Bosveld, F.C.

Bruijn, C., de

Meijgaard, E., van

Steeneveld, G.J.

English

Wageningen Yield 

P1.1 THE QUALITY OF HORIZONTAL ADVECTIVE TENDENCIES IN ATMOSPHERIC MODELS 
FOR THE 3RD GABLS SCM INTERCOMPARISON CASE 
   
Fred C. Bosveld1*, Erik van Meijgaard1, Evert I. F. de Bruijn1 and Gert-Jan Steeneveld2 
 
1 Royal Netherlands Meteorological Institute, De Bilt, The Netherlands 
2 Wageningen University and Research centre, Wageningen, The Netherlands 
  
1. INTRODUCTION 
 
Advective tendencies in 3D atmospheric 
models are intimately coupled to the physical 
parameterization of the model. Although they 
represent genuine physical processes, it is not 
clear to what extent they correspond to the 
actual advective tendencies in the real 
atmosphere. 
 
The accuracy of calculated advective 
tendencies becomes important in the 
simulation of atmospheric profiles with single-
column models. (e.g. Bergot and Guedalia, 
1994; Teixeira and Miranda, 2001). In some 
experiments these models are driven with 
advection terms derived from the analysis of 
3D NWP models (Neggers 2008). The same 
issue also becomes important when 
interpreting column information from advanced 
meteorological profiling sites. In general, one 
would like to interpret the observed changes in 
the column parameters in terms of physical 
tendencies. This can only be done if we can 
correct, with a reasonable accuracy, for the 
effect of changes due to the advective 
tendencies. 
 
Over the years, improvements in the 
parameterization of atmospheric processes, 
increase in model resolution, and the 
assimilation of more detailed observations 
have led to a better representation of the state 
of the atmosphere. Bosveld et al. (2004) 
compared horizontal advective tendencies as 
given by the KNMI regional climate model 
(RACMO), with  tendencies derived from flux 
divergence observations from the Cabauw 200 
m tower in the Netherlands. With a grid cell 
size of 25 km a reasonable agreement during 
daytime convective conditions was found for 
two selected days, one with advection and one 
without advection. This grid cell size assured 
that one land grid cell was situated between 
the Cabauw grid cell and the North Sea, 
preventing a significant horizontal diffusion in 
the model. 
 
In this study we analyze advective tendencies 
for the GABLS 3rd stable boundary layer case 
(Baas et al, 2008). This case is the night from 
1 to 2 July 2006 at Cabauw.  During this night 
a small clear air disturbance passed over the 
Cabauw site resulting in changes in 
temperature, humidity and momentum that 
could not be related to local vertical physical 
processes. We intercompare three 3D 
atmospheric models (RACMO, HIRLAM and 
WRF) with respect to their advective 
tendencies and we compare the outcome of 
one of these models with the observed 
influence of advection on observations of 
Cabauw.  
 
 
Figure 1 Geostrophic wind speed and direction as 
simulated by RACMO. 
 
2. COMPARISON OF MODELS 
 
Three different 3D atmospheric models have 
been used to assess the advective tendencies 
for the GABLS3 case (20060701 12 – 
20060702 12 UTC). All these models are run in  
  
 
 
Figure 2 Horizontal dynamical tendencies of 
temperature. 
 
 
 
 
 
 
 
 
 
  
 
Figure 3. Horizontal dynamical tendencies of specific 
humidity. 
 
 
 
 
 
 
 
 
 
Figure 4. Horizontal dynamical tendencies of zonal wind (left panels) and meridional wind (right panels) for three models. 
 
hind cast mode. Firstly, RACMO with 
initialization and lateral boundaries taken from  
ECMWF analysis. RACMO employs HIRLAM 
dynamics and ECMWF physics. It is run in 25 
km horizontal resolution and 40 levels in the 
vertical. Secondly, HIRLAM which is also 
initialised and forced at the lateral boundaries 
by ECMWF analysis. It is run with 11 km 
resolution and 40 levels in the vertical. Both 
these models are hydrostatic. Thirdly, WRF 2.2 
with initialization and lateral boundaries from 
NCEP-NFL analysis. It is run in a nested mode 
advection terms are taken from the 10 km 
resolution domain. WRF is a non-hydrostatic 
model. For RACMO and HIRLAM simulations 
started at 20060701 00 UTC. For WRF a start 
time of 20060630 12 UTC was used to get rid 
of a deviation due to spin up.  
 
