Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 1
Composition of the Atmosphere The Permanent Gases
Composition of the Atmosphere Variable Gases
Det Global karbonbudsjettet Stor utveksling mellom atmosfære og planter/hav Levetid CO 2 : 820PgC/(100+100) PgC/år = 4 år Mye karbon i dyphavet Veldig tregt tap av karbon til olje/kull/gass Kilde: https://www.carboncyclescience.us/what-is-carbon-cycle
Hvor raskt fjernes CO 2 fra atmosfæren? Levetid (τ): Gjennomsnittlig oppholdstid for et CO 2 molekyl i atmosfæren τ= Masse i atm./opptak(hav+bakke) 820/(100+100) 4 år Justeringstid (adjustment time): Tid det tar for å fjerne et ekstra utslipp til atmosfæren. Naturlige kretsløp var i balanse Mye lengre enn levetiden bl.a. fordi utvekslingstidene med dyphavet og lagrene av olje/kull/gass er lange
Phase 1 Within several decades of CO 2 emissions, about a third to half of an initial pulse of anthropogenic CO 2 goes into the land and upper ocean, while the rest stays in the atmosphere. Within a few centuries, most of the anthropogenic CO 2 will be in the form of additional dissolved inorganic carbon in the ocean. Within a thousand years, the remaining atmospheric fraction of the CO 2 emissions is between 15 and 40% (the carbonate buffer capacity of the ocean decreases with higher CO 2, so the larger the cumulative emissions, the higher the remaining atmospheric fraction).
Phase 2 Within a few thousands of years, the ph of the ocean that has decreased in Phase 1 will be restored by reaction of ocean dissolved CO 2 and calcium carbonate (CaCO 3 ) of sea floor sediments, partly replenishing the buffer capacity of the ocean and further drawing down atmospheric CO 2 as a new balance is re-established between CaCO 3 sedimentation in the ocean and terrestrial weathering. This second phase will pull the remaining atmospheric CO 2 fraction down to 10 to 25% of the original CO 2 pulse after about 10 kyr.
Phase 3 Within several hundred thousand years, the rest of the CO 2 emitted during the initial pulse will be removed from the atmosphere by silicate weathering, a very slow process of CO 2 reaction with calcium silicate (CaSiO 3 ) and other minerals of igneous rocks. Involvement of extremely long time scale processes into the removal of a pulse of CO 2 emissions into the atmosphere complicates comparison with the cycling of the other GHGs. This is why the concept of a single, characteristic atmospheric lifetime is not applicable to CO 2.
Layers of the Atmosphere Layering Based on Temperature Profiles Thermal Layers of the Atmosphere Four distinct layers of the atmosphere emerge from identifiable temperature characteristics with height.
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 2
Characteristics of Radiation Energy radiated by substances occurs over a wide range of wavelengths.
The Solar Constant
The Causes of Earth s Seasons Earth s Revolution and Rotation
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 3
Energy Transfer Processes Surface Atmosphere Radiation Exchange Water vapor and CO 2 are the primary absorbers of longwave radiation (greenhouse gases). The range of wavelengths, 8-15 μm, matches those radiated with greatest intensity by the Earth s surface. This range of wavelengths not absorbed is called the atmospheric window. Atmospheric window
Energy Transfer Processes Conduction As the surface warms, a temperature gradient develops in the upper few centimeters of the ground. Temperatures are greater at the surface than below. Surface warming also causes a temperature gradient within a very thin (a few millimeters) sliver of adjacent air called the laminar boundary layer.
