Cloud Botany with DALES#

Setup#

Cloud Botany is a library of idealised large-eddy simulations forced by and initialised with combinations of simplified vertical profiles. Each profile is parameterised by variables which aim to make the ensemble span a range of conditions corresponding to the variability observed over the EUREC4A region during the boreal winter of 2019/2020. The following table lists these varied parameters and their ranges:

Table 1 Variables governing Cloud Botany simulations#

variable

min

max

unit

description

thls

297.5

299.5

K

sea surface potential temperature

u0

-5

-15

m/s

surface wind

qt0

0.0135

0.015

kg/kg

mixed-layer total specific humidity

qt_lambda

1200

2500

m

humidity scale height

thl_Gamma

4.5

5.5

K/m

lapse rate of thl

wpamp

-0.5

0.18

cm/s

Amplitude of subsidence first mode

dudz

-0.0044

0.0044

1/s

Wind shear1

Availability of simulation output#

Cloud Botany contains simulations at a variety of grid resolutions and domain sizes, and each set of simulations comes with its own output. Most of this output is hosted and made available through DKRZ’s Swiftbrowser, and can be accessed through the eurec4a-intake catalog.

import eurec4a
cat = eurec4a.get_intake_catalog()
botany_cat = cat.simulations.DALES.botany

An overview over what is currently available through this structure is listed under Simulations, and is repeated below for convenience:

dx100m
   nx1536
      profiles
      timeseries
      2D
      3D
      cross_xy
      radiation
      parameters

Output description#

Parameters#

A combination of grid resolution and domain size, e.g. botany_cat.dx100.nx1536, contains its own ensemble of cases. For now, only the combination dx100 and nx1536 can be accessed through the eurec4a-intake catalog, as this is the only configuration in which the full ensemble has been simulated. Other grid configurations might be added at a later stage.

To inspect and use the ensemble, start by loading its parameters:

import pandas as pd
varied_parameters = ['member','thls', 'u0', 'qt0', 'qt_lambda', 'thl_Gamma', 'wpamp', 'dudz', 'location']
parameters = cat.simulations.DALES.botany.dx100m.nx1536.parameters.read()
df_parameters = pd.DataFrame.from_records(parameters)[varied_parameters]
df_parameters
member thls u0 qt0 qt_lambda thl_Gamma wpamp dudz location
0 1 298.5 -10.0 0.01425 1850.0 5.0 -0.00085 0.0022 center
1 2 297.5 -15.0 0.01350 1200.0 4.5 -0.00350 0.0022 corner
2 3 297.5 -15.0 0.01350 1200.0 4.5 0.00180 0.0022 corner
3 4 297.5 -15.0 0.01350 1200.0 5.5 -0.00350 0.0022 corner
4 5 297.5 -15.0 0.01350 1200.0 5.5 0.00180 0.0022 corner
... ... ... ... ... ... ... ... ... ...
98 99 298.5 -10.0 0.01425 2200.0 5.0 -0.00085 0.0022 sweep qt_lambda
99 100 298.5 -10.0 0.01425 2500.0 5.0 -0.00085 0.0022 sweep qt_lambda
100 101 298.5 -10.0 0.01425 3000.0 5.0 -0.00085 0.0022 sweep qt_lambda
101 102 298.5 -10.0 0.01350 1850.0 5.0 -0.00085 0.0022 sweep qt0
102 103 298.5 -10.0 0.01500 1850.0 5.0 -0.00085 0.0022 sweep qt0

103 rows × 9 columns

parameters contains the value of the variables in Table 1, as they vary for each member of the ensemble. The ensemble may be thought of a hypercube in the six-dimensional space spanned by [thls, u0, qt0, qt_lambda, thl_Gamma, wpamp]. The location column indicates where any member fits in this space:

  • The hypercube center represents the middle of the range between the minimum and maximum value of each variable

  • The hypercube corners are constructed by evaluating all parameter combinations at their minimum and maximum (resulting in the next \(2^6 = 64\) simulations).

  • Simulations belonging to a sweep have a single variable vary between its minimum and maximum, while keeping all other variables constant at their center value.

Simulation output#

The actual output from the simulations is stored in the other data sets in the tree listing above. Such data sets can be loaded according to the following example:

import xarray as xr

ds_profiles = botany_cat.dx100m.nx1536['profiles'].to_dask()
ds_profiles
<xarray.Dataset>
Dimensions:    (member: 103, time: 720, zt: 175, zm: 175)
Coordinates:
  * member     (member) int32 1 2 3 4 5 6 7 8 9 ... 96 97 98 99 100 101 102 103
  * time       (time) datetime64[ns] 2020-02-01T00:05:00 ... 2020-02-03T12:00:00
  * zm         (zm) float32 0.0 15.0 30.0 45.3 ... 6.772e+03 6.854e+03 6.938e+03
  * zt         (zt) float32 7.5 22.5 37.65 ... 6.813e+03 6.896e+03 6.98e+03
Data variables: (12/102)
    cfrac      (member, time, zt) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    cs         (member, time, zt) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    dvrmn      (member, time, zt) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    lwd        (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    lwdca      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    lwu        (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    ...         ...
    wthlr      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    wthls      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    wthlt      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    wthvr      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    wthvs      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
    wthvt      (member, time, zm) float32 dask.array<chunksize=(32, 256, 175), meta=np.ndarray>
Attributes:
    Author:   
    Source:   DALES 4.2 git: v4.3-108-gca69cb
    history:  Created on 20220520 at 213340.423
    title:    profiles.001.nc

Briefly summmarised, the individual data sets contain:

Name

What is it?

