Vertical Profiles Window

Vertical Profiles Window supplements the tools already available (Probe, Time-series, Cities, EPSgram) on ecCharts and elsewhere.  It provides information about the vertical structure of the forecast model atmosphere for any location (as selected by the Probe Tool) and any time (as selected by the Time Navigator).  Currently validity times are limited to  6 hour steps up to T+120.  

Fig8.1.8-1: To display Vertical Profile.

  1. From Charts menu, select All points based products.
  2. Select Medium Range and Point based products. Select Vertical Profiles icon.
  3. Select date/time of forecast base time and date/time of forecast valid time.
  4. Select location, either by name or by lat/long.

Vertical Profile display

A single display comprises the following elements:

Temperature, Dewpoint and Dewpoint Depression on (most) Model levels





Fig8.1.8-2: An example of ecCharts vertical profile output.


Fig8.1.8-3: Magnified portion of Fig8.1.8-2 showing the possible overlap between temperatures and dewpoints among the ENS members.  At some levels (here 860hPa taken for illustration) some ENS members forecast dew points are higher than the temperature forecast by other ENS members.  The dew point depression is 0C-20C, to enable the user to see moist environments in more detail.


The vertical profile uses every model level in the lower troposphere up to about 700mb, and every other level higher up than that is used to plot the vertical profiles.  Before the spread metrics (e.g. 25th and 75th percentiles) are computed the model levels from each ENS member are all set to correspond the same (ensemble mean) pressure values. 

Hodograph

Horizontal Winds on Pressure levels


Fig8.1.8-4: An example of ENS and HRES winds plotted as hodographs.  Depending on the case, these can be very informative (e.g. the consistency of significant shear among ENS members).  This example shows significant shear from SE'ly winds at low levels to SW'ly winds at mid-tropospheric levels to W'ly winds in the upper troposphere.

CAPE and CIN diagram

The CAPE and CIN diagram shows the distribution of the most unstable Convective Available Potential Energy (CAPE) for three different categories of Convective Inhibition (CIN) in box and whisker format.   

Fig8.1.8-5: An example of box and whisker plot of the distribution among ENS members of CIN and CAPE.

These diagrams indicate the variation among ENS members of the intensity of convection that may occur (CAPE) together with the likelihood of attaining the release of that convection (i.e. overcoming CIN).  Three arbitrary ranges of CIN are shown: CIN <50J/kg representing a fairly low energy requirement before release of convection,  CIN >200J/kg representing a more substantial energy requirement, and an intermediate value range of CIN.  The vertical scale shows the CAPE energy in J/kg if convection is released.  Box and whisker symbols have their normal meanings.  Black filled circles are shown where there are 5 or fewer ENS members where convection is released.  The numbers of ENS members within each CIN category are given at the top of each column.  The number of members without release of CAPE is shown in the top right hand corner (e.g. CAPE=0: 13 meaning 13 ENS members failed to identify any CAPE in the forecast ENS ascent).


It should be remembered that the CIN and CAPE values indicated are diagnostic.  The diagrams show the general state of the model atmosphere as forecast for that time.  CIN does not indicate whether convective instability will be released, but rather provides an indication of the potential for that release.  It is important the user to assesses the likelihood of CIN values being overcome during the following hours, either by diurnal heating, by dynamically induced uplift of the airmass, or by mechanical uplift caused by flow over mountains etc. 

In principle, CIN, the convective inhibition, can be computed from any model level.  In practice the temperature structure of the forecast atmosphere is scanned in the vertical, working out what CIN is for parcels rising from each level, and then the minimum of the values that correspond to levels in the lowest 350hPa of the atmosphere is stored in MARS (and used in ecCharts etc.).   Conceptually, CIN is always zero or a positive value.  However in practice where the parcel curve (from any of the levels tested) never even reaches the environment curve (i.e. it lies always to the left of it) then CIN is in effect infinite.  Infinite values of CIN is stored as a missing value indicator whenever the (minimum) CIN encountered exceeds a pre-defined very large threshold (e.g. in strong inversions).

CAPE is different in that it is bounded between 0 and some large, non-infinite, value that depends on atmospheric structure.  So CAPE is stored in a different manner that does not include missing values.

