Difference between revisions of "Dynamic tropopause"

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'''''NOTE: Page under construction!'''''
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On this page we describe the implementation of the dynamic tropopause in GEOS-Chem.
  
 
== Overview ==
 
== Overview ==
  
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== Diagnostics ==
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GEOS-Chem is primarily a tropospheric model of atmospheric chemistry and composition.  Its [[NOx-Ox-HC-aerosol]] (aka "full chemistry") simulation employs a detailed chemistry mechanism is used in the troposphere, while a much simpler mechanism (based on simple loss rates by OH and [[Photolysis mechanism|photolysis]]) is invoked in the stratosphere.  Therefore, a robust definition of the tropopause is required.
  
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There are
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The location of the tropopause is computed at each dynamic timestep of a GEOS-Chem simulation, according to the following criteria (in routine <tt>GeosCore/calc_met_mod.F90</tt>
  
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== References ==
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      !==============================================================
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      ! Define the various query fields of State_Met
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      !
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      ! NOTE: For convenience, we set State_Met%InPbl in routine
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      ! COMPUTE_PBL_HEIGHT (in module GeosCore/pbl_mix_mod.F).
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      !
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      ! NOTE: For certain queries we test against level numbers,
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      ! (e.g. LLSTRAT, LLCHEM), but should really test level
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      ! pressure edges, so that this algorithm will be robust if
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      ! we switch to different met fields or interface with
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      ! different ESMs.  Add this at a later time. (bmy, 1/8/18)
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      !==============================================================
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      ! Is this grid box within the troposphere?
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      State_Met%InTroposphere(I,J,L) = &
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            ( State_Met%PEDGE(I,J,L) > State_Met%TROPP(I,J) )
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      ! Is this grid box within the stratosphere or mesosphere?
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      State_Met%InStratMeso(I,J,L) = &
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            ( .not. State_Met%InTroposphere(I,J,L) )
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      ! Is this grid box within the stratosphere (but not mesosphere)?
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      State_Met%InStratosphere(I,J,L) = &
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            ( L <= State_Grid%MaxStratLev .and. State_Met%InStratMeso(I,J,L) )
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      ! Is grid box (I,J,L) within the chemistry grid?
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      IF ( L > State_Grid%MaxChemLev ) THEN
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          ! Chemistry is not done higher than the mesopause
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          State_Met%InChemGrid(I,J,L) = .FALSE.
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      ELSE
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          ! Chemistry grid goes up to stratopause
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          State_Met%InChemGrid(I,J,L) = ( L <= State_Grid%MaxChemLev )
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      ENDIF
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without regard for the tropopause location.
  
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--[[User:Bmy|Bob Y.]] 13:56, 13 September 2010 (EDT)
  
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== Polar cap ==
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== Previous issues that are now resolved ==
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=== Buggy implementation in v7-04-12 ===
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Note that the implementation of the variable tropopause is buggy in versions prior to [[GEOS-Chem_versions_under_development#v7-04-12|GEOS-Chem v7-04-12]].  If you are using versions prior to v7-04-12, you should turn the variable tropopause OFF.
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=== Polar cap ===
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Jennifer Logan (see correspondence below) suggested that we should cap the variable tropopause at 200hPa in near-polar regions (90-60S and 60-90N), to avoid the problem with anomalously high tropopause heights at high latitudes.  This fix was standardized in [[GEOS-Chem v7-04-13]].
 
Jennifer Logan (see correspondence below) suggested that we should cap the variable tropopause at 200hPa in near-polar regions (90-60S and 60-90N), to avoid the problem with anomalously high tropopause heights at high latitudes.  This fix was standardized in [[GEOS-Chem v7-04-13]].
  
