arthur hou nasa goddard space flight center
DESCRIPTION
Space-Based Precipitation Measurements. Arthur Hou NASA Goddard Space Flight Center. JCSDA-HFIP Workshop, 2-3 December 2010, Miami, Florida. Current Generation of Global Precipitation Products. - PowerPoint PPT PresentationTRANSCRIPT
Arthur HouNASA Goddard Space Flight Center
Space-Based Precipitation Measurements
JCSDA-HFIP Workshop, 2-3 December 2010, Miami, Florida
JCSDA-HFIP Workshop, 2-3 December 2010 2
Current Generation of Global Precipitation Products
TRMM radar provided an anchor for rainfall estimates by passive microwave sensors in the tropics and subtropics.
Further advances require better sensors and remote-sensing algorithms (especially for light rain and falling snow).
Current multi-satellite products are based on MW or MW+IR observations from uncoordinated satellite missions using a variety of merging techniques
50N
50S
TRMM Realtime 3hr global rain map at 0.25o resolution
JCSDA-HFIP Workshop, 2-3 December 2010 3
Detailed knowledge of precipitation microphysical properties (particle size distribution, liquid/ice partition, hydrometeor profiles, etc.) is key to improving precipitation retrievals from passive microwave sensors- Dual-frequency or dual-polarimetric radar capabilities
A better understanding of global water fluxes & precipitation characteristics (frequency, intensity, distribution, etc.) in a changing climate requires improved measurements of light rain and snow.
- Light rain and snowfall account for ~50% of precipitation events and significant afractions of precipitation volume outside the Tropics
“High frequency” water vapor channels are key to improving precipitation retrievals over land, especially over frozen terrains
Ground validation must go beyond direct comparison of surface rain rates between ground and satellite measurements to provide the means for improving satellite simulators, retrieval algorithms, & model applications
Near-realtime “asynoptic” observations between those by polar orbiters at fixed local times have high operational values in hurricane monitoring - TMI data account for 16% of all tropical cyclone position fixes made by the
Joint Typhoon Warning Center in a typical year
Lessons from TRMM
JCSDA-HFIP Workshop, 2-3 December 2010 4
GPM Reference Concept
Unify and advance precipitation measurements from space to provide next-generation global precipitation products within a consistent framework
GPM Mission Concept
Key Advancement
Using an advanced radar/radiometer
measurement system to improve constellation
sensor retrievals
Partner Satellites:
GCOM-W1
DMSP F-18, F-19
Megha-Tropiques
MetOp, NOAA-19
NPP, JPSS (over land)
GPM Core Observatory (65o )DPR (Ku-Ka band)GMI (10-183 GHz)
(NASA-JAXA, LRD 2013)
• Precipitation physics observatory
• Transfer standard for inter-satellite calibration of constellation sensors
• Enhanced capability for cinear realtime monitoring ciof hurricanes & cimidlatitude storms
• Improved estimation of cirainfall accumulation
Low Inclination Observatory (40o )GMI (10-183 GHz) (NASA & Partner, 2014)
Coverage & Sampling
• 1-2 hr revisit time over land
• < 3 hr mean revisit time over 90% of globe
JCSDA-HFIP Workshop, 2-3 December 2010 5
GPM Observations from Non-Sun-Synchronous Orbits
Monthly Samples as a Function of the Time of the Day (1o x 1o Resolution)
TRMM: 3652 “asynoptic” samples
GPM Core+LIO: 6175 samples
Core+LIO: 4298 samples
Near real-time observations filling gaps between those of polar orbiters at fixed time of the day for:
• Intercalibration of polar-orbiting msensors over wide range of latitudes
• Near real-time monitoring of mhurricanes & midlatitude storms
• Improved accuracy of rain volume estimation
• Resolving diurnal variability in mrainfall climatologym
JCSDA-HFIP Workshop, 2-3 December 2010 6
NASA-JAXA GPM Core Observatory
Increased sensitivity (~12 dBZ) for light rain and snow detection relative to TRMM
Better measurement accuracy with differential attenuation correction
Detailed microphysical information (DSD mean mass diameter & particle no. density) & identification of liquid, ice, and mixed-phase regions
Dual-Frequency (Ku-Ka band) Precipitation Radar (DPR):
Multi-Channel (10-183 GHz) GPM Microwave Imager (GMI):
Higher spatial resolution (IFOV: 6-26 km)
Improved light rain & snow detection
Improved signals of solid precipitation over land (especially over snow-covered surfaces)
4-point calibration to serve as a radiometric reference for constellation radiometers
Combined Radar-Radiometer Retrieval
DPR & GMI together provide greater constraints on possible solutions to improve retrieval accuracy
Observation-based a-priori cloud database for constellation radiometer retrievals
Core Observatory Measurement Capabilities
JCSDA-HFIP Workshop, 2-3 December 2010 7
JAXA/NICT Dual-Frequency Precipitation Radar
heavy rainRain-ratelight rain/snow
Rai
nra
te O
ccu
rren
ce
mid- & high- latitude rain & snow
Measurable range by 35.55 GHz radar Measurable range
by 13.6GHz radar
tropical rain
Courtesy Z. Haddad
GPM
TRMM
~12.5 mm/h~1.5 mm/h
Rain Rate (mm/h)
Simulated Error Std Dev in Rain Retrieval
Per
cen
t
DPR capabilities relative to TRMM PR
CloudSat data show that light rain rates between 0.2-0.5 mm/hr account for 16% of the rain volume < 2.0 mm/hr.
