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Advances in the assessment of the MW-IR blended technique for rain rate measurement by remote sensing. Vincenzo Levizzani and Francesca Torricella Satellite Meteorology Group ISAC-CNR Italy. - PowerPoint PPT Presentation
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DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Advances in the assessment of the MW-IR blended technique for rain rate measurement by remote sensing
Vincenzo Levizzani and Francesca Torricella
Satellite Meteorology GroupISAC-CNR Italy
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Previous applications devoted to the production of rainfall accumulations on a 6 to 48 hours basis or more
The application to flood forecasting requires to assess the reliability of the method in producing instantaneous rain rate maps
To this end we work along a few main directions:
• Improving (especially over land) the algorithm applied to MW TB;
• Assessing the capability of the statistical histogram matching approach in propagating the information on rainfall between two MW calibrations; • Validation of rain rate fields produced by means of Turk’s technique comparing them with raingauges measurements (from dense, nearly homogeneous, short time reporting networks) from literature.
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Available at SatMet group in Bologna the new GPROF version 6 (Goddard profiling algorithm, Kummerow et al., 2001)
After careful comparison of GPROF5 RR estimates with ground validation data, authors are releasing the GPROFv6, modified to match PR and ground observations.
We needed to:• adapt the GPROF structure in order to manage SSM/I data, needed for
proper coverage of non-tropical areas, i.e. to prepare an interface to adapt
SSM/I data to the RU software; • insert the new algorithm in the RU structure, and compare its performances with the NESDIS (Ferraro et al., 1997) algorithm.• test the new algo on weather conditions, geographical areas and cases relevant to the Projects.
Improving over land the algorithm applied to MW TB
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
The GFROFv6: an algorithm for TRMM/TMI , SSM/I and AMSR-E instruments (McCollum and Ferraro, 2003)
The new version eliminates the global high bias with respect to gauges
This is done using coincident TMI and PR to derive relationships betweenRR and TB85V for both stratiform and convective rain
The probability of convection is derived form PR-estimates and used tocalibrate PMW* predictors of convection
The resulting rainfall estimates compare quite well with PR data and GPCP**monthly rainfall product.
* Passive MW** GPCP: Global Precipitation Climatology Project
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
LATITUDE
GPROFv6 performancesmean monthly rain (1998-2000)
mm
Zonal rainfall profilesusing the three rainfallproducts (v5, v6, PR).
Overall v6 is relativelyunbiased respect to GPCP.
underestimation
overestimation
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Open issues in GPROFv6(applied to SSM/I data)
• No rain detected at high latitudes (where there is less convective rainfall)
• No rain estimation over frozen surfaces such as snow
MONTHLYMEANJAN 2002
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Assessing the capability of the histogram matching Assessing the capability of the histogram matching approach in propagating the information on approach in propagating the information on
rainfall between two MW calibrationsrainfall between two MW calibrations
The method follows to some extentthe evolution of the event before-after the MW calibrationPrevious calibration: 3 hours old!
10 Nov 2001 08:00 UTC
MW cal
08:30 UTC
08:03 UTC
3 25mm/h
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
From the previous slide it is apparent…
The RR values are depressed due to the smoothing process involved in the method (i.e. the TB-RR relationships derived from coincident data are averaged on 5 x 5 boxes regions to avoid discontinuities at box boundaries). For non-global applications avoid the smoothing (?)
lat0
lon0 +lon
overpass-2 swath (TMI)
overpass-1swath(SSM/I)
lon0
grid
Global grid for geo-locatingRR/TB relationships
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Validation of rain rate fields produced Validation of rain rate fields produced by means of Turk’s techniqueby means of Turk’s technique
Validation of an Operational Global Precipitation Analysis at Short Time Scales F. Joseph Turk, Elizabeth E. Ebert, Hyun-Jong Oh, Byung-Ju Sohn, Vincenzo Levizzani, Eric A. Smith, and Ralph Ferraro
Proc. 1st IPWG Workshop, Madrid, 23-27 Sept., 2002, in press.
Rain gauges-RU scatter plotsfor several time average intervals(1° spatial scale)
Gauges from the AWS (Automated WeatherStation) network of the KMA (Korean Meteorological Agency)
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Validation of rain rate fields produced Validation of rain rate fields produced by means of Turk’s techniqueby means of Turk’s technique
Gauge averaging time: 2 minutes window centered about the GMS observation timeAs expected all three parameters improve as either the averaging period is increased or the grid size is coarsened!
0.50.5
2
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Validation of rain rate fields produced Validation of rain rate fields produced by means of Turk’s techniqueby means of Turk’s technique
Gauge averaging time: 20 minutes window centered about the GMS observation time. Sharp improvement when widening the time window.
0.5
0.5
2
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Multispectral characterization of storm top
Vincenzo Levizzani, Elsa Cattani, Francesca Torricella and Maria João Costa
Satellite Meteorology GroupISAC-CNR Italy
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
Multispectral studies of cloud top to
identify severe weather features.
For example characterization of plumes
of ice crystals and link their formation to
precipitation formation mechanisms. The
idea is to explore the forecasting
potential
Observations of storm top plumes
suggest that very small ice crystals are
responsible for large increases in the
cloud top reflectance field at 3.7 μm.
Radiative transfer simulations using
several ice crystal habits indicate that
indeed small ice crystals are a likely
cause of such high reflectance values.
Only certain types of crystals, whose
dimensions are sufficiently small, are
compatible with reasonable plumes
optical depths and therefore correctly
reproduce the observed reflectance and
brightness temperature values.
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
8 Nov. 1998
Multispectral image from
TRMM VIRS over the
Kwajalein Atoll with
superimposed PR-derived
rain areas (stippled pixels).
The graphs report cloud top
temperature vs effective
radius.
While the 3.7 m product
(top) correctly identifies the
cloud top structure and
delimits the various
microphysical zones, the 1.6
m channel response
(bottom) suffers from
contamination from the lower
levels in the cloud. Numbers
on the graphs refer to the
numbered boxes in the
image.
Research conducted in
cooperation with D.
Rosenfeld, Hebrew Univ.
Jerusalem.
Multispectral studies of cloud top with applications to precip. estimations.
DUSSELDORF 27-28 May, 2003 "MUSIC/CARPE DIEM Workshop
The classification scheme of convective clouds into microphysical zonesaccording to the shape of the temperature – effective radius relations
Note that in extremely continental clouds re at cloud base is very
small, the coalescence zone vanishes, mixed phase zone starts at T<-15oC, and the glaciation can occur at the most extreme situation at the height of homogeneous freezing temperature of –39oC. In contrast, maritime clouds start with large re at their base, crossing the
precipitation threshold of 14 m short distance above the base. The deep rainout zone is indicative of fully developed warm rain processes in the maritime clouds. The large droplets freeze at relatively high temperatures, resulting in a shallow mixed phase zone and a glaciation temperature reached near –10oC
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed PhaseRainout
Coalescence
General
Diffusional growth
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Rainout
Coalescence
Maritime
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Coalescence
Continental - moderate
Diffusional growth
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Continental - extreme
Diffusional growth
Rosenfeld and Lensky, 1998