Mesoscale environments related to
precipitation extremes and severe events in
convective situations over SESA, their
simulation with high resolution models.
Matilde Nicolini,
Yanina García Skabar and Paola Salio
CIMA-DCAO-CONICET-UBA-SMN
2ND MEETING OF IFAECI (UMI 3351) Buenos Aires. Argentina
April 2011
Current Objectives:
• investigate the mechanisms controlling deep
moist convection in the north-central domain of
Argentina and to focus on short range prediction
of these mechanisms.
• improve short range mesoscale numerical
prediction with emphasis in different forcings of
convection, from two different strategies: an
explicit deterministic prediction of convection
with high resolution and an ensemble forecast
that allows a probabilistic approach.
OUTLINE
 Diurnal cycle in convergence patterns in the
boundary layer east of the Andes and
convection
 Discussion of the BRAMS simulation of a flashflood convective event
 Discussion of the BRAMS forecast performance
and sensitivity experiments in a squall line event
 Present and Future work
Diurnal cycle in convergence patterns in the
boundary layer east of the Andes and convection
Purpose
To progress in the study of the mechanisms that control the
diurnal cycle of precipitation and convection in subtropical
latitudes east of the Andes during summer
Hypothesis
If nocturnal convergence in the boundary layer exists
over the broad valleys east of the Andes then it may be
efficient in triggering or intensifying deep moist convection that may have started earlier during the afternoon if moisture
is available and conditional instability prevails-.
Methodology:
SALLJEX was performed in Southeastern South America from November 15, 2002 to
February 15, 2003 to monitor, quantify and analyze the low-level circulation over this
region and its related precipitation. Enriched analyses were generated ingesting all
available data with a higher spatial and temporal resolution than that available for
the region, following a downscaling methodology, using Brazilian Regional
Atmospheric Modeling System (BRAMS, www.brams.cptec.inpe.br).
20 km
80 km
BRAMS was applied to obtain analysis
every three hours, with a horizontal
resolution of 80 km covering mostly
South America and an enhanced inner
domain with 20 km resolution for the
region encompassing Central and
Northern Argentina, southern Brazil,
Bolivia, Paraguay and Uruguay
To identify the convective systems and their life cycle IR brightness temperature data
was employed at half hourly intervals with a horizontal resolution of 4km over the
area between 10ºS-40ºS and 40ºW- 75ºW, data online at
http://lake.nascom.nasa.gov/).
The present study is organized around a two weeks long period (since January 24 up
to February 7/2003) during SALLJEX that followed a cold incursion and during which
different environmental conditions prevailed.
Questions:
¿Are the 20 km resolution enriched analyses with
SALLJEX data capable to reproduce a diurnal cycle of
convergence/divergence and rising/subsiding motions
at the top of the boundary layer, that may be related to
a northwestern mountains-central plain flow regime?
and
¿To which extent these circulations are sufficient by
themselves to support deep convection or else other
ABL circulation patterns as the east of the Andes lowlevel jet are more effective depending on the synoptic
situation?
The study period was characterized by two different main
synoptic conditions:
 January 24 to 30: persistent anticyclonic circulation
(intensified South Atlantic Convergence Zone, SACZ) and a
quasi-stationary front at the southern border of the domain.
Subsidence and diabatic warming in the subtropical
boundary layer favored relatively dry conditions over central
Argentina.
 January 31 to February 7: extreme heat wave with a weak
SACZ and the presence of an intense thermal low over
northwestern Argentina enhancing a northerly flow and
coherently the presence of the east of the Andes low-level
jet (SALLJ). Warm and moist horizontal advection
dominated over Argentina.
Anticyclonic situation
SALLJ dominated situation
During anticyclonic conditions
Average ABL conv/div in the area shows that mesoscale
zonal circulations (mountain/broad plain) dominate over
meridional circulations in the average total convergence
values at night and divergence dominates in the afternoon.
Moisture and/or zonal convergence are not enough to support
both nocturnal and daytime convection over the northern
plains. Southward (35S), convection is triggered in the
evening and intensified at night forced by a quasi-stationary
frontal zone (not shown in the figures).
During strong and shifted to the south SALLJ
Average ABL conv/div in the area shows that meridional
circulation (more efficient to advect moisture) dominates (over
zonal circulations) convergence values at night while zonal
circulation dominates the divergence in the afternoon over the
plains.
