Thermodynamic diagrams allow for analysis of temperature, moisture, pressure and wind in the atmosphere. These vertical measurements, or soundings, are taken by sending up a weather balloon with a light-weight instrument equipped with a radio transmitter that sends measured data back to a receiver on the earth. This is called a rawinsonde. A radiosonde, often used synonymously, consists of the measuring devices while the rawindsonde refers to the addition of radio tracking capabilities to determine wind speeds and directions as well. The rawinsonde network worldwide has more than 900 radiosonde sites, the contiguous United States contributing over 90 launch sites. The rawinsonde observations, or raobs, are taken twice daily at 00:00 and 12:00 UTC (Universal Time Clock) or equivalently, GMT (Greenwich Mean Time), 365 days per year. (For an excellent description of rawinsondes, see
http://www.aos.wisc.edu/~hopkins/wx-inst/wxi-raob.htm).
By plotting the soundings of temperature and dew point temperature,
one can investigate how adiabatic processes will determine instability
and be used to help predict severe weather. It is known that
certain profiles indicate certain weather to be expected.

This lab will familiarize you with the pseudo-adiabatic
diagram and introduce you to important concepts of thunderstorm
development. You will learn about stability indices and be able
to determine conditions favorable for the outbreak of severe weather. |

The psuedo-adiabatic diagram at first looks like a very confusing
chart full of lines running in many different directions. With
further study, however, you will find that it is indeed a *very
confusing chart full of lines running in many different directions!*
However, once we take apart the diagram and look at each line
individually, we will soon make sense of these lines. When you
get past the part of searching for the right line, the information
is easily attainable.

The Vertical Axis: The vertical
axis marks pressure levels. It starts with 1050 mb and decreases
upward along the axis. These *isobars* run horizontally
straight across the page. The spacing reflects the fact that
pressure decreases exponentially with respect to height.

The Horizontal Axis: The hori-zontal
axis marks temperatures in degrees Celsius, increasing to the
right. These *iso-therms* run straight up and down

Sloping Solid Lines at **~**45°:
These lines are lines of constant **potential temperature, ,
or ***isentropes*. These are equiva-lently know as *dry
adiabats*. They are labeled every 10°K (equivalent to
10°C) starting from 273°K, or 0°C at 1000 mb.
If air is lifted dry adiabatically, the temperature will conserve
potential temperature, but its actual temperature will cool according
to what is measured along this line. Remember, air will cool
10C for every kilometer it is lifted adiabatically.

Small Dotted Lines at a Small Angle from the Horizontal: These lines represent heights, in kilometers, above the surface assuming standard sea level pressure of 1013.25 mb. These lines slope gently up to the left.

Sloping Solid Lines at a Small Angle from
the Vertical: These lines indicate lines of constant **saturation**
**mixing ratio, w _{s}**, indicating the maximum amount
of water vapor the air can hold, given in grams of vapor per kilogram
of dry air. They can also be considered to be lines of constant
mixing ratio,

Sloping Dashed Lines:** **These
lines are *pseudo*, or *wet adiabats*, also known as
lines of **equivalent potential temperature, _{e}._{
}**Following these lines is identical to lifting
a parcel wet adiabatically. At lower temperatures, less vapor
is condensing releasing less latent heat; hence the line's slope
approaches that of the dry adiabat.