Horizontal dynamical tendencies are derived 
by applying the advective operator to the 
parameters of interest, here temperature, 
humidity and momentum. For the semi 
Lagrangian scheme of RACMO we also 
estimate the tendencies directly from the 
calculation of the dynamical equations. We 
have found the same results for the two 
methods. 
 
The passage of a clear air disturbance during 
the simulated night is well illustrated in figure 1 
which shows the geostrophic wind speed and 
direction. The geostrophic wind speed starts to 
increase at noon of the second day (which is 
after the case period), but the geostrophic wind 
directions shows a marked deviation during the 
night. 
 
Figure 2 shows horizontal dynamic tendencies 
the temperature for the three models. A distinct 
warm advection is observed in RACMO and 
HIRLAM, which reaches the surface at 
midnight. HIRLAM gives a stronger signal then 
RACMO. WRF however does not show this 
feature. 
 
Horizontal dynamical tendencies of specific 
humidity are displayed in figure 3. All three 
models show moisture advection during the 
first half of the night in the lowest part of the 
atmosphere. Details around midnight are 
different, with HIRLAM giving more small scale 
structures. 
 
Figure 4 shows horizontal dynamic tendencies 
of the zonal and meridional wind. As for 
temperature, RACMO and HIRLAM show the 
same features although the details and 
strength differ again. WRF shows only a weak 
signal. 
3. LOCAL OBSERVATIONS 
 
Observed tendencies at one location are 
typically the sum of physical and dynamical 
tendencies. Deriving information on advective 
tendencies from local observations is only 
possible when we have detailed information on 
the physical tendencies. In general this 
information is not available. However, during 
stable conditions the air layer above the 
turbulent stable boundary layer becomes 
decoupled from the surface making the 
physical tendencies in the vertical column 
relatively small. Here we use this feature to 
qualitatively assess whether the advective 
tendencies from the models are actually 
observed at Cabauw. For this we observations 
at the 200 m level which for this night is well 
above the turbulent boundary layer. 
 
We use a simple model in which the 200 m 
wind, temperature and specific humidity are 
initialized by the observed values at sunset 
and then integrated forward in time with the 
advective tendencies of RACMO for this 
height. For momentum the geostrophic wind 
and the Coriolis acceleration is taken into 
account. Geostrophic wind is taken from the 
network of automatic weather station in the 
Netherlands. We also applied this simple 
model with advective tendencies as they are, 
in the end, prescribed for the GABLS3 SCM 
case.  For wind we also applied the model with 
no advection. 
 
Figure 5 shows the observed and modelled 
temperature. A significant cooling is observed 
probably due to  turbulent transport towards 
the surface and radiative cooling. A small 
wiggle is observed with an amplitude of 1 K   
which is also observed in the RACMO run. A 
piece wise linear approximation of the racmo 
dynamical tendency is used for the case 
description. Figure 6 shows the specific 
humidity. A well defined deviation with 
amplitude of 1 g/kg is observed around 
midnight, which is reasonable represented by 
RACMO. The case is described with a bit 
larger amplitude in dynamical tendency. Figure 
7 shows a hodogram of the wind together with 
the observed geostrophic wind. Also shown is 
a model integration with RACMO advection 
and with no advection. Here we see that the 
effect of advection of momentum is quite 
complex due to interaction with the Coriolis 
force and the changing geostrophic wind. 
RACMO advection is not able to give a good 
representation of the observed 200 m wind. 
The dynamic tendency of the case is found by 
trial and error with this simple advective model.  
 
 
Figure 5. Temperature evolution at 200 m. 
Observations and when RACMO and CASE 
advection is applied on sunset temperature. 
 
 
 
 
Figure 6. Specific humidity evolution at 200 m. 
Observations and when RACMO and CASE 
advection is applied on sunset temperature. 
 