Dimensions

Output frequency

profiles

Vertical profiles of dynamic, thermodynamic, radiation, and microphysical slab statistics

[member, time, z]

5 min

timeseries

Surface and bulk statistics

[member, time]

1 min

2D

Vertically integrated and surface diagnostics

[member, time, x, y]

5 min

3D

Full field dumps of prognostic variables and liquid water specific humidity

[member, time, x, y, z]

1 hour

cross_xy

Extracted horizontal cross-sections of prognostic variables and liquid water specific humidity

[member, time, x, y, z]

5 min

radiation

Radiation model output at surface and top of atmosphere

[member, time, x, y]

1 hour

Examples and visualisations#

Here are three short examples of accessing and plotting Botany output.

import matplotlib.pyplot as plt
import numpy as np
from pandas.plotting import register_matplotlib_converters
register_matplotlib_converters()
plt.style.use(["./mplstyle/book", "./mplstyle/wide"])

An overview over the initial profiles of Botany#

# Profiles of vertical velocity, from variations in first-mode amplitude
def expsinw(z, ampwp, w0=0.0045, Hw=2500, Hwp=5300):
    '''
    Vertical profiles for imposed, large-scale subsidence velocity
    '''
    w_0 = -w0*(1-np.exp(-z/Hw))
    w_1 = ampwp*np.sin(2.*np.pi/Hwp*z)
    w_1[z>Hwp] = 0.
    return w_0 + w_1

wpamp = np.unique(pd.DataFrame.from_records(parameters)[['wpamp']].to_numpy())

ds_initial = ds_profiles.isel(time=0).sel(zt=slice(0, 5000))

kws = {'y'          : 'zt',
       'add_legend' : False,
       'linewidth'  : 0.5,
       'c'          : 'k'}

fig, axs = plt.subplots(ncols=4, sharey=True, figsize=(10,5))

ds_initial['thl'].plot.line(ax=axs[0], **kws)
ds_initial['qt'].plot.line(ax=axs[1], **kws)
ds_initial['u'].plot.line(ax=axs[2], **kws)

for i, wpampi in enumerate(wpamp):
    axs[3].plot(expsinw(ds_initial['zt'], wpampi), ds_initial['zt'], linewidth=0.5, c='k')
axs[3].set_xlabel('w [m/s]')
    
for i in range(axs.size):
    axs[i].set_title('')
    if i > 0:
        axs[i].set_ylabel('')

plt.show()
_images/botany_dales_13_0.png

Variability of cloud fraction with surface wind#

One way to study how simulation output varies with the parameters is to add a variable of interest to one’s loaded xarray.Dataset:

from cycler import cycler

fig = plt.figure()
ax = plt.gca()
ax.set_prop_cycle(cycler(color=plt.cm.cividis(np.linspace(0, 1, 7))))

# Add u0 to the profiles output
ds_u = ds_profiles.assign(df_parameters[['member','u0']].set_index('member').to_xarray())

# Plot mean cloud fraction profiles grouped by surface wind over the last 100 time steps of all simulations
ds_u[['cfrac','u0']].isel(time=slice(-100,-1)).sel(zt = slice(0,4000)).mean(dim='time').groupby('u0').mean()['cfrac'].plot.line(ax=ax, y='zt')
plt.show()
_images/botany_dales_15_0.png

Example visualisation of water vapour, clouds, rain and cold pools#

For the last time (60 hours after initialisation) for the “center” of the hypercube of simulations (member 1), we might visualise the vertically integrated total specific humidity (the total water path twp), the cloud-top height (cldtop), the rain-water path (rwp) and an indicator for the extent of cold pools (the local mixed-layer height, hmix), as follows:

cb_kw = {'fraction' : 0.05}

ds_2D = botany_cat.dx100m.nx1536['2D'].to_dask().sel(member=1).isel(time=-1)
ds_2D
fig, axs = plt.subplots(ncols=3, sharex=True, sharey=True, figsize=(14.5,4))

# Total water path
ds_2D['twp'].plot(ax=axs[0], vmin=33 ,vmax=40, cbar_kwargs=cb_kw)

# Cloud-top height and rain water path
ds_2D['cldtop'].plot(ax=axs[1],cmap='Greys_r', vmin=500, vmax=2000, cbar_kwargs=cb_kw)
rwp_masked = xr.where(ds_2D['rwp'] > 1e-5, ds_2D['rwp'], np.nan)
rwp_masked.plot(ax=axs[1], cmap='Blues', vmin=0, vmax=0.2, alpha=0.8, cbar_kwargs=cb_kw)

# Mixed-layer height
ds_2D['hmix'].plot(ax=axs[2],cmap='RdBu_r', vmin=50, vmax=1000, cbar_kwargs=cb_kw)

plt.show()
_images/botany_dales_17_0.png

Visualisations page#

In addition to the data sets described above, a more thorough set of visualisations indicative simulation output is available. This visualisation set contains simple overviews and movies for each simulation in the library. They can be quite useful for attaining a basic idea of what each simulation produced without having to load the data. These visualisations are hosted on a personal server, so in contrast to the data hosted on DKRZ, we warn that its maintenance and availability may be patchy.


1

Wind shear is only varied as a sweep over eight simulations and is otherwise constant. As such, it is not to be regarded as part of the core variables that are varied in Cloud Botany.