Example Vertical Profile Displays

Vertical Profile and ecCharts of CIN and CAPE

Fig8.1.8-6: Vertical profile at Mao (Mahon), Menorca, Spain  (arrowed) with HRES CIN and CAPE, all from ecCharts:  T+108 VT 18UTC 12 Aug 2020, DT 00UTC 8 Aug 2020. 

In Fig8.1.8-6:

In the Vertical Profile:

The spread of temperature and/or dew point temperatures could be due to differences among the ENS models in:

On the CAPE diagram:

In general, there is no apparent relation between CIN and CAPE:

In this example:

Other cases will of course have different characteristics.

Vertical Profile and ecChart of Probability of Convective Precipitation

Fig8.1.8-7: A forecast vertical profile for Premuda, Croatia T+90 VT 06UTC 18 Aug 2020, DT 00UTC 14 Aug 2020 . The corresponding ecChart shows the forecast probability for convective precipitation (same model runs).

In the case shown in Fig8.1.8-7 many ENS members suggest CIN can be fairly easily overcome (CIN <50J/kg)  releasing quite vigorous convection (large CAPE values - ENS control ~3500J/kg, HRES ~3000J/kg).   The probability of precipitation chart shows that <35% of ENS members are producing showers totalling >1mm in the period 00UTC to 06UTC.   Nevertheless the CIN/CAPE diagram suggests that quite active convection with heavier showers has been quite possible during the preceding 6hr period given sufficient energy input to overcome CIN - this might be dynamical or mechanical uplift. As this was night time it seems more likely that solar heating during the morning will overcome the CIN leading to active convective cells.


It is wise to consider both the probability of convective precipitation charts and the vertical profiles together rather than using either alone to assess the possibility of active convective cells.


Vertical Profile Sequence showing variation of CIN and CAPE through 24 hours

Fig8.1.8-8: Sequence of forecast vertical profiles for Brindisi, Italy illustrating the variation in CIN and consequent availability of CAPE through a full 24h diurnal cycle in which the structure of the atmosphere above the lowest layers remains largely unchanged. Here, for simplicity, CIN is defined as: low CIN<50J/kg, moderate 50J/kg<CIN<200J/kg, large CIN>200J/kg.

In Fig8.1.8-8:

Although this case does not definitively highlight active convection, the hodographs indicate some vertical shear through the model atmosphere which would be conducive to organised deep moist convection if large CAPE were available and were released.


Forecast vertical profiles in the vicinity of a mobile cold front

Fig8.1.8-9: The ENS forecast frontal zones from the cyclone database products (example) T+120hr VT:00UTC 22 Aug 2020, DT:00UTC 17 Aug 2020.  Inset shows magnified area around Denmark.  Animation of cyclone database products allows an assessment of the developing spread and changing intensity of frontal features.  


Fig8.1.8-10: An example of forecast vertical profiles in the vicinity of a mobile cold front crossing Denmark, T+120hr VT:00UTC 22 Aug 2020, DT:00UTC 17 Aug 2020.  There are a range of forecast positions of the front among the ENS solutions but HRES (thick solid) and ENS Control (thick dotted) both position the front approximately between Copenhagen and Odense.  The East/West section through this zone illustrates the differences in the structure of the model atmospheres, particularly in the spread of the ENS temperatures and dewpoints. The pale blue colouring approximately encloses the range of ENS positions for the front.

In Fig8.1.8-10 the airmasses to the east and west of the frontal zone have some well-marked identifying features:

The remaining vertical profiles illustrate the transition between the air masses through the frontal zone with characteristics of both evident to a greater or less extent depending upon the positioning of the front by each ENS member.

Some other interesting features can be identified; mostly the HRES and Control runs (single thick lines) are representative of the ensemble, but in some respects they are not - e.g. Control has anomalously warm low level air well ahead of the front (55N 15E).


The ECMWF front spaghetti plot (Fig8.1.8-9) indicates that:

When assessing the timing (and activity) during the passage of a front at a given location it is wise to examine:


Additional Sources of Information

(Note: In older material there may be references to issues that have subsequently been addressed)

Read more information onUsing ECMWF's new ensemble vertical profiles”.

See summer 2018 ECMWF Newsletter article (P39-44).

IFS model levels for: HRES, ENS (137). Note: every model level is used in the lower troposphere up to about 700mb, and only every other level higher up.