With Ku and Ka bands, GPM will capture ~98% of total global rain volume. Courtesy
of Wes Berg
40N-40S
JCSDA-HFIP Workshop, 2-3 December 2010 8
GMI capabilities
4 in/hr
G. Skofronick-Jackson
AMSU-B 89 GHz AMSU-B 183.3 ± 7 GHz
NOAA NEXRAD Data Snow Retrieval
g m3
Radar reflectivity of the March 5-6, 2001 New England blizzard (75 cm of snow fell on Burlington, VT)
Cannot distinguish surface from cloud effects.
Surface effects screened by water vapor. Snowfall appears as low brightness temperatures
Feasibility demonstration of snowfall retrieval using HF channels
AMPR (Aircraft) GMI (Core) AMSR-E TMI SSMIS
Comparison of GMI resolution with other radiometers
Synthesized Brightness Temperatures (R. Hood)
JCSDA-HFIP Workshop, 2-3 December 2010 9
Constellation microwave sensor channel coverage
Mean Spatial Resolution (km)
Different center frequencies, viewing geometry, and spatial resolution must be reconciled
Channel 6 GHz
10 GHz
19 GHz
23 GHz
31/36 GHz
50-60 GHz
89/91 GHz 150/166 GHz
183/190 GHz
AMSR-E 6.925V/H
10.65V/H
18.7V/H
23.8V/H
36.5V/H
89.0 V/H
GMI 10.65 V/H 18.70 V/H 23.80 V 36.50 V/H 89.0 V/H 165.5 V/H 183.31 V
MADRAS 18.7 V/H 23.8 V 36.5 V/H 89.0 V/H 157 V/H
SSMIS 19.35 V/H 22.235 V 37.0 V/H 50.3-63.28 V/H 91.65 V/H 150 H 183.31H
MHS 89 V 157 V 183.311 H 190.311 V
ATMS 23.8 31.4 50.3-57.29 87-91 164-167 183.31
V – Vertical Polarization H – Horizontal Polarization
Channel 6 GHz 10 GHz 19 GHz
23 GHz
31/36 GHz
50-60 GHz
89/91 GHz
150/166 GHz
183 GHz
AMSR-E 56 38 21 24 12 5
GMI 26 15 12 11 6 6 6
MADRAS 40 40 40 10 6
SSMIS 59 59 36 22 14 14 14
MHS 17 17 17
ATMS 74 74 32 16 16 16
Passive Microwave Sensor Characteristics in the GPM Era
JCSDA-HFIP Workshop, 2-3 December 2010 10
Inter-Satellite Calibration of Microwave Radiometers
• Objective: Quantify and reconcile differences between similar but not identical microwave radiometers to produce self-consistent global precipitation estimates
• X-Cal (Imagers): Convert observations of one satellite to virtual observations of another using non-Sun-synchronous satellite as a transfer standard (e.g. TMI or GMI)
GPM International X-Cal Working Group (NASA, NOAA, JAXA, CNRS, EUMETSAT, CMA, CONAE, GIST, & universities) in coordination with WMO/CGMS GSICS
- Develop corrections for recurring instrument errors and implementation strategy for routine intercalibration of constellation radiometers
- Bias correction a function of orbital phase and solar beta angle
- Agreement between different methods ~ 0.3 K
TMI Bias Correction Table (K)
• X-Cal (Sounders):
- Double differencing using forecast residual as primary transfer standard to provide a basis for calibration consistency
- Collaboration with NWP centers
NOAA 17 183 ±3 GHz (Ocean)
(MHS-ECMWF)-(AMSU_B-ECMWF)
Courtesy of Bauer (ECMWF) Hanna, Weng, & Yan (NOAA)
JCSDA-HFIP Workshop, 2-3 December 2010 11
GPM Strategy to Global Precipitation Estimation
RAIN
SNOW
Meneghini et al., NASA/GSFC
