SMAP Radiometer-Only Tropical Cyclone Size and Strength

Transcription

1 SMAP Radiometer-Only Tropical Cyclone Size and Strength Alexander Fore, Simon Yueh, Wenqing Tang, Bryan SCles, Akiko Hayashi Jet Propulsion Laboratory, California InsCtute of Technology 218 California InsCtute of Technology, Government Sponsorship acknowledged

2 SMAP Overview 6 m antenna Radiometer resolucon: 4 km Primary Science Objec/ves Global, high-resolucon mapping of soil moisture and its freeze/ thaw state to Link terrestrial water, energy, and carbon-cycle processes EsCmate global water and energy fluxes at the land surface QuanCfy net carbon flux in boreal landscapes Extend weather and climate forecast skill Develop improved flood and drought prediccon capability Mission Implementa/on Partners JPL (project & payload management, science, spacecraft, radar, mission operations, science processing) GSFC (science, radiometer, science processing) Launch January 31, 2 on Delta 732-1C Launch System Orbit Polar Sun-synchronous; 685 km altitude Duration 3 years Payload L-band (non-imaging) synthetic aperture radar (JPL) L-band radiometer (GSFC) Shared 6-m rotating (13 to 14.6 rpm) antenna (JPL) h"p://smap.jpl.nasa.gov/ NRC Earth Science Decadal Survey (27) recommended SMAP as a Tier 1 mission

3 SFMR vs SMAP for Ignacio at :53:5 SFMR vs SMAP for Ignacio at :53: SFMR SPD 5km SFMR SPD 4 km SMAP SPD SFMR RR 5 km SFMR RR 4 km Wind Speed [m/s] Rain Rate [mm/hr] : 2: 3: 4: 5: 6:

4 SFMR Matchups for SFMR > 2 m/s SFMR > m/s DTime Counts Bias STD Corr Counts Bias STD Corr Average SFMR along-track to 6 km, pick point of nearest approach to SMAP cell. Use best-track to shic SFMR tracks to SMAP observacon Cme.

5 SMAP Wind Speed [m/s] SMAP vs SFMR; Best Fit Slope:.96; Corr:.81 Mean Pct Error > m/s: SMAP Best Fit 1:1 36 min matchup Cme SFMR Wind Speed [m/s]

6 SMAP Wind Radii We validate against the ATCF B-deck datasets. For each SMAP cyclone hit: Compute contours at (34, 5, 64) knot wind thresholds. Extract longest contour in each compass quadrant and compute the 9% threshold value.

7 Wind Radii Results SMAP wind radii are in reasonable agreement with ATCF B-deck radii: ATCF wind radii escmates have ~ 2-4% error. Good correlacon to ATCF radii. SMAP relacvely unbiased. SMAP Wind Radii [km] kt 5kt 64kt SMAP wind radii versus NHC wind radii Counts SMAP wind radii versus NHC wind radii 34 kt; Median:.4; CDF68: 42.14; CORR:.86 5 kt; Median: 1.63; CDF68: 24.99; CORR: kt; Median: 8.96; CDF68: 21.63; CORR: NHC Wind Radii [km] SMAP RXX NHC RXX [km]

8 Summary Using SFMR we find good agreement to about 4 ms -1 PosiCve bias between 3-4 ms -1 no larger than 3 ms -1 Overall STD as compared to SFMR is on the order of 4 ms -1 for wind speeds larger than ms -1 Comparisons to ATCF B-deck datasets shows SMAP provides reasonably unbiased size escmates with good correlacon to ATCF values. Overall, SMAP can provide valuable informacon on Tropical Cyclone size and averaged intensity. Peer-reviewed publicacons: S. H. Yueh et al., "SMAP L-Band Passive Microwave ObservaCons of Ocean Surface Wind During Severe Storms," in IEEE TransacCons on Geoscience and Remote Sensing, vol. 54, no. 12, pp , Dec A. G. Fore, et al., "Combined AcCve/Passive Retrievals of Ocean Vector Wind and Sea Surface Salinity With SMAP," in IEEE TransacCons on Geoscience and Remote Sensing, vol. 54, no. 12, pp , Dec N. Reul, et al., A new generate of Tropical Cyclone Size measurements from space, in BAMS, Early release (online) /BAMS-D

9 SFMR vs SMAP for PATRICIA at :1:13 21 SFMR SPD 5km SFMR SPD 4 km SMAP SPD SFMR RR 5 km SFMR RR 4 km SFMR vs SMAP for PATRICIA at :1: Wind Speed [m/s] Rain Rate [mm/hr] :3 17: 17:3 18: 18:3 19: 19:3

10 From SFMR stat plot 36 minutes / 6 km avg SFMR Wind Speed Bin Bias STD Counts n/a

11 Shic SFMR tracks using best-track (Cme, locacon) to SMAP Cme IdenCfy closest points of approach to SWC; may be mulcple SFMR Track For each closest point of approach: Average SFMR along-track to 6 km centered on that point Keep if closer than 12.5 km and Cme offset less than 36 min 6 km SMAP SWCs 6 km Closest points of approach to SWC center km SWC spacing

12 SMAP / RapidScat / WindSat collocacons (3m) Only extract joint collocacons within 3 minutes of SMAP. 3.7 million matchups. Use WindSat to remove rainy observacons. Find nearly zero speed bias up to 26 m/s, not enough data past that. 2d histogram does not show any trend of increasing SMAP speed bias as compared to RapidScat Speed Error [m/s] SMAP/RapidScat Wind Speed Matchups WindSat / SSMI/S indicate no rain; Within: 3 minutes Speed Bias Speed STD Mean of SMAP/RapidScat Wind Speed [m/s] SMAP Wind Speed [m/s] D Histogram of SMAP/RS wind Speeds [db Counts] Within: 3 minutes; total RapidScat Wind Speed [m/s]

13 SMAP / RapidScat / WindSat collocacons (9m) Same as previous with 9 minute collocacon Cme. 13 million matchups. Find very small speed bias up to 3 m/s (order 1 m/s). 2d histogram show data distributed near 1:1 line, no evidence of large posicve SMAP bias near 3 m/s as compared to RapidScat. Speed Error [m/s] SMAP/RapidScat Wind Speed Matchups WindSat / SSMI/S indicate no rain; Within: 9 minutes Speed Bias Speed STD Mean of SMAP/RapidScat Wind Speed [m/s] SMAP Wind Speed [m/s] D Histogram of SMAP/RS wind Speeds [db Counts] Within: 9 minutes; total RapidScat Wind Speed [m/s]

14 SMAP TB Wind Speed Averaged SFMR Wind Speed [m/s] Wind Speed bias versus SFMR rain rate (SFMR spd > 2 m/s) Insufficient data 6 SFMR 6 km average 8 SFMR > 2 m/s Match-up Cme within 36 min Averaged SFMR Rain Rate [mm/hr]

15 j+1 L2A Gridding Mean Number of L1B TBs per SWC Mean Number of L1B TBs per look in a SWC H/Fore H/Aft V/Fore V/Aft 2 j Cross Track Index j-1 km i-1 i i+1 Aggregate NEDT By Flavor Aggregate NEDT By Flavor H/Fore H/Aft V/Fore V/Aft Cross Track Index