Higher moisture values during this period and convergence
related to a propagating frontal zone are efficient to trigger
convection in the afternoon at 35S (even if mean zonal
divergence dominates in the area). It propagates northward
and intensifies during night in a domain dominated by
meridional convergence related to the SALLJ.
Both the patterns of divergence related to ABL mesoscale
circulations and deep convection present a nocturnal phase in
their diurnal cycles.
Mesoscale circulations are altered once deep convective
circulations dominate over the plains.
0,1
0,08
0,06
Mesoscale
circulations east
of the Andes
0,04
0,02
0
-0,02
-0,04
-0,06
a)
24
25
26
27
28
29
30
31
1
2
3
4
5
6
7
0,08
0,06
Div. Total
09 UTC
Div. Zonal
Div. Merid.
0,04
0,02
Mountain-plain
breeze
Diurnal cycle
0
-0,02
-0,04
-0,06
-0,08
-0,1
b)
24
25
26
27
28
29
30
31
1
2
3
4
5
6
7
0,1
21 UTC
0,08
0,06
Nicolini, M., Garcia
Skabar, Y., (2010)
0,04
0,02
0
-0,02
-0,04
-0,06
Div. Total
Div. Zonal
Div. Merid.
-0,08
c)
24
25
26
27
28
29
30
31
1
2
3
4
5
6
7
BRAMS SIMULATION OF AN INTENSE FLOOD
EVENT OVER CENTRAL ARGENTINA
Methodology:
BRAMS 3.2 Brazilian Regional Atmospheric Modeling
System version 3.2
Simulation period : March 2007 from 25 to 31 at
12UTC
Two-way grid interactive nesting technique
Number of atmospheric levels: 30;
vertical cordinate: shaved eta
Horizontal Resolution: Grid 1 - 50 km Grid 2 - 12.5
km, Grid 3 - 3.125 km
GDAS analyses from NOAA/NCEP as initial and
boundary conditions.
Model includes topography data (1km resolution)
terrain land use (1km resolution), soil types (50km
resolution), weekly sea surface temperatures
daily soil moisture heterogeneous fields from
USP/CPTEC
Parameterizations:
Shallow cumulus:Sousa and Silva;
Deep convection: Grell; Explicit convection on Grid 2 and 3
Radiative: Chen and Cotton;
Horizontal diffusion:Smagorinsky;
Vertical diffusion: Mellor-Yamada;
Microphysics: 8 water species, bulk water scheme
Purpose:
To describe the synoptic and
mesoscale environment with
particular emphasis in the relationship
convective precipitation/ LLJ.
To evaluate BRAMS performance in
simulating an extreme rainfall
situation
800
-30
MONTE CASEROS AERO
Monte Caseros
700
CONCORDIA AERO
Sauce Viejo
Concordia
SAUCE VIEJO AERO
PARANA AERO
PARANA INTA
-32
600
Paraná
EL TREBOL
El Trebol
ROSARIO AERO
Rosario
500
GUALEGUAYCHU AERO
Gualeguaychú
-34
400
Junín
Buenos Aires
SAN FERNANDO
JUNIN AERO
SAN MIGUEL
AEROPARQUE BUENOS AIRES
BUENOS AIRES
EL PALOMAR AERO
CASTELAR
MORON AERO
INTA
Ezeiza
300
-62
-60
EZEIZA AERO
-58
200
Observed
Grid 3
Grid 2
CMORPH
AEROPARQUE
BUENOS AIRES
JUNIN AERO
GUALEGUAYCHU
AERO
ROSARIO AERO
EL TREBOL
CONCORDIA
AERO
MONTE
CASEROS
AERO
0
PARANA AERO
100
SAUCE VIEJO
AERO
Observed precipitation
over central Argentina,
CMORPH (blue) and
models forecast by (red
and yellow) different grids
accumulated between
March 26 to 31, 2007.
Grid 2 represents the
precipitation forecast for
12.5 km and Grid 3 for
3.125 km respectively.
