reduction of uncertainties in the in the tropicszagarn/old/var/phdthesispres_nz.pdf · dynamical...
TRANSCRIPT
Dynamical aspects of Dynamical aspects of
atmospheric data assimilation atmospheric data assimilation
in the tropics in the tropics
Nedjeljka ŽagarNedjeljka Žagar
Department of MeteorologyDepartment of Meteorology
Stockholm UniversityStockholm University
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Reduction of uncertainties
in the
atmospheric analysis fields
in the tropics
Purpose Purpose
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Definition Definition
Observations (V,T,p,q)
A priori information
(model)
Analysis Weather forecast
Mass field
Climate simulations
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Ingredients of the analysis Ingredients of the analysis
Observations:
Wind and mass information Wind and mass information
Smagorinsky (1969): ”... First of all, not all data are equal in their information-yielding capacity. Some are more equal than others…”
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
W I N D SW I N D S w a n t e d
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
À Observations:
Imbalance between the mass- and wind-field information in the present Global Observing System
¸ Balance properties:
Different in the tropics than in the mid-latitudes
� A priori information:
Physical laws governing the atmospheric flow
About the ingredients ... About the ingredients ...
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
ImprovementsImprovements
À New wind observing systems
H Improvements of data assimilation procedures
d Improvements of the models’s parameterizations and resolution
Subject of the thesis
work
Thesis assumes the model is excellent
Balance relationships in the tropics
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Ð New wind observing systems
New wind data New wind data
Atmospheric Dynamic Mission
Peculiarity of ADM
line-of-sight (LOS) winds
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Assimilation procedureAssimilation procedure
x
JbJo Joobs
obs
obs obs
xb
xa analysis
background
t1 t2
Jo
obs
time
JoJo
obs
Jo
Jo
obs
* ** ** * * * ** *
* * *
* ** ** * *
* ** ** * *
* ** ** * *
* ** ** * *
* ** ** * *
Jo distance to observations
Jb distance to the background J=Jo+Jb , minimal
3D-Var
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Assimilation procedureAssimilation procedure
x
JbJo Joobs
obs
obs obs
xb
xa analysis
background
t1 t2
Jo
obs
time
JoJo
obs
Jo
Jo
obs
* ** ** * * * ** *
* * *
* ** ** * *
* ** ** * *
* ** ** * *
* ** ** * *
* ** ** * *
Jo distance to observations
Jb distance to the background J=Jo+Jb , minimal
4D-Var
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Errors Errors
B I M P O R T A N TI M P O R T A N T
h Observations and a priori information are combined according to their error characteristics
( ) ( ) ( ) ( )b1b1 xxBxxyxRyxx −−+−−=+= −− TT
bo JJJ21
21)(
vector of observations background error covariance matrix
observation error covariance matrix
distance to background state (first guess)distance to observations
total distance
background state
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Why is the B matrix important?Why is the B matrix important?
Observations are too few
Observed information needs to be spread to nearby points and levels in a dynamically consistent way
z
x
y
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
z
x
y
T
T
T
T
T
TT T
TT
T
TT
TT
T
TT
TT
TT
TT
T
T
T
@ To the same variable
Univariate analysisUnivariate analysis
Information spreadingInformation spreading
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
‘ Also to other variables
Multivariate analysisMultivariate analysis
z
x
y
T
T
T
T
TT T
TT
T
TT
TT
T
TT
TT
TT
TT
T
T
T
V,
, V
V,
V,
V,
V, V,V,
V,V,
V,, V
, V , V
, V, V
, V
, V
, V, V
, V
, V
, V, V
, V, V
TV
Information spreadingInformation spreading
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Information spreadingInformation spreading
Ð Also to other variables in the tropics
Multivariate analysisMultivariate analysis
z
x
y
T
T
T
T
TT T
TT
T
TT
TT
T
TT
TT
TT
TT
T
T
T
V,
, V
V,
V,
V,
V, V,V,
V,V,
V,, V
, V , V
, V, V
, V
, V
, V, V
, V
, V
, V, V
, V, V
TV
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Methodology Methodology
General philosophy: to simplify
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Multivariate tropical analysis Multivariate tropical analysis
l Mid-latitudes: Rossby waves
� Tropics: Rossby, Kelvin, mixed Rossby-gravity and inertio-gravity waves
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Multivariate tropical analysis Multivariate tropical analysis
Mid-latitude approach
ø Mid-latitudes: Rossby waves
d Tropics: Rossby, Kelvin, mixed Rossby-gravity and inertio-gravity waves
singl
e zo
nal w
ind
obse
rvat
ion
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Multivariate tropical analysis Multivariate tropical analysis
Mid-latitude approach
h Mid-latitudes: Rossby waves
à Tropics: Rossby, Kelvin, mixed Rossby-gravity and inertio-gravity waves
singl
e zo
nal w
ind
obse
rvat
ion
A new modelling approach
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Impact of ADM winds Impact of ADM winds
”Truth”: equatorial Rossby wave
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Impact of ADM winds Impact of ADM winds
”Truth”: equatorial Rossby wave
Height data
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Impact of ADM winds Impact of ADM winds
”Truth”: equatorial Rossby wave
Height dataHeight & ADM winds
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
Methodology Methodology
Question: How does the new methodology work in the ”real” (numerical weather prediction) framework?
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
How does it work? How does it work?
x In average about 60-70%
Unexplained variance ratio
h
u
v
100 hPa
500 hPa
900 hPa
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
On the way back On the way back
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
What have I achieved? What have I achieved?
p Developed an approach to multivariate analysis in the tropics based on equatorial waves coupled to convection
à Applied it for studing the impact of new wind observations
° Found that the same wave structures are present in an NWP system
Dynamical aspects of atmospheric data assimilation in the tropics Dynamical aspects of atmospheric data assimilation in the tropics 19 May 200419 May 2004
What remains to be done? What remains to be done?
à Solving the methodology extention into the global NWP domain
h Representing the unexplained part of the variance field and remaining variables
” Taking into consideration discrepancy between theorethical assumptions and ”real” forecast error patterns