Energy Transfer Processes Convection The temperature gradients in the laminar boundary layer induce energy transfer upward through convection. This occurs any time the surface temperature exceeds the air temperature, typically occurring in the middle of the day. At night, the surface cools more rapidly that air and energy is transferred downward. Convection can be generated by two processes in fluids. Free Convection Mixing related to buoyancy, warmer, less dense fluids rise Forced Convection Initiated by eddies and other disruptions to smooth, uniform flow
Energy Transfer Processes Free Convection Forced Convection
The Global Energy Budget
Energy Transfer Processes Net Radiation and Global Temperature Earth s radiation balance is a function of an incoming and outgoing radiation equilibrium. Balances occur on an annual global scale and diurnally over local spatial scales. (1-α) I = σ T 4 α albedo I solar constant / 4 T = [(1-α)I/σ] -4 T = -18 C
Energy Transfer Processes
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 4
The Equation of State Pressure, temperature, and density are related to one another and their relationship can be described through the equation of state (ideal gas law). The equation of state results in the following: p = ρ R T p ρ R Pressure Density Gas constant At constant temperatures, an increase in air density will cause pressure to increase. Under constant density, an increase in temperature will also cause an increase in pressure.
The Distribution of Pressure Pressure Gradients The pressure gradients provide the movement of air commonly known as wind. The strength of the pressure gradient force determines the horizontal wind speed. Horizontal Pressure Gradients Typically, small gradients exist across large areas. Concentrated weather features, such as hurricanes and tornadoes, display larger pressure gradients across small areas. Vertical Pressure Gradients Vertical pressure gradients are greater than extreme examples of horizontal pressure gradients as pressure always decreases with altitude.
The Distribution of Pressure Hydrostatic Equilibrium Gravity balances strong vertical pressure gradients to create hydrostatic equilibrium. Local imbalances create various up- and downdrafts p/ z = -ρg
Forces Affecting the Speed and Direction of the Wind The Coriolis Force Objects in the atmosphere are influenced by Earth s rotation. Overall, the result is a deflection of moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. F c = 2Ωsin(φ)v Force/mass (acceleration) Ω φ v Earth s rotation rate Latitude velocity
Forces Affecting the Speed and Direction of the Wind The Coriolis Force
Anticyclones, Cyclones, Troughs, and Ridges Cyclones
Anticyclones, Cyclones, Troughs, and Ridges Anticyclones
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 5
Water Vapor and Liquid Water Evaporation and Condensation
Indices of Water Vapor Content Vapor Pressure Saturation vapor pressure is the vapor pressure of the atmosphere when it is saturated. The movement of water vapor molecules exerts vapor pressure on surfaces.
Indices of Water Vapor Content Vapor Pressure Saturation vapor pressure is temperature dependent. At low temperatures the saturation vapor pressure increases slowly, but it increases rapidly at higher temperatures. It is not a linear increase. Nonlinear increase in saturation vapor pressure with increase in temperature.
Processes That Cause Saturation Air can become saturated in three ways: The addition of water vapor Mixing cold air with warm air Moist air by cooling the air to dew point
Factors Affecting Saturation and Condensation Effect of Curvature Larger drops have less curvature than smaller ones.
Factors Affecting Saturation and Condensation Effect of Solution Small droplets require higher RHs to remain liquid.
Factors Affecting Saturation Ice Nuclei Atmospheric water does not normally freeze at 0 C. Supercooled water refers to water having a temperature below the melting point of ice but nonetheless existing in a liquid state. Ice crystal formation requires ice nuclei, a rare temperaturedependent substance similar in shape to ice (six-sided). Examples: clay, ice fragments, bacteria, etc. Ice nuclei become active at temperatures below -4 C Between -10 and -30 C, saturation may lead to ice crystals, supercooled drops, or both. Below -30 C, clouds are composed solely of ice crystals. At or below -40 C spontaneous nucleation, the direct deposition of ice with no nuclei present, occurs.
Cooling the Air to the Dew or Frost Point Diabatic Processes Diabatic process involves the addition or removal of energy. Example: Air passing over a cool surface loses energy through conduction.
