: Development of Clouds
Raindrop Formation in Clouds
Larger droplets fall and collide with smaller droplets, forming larger raindrops.
The terminal velocity of droplet sizes varies, affecting their descent rate during precipitation.
Page 8: Characteristics of Clouds
Definition and Properties
Clouds are visible aggregates of tiny water droplets or ice crystals in the atmosphere.
Their properties change based on the phase of water, particle sizes, and shapes of ice crystals.
Page 9: Collision and Coalescence Process
Mechanics of Raindrop Formation
Warmer cloud tops facilitate the collision and coalescence of droplets.
Factors influencing coalescence include droplet sizes, cloud thickness, and electrical charges.
Page 10: Rain Production Factors
Conditions Affecting Rain
Various factors such as the liquid water content of clouds and updrafts play crucial roles in determining rainfall types.
Thin clouds result in light drizzle, whereas thick clouds produce heavy rain showers.
Page 11: Raindrop Growth in Clouds
Transformation of Cloud Droplets
Cloud droplets experience growth through collision and coalescence, resulting in larger raindrops emerging from the cloud.
Page 12: Precipitation Forming Processes
Types of Clouds and Precipitation
Different atmospheric conditions lead to varying precipitation forms such as rain or snow, depending on air temperature.
Page 13: Types of Precipitation
Drizzle and Rain
Defined by droplet sizes, where smaller droplets may evaporate before reaching the ground (virga).
Page 14: Classes of Precipitation
Class | Definition |
|---|---|
Rain | Liquid droplets between 0.5 and 7 mm in diameter |
Drizzle | Subset of rain with droplets less than 0.5 mm |
Sleet | Freezing raindrops, a mix of snow and rain |
Snow | Complex ice crystals |
Hail | Balls of ice between 5 and 125 mm in diameter |
Page 15: Ice-Crystal (Bergeron) Process
Conditions for Ice-Crystal Formation
Cold clouds dominate mid- and high latitudes, where both liquid and solid particles are present.
Ice crystals grow at the expense of supercooled water droplets due to differences in vapor pressure.
Page 16: Growth of Ice Crystals
Mechanism of Growth
Ice crystals grow by attracting nearby vapor molecules, leading to the formation of larger ice structures within clouds.
Page 17: Saturation and Equilibrium
Water Droplets and Ice Crystals
When in equilibrium with surrounding vapor, both ice crystals and water droplets exist at similar temperatures, such as -15°C.
Page 18: Saturation Vapour Pressure Curve
Importance of the Curve
Illustrates differing saturation levels between water and ice depending on temperature and is crucial in understanding precipitation formation.
Page 19: Pressure Gradient Effects
Movement of Vapor Molecules
A pressure difference causes vapor to move from liquid droplets to ice crystals, aiding in their growth as surrounding temperatures decrease.
Page 20: Nakaya Diagram
Snow Crystal Morphology
Illustrates how snow crystal forms change with temperature and levels of supersaturation.
Page 21: Classification of Snow Crystals
Types of Snow Crystals
Common types of snow include broken, rimed, clustered, and wet crystals based on their structural variations.
Page 22: Growth Mechanisms of Ice Crystals
Accretion Processes
Ice crystals grow larger through collision with supercooled droplets, potentially forming graupel or ice pellets.
Page 23: Snow Characteristics
Snow Accumulation Conditions
Snow forms when temperature remains below freezing, allowing flakes to aggregate into larger structures.
Page 24: Snowflake Formation
Conditions Affecting Snowflakes
When snowflakes pass through warmer air, they may develop films of water, causing them to stick together.
Page 25: Sleet Generation
Transitional Precipitation Types
Sleet represents a combination of rain and snow, often leading to hazardous conditions.
Page 26: Freezing Rain/Drizzle
Onset of Freezing Conditions
Supercooled rain freezes upon contact with cold surfaces, creating ice accumulation.
Page 27: Ice Pellets
Definition of Ice Pellets
Ice pellets are essentially frozen rain, exhibiting a clear ice layer around snowflakes or graupel.
Page 28: Hail Formation
Hail Production Conditions
Hail forms through the accretion of supercooled water around larger particles, developing distinct layers as it rises and falls in clouds.
Page 29: Dew Formation
Understanding Dew
Dew forms through condensation on cold surfaces during warm air conditions, not seen as significant in the hydrological cycle.
Page 30: Mist and Fog
Low Elevation Clouds
Mist and various types of fog are essentially low-elevation clouds formed from saturated air near the ground.
Page 31: Cloud Seeding
Artificial Precipitation Induction
The process of cloud seeding involves injecting nuclei to produce smaller precipitation, potentially aiding in drought conditions.
Page 32: Summary of Key Concepts
Main Points Recap
(Information from Pages 33 to 49 not provided)
Page 34: Overview of Today's Topics
Planned Discussion Points
Types of Precipitation
Precipitation Chemistry
Distribution and Mechanisms
Measurement Techniques
Analyzing Rainfall Data
Page 35: Occult Precipitation
Fog Drip
Water droplets from fog can accumulate, particularly in coastal environments, and can be harvested as a significant water source in arid regions.
