David Larys Cold Tracer Code

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David Larys Cold Tracer Code
Overview of the Cold Tracer Introduce a new
tracer (Cold Tracer) that varies between 0 and 1
(non-dimensional).
Cold Tracer Production Cold tracer is produced
when temperature falls below the NAT formation
threshold temperature. Production does not
depend on sunlight or on how far the air
temperature is below the NAT threshold
temperature, but is restricted to latitudes
poleward of 40 degrees. Production time scale is
set to 4 hours, but production slows down as the
Cold Tracer approaches the value 1. Production
(1-x)/(4 hours) if T lt Tnat
Cold Tracer Loss Cold tracer is lost in
sunlight. The loss rate does not depend on the
solar zenith angle, only the presence of sunlight
is needed. Loss -x/(10 days) Southern
Hemisphere if in sunlight Loss -x/(5 days)
Northern Hemisphere if in sunlight
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David Larys Cold Tracer Code
Cold Tracer Equation Cold tracer rate of change
is given by the Production Loss dx/dt
(1-x)/(4 hours) x/(5 or 10 days) If conditions
are right for production or loss.
Ozone Loss The cold tracer acts to destroy
ozone, but only if in sunlight. Once again, the
exact solar zenith angle is not considered, only
if the location is in any sunlight Ozone loss
-x O3 / (20 days)

• Whats Needed
• NAT Threshold Temperature to turn on Cold
  Tracer Production
• Solar Zenith Angle to turn on Cold Tracer and
  Ozone Loss

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David Larys Cold Tracer Code

• Nat Threshold Temperature (2 Methods)
• Formula based on Pressure only (old method).
  Function fit for NAT PSC formation temperature as
  a function of pressure based on typical
  stratospheric values of water and nitric acid.
• Table Lookup based on Latitude, Pressure, and
  Month (new method). Table of NAT PSC formation
  temperatures values based on a water and nitric
  acid climatology using data from 1991 to 1998.
  The nitric acid observations used were taken from
  UARS MLS, UARS CLAES, ATMOS, CRISTA, and ILAS.
  The water observations used were taken from UARS
  MLS, UARS MLS UTH, UARS HALOE, MOZAIC, and ATMOS.

Table Description 12 Months Latitudes 32
latitudes from 85 to 85 degrees. Pressures 24
pressure from 1000 to 0.5 hPa.
Note Current Lary code is set up for 3D
interpolation, but at present there is no time
interpolation. Month is just an integer (1-12).
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David Larys Cold Tracer Code
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David Larys Cold Tracer Code
Nat Temperature Climatology
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David Larys Cold Tracer Code
Nat Temperature Climatology
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David Larys Cold Tracer Code
Solar Zenith Angle Larys code requires day of
year, local solar time in hours, and latitude.
In addition, altitude in kilometers is required
for calculation of the maximum solar zenith angle
(a function fit) for daylight determination.

• Calculation
• Calculate solar zenith angle (day of year, local
  time, latitude)
• Calculate maximum solar zenith angle (altitude)
• If (solar zenith angle) is less than (maximum
  solar zenith angle) then location is in daylight.

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David Larys Cold Tracer Code
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David Larys Cold Tracer Code
NOGAPS ISSUES Larys code is complete and runs on
Linux workstations and laptops using intel
fortran compiler. However, it is based on
processing single points and might slow down
NOGAPS Inputs X current state of cold
tracer. A Altitude in km. P
Pressure in mb. T Temperature in
Kelvin. Time Local solar time in
hours. Nday Integer day of the year. IM
Integer month of the year. Geolat Geographic
latitude in degrees.
Outputs dX current time derivative of
X. zk rate of ozone loss term (-zkXO3)
Usage CALL COLDTRACER(x,dx,zk,a,p,t,nday,im,ti
me,geolat)
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David Larys Cold Tracer Code

• NOGAPS ISSUES (cont)
• The Lary cold tracer equation should be simple to
  code into NOGAPS directly
• Similar to existing chemistry.
• Incorporate his lookup table in a format similar
  to NOGAPS ozone and water vapor tables and use
  the NOGAPS interpolation procedure.
• Locate (or calculate) a variable that determines
  daylight at each grid point.

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NOGAPS Cold Tracer

• Some Components of the Lary Cold Tracer are now
  in NOGAPS and have been tested.
• Added new subroutine ct_chem.f ? calculated cold
  tracer production and loss, and updates cold
  tracer field. Also, calculates an ozone loss
  rate coefficient.
• Added new subroutine tpsc.f ? inputs 3D pressure
  fields (hPa), outputs 3D nat formation
  temperature field, tnat (K).
• Added new subroutine calls to diabat.f, similar
  to other chemistry calls. Added new logical
  parameter to diabat.f arguments.
• Changed call to diabat.f in spctrl.f to reflect
  the extra logical argument for using the cold
  tracer

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NOGAPS Cold Tracer
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NOGAPS Cold Tracer
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NOGAPS Cold Tracer
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NOGAPS Cold Tracer
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NOGAPS Cold Tracer
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NOGAPS Cold Tracer

• Still to do
• Couple ozone loss to cold tracer.
• Add climatological nat temperatures.
• Add cold tracer initialization similar to ozone
  initialization.
• Add 40 degree latitude cut-off for cold tracer
  production.
• Add high altitude sunlight.