# Presentation: 500770

## Chapter 3

***Energy Balance and Temperature***

## Atmospheric gases, particulates, and droplets all reduce the

- intensity of solar radiation (**insolation**) by **absorption**,
- a process in which radiation is captured by a molecule.
- It is important to note that absorption represents an
- energy transfer to the absorber.
- This transfer has two effects:
- the absorber gains energy and warms, while the
- amount of energy delivered to the surface is reduced.

## The reflection of energy is a process whereby radiation 

- making contact with some material is simply redirected
- away from the surface without being absorbed.
- The percentage of visible light reflected by an object
- or substance is called its **albedo**. When light strikes
- a mirror, it is reflected back as a beam of equal intensity,
- in a manner known as **specular reflection**.
- When a beam is reflected from an object as a
- larger number of weaker rays traveling in different
- directions, it is called **diffuse reflection**, or **scattering**.

## In addition to large solid surfaces, gas molecules, particulates, and small droplets scatter radiation.

- Although much is scattered back to space,
- much is also redirected forward to the surface.
- The scattered energy reaching Earth’s surface
- is thus **diffuse radiation**, which is in contrast to
- unscattered **direct radiation**.

## Scattering agents smaller than about one-tenth the 

- Scattering agents smaller than about one-tenth the
- wavelength of incoming radiation disperse radiation
- through **Rayleigh scattering**, which is particularly
- effective for those colors with the shortest wavelengths.
- Thus, blue light is more effectively scattered by
- air molecules than is longer-wavelength red light.

## Microscopic aerosol particles are considerably larger

- than air molecules and scatter sunlight by a process
- known as **Mie scattering**, which does not have nearly
- the tendency to scatter shorter wavelength radiation
- that Rayleigh scattering does. Mie scattering causes
- sunrises and sunsets to be redder than they would due
- to Rayleigh scattering alone, so episodes of heavy
- air pollution often result in spectacular sunsets.

## The sky appears blue because gases and particles in the atmosphere scatter some of the incoming solar radiation in all directions. Air molecules scatter shorter wavelengths most effectively. Thus, we perceive blue light, the shortest wavelength of the visible portion of the spectrum.

## Sunrises and sunsets appear red because sunlight travels a longer path

- through the atmosphere. This causes a high amount of scattering to remove
- shorter wavelengths from the incoming beam radiation. The result is sunlight
- consisting almost entirely of longer (e.g., red) wavelengths.

## The water droplets in clouds are considerably larger than

- suspended particulates reflecting all wavelengths of
- incoming radiation about equally, which is why clouds
- appear white or gray. Because of the absence of
- preference for any particular wavelength, scattering
- by clouds is sometimes called **nonselective scattering**.

## What happens to the incoming solar radiation?

***What happens to the incoming solar radiation?***

- Incoming solar radiation available is subject to a number of processes as it passes through the atmosphere.

## What happens to the incoming solar radiation?

**Reflection by clouds****19%**

***What happens to the incoming solar radiation?***

- About 19% is reflected by clouds.

## What happens to the incoming solar radiation?

- About 45% is absorbed by the surface of earth.

**Absorption****by surface****45%**

**Reflection by clouds****19%**

## What happens to the incoming solar radiation?

**Reflection by clouds****19%**

**Absorption****by surface****45%**

**Absorption by atmosphere****25%**

***What happens to the incoming solar radiation?***

- About 25% is absorbed by the atmosphere.

## What happens to the incoming solar radiation?

**Reflection by clouds****19%**

**Absorption****by surface****45%**

**Absorption by atmosphere****25%**

**Reflection by ground ****5%**

***What happens to the incoming solar radiation?***

- About 5% is reflected by the ground.

## What happens to the incoming solar radiation?

**Reflection by clouds****19%**

**Scattering by atmosphere****6%**

**Absorption****by surface****45%**

**Absorption by atmosphere ****25%**

**Reflection by ground ****5%**

***What happens to the incoming solar radiation?***

- About 6% is scattered by the atmosphere

## In Summary: What happens to the incoming solar radiation?

**Reflection by clouds****19%**

**Scattering by atmosphere****6%**

**Absorption****by surface****45%**

**Absorption****by atmosphere ****25%**

**Reflection by ground ****5%**

***In Summary:****** What happens to the incoming solar radiation?***

**19% + 45% + 25% + 5% + 6% = 100%**

## Incoming solar radiation available is subject to a number of processes as it passes through the atmosphere. The clouds and gases of the atmosphere reflect 19 and 6 units, respectively, of insolation back to

- space. The atmosphere absorbs another 25 units. Only half of the insolation available at the top of the atmosphere actually reaches
- the surface, of which another 5 units are reflected back to space.
- The net solar radiation absorbed by the surface is 45 units.

## The difference between absorbed and emitted longwave

- radiation is referred to as the **net longwave radiation**.
- Shortwave and longwave radiation are not
- separate entities as far as the heating of the atmosphere
- and surface are concerned. When either is absorbed, the
- absorber is warmed. It is therefore natural to combine
- longwave and shortwave into **net allwave radiation**,
- or simply **net radiation**, defined as the difference between
- absorbed and emitted radiation, or equivalently,
- the net energy gained or lost by radiation.

