Bajaj Allianz Life Insurance Company - Insurer Innovation Award 2024
TU4.T10.4.pptx
1. Spaceborne synthetic aperture radar (SAR) applications in marine meteorology Xiaofeng Li NOAA/NESDIS Acknowledgment Zheng Weizhong and William Pichel, NOAA/NESDIS Xiaofeng Yang, Institute of Remote Sensing Application, CAS NOAA Gilmore Creek Ground Station, Alaska
2. Outline Motivation SAR Observation and WRF model simulation of Marine Atmospheric Boundary Layer (MABL) phenomena Atmospheric Gravity Waves Atmospheric Vortex Streets Katabatic Winds Storm pattern Summary
3. Motivation SAR Provides high resolution (tens to hundreds m) all day/night synoptic observation of ocean surface. Community weather model now provides time series of sub-km actual atmospheric circulation fields. Synergy of the two to understand the actual atmospheric conditions that lead To the generation and evolution of these phenomena in the MABL.
4. SAR applications in Marine meteorology atmospheric lee waves atmospheric disturbances atmospheric boundary layer rolls atmospheric fronts katabatic winds, gap winds Hurricanes island wakes cold air outbreaks Storms atmospheric vortex streets Land breeze Cloud line …
5. 1. Atmospheric Gravity Wave Observations Upstream Waves: Waves propagates against the mean flow Lee wave has two types of wave patterns: the transverse wave type where the wave crests are nearly perpendicular to the wind direction (2) the diverging wave type where the wave crests are orientated outwards from the center of the wake.
13. 1. Atmospheric Gravity Wave Observations Lee Wave (diverging waves, Example 2) Wind Direction Constant lee wave phase lines Chunchuzov, Vachon, and Li, Remote Sensing of Environment, 74, 343-361, 2000.
21. Noah land‐surface model.Boundary conditions are specified by linearly interpolating the NCEP 6 hourly final analyses (FNL) at a resolution of 1° × 1° degree. The digital elevation of 30 s USGS topography data.
22. 1. Atmospheric Gravity Wave Observations WRF Simulation results at the imaging time Vertical velocity Horizontal velocity
23. 1. Atmospheric Gravity Wave Observations Lee Wave 3 Standing Waves MODIS true color image acquired about 8.5 h prior to the Envisat ASAR pass in Google Earth.
25. 1. Atmospheric Gravity Wave Observations Lee Wave 4 Comparison of WRF simulated surface wind speed with the independent SAR measurements
26. 1. Atmospheric Gravity Wave Observations AGW Summary AGM patterns can be identified on SAR image. Most of the waves generated by flow over bump observed by SAR are on the lee side of the bump, and has two types of wave patterns. The terrain-forced stmospheric lee waves can be simulated using the WRF model. Model reveals evolution of the AGW. Upstream waves happen when Froude number is close to 1. They are elevation waves. They are explained well with FeKDV model.
27. 2. Atmospheric Vortex Streets (AVS) Atmospheric vortex-street patterns on the lee side of a flow obstacle double row of counter rotating vortex pairs shedding alternately near the edge of the obstacle No observation in the atmosphere prior to the satellite age due to AVS scale (100-400 km): too small to be delineated by a synoptic observation network and too large to be observed by a single station h/a is the basic property of an atmospheric vortex streets Uo is the wind speed, Ue is the vortex shedding velocity
28. 2. Atmospheric Vortex Streets (AVS) NASA space shuttle picture cloud pattern (1) NASA space shuttle picture cloud pattern (2)
29. 2. Atmospheric Vortex Streets (AVS) Aircraft photo (Ferrier et al. Vol. 17, No. 1, 1-8, International J. of Remote Sensing, 1996)- sediment pattern Landsat-7 (Defelice et al. Vol. 81,No.5, 1047-1048, BAMS, 2000)-cloud pattern SAR Wind Pattern. IEEE/TGARSS Feb. 2004
38. 3. Katabatic Wind The black solid line is the topography; the red dash line represents the horizontal wind speed simulated by the model, the blue line represents the sea surface wind derived from SAR measurements, and the green dash line represents the near surface descending wind speed
49. 4 Storm and Precipitation Storm Summary: WRF can capture wind and rain pattern in the storm Heavy rain in the hurricanes damps NRCS. Moderate rain has less effect in C-band NRCS than wind does in the regular storm case
50. 5 Summary We have set up WRF model to simulate SAR observed MABL phenomena WRF model captures the basic characteristics AGV, AVS, Katabatic and Storm The 1-km resolution WRF model gives detailed structures of the phenomena This leads to the understanding of generation and evolution of these phenomena Synergy of SAR and WFR provides great opportunity for detailed study of MABL Phenomena
