1. Satellite Derived Mid- Upper Level Winds
Cegeon Chan
MET 315: Remote Sensing

2. Outline Importance Instruments Location Tracking Height Assignment
Quality Control
Accuracy
Summary

3. Importance Over oceanic regions Dvorak Technique Wind vectors
Numerical Weather Prediction

4. Different Types
cloud-drift
2) Water Vapor
3) Sounder WV
4) Visible

5. What does it look like? Capable of gathering water vapor fields
Measure infrared energy

6. Imager Sounder Responsible for NH and SH Responsible for the tropics
Low Frequency
Responsible for the tropics
High Frequency

7. Tracking Background Similar to cloud tracking
Algorithm is housed within McIdas!
Very sensitive
Rule: at least 3 images to derive winds to produce 2 vectors
Measures consistency between successive images

8. Tracking Procedure Take a small area
Isolate the lowest cloud brightness temperature within a pixel array

9. Tracking Procedure (cont.)
Compute bi-directional gradients are computed
Cloud-free environments
Generally in moist regimes

10. Height Assignment
Goal is to ascertain the height level of the feature you tracked
Can be complicated if there are multiple moist layers

11. Height Assignment (more)
Convert measured radiance into Brightness Temperature
This value is collocated with a model guess temperature
S. Velden, Christopher, Christopher M. Hayden, Steven J. Nieman, W. Paul Menzel, Steven Wanzong, James S. Goerss, 1997: Upper-Tropospheric Winds Derived from Geostationary Satellite Water Vapor Observations. Bulletin of the American Meteorological Society: Vol. 78, No. 2, pp. 173–173

12. Quality Control Algorithm
Slow – using cloud drift winds
Add 8% for 10m/s
Incorporate satellite winds into analysis
Remove those differing significantly from analysis
Yellow = minus satellite
Red = Plus satellite

13. Accuracy – how good is it?
A particular single level does not represent a layer
Generally good for 50 mb

14. Sources of Errors Assumption of clouds and water vapor
Image registration errors
Target identification and tracking errors
Inaccurate height assignment

15. Summary Great applications – oceanic analysis, tropical cyclones
Improved numerical weather analysis and prediction systems
Similar to cloud tracking method
Tendency to be slow

16. Got Questions?