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

**Surface**

**Atmosphere**

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- SWabsorption**= 45 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- Outgoing radiation**= 100 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- SWabsorption**= 45 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- Outgoing radiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- SWabsorption**= 45 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- Outgoing radiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

- LW lost to space **= 70 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- SWabsorption**= 45 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

- LW lost to space**= 54 + 16 units****= 70 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- Net LW loss**= 54 units**

- SWabsorption**= 45 units**

- Net LW loss**= 16 units**

- Outgoing radiation**= 100 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- Net radiation foratmosphere**= 25-54 units****= -29 units**

- Net LW loss**= 54 units**

- SWabsorption**= 45 units**

- Outgoing radiation**= 100 units**

- LW lost to space= 4 + 66 units**= 70 units**

- Net LW loss**= 16 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

- LW lost to space= 4 + 66 units**= 70 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- Net radiation foratmosphere**= 25-54 units****= -29 units**

- Net LW loss**= 54 units**

- Net radiation foratmosphere**= 45-16 units****= 29 units**

- SWabsorption**= 45 units**

- Net LW loss**= 16 units**

- Outgoing radiation**= 100 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## In Summary:  What is net radiation?How does the atmosphere and the earth’s surface effect it?

- Top of atmosphere

- Input of SWradiation**= 100 units**

- SW reflection byatmosphere and surface**= 30 units**

- LW lost to space= 4 + 66 units**= 70 units**

**Surface**

**Atmosphere**

- SWabsorption**= 25 units**

- Net radiation foratmosphere**= 25-54 units****= -29 units**

- Net LW loss**= 54 units**

- Net radiation foratmosphere**= 45-16 units****= 29 units**

- SWabsorption**= 45 units**

- Net LW loss**= 16 units**

- Outgoing radiation**= 100 units**

- Net radiation is the end result of the absorption of insolation and the absorption and radiation of longwave radiation. The surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***In Summary:******  What is net radiation?******How does the atmosphere and the earth’s surface effect it?***

## Net radiation is the end result of the absorption of insolation and the 

- absorption and radiation of longwave radiation. The surface has a net
- radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

## Convection is a heat transfer mechanism involving the mixing of a fluid. 

- In free convection, local heating can cause a parcel of air to rise
- and be replaced by adjacent air.

## Forced convection (also called mechanical turbulence) occurs when

- a fluid breaks into disorganized swirling motions as it undergoes a
- large-scale flow. Air is forced to mix vertically because of its
- low viscosity and the deflection of wind by surface features.

## When energy is added to a substance, an increase in 

- temperature occurs that we physically sense
- (**sensible heat**).
- The magnitude of temperature increase is related to
- two factors, the first of which is **specific heat**,
- defined as the amount of energy needed to produce
- a given temperature change per unit mass of the substance.
- The temperature increase resulting from a surplus of energy
- receipt also depends on the *mass *of a substance.

## Latent heat is the energy required to change the

- phase of a substance (solid, liquid, or gas).
- In meteorology we are concerned with the heat
- involved in the phase changes of water.
- In the case of melting ice, the energy is called
- the *latent heat of fusion*. For the change of phase
- from liquid to gas, the energy is called
- the *latent heat of evaporation*.

## For an object in thermal equilibrium:  Energy Gain = Energy Loss.    The atmosphere has a deficit of -29 units.

- Top of atmosphere

- SW radiationabsorbed**25 units**

**Surface**

**Atmosphere**

***For an object in thermal equilibrium:  Energy Gain = Energy Loss.    ******The atmosphere has a deficit of -29 units.***

- Net LWradiation**-54 units**

- Net radiation= -29 units

## For an object in thermal equilibrium:  Energy Gain = Energy Loss.    The Earth’s surface has a net radiation gain of 29 units. 

- Top of atmosphere

- SW radiationabsorbed**25 units**

**Surface**

**Atmosphere**

- Net LWradiation**-54 units**

- SW radiationabsorbed**45 units**

- Net LWradiation**-16 units**

- Net radiation= -29 units

- Net radiation= 29 units

- Replace this text with relevant material... Net radiation is the end result of the absorption of insolation of SW radiation absorbed at the surface for 45 units and the net LW loss of 16 units. So the surface has a net radiation surplus of 29 units, while the atmosphere has a deficit of 29 units.

***For an object in thermal equilibrium:  Energy Gain = Energy Loss.    ******The Earth’s surface has a net radiation gain of 29 units. ***

## Convection “exists” to ensure the equilibrium energy balance.Behold!  “To the rescue” the Convective Fluxes, sensible and latent heat 

- Top of atmosphere

- SW radiationabsorbed**25 units**

**Surface**

**Atmosphere**

- Net LWradiation**-54 units**

- Sensible heat by convection**8 units**

- Latent heatby convection**21 units**

- Net radiation= -29 units

- Convection heat gain= 29 units

- SW radiationabsorbed**45 units**

- Net LWradiation**-16 units**

- Net radiation= 29 units

- Convection moves sensible and latent heat energy.  In the atmosphere 8 units from sensible heat due to convection and 21 units of energy from latent heat due to convection.

