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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GEOS-Chem archives tropopause pressure at two different places in the
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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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timestepping algorithm.
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#The ND67 diagnostic is archived directly after reading the tropopause pressure from disk. No further processing is done to the tropopause pressure before saving to ND67. '''''Therefore, ND67 should be directly comparable to the tropopause pressure as stored in the “raw” GEOS met data files.'''''<br><br>
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      !==============================================================
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#On each dynamic timestep (typically 15 or 30 mins), the tropopause pressure poleward of 60N and 60S is capped at 200 hPa. This ensures that SMVGEAR or KPP chemistry will not be performed at unrealistically high altitudes in the polar regions. The ND55 diagnostic is archived at the end of each dynamic timestep. '''''Therefore, ND55 represents the tropopause pressure (including the polar cap) that is used to diagnose where the GEOS–Chem tropopause occurs at each dynamic timestep.'''''
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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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== References ==
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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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