- Radar for vertical structural details- Radiometers for horizontal coverage
- A radar-radiometer system for a common transfer standard
DPR Retrievals:
• A characteristic size parameter (D 0) of the PSD estimated from the difference (in dB) between Ku- and Ka-band radar reflectivity factors
• Ambiguities include unknown shape parameter () of the gamma PSD distribution and the snow mass density ()
• Characteristic number concentration of PSD is given by D 0 and the radar equation
• Step-by-step estimation of attenuation correction based on PSD estimates
• Precipitation rate and the equivalent water content are derived from the PSD for an assumed velocity distribution
JCSDA-HFIP Workshop, 2-3 December 2010 12
Combined DPR+GMI retrievals
• Using GMI radiance measurements as additional constraints on the DPR profiling algorithm:
Assumptions regarding the particle size distribution, ice microphysics, cloud water and water vapor vertical distribution are refined using a variational procedure that minimizes departures between simulated and observed brightness temperatures - according to the sensitivity of simulated brightness temperatures to assumptions in DPR retrievals.
• Retrievals are consistent with both DPR reflectivities and GMI radiances wwithin a maximum-likelihood estimation framework.
• Construction of an a-priori database that relates hydrometeors to bbrightness temperatures over the range of observed T b values for pprecipitation retrievals from constellation radiometers.
• Pre-launch algorithm advances focus on retrievals of solid precipitation pand physical retrievals over land:
- Modeling of nonlinear, under-constrained relationships between physical characteristics of precipitation particles and microwave observations
- Characterization of land surface variability/emissivity
JCSDA-HFIP Workshop, 2-3 December 2010 13
GPM Joint Field Campaigns:• Joint campaign with Brazil on warm rain retrieval over land in Alcântara, 3-24 March 2010
• Light Precipitation Validation Experiment (LPVEx): CloudSat-GPM light rain in shallow melting layer situations in Helsinki, Finland, 15 Sept - 20 Oct 2010
• Mid-Latitude Continental Convective Clouds Experiment (MC3E): NASA-DOE field campaign in central Oklahoma, Apr-May 2011
• High-Latitude GPM Cold-Season Precipitation Experiment (GCPEX): Joint campaign with Environment Canada on snowfall retrieval in Ontario, Canada, Jan-Feb 2012
• Hydrological validation with NOAA HMT in 2013 (under development)
International Collaborations on GPM GV
Pre-CHUVA (2010)
MC3E (2011)
NASA-EC Snowfall (2012)
LPVEx (2010)
15 Active International Projects
• Joint field campaigns• National networks and other ground assets (radar, gauges,
etc.)• Hydrological validation sites (streamflow gauges, etc.)
JCSDA-HFIP Workshop, 2-3 December 2010 14
•Intercalibrated constellation radiometric data reconciling differences in center frequency, viewing geometry, resolution, etc.
