STORMS & PRECIPITATION S6E4. Types of Storms: Thunderstorm Tornado Snowstorm Hurricane.
A Comparison of Two Microwave Retrieval Schemes in the Vicinity of Tropical Storms Jack Dostalek...
-
Upload
evangeline-nichols -
Category
Documents
-
view
216 -
download
1
Transcript of A Comparison of Two Microwave Retrieval Schemes in the Vicinity of Tropical Storms Jack Dostalek...
1
A Comparison of Two Microwave Retrieval Schemes in the Vicinity of Tropical Storms
Jack DostalekCooperative Institute for Research in the Atmosphere, Colorado State University
Galina Chirokova and Kate MusgraveCooperative Institute for Research in the Atmosphere, Colorado State University
Mark DeMariaNational Hurricane Center
2
CIRA has developed tropical cyclone (TC) products using remotely sensed data.
Microwave data is particularly helpful in tropical cyclones due to insensitivity to most clouds
Temperature retrievals derived from Advanced Microwave Sounding Unit (AMSU) data have been extensively used• Flies aboard NOAA-15 (1998), -16, -17, -18, -19, MetOp-A, MetOp-B,
Aqua satellites
The temperature retrievals can be used to derive the height field which can be used to derive a non-divergent wind field
Estimate values of interest to TC forecasters such as:• Minimum pressure• Intensity (maximum wind speed)• Radius of maximum winds• Radius of 34-, 50-, 64-kt winds
Background
AMSU Wind Analysis
Initial Estimates (Minimum Pressure, Intensity, Radius of Maximum Winds)
Statistical Fitting for Improved Estimates
Multiplatform Satellite Surface Wind Analysis
Surface Wind Estimate
Data
AMSU Temperature Profiles
GFS for Boundary Conditions
Operational Fix Entry Operational Fix Entry3
+ +
4
AMSU temperature profiles for the TC products currently come from a statistical retrieval technique > 10 years old
NESDIS’ current operational microwave retrieval algorithm is the Microwave Integrated Retrieval System (MIRS)• 1D VAR retrieval scheme• Flexible, can use with AMSU, SSM/I, or ATMS• Also retrieves vertical profile of water vapor mixing ratio
An Issue
How does the quality of the initial estimates of the TC products compare when the temperature profiles come from the statistical technique vs. MIRS?
A Question
5
How do the MIRS temperature retrievals compare to the statistical retrievals with respect to collocated dropsondes?
• MIRS data first available in 2012
• Dropsondes from 2012 Atlantic season (Ernesto, Isaac, Sandy)
• Statistical and MIRS retrievals from AMSU aboard NOAA-18
• Collocation: retrievals must be within 50 km and 1 hour of dropsonde
But First
6
7
8
Do the higher quality soundings translate into better first estimates of minimum pressure, intensity, and radius of maximum wind?• 33 matchups from the 2012 Atlantic hurricane season (Chris, Debby,
Ernesto, Gordon, Isaac, Leslie, Sandy)
• Comparisons are made with respect to the best track
• The bias and rmse in the following plots are “large”, but in the flow of the processing, these estimates are of the first guess. Improvement from the statistical technique to the MIRS algorithm is what is sought
Overall the MIRS temperatures are closer to the dropsonde temperatures than the statistical technique
Results of Temperature Comparison
Back to the Main Question
9
Both have high bias
Lower bias with MIRS
Lower RMSE with MIRS
10
Both have low bias, consistent with high bias on minimum pressure (assuming similar environmental surface pressures)
MIRS bias smaller in magnitude
RMSE same
11
Both have very high bias – again these values are refined later on
Larger bias with MIRS
Lower RMSE with MIRS
12
Summary MIRS temperature soundings are an improvement over the older, statistical
technique
This improvement does translate into an (overall) improvement in the initial estimates of minimum pressure, intensity, and radius of maximum winds
Future Work More cases
Temperature profiles – Why isn’t the MIRS better at all levels?
Check quality of operational fix entries (definitely need more cases for this step)
Include moisture effects (MIRS also gives water vapor mixing ratio profile)
Other parameters (MPI, vertical velocity profile)