**
THERMODYNAMIC DIAGRAMS (TO SHOW WORK) FOUND HERE
**

:To find the temperature
of a parcelTo find the temperature of a parcel lifted dry adiabatically, find the initial point (given temperature and pressure) and travel upwards parallel to the nearest dry adiabat. Since the wet adiabats diverge with decreasing pressure, when lifting a parcel wet adiabatically it is important to stay equidistant between two wet adiabats. Do not go parallel to just one! |

**1. WHAT IS THE TEMPERATURE OF A PARCEL LIFTED DRY ADIABATICALLY**

*a) from 30°C @1000mb to 700mb? T_{p}=*

b) from 15°C @1000mb to 600mb? T_{p}=

c) from -10°C @900mb to 650mb? T_{p}=

**2.WHAT IS THE TEMPERATURE OF A PARCEL LIFTED WET ADIABATICALLY**

**T _{p}=
**b) from 15°C @1000mb to 600mb?

**3. WHAT IS THE TEMPERATURE OF A PARCEL STARTING FROM 32°C@1000
**

*a) lifted dry adiabatically to 850 mb and wet adiabatically
to 400mb? T_{p}=*

b) lifted dry adiabatically to 650 mb and wet adiabatically to 300mb? T_{p}=

:
To find w or w_{s}The mixing ratio (w) is determined by locating
the value of the constant mixing ratio line at the given pressure
and dew point. To find the saturation mixing ratio
(w (that
is, what the mixing ratio would be if the parcel were saturated),
locate the value of the constant mixing ratio line at the given
pressure and _{s})temperature. For both processes, interpolate
(approximate the value between to known values by the fractional
distance between each one) if necessary. Mixing ratio is a function
of vapor content, while saturation mixing ratio is a function
of temperature, so. |

**4. IF , WHAT IS THE RELATIVE HUMIDITY
OF A PARCEL AT THE SURFACE ( ASSUME TO BE 1000MB UNLESS OTHERWISE
INDICATED)?**

*a) T= 24°C Td= 8°C w= w_{s}= RH=*

b) T= 5°C Td=-2°C w= w_{s}= RH=

c) T=30°C Td=10°C p=850mb w= w_{s}= RH=

Potential temperature () is defined as the temperature
air would be if brought dry adiabatically to 1000 mb. It allows
one to determine the amount of internal energy air has. |

**5. WHAT IS THE POTENTIAL TEMPERATURE OF AIR **

*a) at 500 mb with a temperature of -11°C?
b) at 850 mb with a temperature of 2°C ?
c) Which is potentially warmer? T=8°C @ 500mb or T=21°C
@ 1000mb? Explain your answer. How would you evaluate
for question 5c?
*

thickness of a layer is the vertical distance
between two levels of constant pressure. In usage it is the vertical
distance between to isobaric surfaces. Since warm air is less
dense than cold air (at the same atmospheric pressure), to travel
through a layer of air that is warmer will require a greater vertical
distance to drop a given amount of pressure.Think about it:
Does it make sense for the isoheights to slant upward toward
the left? |

**6. WHAT IS THE 1000-500 MB THICKNESS OF A LAYER WHOSE AVERAGE
TEMPERATURE IS **

*a) 25°C ? Z=*

b) 0°C ? Z=

c) What is the relationship between thickness and temperature?

To find the LCL: The LCL, or Lifting Condensation Level,
is the level at which dynamically lifted air reaches saturation.
To find the LCL, locate the intersection of the constant mixing
ratio line through the surface dew point with the dry adiabat
through the surface temperature. |

**7. FIND THE LCL IF THE SURFACE TEMPERATURE AND DEW POINT ARE**

*a) 25°C and 20°C, respectively. LCL= mb*

b) 18°C and -1°C, respectively. LCL= mb

c) 25°C and 20°C, respectively @ 900mb. LCL= mb

To find e:
equivalent potential temperature (is defined to be the potential energy of the air if
all the latent heat has been used to heat the parcel. Remember,
"latent" means "hidden". Therefore, if all
the water vapor is condensed, the latent heat of condensation
will be released into the parcel. To find _{e})
_{e}, lift
a parcel dry adiabatically until it reaches the LCL and wet adiabatically
after that until all the vapor is condensed. Since all the vapor
is removed and no latent heat is being released, the wet adiabat
will be parallel to the dry adiabat. When that occurs, follow
a dry adiabat back to 1000 mb. There is a simpler method, however.
Once the LCL is reached, the wet adiabat that is followed is
the equivalent potential temperature. Hence, wet adiabats are
also known as lines of constant equivalent potential temperature.
_{e} is conserved (constant) in all adiabatic processes. |