-56
Synoptic Forcing
Meridional wind at 30S
200 hPa Streamlines
and wind intensity Equivalent potential temperature
Vertically Integrated Moisture flux and its convergence
0
Rosario
Buenos Aires
Salta
0Z1APR2007
12Z31MAR2007
0Z31MAR2007
12Z30MAR2007
0Z30MAR2007
12Z29MAR2007
0Z29MAR2007
12Z28MAR2007
0Z28MAR2007
12Z27MAR2007
0Z27MAR2007
12Z26MAR2007
0Z26MAR2007
12Z25MAR2007
0Z25MAR2007
12Z24MAR2007
0Z24MAR2007
12Z23MAR2007
0Z23MAR2007
12Z22MAR2007
0Z22MAR2007
12Z21MAR2007
0Z21MAR2007
Temporal Evolution of GPS-Precipitable water
70
60
50
40
30
20
10
Convective and Stratiform Precipitation estimated by the
CMORPH and IR area and the relationship with the LLJ
90000
10
B
80000
C
A
5
70000
60000
0
50000
-5
40000
30000
-10
20000
-15
10000
12Z31MAR2007
00Z31MAR2007
12Z30MAR2007
00Z30MAR2007
12Z29MAR2007
00Z29MAR2007
12Z28MAR2007
00Z28MAR2007
12Z27MAR2007
00Z27MAR2007
12Z26MAR2007
00Z26MAR2007
-20
12Z25MAR2007
0
Stratiform and convective estimated precipitation for all systems that
affect the central region of Argentina between March 25 to April 1,
2007 (green and purple). Meridional wind at 30ºS averaged between
63 and 58ºW and its ageostrophic component (pink and blue
respectively) calculated from grid 3.
PERFORMANCE AND SENSITIVITY STUDY
OF BRAMS FORECAST
Purpose
To progress in the forecast of MCS events and specifically to
evaluate the performance of BRAMS forecast and study the
sensitivity to different initial conditions, horizontal and vertical
resolution and settings on cloud microphysics scheme in a prefrontal squall line event.
Case study:
During early morning of January 12, 2010
an extended convective line developed in
association with a cold front that
propagated over the central and northern
part of Buenos Aires Province, Argentina.
Methodology:
• 12 Numerical forecasts of the case study were performed using the Brazilian model
Regional Atmospheric Modeling System (BRAMS), reaching a horizontal resolution of
around 2km, using different initial conditions, horizontal and vertical resolution and
settings on cloud microphysics scheme.
• Model forecast performance was evaluated against measurements from radar,
disdrometer, CMORPH estimations (8km-30min) and surface observations.
•ETA-SMN forecast initialized 11 January at 12UTC was used as initial and boundary
conditions.
•Convection parameterizations is turned off in 8 and 2 km resolution
•Microphysics parameterizations with 8 water species and bulk water scheme
following Walko et al, 1995.
•Current experimental forecast BRAMS 4.2
setting at National Weather Service
•50 vertical levels (20 m near surface)
•Model forecast performed for 18 hours,
from 18 UTC to 12 UTC of next day
initialized with a 6 hours ETA model forecast
•Both mixing ratio and number concentration species
are predicted
Comparison against radar data squall line
reflectivity evolution at 3 KM.
Ensemble
Forecasts
FCST 07
CAPPI
Ezeiza Radar
All forecasts present a
squall line reflectivity
pattern similar to radar
observations but
forecasts depict larger
reflectivity values,
compared with Ezeiza
radar that has a
tendency to
underestimation.
Comparison against CMORPH
estimations
8KM 30 min resolution
Area with accumulated precipitation
>15mm/30min
Ensemble
6000
Ens-desv
Ens-desv
CMORPH
FCST07
5000
3000
2000
1000
Hour UTC
0
11
:3
0
10
:3
0
09
:3
0
08
:3
0
07
:3
0
06
:3
0
:3
0
05
:3
0
04
:3
0
03
:3
0
02
:3
01
:3
0
0
00
KM2
4000
Comparison against disdrometer
accumulative Precipitation 10 min
10 min accumulated precipitation in Castelar
12
Ensemble
Ens-desv
Ens+desv
FCST07
Disdrometer
10
mm
8
6
4
2
Hour UTC
0
:0
12
0
:3
11
0
:0
11
0
:3
10
0
:0
10
0
:3
09
0
:0
09
0
:3
08
0
:0
08
0
:3
07
0
:0
07
0
:3
06
0
:0
06
0
:3
05
05
:0
0
0
Surface automatic stations
Pergamino
San Pedro
2m Temperature
2m Temperature
10min acc. Precipitation
10min acc. Precipitation
Wind Speed 10m
Wind Speed 10m
Obs
FCST07
Ensemble
Boedo-Bs.As.
