Aerological diagrams

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Aerological diagrams

• Radiosonde (or rawinsonde) data
• Maps
• Vertical profiles

Instrument contains Hygristor, thermistor,
aneroid barometer, and radio transmittor At the
ground, a highly directional radio direction
finding antenna is used to obtain the wind speed
and direction at various levels in the atmosphere
by tracking the radiosonde and determining the
azimuth and elevation angles.
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Aerological diagrams

• Hydrostatic balance
• Ideal gas law
• Hypsometric equation

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Aerological diagrams different types
emagram
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Stuve
pressure
temperature
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Stuve
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Skew T log p
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Fig 1d. Elements of a tephigram. First, the 5
lines are shown separately, and then they are
combined in the lower-right image.
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tephi
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Psychrometric chart
RH 100 e/es 100 r/rs mixing ratio r
mass of water vapor
mass of air r 622 e/p g/kg
e
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• LCL (lifting condensation level)
• Applications
• Determine the height of the base of cumulus
  clouds, given surface observations of T and Td
• Determine the cloud base temperature

HLCL
ground
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potential temperature
wet-bulb potential temperature
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equivalent potential temperature
saturated equivalent potential temperature
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Wet bulb energy balance LE H LE 6 u
esat(Tw)-e H 4 u T-Tw (Regnault balance)
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Applications
1. Layer thickness (between po and p)
Dz
Dz 100 DT
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2. Precipitable water
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3. Chinook (Fohn) effect
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east
west
Cascade Mountains
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4. subsidence
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5. Turbulent mixing, mixed layer (stratus), MCL
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Oakland
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Conserved or not conserved?
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equilibrium level
severe
benign
LFC
no convection
convective inhibition
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stability
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Local vs non-local stability
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Conditional vs absolute stability
Case II
qe
d
lt 0
dz
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Absolutely stable
Conditionally unstable
Absolutely unstable
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Typical wet-season tropical sounding
qe
d
lt 0
Conditional instability
dz
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Latent instability
WLR wet-bulb lapse rate
deep convection source layer
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Potential instability
or
Potential instability
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Lifting a potentially unstable layer
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Stability indices
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Significant level indices

• TP Tropopause level (mb)
• THCK 1000-500 mb thickness layer-mean
  temperature
• WB0 Wet bulb zero, Tw 0C ideally 7-9,000ft
  MSL, yet well below the FL
• PWAT Precipitable water (mm) the higher the
  better
• LCL Lifting condensation level (mb, from surface
  data) the lower the better
• TOTL Total totals index T 850 Td 850 - 2T 500
  (C) the higher the better, thunderstorms
  probable when TOTLgt50
• Cross totals CTOT Td850 - T500 vertical totals
  VTOT T850 - T500
• KINX K index T 850 Td 850 -T 500 -(T-Td)700
  (C) the higher the better
• SWET Sweat index or severe weather threat - the
  higher the better, for severe storms, SWgt300
• SWET 12Td850 20(TOTL-49) 2U850 U500
  125(0.2sinf)
• where f wind direction 500 - wind direction 850
  
• U is expressed in kts and TOTL-49
  is set to 0 if TOTLlt49
• MLTH and MLMR mean mixed layer (lowest 500 m)
  potential temp and mixing ratio

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PARCEL indices
Lifted index uses Actual sfc temp or Estimated
max sfc temp or Mean mixed-layer temp
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Showalter index
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PARCEL indices

• LIFT Lifted index (C, using surface data or 100
  mb layer above surface) must be negative LI
  T500 T parcel,near-sfc lowest 500 mb is often
  used
• LFTV lifted index, but Tv is used.
• SHOW Showalter index (C, as LI but starts from
  850mb) must be negativeSHOW T500 T
  parcel,850
• CAPE Convective available potential energy -
  should be over 500J/kg
• CAPV CAPE using Tv
• CINS Convective inhibition (external energy) -
  ideally 100-300 J/kg
• CINV CIN using Tv
• CAP Cap strength (C) Tenv -Tparcel _at_LCL - should
  be lt5C
• LFC Level free convection (LFCT and LFCT) (mb) -
  should be close to the LCL
• EQL Equilibrium level or level of neutral
  buoyancy (EQLT and EQLV)(mb) - should be high
• MPL Maximum parcel buoyancy level (mb) - level
  where buoyancy (Tp-Tenv) is maximum

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Wind parameters

• STM Estimated storm motion (knts) from
  0-20,000ft AGL layer, spd 75 of mean, dir 30 deg
  veer (to the right) from mean wind.
• HEL Storm relative helicity 0-10,000ft AG (total
  value)
• SHR Positive shear magnitude 0-3000m AG (sum of
  veering shear values)
• SRDS Storm relative directional shear 0-3000m AG
  (directional difference of storm relative winds)
• EHI Energy helicity index (prop to positive
  helicity CAPE)
• BRN Bulk Richardson number 500-6000m AG (BRN
  CAPE/.5BSHR2)
• BSHR Bulk shear value (magnitude of shear over
  layer), shear calculated between 1000-500 mb or
  500 m 6000 m AGL

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possible mid-term questions

• Some stability parameters, such as lifted index
  and CAPE, can be calculated in terms of the
  actual temperature T or virtual temperature Tv.
• Which one is more representative of underlying
  physical processes? Explain.
• Assuming surface values T32C, Td22C,
  T500-7C, calculate Tv at the surface, and the
  lifted index LI based on both T and Tv.
• Using a given sounding on a tephigram,
  graphically determine, for an air parcel at 850
  mb, the following Tw , r, rs, e, es, RH, q, qw,
  qe, qe,
• For the same sounding, determine the following
• SHOW
• TTOT
• PWAT (use finite difference technique described
  in course handout)
• CAPE

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LIFT-7 K CAPE1974 J/kg CIN-24 J/kg LCL 900
mb LFL 836 mb
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