Cooling the Air to the Dew or Frost Point Adiabatic Processes Cloud formation typically involves temperature changes with no exchange of energy (adiabatic process), according to the first law of thermodynamics. Rising air expands through an increasingly less dense atmosphere, causing a decrease in internal energy and a corresponding temperature decrease. Parcels expand and cool at the dry adiabatic lapse rate (DALR), 1 C/100 m. Parcels may eventually reach the lifting condensation level, the height at which saturation occurs. Parcels then cool at the saturated adiabatic lapse rate (SALR), ~0.6 C/100.
Cooling the Air to the Dew or Frost Point Adiabatic Processes Dry adiabatic cooling.
Cooling the Air to the Dew or Frost Point The environmental (ambient) lapse rate (ELR) refers to an overall decrease in air temperature with height. This rate, which changes from place to place, stems from the fact that air located farther from surface heating is typically cooler than that nearer the surface. A comparison of adiabatic and environmental cooling rates.
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 6
Mechanisms That Lift Air Orographic uplift: Occurs when a mass of air is deflected over or around a terrain, usually a hill or a mountain. This upward movement of air results in adiabatic cooling. This promotes the development of clouds and precipitation. Rain shadow: Air compresses as it descends down the terrain and results in little to no precipitation.
Mechanisms That Lift Air Frontal lifting: Occurs when two air masses converge at the front. This can occur when cold air advances toward warm air (cold front) or when warm air advances toward cold air (warm front). Clouds develop as a result of these two situations. Cold front example Warm front example
Mechanisms That Lift Air Convergence: Occurs when there is a horizontal movement of air into a region. When air converges along the Earth's surface, it is forced to rise since it cannot go downward.
Mechanisms That Lift Air Localized convection: Occurs when differential heating at the surface causes air to lift. The air expands and cools as it lifts, causing cloud development.
Static Stability & Environmental Lapse Rate Absolutely unstable: This occurs when a parcel of air is lifted and it continues to move upward regardless of saturation. If the environmental lapse rate (ELR) exceeds the dry adiabatic lapse rate (DALR), the air is absolutely unstable.
Static Stability & Environmental Lapse Rate Absolutely stable: This occurs when a parcel of air returns to its original location after being displaced. If the environmental lapse rate (ELR) is less than the saturated adiabatic lapse rate (SALR), the air is absolutely stable.
Static Stability & Environmental Lapse Rate Conditionally unstable: This occurs when the environmental lapse rate (ELR) is between the dry adiabatic lapse rate (DALR) and the saturated adiabatic lapse rate (SALR). An air parcel become saturated at the lifting condensation level (LCL) and it will become buoyant if lifted to a critical altitude called the level of free convection (LFC).
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 7
Growth of Cloud Droplets Introduction
Growth of Cloud Droplets Growth by Condensation Condensation nuclei form most cloud drops but after all the available condensation nuclei have attracted water, any further condensation can only occur on existing droplets. With so many droplets competing for a limited amount of water, none can grow very large by condensation. Two other processes are responsible for further droplet growth.
Growth of Cloud Droplets Growth in Warm Clouds Condensation nuclei form most cloud drops but after all the available condensation nuclei have attracted water, any further condensation can only occur on existing droplets. Collision coalescence causes precipitation of warm clouds. Collision coalescence begins with large droplets, called collector drops, which have high terminal velocities. As the collector drops fall, they overtake smaller droplets in its path and provides the opportunity for collisions and coalescence.
Growth of Cloud Droplets Growth in Cold and Cool Clouds Cold clouds have temperatures below 0 C and consist of ice crystals. Cool clouds have temperatures above 0 C in the lower range and subfreezing conditions in the higher range. Clouds may be composed of liquid water, supercooled water, and/or ice. The coexistence of ice and supercooled water is critical to the creation of cool cloud precipitation the Bergeron Process.
Growth of Cloud Droplets Growth in Cold and Cool Clouds By deposition of vapor
Growth of Cloud Droplets Growth in Cold and Cool Clouds Riming occurs when liquid water freezes onto ice crystals producing rapid growth. Aggregation occurs when the joining of multiple ice crystals through the bonding of surface water builds ice crystals to the point of overcoming updrafts. Collision combined with riming and aggregation allows the formation of precipitation within 1/2 hour of initial formation.