Ongoing research…
Case studies approach
• Evaluate the performance of the model in capturing
the forcing mechanisms in different scales that
determine the timing, location, convective mode and
propagational characteristics in different case
studies, with emphasis in extreme cases.
• Some cases may be strongly forced by synoptic
features like the example of the pre-frontal squall line
but others may be controled by contrasts in surface
physiography (topography, vegetation, soil moisture)
or by storms-generated outflow boundaries.
Challenges
• It is essential to advance on Radar calibration and improve
reflectivity estimation from forecast variables, using algorithms
that include mixing ratio as well as number concentration for the
different microphysical species.
• Also to develop an objective and appropiate methodology to
validate high resolution forecasts.
• There are observational demands for increased mesoscale
data (raingauge and conventional surface stations, rawinsonde,
Doppler radars) over Argentina for future improvement of high
resolution models.
• Parameterization of planetary boundary layer and microphysical
processes need further testing given their control in convection
initiation and evolution
Some questions to be answered:
• Is the genesis of convection related to topographical
features such as convergence zones or mountain/plains
solenoids?→accurate representation of topography and of
surface characteristics?
• Is the spacing of 2 km small enough to resolve: convection,
LLJ strength, timing and location?
• Is the model accurately initialized with soil moisture
contrasts that may favor formation of drylines and therefore
cloud development during early stages of the simulation?
•
Does higher resolution lead to greater skill of convective
characteristics and of quantitative precipitation forecast?
• Is there any improvement in the prediction of precipitation at
the exit region of the LLJ and their diurnal cycle respect to
regional models?
CHUVA Project
Leader: Luiz Agusto Toledo Machado
Experiments
Sites for
the field
campaign
New experiment at Foz de Iguazu
From 10-2012 to 1-2013
Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud
resolVing modeling and to the GPM (GlobAl Precipitation Measurement)
Scientific questions:
•
How to estimate rainfall from warm and deep clouds?
•
What is the contribution of rain from warm clouds to the total precipitation in different
regions of Brazil?
•
How to improve both space and time precipitation estimation of rainfall over the
continent for the GPM constellation?
•
What are the average characteristics (3D - cloud processes) of the main regimes of
precipitation in Brazil?
•
What is the contribution of the aerosol in the process of formation of precipitation?
•
What are the main surface and boundary layer processes in the formation and
maintenance of clouds?
•
How cloud microphysics and electrification processes evolves during the cloud life
cycle?
•
How to improve precipitation estimation and cloud microphysics description by using
conventional and polarimetric radar?
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4.2 INSTRUMENTATION PACK
The following instruments will compose the typical instrumentation pack to be used in the field
campaign:
1. Dual Polarization Doppler X band radar (see figure 4)
2. EZ Lidar ALS450 (see Figure 4)
3. Microwave Radiometer MP3000 (see Figure 4)
4. 6 Laser Disdrometer (Figure 5)
5. 3 Meteorological Surface Stations
6. 2 Field Mill - Campbell
7. Radiosonde RS-92
8. Turbulent fluxes of heat and moisture
9. GPS Station
10. Soil Moisture
11. Airplane equipped with cloud microphysical instrumentation (only some campaigns)