***Convection “exists” to ensure the equilibrium energy balance.******Behold!  “To the rescue” the Convective Fluxes, sensible and latent heat ***

## Therefore,  Convection “exists” to ensure the equilibrium energy balance.“To the rescue” -- the Convective Fluxes, sensible and latent heat.

- Top of atmosphere

- SW radiationabsorbed**25 units**

**Surface**

**Atmosphere**

- Net LWradiation**-54 units**

- Sensible heat by convection**8 units**

- Latent heatby convection**21 units**

- SW radiationabsorbed**45 units**

- Latent heat by convection-**21 units**

- Net LWradiation**-16 units**

- Sensible heat by convection-**8 units**

- Net radiation= -29 units

- Convection heat gain= 29 units

- Net radiation= 29 units

- Convection heat loss= -29 units

- Therefore,  ***Convection “exists” to ensure the equilibrium energy balance.******“To the rescue” -- the Convective Fluxes, sensible and latent heat***.

***For an object in thermal equilibrium:  Energy Gain = Energy Loss.    ******The surface has a deficit of -29 units due to sensible and latent heat for convection (evaporation and heat transfer due to convection).***

## Recall energy entering and leaving through the top of the atmosphere:100 units incoming = -25 reflected to space, -5 units reflected to space by the earths surface (30% Albedo) -4 units emitted from Earth’s surface to space and -66 units emitted to space form the atmosphere, therefore... 

- Top of atmosphere

- SW radiationabsorbed**25 units**

**Surface**

**Atmosphere**

- Net LWradiation**-54 units**

- Sensible heat by convection**8 units**

- Latent heatby convection**21 units**

- SW radiationabsorbed**45 units**

- Latent heat by convection-**21 units**

- Net LWradiation**-16 units**

- Sensible heat by convection-**8 units**

- Net radiation= -29 units

- Convection heat gain= 29 units

- Net radiation= -29 units

- Convection heat loss= -29 units

- 0 total – No net Gain or Loss.  So the planet is not warming up or cooling off from one  year to the next!  The Earth is in thermal equilibrium and so is the surface and atmosphere.  A natural balance is struck by the earth-atmosphere system.  For any amount of Solar incoming Insoluion, even if it were different from what we have now, athere would be some (but new) equilibrium point.

***Recall energy entering and leaving through the top of the atmosphere:******100 units incoming = -25 reflected to space, -5 units reflected to space by the earths surface (30% Albedo) -4 units emitted from Earth’s surface to space and -66 units emitted to space form the atmosphere, therefore... ***

## Both the surface and atmosphere lose exactly as much energy as they gain. The surface has a surplus of 29 units of net radiation, which is offset by the transfer of sensible and latent heat to the atmosphere.

- The atmosphere offsets its 29 units of radiation deficit by the
- receipt of sensible and latent heat from the surface.

## The interactions that warm the atmosphere are often 

- collectively referred to as the **greenhouse effect**,
- but the analogy to a greenhouse is not strictly accurate.
- The greenhouse gases of the atmosphere do not impede
- the transfer of latent and sensible heat. Thus, it
- would be more accurate if the term “greenhouse effect”
- were replaced by “atmospheric effect.”
- The greenhouse effect keeps Earth
- warmer by absorbing most of the longwave radiation
- emitted by the surface, thereby warming the
- lower atmosphere, which in turn emits radiation downward.

## One of the most immediate and obvious outcomes of radiation gain or loss 

- is a change in the air temperature. The map depicts differences between
- mean temperatures in January and July through the use of **isotherms**,
- which are lines that connect points of equal temperature.

## Certain geographical factors combine to influence temperature patterns across 

- the globe. These factors include latitude, altitude, atmospheric circulation patterns,
- local conditions, continentality, (the effect of an inland location that favors greater
- temperature extremes) and ocean current characteristics along coastal locations.

## The daily mean is defined as the average of the 

- maximum and minimum temperature for a day.
- The **daily temperature range** is obtained by
- subtracting the minimum temperature from the maximum.
- The **monthly mean temperature** is found by
- summing the daily means and dividing by
- the number of days in the month.
- The **annual mean temperature **is obtained by
- summing the monthly means for a year and dividing by 12.
- The **annual range** is obtained as the difference
- between the highest and lowest monthly mean temperatures.

## If low temperatures are accompanied by windy conditions,

- a person’s body loses heat much more rapidly than it would
- under calm conditions due to an increase in sensible heat loss.
- It is common for weather reports to state both the actual
- temperature and how cold that temperature actually feels,
- the **wind chill temperature index**.

## Thermodynamic diagrams (such as the Stuve above) depict the vertical profiles of temperature and humidity with height above the surface enabling forecasters to determine the height and thickness of existing clouds and the ease with which the air can be mixed vertically. The data on the charts are obtained from radiosondes that are carried aloft by weather balloons 

- twice a day at weather stations across the globe.

## The next chapter examines

**The next chapter examines**
**atmospheric pressure and wind.**