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:'''''[mailto:jlogan@seas.harvard.edu Jennifer Logan] wrote:'''''
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Jennifer Logan wrote:
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<blockquote>After looking at the two papers I sent, I think we should restrict the tropopause at latitudes > 60 deg. to pressures greater than 200 mb (about 11 km).  From Fig. 3 in Seidel and Randel, there are tropopause (TP) heights as high as 13.5 km in the Antarctic (median height is ~9.8 km, 250 mb), but I don't think we want to be doing trop. chem there. The median TP pressure at ~80 N is ~300 mb, compared to ~250 mb at 70-85 S.  The extratropical TP heights are higher (lower pressure) in the SH than in the NH according to Fig. 3.</blockquote>
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<blockquote>This approach is also very easy to explain in a paper.</blockquote>
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<blockquote>Jennifer</blockquote>
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=== Problem reading GEOS-4 TROPP files ===
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'''''[mailto:davem@atmosp.physics.utoronto.ca Dave MacKenzie] wrote:'''''
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:We encountered an I/O Error 29 with file 69 when trying to run GEOS4 v8-01-01 with the variable tropopause turned on at 4x5 resolution.  When I investigated this problem further, I found that there was no code written to copy and unzip the <tt>YYYYMMDD.tropp.4x5.gz files</tt>.  Since I didn't see any mention of this online for v8-01-01 or newer versions, I thought I should bring it to your attention.
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:The <tt>*.tropp*</tt> files are accessed in <tt>i6_read_mod.f</tt> but there is only code included to use the data in those files and erase them from the <tt>TEMP</tt> directory.  No code was included to actually copy them into the <tt>TEMP</tt> directory and unzip them.  I wrote in a few lines of code and our problems disappeared.  After running the code for one day, it finished smoothly with no problems.  Then I tried running it for 2 years and it crashed after two months (I/O error 67 in file 72, input statement requires too much data).  I don't know if it's a related problem to the changes I made or something else, but I thought I'd bring this to your attention.  Thanks!
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'''''[mailto:yantosca@seas.harvard.edu Bob Yantosca] replied:'''''
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:Yes...the TROPP files for GEOS-4 were an afterthought.  We have always stored the GEOS-4 data as uncompressed, in order to avoid the problem.  That might be a good solution if you have the disk space.
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--[[User:Bmy|Bob Y.]] 16:44, 18 February 2009 (EST)
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<blockquote>
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After looking at the two papers I sent, I think we should restrict the tropopause at latitudes > 60 deg. to pressures greater than 200 mb (about 11 km).  From Fig. 3 in Seidel and Randel, there are tropopause (TP) heights as high as 13.5 km in the Antarctic (median height is ~9.8 km, 250 mb), but I don't think we want to be doing trop. chem there. The median TP pressure at ~80 N is ~300 mb, compared to ~250 mb at 70-85 S.  The extratropical TP heights are higher (lower pressure) in the SH than in the NH according to Fig. 3.
  
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== Outstanding issues ==
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This approach is also very easy to explain in a paper.
  
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--[[User:Bmy|Bob Y.]] 12:44, 13 September 2010 (EDT)
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Jennifer
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</blockquote>

Latest revision as of 14:40, 13 July 2023

On this page we describe the implementation of the dynamic tropopause in GEOS-Chem.

Overview

GEOS-Chem is primarily a tropospheric model of atmospheric chemistry and composition. Its NOx-Ox-HC-aerosol (aka "full chemistry") simulation employs a detailed chemistry mechanism is used in the troposphere, while a much simpler mechanism (based on simple loss rates by OH and photolysis) is invoked in the stratosphere. Therefore, a robust definition of the tropopause is required.

The location of the tropopause is computed at each dynamic timestep of a GEOS-Chem simulation, according to the following criteria (in routine GeosCore/calc_met_mod.F90 

      !==============================================================
      ! Define the various query fields of State_Met
      !
      ! NOTE: For convenience, we set State_Met%InPbl in routine
      ! COMPUTE_PBL_HEIGHT (in module GeosCore/pbl_mix_mod.F).
      !
      ! NOTE: For certain queries we test against level numbers,
      ! (e.g. LLSTRAT, LLCHEM), but should really test level
      ! pressure edges, so that this algorithm will be robust if
      ! we switch to different met fields or interface with
      ! different ESMs.  Add this at a later time. (bmy, 1/8/18)
      !==============================================================

      ! Is this grid box within the troposphere?
      State_Met%InTroposphere(I,J,L) = &
           ( State_Met%PEDGE(I,J,L) > State_Met%TROPP(I,J) )

      ! Is this grid box within the stratosphere or mesosphere?
      State_Met%InStratMeso(I,J,L) = &
           ( .not. State_Met%InTroposphere(I,J,L) )

      ! Is this grid box within the stratosphere (but not mesosphere)?
      State_Met%InStratosphere(I,J,L) = &
           ( L <= State_Grid%MaxStratLev .and. State_Met%InStratMeso(I,J,L) )

      ! Is grid box (I,J,L) within the chemistry grid?
      IF ( L > State_Grid%MaxChemLev ) THEN

         ! Chemistry is not done higher than the mesopause
         State_Met%InChemGrid(I,J,L) = .FALSE.

      ELSE

         ! Chemistry grid goes up to stratopause
         State_Met%InChemGrid(I,J,L) = ( L <= State_Grid%MaxChemLev )

      ENDIF

without regard for the tropopause location.

--Bob Y. 13:56, 13 September 2010 (EDT)

Polar cap

Jennifer Logan (see correspondence below) suggested that we should cap the variable tropopause at 200hPa in near-polar regions (90-60S and 60-90N), to avoid the problem with anomalously high tropopause heights at high latitudes. This fix was standardized in GEOS-Chem v7-04-13.

Jennifer Logan wrote:

After looking at the two papers I sent, I think we should restrict the tropopause at latitudes > 60 deg. to pressures greater than 200 mb (about 11 km). From Fig. 3 in Seidel and Randel, there are tropopause (TP) heights as high as 13.5 km in the Antarctic (median height is ~9.8 km, 250 mb), but I don't think we want to be doing trop. chem there. The median TP pressure at ~80 N is ~300 mb, compared to ~250 mb at 70-85 S. The extratropical TP heights are higher (lower pressure) in the SH than in the NH according to Fig. 3.

This approach is also very easy to explain in a paper.

Jennifer

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