12. Rain gauges
13. CCD cameras
14. Vertical pointing radar – micro rain radar (Figure 6)
15. Low-light Level CCD cameras
Satellites images: NOAA, TRMM, Megha-Tropique, AQUA, GOES and MSG
CPTEC analysis
Radiosondes from Brazilian network
Surface Station (raingauge)
Brasildat network - Brazilian lightning detection network): http://www.rindat.com.br
STARNET (South American lightning network) - http://www.zeus.iag.usp.br
At some sites the basic pack information will be complemented by others instruments available like
X Band dual polarization and Doppler radar (Alcântara)
1S-Band Doppler radar (Belém, Manaus, Curitiba, São Roque, Pelotas and Fortaleza)
Micrometeorological Tower (Maranhão- Amazonas – Santa Maria) 4
Salto Grande –
Long Period
140 stations
San Luis
Long Period
Dry region
40 stations
20
20
Probability Density Functions
18
Probability Density Functions
18
16
16
14
14
12
3B42_V6
12
3B42_V6
10
CMORPH
10
CMORPH
Obs CMORPH
8
6
6
4
4
2
Obs CMORPH
8
2
0
0.1
1
3
5
10
15
20
30
0
50
0.1
1
3
5
10
15
20
30
50
2
3
1.8
2.5
1.6
Bias Score
3B42_V6
1.5
CMORPH
1
1
3
5
10
15
20
30
50
3B42_V6
1.2
1
0.8
1
3
5
10
15
20
30
50
CMORPH
0.6
0.4
0.5
Bias Score
0
Bias Score
1.4
2
0.2
0
Bias Score
Fcst
01
Comp. Time
12hs FCST
Initialization
time
Grid resolution
Microphysics
Mean diameter is specified and
number concentration is
diagnosed
4hs 30’
12th at 00UTC
8 -2km /39 lev
(DZ=50m)
02
5hs 10’
03
4hs 10’
04
5hs 00’
8 -2km / 45lev
(DZ=30m)
05
8hs 30’
5-1.25km /
39lev
06
10hs 00’
Mean diameter is diagnosed
from forecasted mixing ratio
and number concentration
11th at 21UTC
12th at 00UTC
same as in forecast 01
5-1.25km /45lev
(DZ=30m)
07
08
09
11th at 21UTC
6hs 40’
11th at 18UTC
10
11th at 15UTC
11
11th at 12UTC
12
4hs 00’
12th at 00UTC
8 -2km / 50lev
(DZ=20m)
2km / 50lev
(DZ=20m)
same as in forecast 02
Ensemble mean and FCST07
Sensitivity to initial condition
16
CMORPH 5:30UTC
FCST07
Ens-desv
Ens
16
Ens+desv
14
14
12
12
10
10
8
%
%
CMORPH 4:30UTC
6
4
4
2
2
0
0
15<PP<20
20<PP<25
25<PP<30
10<PP<15
30<PP
FCST04
FCST05
CMORPH 4:30UTC
FCST06
14
14
12
12
10
10
%
%
FCST01
8
6
4
4
2
2
0
0
15<PP<20
20<PP<25
25<PP<30
20<PP<25
25<PP<30
30<PP
30<PP
CMORPH 5:30UTC
FCST01
20<PP<25
25<PP<30
FCST02
8
6
10<PP<15
15<PP<20
16
16
CMORPH 5:30 UTC
FCST07
FCST10
Sensitivity to microphysics scheme
Sensitivity to horizontal and vertical resolution
CMORPH 4:30UTC
CMORPH 5:30UTC
FCST09
8
6
10<PP<15
CMORPH 4:30UTC
FCST08
FCST11
10<PP<15
15<PP<20
30<PP
Area with reflectivity > 40 dBZ at 3km
FCST07
ens-desv
ensemble
ens+desv
obs 30dBZ
obs 40dbz
9000
8000
7000
5000
4000
3000
2000
1000
hour UTC
0
:3
0
11
:5
0
10
:1
0
10
:3
0
09
:5
0
08
:1
0
08
:3
0
07
:5
0
06
:1
0
06
:3
0
05
:5
0
04
:1
0
04
:3
0
03
:5
0
02
:1
0
02
:3
0
01
:5
00
:1
0
0
00
Km 2
6000
Results
• All members of the ensemble forecast represent a squall line
reflectivity pattern similar to the observed by the radar, but more
intense and predicted approximately two hours later. This same
delay was observed in ETA SMN forecasts that were used as
initial and boundary conditions.
• Sensitivity to different initial conditions, horizontal and vertical
resolution and settings on cloud microphysics scheme were
identified.
• It is difficult to define which forecast is better or worse, it
depends on the focus of interest. Different results are achieved
depending on the variables, pp thresholds, vertical levels,
times.
Environment associated with deep moist convection under
SALLJ conditions: a case study
Borque et al., 2010, Wea. and For. Vol. 25,
3970–986
Vertical cross section of potential
temperature wind barbs and
meridional component of the wind at
25°S. All panels cover a longitudinal
range from 65°W to 54°W, at 3 h apart