**8. WHAT IS THE EQUIVALENT POTENTIAL TEMPERATURE OF 7a, 7b AND
7c FROM QUESTION #7 ABOVE?**

*a) _{e}=
b) _{e}=
c) _{e}=*

To find the CCL and the
CT:
CCL, or Convection Condensation Level,
is the height to which a parcel of air, if heated sufficiently
from below, will rise adiabatically until condensation begins.
In the most common case, this is the height of the base of cumulus
clouds which are produced by thermally-induced turbulent eddies
(convection solely from surface heating). The convective temperature
is the surface temperature that must be reached to start the formation
of convective clouds by solar heating of the surface layer. To
find the CCL, find the intersection of the constant mixing ratio
line through the surface dew point with the observed temperature
sounding, as measured by a radiosonde. To find the convective
temperature, find the CCL and follow a dry adiabat down to the
surface pressure isobar. |

To find the LFC and the
EL:
LFC, or Level of Free Convection, is
the level at which a lifted parcel of air becomes unstable. This
would indicate the beginning of the region where the air will
now experience positive buoyant energy (PBE). The EL,
or equilibrium level, is where the air again becomes stable, and
experiences negative buoyant energy (NBE). To find the
LFC, lift a parcel dry adiabatically until the LCL and wet adiabatically
thereafter. When the parcel becomes warmer than the environmental
temperature, the point of intersection is the LFC. The EL is
found at the point of intersection of the parcel trace and the
observed sounding where the parcel becomes colder than the environment.
Whenever the parcel trace and the observed sounding intersect,
it is either the LFC or the EL. |

Part Two
Given the following sounding, plot on a thermodynamic
diagram and answer the following questions. Draw the temperature
sounding in red, the dew point sounding in green, and the parcel's
profile in blue. Show all work. Answers to the essays (6,7&8) must be typed. |

**THERMODYNAMIC DIAGRAMS (TO SHOW WORK) FOUND HERE
**

Pressure | Temperature | Dew Point | Wind |

**1. WHAT IS THE RELATIVE HUMIDITY AT THE SURFACE AND AT 700
MB?**

**2. LABEL THE LCL. FIND THE CCL AND CONVECTIVE TEMPERATURE.
LABEL THE LFC AND EL. COLOR IN REGIONS OF POSITIVE AND NEGATIVE
BUOYANT ENERGY.**

**3. WHAT IS THE POTENTIAL TEMPERATURE OF THE ENVIRONMENT AT
500 MB?**

**4. DETERMINE WHETHER THE 800-700 MB LAYER IS CONVECTIVELY UNSTABLE.
WHY? GIVE THE VALUES OF E** **AT THE TOP AND THE BOTTOM OF
THE LAYER.**

**5. DETERMINE THE SI, LI, K-INDEX, TOTAL TOTALS INDEX, AND THE
SWEAT INDEX FOR THE SOUNDING. SHOW ALL WORK.**

**6. HOW DOES THE PBE AFFECT THE INTENSITY OF THUNDERSTORMS,
IF THEY FORM? HOW DOES THIS AFFECT THE POTENTIAL FOR SEVERE WEATHER?**

**7. DISCUSS THE SIGNIFICANCE OF THE CAP. WHAT IS THE EFFECT
OF NBE?**

**8. BASED ON YOUR ANSWERS TO THE ABOVE, WHAT IS YOUR FORECAST?
EXPLAIN HOW EACH STABILITY PARAMETER IS USED TO JUSTIFY
YOUR FORECAST. EXPLAIN THE PHYSICAL REASONING BEHIND EACH INDEX.
WHAT ARE UNCERTAINTIES IN YOUR FORECAST?**