 
 
 
Figure 7. Horizontal wind evolution at 200 m. 
Observations and when RACMO and CASE 
advection is applied on sunset wind vector. Also 
shown is evolution when no advection is applied and 
shown is the geostrophic wind evolution. B indicates 
begin of time series (sunset) and E indicates end of 
time series (11 hours later). Timestep is 10 minutes. 
 
 
 
Figure 8. Zonal (U) and meridional (V) dynamical  
wind tendencies of RACMO and as described for the 
case. 
 
Figure 8 shows zonal and meridional 
dynamical tendencies of RACMO and of the 
case. Especially the meridional component 
differ substantially. 
 
4. DISCUSSION AND CONCLUSIONS 
 
Comparing advective tendencies from 3D 
models shows that two of them (RACMO and 
HIRLAM) give comparable results although 
details and magnitudes may differ. The third 
model (WRF) shows much weaker tendencies. 
This might be explained by the longer 
integration time needed to avoid spin-up 
problems in this model resulting in a less good 
forecast or diffusion of sharp transitions in the 
horizontal fields. 
 
No significant differences in advective 
tendencies have been found when comparing 
two versions of the same model (HIRLAM) with 
differing physical parameterizations, not shown 
here. This suggests that advective model 
tendencies for clear sky stable boundary layer 
conditions represent real world conditions. For 
more complex situations with for example 
clouds the dependency of dynamical 
tendencies on the actual parameterization 
might be much larger. 
 
By using local observation at heights where the 
atmospheric flow is decoupled from the surface 
we have been able to assess the influence of 
advective tendencies on wind, temperature 
and specific humidity and to compare these 
estimates from observations with model output. 
From this comparison the advective tendencies 
have been derived that are prescribed in the 
GABLS3 SCM intercomparison and evaluation 
case. 
 
For more information on this case see 
www.knmi.nl/samenw/gabls. 
 
5. REFERENCES 
 
Baas, P., F.C. Bosveld, and G.-J. Steeneveld 
(2008). GABLS 3rd case Cabauw case selection 
and description. 18th Symposium on Boundary 
Layer and Turbulence, 9-13th June 2008, 
Stockholm, Sweden. American Meteorological 
Society (8A.4). 
Bergot, T. and D. Guedahlia, 1994: Numerical 
Forecasting of Radiation Fog: Part I: Numerical 
Model and Sensitivity Tests, Mon. Wea. Rev., 
122, 1218-1230. 
 
Bosveld, F.C., E. van Meijgaard, E. Moors, and C. 
Werner (2004). Interpretation of eddy-
correlation flux observations at different levels 
along the Cabauw 200 m meteorological mast. 
16th AMS symposium on Boundary Layer and 
Turbulence, 9-13th Aug 2004, 2004, Portland 
(ME), USA, American Meteorological Society. 
 
Bosveld, F.C., E.I.F. de Bruijn and A.M.M. Holtslag 
(2008). Intercomparison of Single-Column 
Models for GABLS3: Preliminary results. 18th 
Symposium on Boundary Layer and 
Turbulence, 9-13th June 2008, Stockholm, 
Sweden. American Meteorological Society 
(8A.5). 
 
Neggers R. (2008). The KNMI Parameterization 
Testbed: Motivation, Configuration and 
Preliminary results 18th Symposium on 
Boundary Layer and Turbulence, 9-13th June 
2008, Stockholm, Sweden. American 
Meteorological Society (8A.7) 
  
Teixeira, J. and P.M.A. Miranda, 2001: Fog 
prediction at Lisbon Airport using a one-
dimensional boundary layer model, Meteorol. 
Appl., 8, 497-505. 
 
 
 


Intercomparison of Single-Column Models for GABLS3: Preliminary results.

Interpretation of eddycorrelation flux observations at different levels along the Cabauw 200 m meteorological mast.

Numerical Forecasting of Radiation Fog: Part I: Numerical Model and Sensitivity Tests,

The KNMI Parameterization Testbed: Motivation, Configuration and Preliminary results 18th

The quality of horizontal advective tendencies in atmospheric models for the 3rd GABLS SCM intercomparison case

Name not available

The quality of horizontal advective tendencies in atmospheric models for the 3rd GABLS SCM intercomparison case

Abstract

Similar works

Full text

Available Versions

Wageningen Yield

Name not available