1 / 19

Towards improved QPE with a local area X-band radar in the framework of COPS

Towards improved QPE with a local area X-band radar in the framework of COPS. F. Tridon, J. Van Baelen and Y. Pointin Laboratoire de Météorologie Physique, UMR CNRS/UBP 6016 24, avenue des Landais, 63177 Aubière Cedex, France (F.Tridon@opgc.univ-bpclermont.fr). Introduction (1).

keahi
Download Presentation

Towards improved QPE with a local area X-band radar in the framework of COPS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Towards improved QPE with a local area X-band radar in the framework of COPS F. Tridon, J. Van Baelen and Y. Pointin Laboratoire de Météorologie Physique, UMR CNRS/UBP 6016 24, avenue des Landais, 63177 Aubière Cedex, France (F.Tridon@opgc.univ-bpclermont.fr)

  2. Introduction (1) • Radar technology: tool for quantitative rainfall measurements • Main parameters: • Reflectivity factor : Z (mm6.m-3) • Rainrate: R (mm.h-1) • Drop Size Distribution: DSD (l-1.mm-1) • Power law relationship: Z = aRb • Variability of DSD • Use of unique Z-R relationship for one precipitating event

  3. Introduction (2) • Objective: Quantitative precipitation estimation on a small catchment basin with a simple scanning X-band radar • Use of a nearby vertically looking MicroRain Radar to: • study the properties of precipitation (DSD) with a high resolution • do a classification of different rain regimes within the same precipitating event • derive specific Z-R relationships for these regimes • Check the efficiency of these specific Z-R relationships against a single one

  4. X-band radar (9.41GHz) • Elevation: 5° • High resolution: • Time: 30 s • Azimuth: 2° • Range: 60 m • Max range: 20 km

  5. Micro Rain Radar (K-band, 24.1GHz) • Doppler spectra of 63 bins (0 to 12 m.s-1) over 32 range gates every 10 s • Relation between drop diameter and terminal fall velocity (Atlas et al. 1973): • Profile of DSD

  6.  Derivation of rain parameters: • Attenuation coefficient • Iterative attenuation correction • Reflectivity factor • Rain rate

  7. June 15, 07 (IOP 3b) • Synoptic-scale through moving northeastwardly giving stratiform precipitation with weak showers over the COPS area

  8. DSD temporal evolution • Grayscale: Number of raindrops in size interval • Bold solid line: Median-volume diameter • Thin solid lines: 10th and 90th percentiles of distribution of liquid rain water content over raindrop diameters •  measure of the width of the raindrop size distribution

  9. anomaly DSD temporal evolution • 1st period: small drops, narrow spectra, high variability • 2nd period: large drops, wide spectra, medium variability • 3rd period: low variability 1 2 3

  10. Anomaly less visible near the ground • MRR measurement issue due to: • strong updraft • heavy attenuation • bad noise level estimation

  11. Z-R relationships Global Specific 1 2 3

  12. Corresponding rainfall Rainrate Cumulative rainfall

  13. August 8-9, 07 (IOP 14b) • An intense large-scale precipitating system spread over the COPS area during all the night

  14. DSD temporal evolution • 1st period: medium drops, medium variability • 2nd period: small drops, narrow spectra, low variability • 3rd period: small drops, narrow spectra, medium variability • 4th period: high variability 1 4 2 3

  15. Z-R relationships Global Specific 1 4 2 3

  16. Corresponding rainfall Rainrate Cumulative rainfall

  17. Conclusions and perspectives High variability of rain even within a stratiform precipitation system Detection of temporally stable regimes of precipitation with significantly different Z-R relationships Derivation of the equivalent exponential or gamma distribution to explain the difference between the Z-R relationships Next step: apply these specific Z-R relationships on the X-band reflectivity

  18. Conclusions and perspectives 3 2 1 1 3 4 2  Problem: How to detect these regimes with a single parameter X-band radar ? Periods of increasing, stagnating and decreasing intensity can be part of the same temporally stable regime of precipitation

  19. Thanks for your attention Questions ?

More Related