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 8
Single-Cell and Three-Cell Models
Semipermanent Pressure Cells
Semipermanent Pressure Cells
Major Wind Systems Monsoons
Major Wind Systems Foehn, Chinook, and Santa Ana Winds Foehn winds flow down the side of mountain slopes. Air undergoes compressional warming. They are initiated when midlatitude cyclones pass to the southwest of the Alps. Chinooks are similar winds on the eastern side of the Rocky Mountains and form when low pressure systems occur east of the mountains. Both Foehn and Chinook winds are most common in winter. Santa Ana winds occur in California during the transitional seasons, especially autumn, when high pressure is located to the east. The Santa Ana winds often contribute to the spread of wildfires.
Major Wind Systems Sea and Land Breezes
Major Wind Systems Valley and Mountain Breezes
Ocean Atmosphere Interactions: ENSO A O O A Normal / LaNina situation El Nino situation partly reversed
Ocean Atmosphere Interactions: ENSO
Ocean Atmosphere Interactions: ENSO
Ocean Atmosphere Interactions: ENSO
Ocean Atmosphere Interactions: NAO NAO + NAO -
Ocean Atmosphere Interactions: NAO North Atlantic Oscillation The NAO is in a positive phase when the pressure gradient is greater than normal and negative when it is less than normal.
Ocean Atmosphere Interactions: NAO NAO+ NAO- Based on pressure difference Azores - Reykjavik
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 9
Air Masses and Their Source Regions Introduction Air masses contain uniform temperature and humidity characteristics. They affect vast areas. Fronts are boundaries between different air masses. Fronts are spatially limited and usually linked to midlatitude cyclones.
Air Masses and Their Source Regions Source Regions
Air Mass Formation Continental Polar (cp) and Continental Arctic (ca) Air Masses
Fronts Midlatitude Cyclone
Fronts Cold Fronts A cold front is a mass of cold air advancing toward warm air. Typically associated with heavy precipitation, rain, or snow, combined with rapid temperature drops.
Fronts Warm Fronts
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 14
Atmospheric Pollutants Introduction
Atmospheric Pollutants Sulfur Compounds Sulfur compounds can occur as gaseous or aerosol forms. Natural sources: steam vents, volcanic eruptions, sea spray. Anthropogenic sources: burning sulfur containing fossil fuels (particularly coal and oil) and ore smelting. Sulfur dioxide (SO 2 ) is a respiratory irritant. Forms sulfate aerosols that contributes to acid fog and acid rain.
Atmospheric Pollutants Photochemical Smog Ozone, NO 2, formaldehyde, and other gases combine with solar radiation to form Los Angeles-type photochemical smog. Ozone causes respiratory and heart problems. High levels of ozone result in environmental degradation.
Loss agricultural production due to ozone Tropospheric ozone: Crops Department of Geosciences
Atmospheric Conditions and Air Pollution Effect of Atmospheric Stability Inversions can trap pollutants near the Earth s surface.
Chapter Lectures Understanding Weather and Climate Seventh Edition Frode Stordal University of Oslo Redina L. Herman Western Illinois University Chapter 15
The Köppen System
The Köppen System A Tropical. Climates in which the average temperature for all months is greater than 18 C. Almost entirely confined to the region between the equator and the tropics of Cancer and Capricorn. B Dry. Potential evaporation exceeds precipitation. C Mild Midlatitude. The coldest month of the year has an average temperature higher than 3 C (or 0 C) but below 18 C. Summers can be hot. D Severe Midlatitude. Winters have at least occasional snow cover, with the coldest month having a mean temperature below 3 C (or 0 C). Summers are typically mild. E Polar. All months have mean temperatures below 10 C.