Page 36: Rime
Formation Characteristics
Rime forms similarly to fog drip but involves supercooled droplets freezing on contact with surfaces.
Page 37: Dew and Frost
Cold Surface Condensation
Dew, frost, and hoar frost occur when saturation around a cooled surface leads to condensation or deposition.
Page 38: Precipitation Chemistry
Chemical Composition Influencing Factors
Chemical composition relies significantly on nuclei, aerosols, including CO2, NO, and SO2 presence. Typically, natural rainwater is slightly acidic.
Page 39: Acid Rain Understanding
Impacts of Acid Rain
Acid rain negatively affects ecosystems, mobilizing aluminum from soils and leaching essential nutrients.
Page 40: Monitoring Precipitation Chemistry
Sampling and Analysis Methods
Various strategies like wet and dry sampling provide insights into precipitation’s chemical composition.
Page 41: Soils and Bedrock Interaction
Acid Neutralization Potential
Different soils and bedrock compositions impact their ability to neutralize atmospheric deposition of acidity.
Page 42: Canadian Monitoring Network
Precipitation Data Collection
Continuous monitoring entails assessing various major ions and toxic substances to inform environmental policies.
Page 43: Average Annual Precipitation in Canada
Variability by Region
Map illustrating annual precipitation data across various Canadian provinces with differences highlighted.
Page 44: Precipitation Distribution Types
Lifting Mechanisms
Convergent Lifting
Orographic Lifting
Convectional Lifting
Frontal Lifting
These mechanisms govern rainfall intensity, total amounts, and spatial patterns.
Page 45: Psychrometric Relationships
Interconnection of Temperature and Humidity
Diagram illustrating how temperature and humidity are interrelated, crucial for understanding precipitation behavior.
Page 46: Orographic Lifting
Characteristics and Effects
Orographic lifting leads to moisture condensation and precipitation on windward slopes, contributing to the creation of rain shadows on leeward (downwind) sides.
Page 47: Orographic Effects in New Zealand
Case Study
Illustrative data showing moisture stripping effects and precipitation distribution across the South Island of New Zealand.
Page 48: Frontal Lifting
Fronts and Precipitation
An overview of cold and warm fronts, their formation, and their impacts on precipitation patterns in varying air masses.
Page 49: Movement of Air Masses
Characteristics of Polar to Tropical Fronts
Describes fronts corresponding with the ITCZ and polar areas, showing their precipitation dynamics.
Page 50: Convergent Lifting Mechanics
Dynamics of Converging Air
The convergence of air flows leading to areas of low pressure causing uplift and subsequent precipitation development.
Page 51: Convectional Lifting
Principle Dynamics
Cool and warm air interactions play a significant role in the convection process, leading to localized precipitation patterns.
Page 52: Resources for Further Learning
Educational Links
Suggested links for deeper exploration of atmospheric science concepts relevant to precipitation.
Page 53: Evaluation of Canadian Weather Precipitation
Overall Evaluation of Patterns
Overview of precipitation events in Canada and associated climatic impacts.
Page 54: Precipitation Types and Patterns
Summary of Previous Discussions
Reviews the nature of precipitation types and their associations with temperature profiles and atmospheric conditions.
Page 55: Vegetation and Precipitation
Influences and Interactions
Investigations into how vegetation influences rainfall interaction, interception, and ground moisture retention.
Page 56: Canopy Characteristics
Influence on Rainfall Interception
Various tree species, their characteristics, and how they affect rainfall patterns through interception.
Page 57: Teak Plantation Observations
Ecological Interactions
Observations from a teak plantation in Tanzania with a focus on their role in precipitation dynamics.
Page 58: Net Precipitation Calculation
Rainfall Budget Analysis
Net precipitation can be determined by subtracting interception from gross rainfall totals, influencing hydrological analyses.
Page 59: Implications for Soil and Water Management
Holistic Considerations in Forest Management
The importance of understanding precipitation effects on soil moisture, chemistry, and forest management practices.
Page 60: Throughfall Measurement Variances
Measurement Insights
Different techniques for measuring throughfall and their implications for precipitation research.
Page 61: Stemflow Measurement Techniques
Innovations in Measurement
Emerging methods for quantifying stemflow and their contributions to overall precipitation studies.
Page 62: Ponded Stemflow Observations
Case Studies
Observations taken from Okanagan Mountain Park, showcasing seasonal variations in stemflow behavior.
Page 63: Trends in Stemflow Measurement
Seasonal Variability
Analyzing stemflow patterns year-round in specific regions and their impact on environmental conditions.
Page 64: Magnitude of Components
Statistical Overview
Evaluation of stemflow and interception components across different forest types, highlighting outliers.
Page 65: Precipitation Measurement Technologies
Instrumentation Overview
Includes both recording and non-recording measurements, essential for meteorological data collection.
Page 66: Weighing Gauge Technology
Progress in Precipitation Measurement
Weighing gauges offer innovative solutions for recording total precipitation and inform on temporal variations.
Page 67: Tipping Bucket Gauge Mechanism
Functionality and Utility
Tipping bucket gauges measure rainfall through set depths, providing efficiency in precipitation data collection.
Page 68: Surrogate Measurements of Precipitation
Remote Sensing Innovations
Emphasis on ground-based radar and satellite imaging technology for precipitation measurement and atmospheric observation.
Page 69: Weather Radar Applications
Functionality of Weather Radars
Utilizing radar technology to locate precipitation, analyze motion, and forecast meteorological events.
Page 70: Snow Measurement and Observations
Measurement Procedures
Presentation of accumulated snow data and methodologies for temperature and precipitation analysis.
Page 71: Canadian Weather Radar Network Insights
Operational Overview
Insights into the operational capacities and outreach of the Canadian weather radar network.
Page 72: Satellite Remote Sensing Technologies
Two-Sensor Functionality
Overview of radar and microwave sensors used in precipitation detection and intensity measurements.
Page 73: Snow Accumulation Analysis
Seasonal Accumulation Data
Statistical representation of snow accumulation across Canadian territories, showing climate impacts over time.
Page 74: Measurement Limitations and Errors
Source of Errors in Measurement
Discusses gauge distribution, representative sampling, and issues such as wind undercatch impacting data accuracy.
Page 75: Wind Undercatch Impacts
Precipitation Gauge Performance
Describes how wind can affect drop trajectories and the accuracy of precipitation readings.
Page 76: Measurement Techniques and Challenges
Accuracy Factors
Various factors contribute to measurement inaccuracies, including gauge placement and environmental conditions.
Page 77: Common Shields in Use
Comparison of Shield Effectiveness
Evaluates the aerodynamic properties of different shield types used to enhance gauge measurements.
Page 78: Specific Types of Gauges
Overview of Modern Measurement Tools
Examination of various gauges used globally for accurate precipitation tracking.
Page 79: Additional Limitations in Measurement
Factors Impacting Results
Explores further complications such as wetting loss, environmental challenges, and gauge calibration.
Page 80: Measuring Snowfall Variations
Various Gauge Types Used Internationally
Review of different international standards for measuring snowfall and their respective efficacies.
Page 81: Gauge Performance Under Wind Conditions
Performance Metrics
Wind speed tests compare gauge performance across different styles and types under varying environmental conditions.
Page 82: Assessment of Gauge Effects
Effects of Surrounding Environment
Analysis of gauge catch performance concerning surrounding vegetation and environmental shielding.
Page 83: Snow Measurement Challenges
Specific Challenges Encountered
Discusses issues related to capping, plugging, and frost effects on snow measurement equipment.
Page 84: Estimating Areal Average Precipitation
Calculation Techniques
Evaluates various methods for calculating average precipitation across larger drainage basins to ensure accuracy.
Page 85: Thiessen-Weighted Average Methodology
Application of Thiessen Method
How to apply the Thiessen method for non-uniform gauge distributions to acquire more precise precipitation data.
Page 86: Isohyetal Method Application
Utilizing Isohyets
Outlines procedures for drawing precipitation isohyets and measuring area for weighted precipitation calculations.
Page 87: Rainfall Data Analysis Techniques
Challenges in Data Gathering
Discusses gaps in data and how these can complicate analyses, especially in mountainous regions.
Page 88: Statistical Analysis of Hydrologic Data
Considerations for Sampling
Outlines fundamental requirements for statistical sampling in hydrology to ensure data reliability and representativeness.
Page 89: Probability and Frequency Analysis
Key Concepts
Understanding the probability and frequency of rainfall amounts is crucial for assessing long-term weather patterns.
Page 90: Evaluation of Exceedance Probability
Statistical Modeling
Examples of threshold levels for annual precipitation data and their relevance to hydrology and meteorological forecasting.
Page 91: Calculating Return Periods
Significance of Recurrence Intervals
Discusses the return period as a critical parameter for predicting rainfall occurrences and planning infrastructures.
Page 92: Rainfall Intensity Analysis
Understanding Intensity Metrics
Relationship between intensity and cumulative rainfall illustrated across various time frames for event planning.
Page 93: IDF Analysis Overview
Significance in Infrastructure Design
Understanding rainfall behavior is vital for creating effective stormwater management structures such as drains and culverts.
Page 94: Annual Maximum Rain Meets Frequency Analysis
Identifying Peak Rainfall Events
Analyzes the largest rain events across different durations for comprehensive risk assessment in meteorological studies.
Page 95: Short Duration Rainfall Trends
Analyzing Intensity-Duration Frequency Data
A comprehensive view of cumulative precipitation and how it varies over shorter durations allows for better event prediction.
Page 96: Psychrometric Relationships Recap
Understanding the Psychrometric Curve
Diagrammatic representation of the interplay between temperature, humidity, and vapor pressure, aiding in analysis of hydrological conditions.