- Converting observations of one satellite to virtual observations of another using non-Sun-synchronous satellite as a transfer standard
- GMI employs an encased hot load design (to minimize solar intrusion) and noise diodes for nonlinearity removal to attain greater accuracy & stability
•Unified precipitation retrievals using a common cloud database constrained by DPR+GMI measurements from the Core Observatory
GPM Core: Reference Standard for Constellation Radiometers Next-Generation Global Precipitation Products
Optimally matching observed Tb with simulated Tb from an a priori cloud database
Simulated Tb Observed Tb
TRMM uses a model-generated cloud database
GPM uses a DPR/GMI-constrained database
Prototype GPM Radiometer Retrieval
Comparison of TRMM PR surface rain with TMI rain retrieval using an cloud database consistent with PR reflectivity and GMI multichannel radiances
~ 10 km
TB observedTB model #1
JCSDA-HFIP Workshop, 2-3 December 2010 15
GPM Data Products
JCSDA-HFIP Workshop, 2-3 December 2010 16
Applications for hurricane monitoring & prediction
Hurricane Tracking Numerical Weather Prediction
ECMWF Hurricane Charley track forecasts from analysis 2004081112
Cyclone disappeared in operational forecast without rain assimilation
Rain Ass
Courtesy of P. Bauer/ECMWF
Position Error in Nautical Miles
Precipitation observations are in operational use at ECMWF, NCEP, JMA, and other NWP centers.
JCSDA-HFIP Workshop, 2-3 December 2010 17
• GPM is an international satellite mission that will unify and advance precipitation measurements from a constellation of microwave sensors for scientific research and societal applications.
– GPM is in the implementation phase at NASA and JAXA– Core Observatory Launch Readiness Date: 21 July 2013
• Key advances include
– More accurate instantaneous precipitation information, especially light rain & solid precipitation
– Better space-time coverage through international partnership– High spatial resolution (DPR & GMI on Core Observatory)– Next-generation global precipitation products building on
intercalibrated constellation radiometric measurements and unified physical retrievals using a common observation-constrained hydrometeor database
• NASA Precipitation Processing System is currently producing
– Prototype intercalibrated L1 products for TMI, SSMI, AMSR-E, SSMIS, & WindSat
– L3 merged global precipitation products using TMI, SSMI, AMSR-E, AMSU, & MetOp in near real-time for research & applications
Summary (1/2)
JCSDA-HFIP Workshop, 2-3 December 2010 18
• GPM is a science mission with integrated applications goals:
– MW imaging and precipitation rates available within 1 hr of observation from two GMI’s in non-Sun-synchronous orbits for near real-time applications
– DPR reflectivity and combined DPR+GMI precipitation products available within 3 hr of observation
• Ground validation is key to pre-launch algorithm development and post-launch product evaluation.
- NASA is conducting a series of joint field campaigns with domestic & international partners to refine algorithm assumptions & parameters.
- Synergy with NWP in areas such as radiometer intercalibration, observation operator development, and model physics improvement
Summary (2/2)
JCSDA-HFIP Workshop, 2-3 December 2010 19
Additional Information
JCSDA-HFIP Workshop, 2-3 December 2010 20
* Minimum detectable rainfall rate is defined by Ze=200 R1.6 (TRMM/PR: Ze=372.4 R1.54 )
Item KuPR at 407 km KaPR at 407 km TRMM PR at 350 km
Antenna Type Active Phased Array (128)
Active Phased Array (128)Active Phased Array
(128)
Frequency 13.597 & 13.603 GHz 35.547 & 35.553 GHz 13.796 & 13.802 GHz
Swath Width 245 km 120 km 215 km
Horizontal Reso 5 km (at nadir) 5 km (at nadir) 4.3 km (at nadir)
Tx Pulse Width 1.6 s (x2) 1.6/3.2 s (x2) 1.6 s (x2)
Range Reso 250 m (1.67 s) 250 m/500 m (1.67/3.34 s) 250m
Observation Range 18 km to -5 km (mirror image around nadir)
18 km to -3 km (mirror image around nadir)
15km to -5km (mirror image at nadir)
PRF VPRF (4206 Hz170 Hz) VPRF (4275 Hz100 Hz) Fixed PRF (2776Hz)
Sampling Num 104 ~ 112 108 ~ 112 64
Tx Peak Power > 1013 W > 146 W > 500 W
Min Detect Ze (Rainfall Rate)
< 18 dBZ( < 0.5 mm/hr )
< 12 dBZ (500m res)( < 0.2 mm/hr )
< 18 dBZ( < 0.7 mm/hr )
Measure Accuracy within ±1 dB within ±1 dB within ±1 dB
Data Rate < 112 Kbps < 78 Kbps < 93.5 Kbps
Mass < 365 kg < 300 kg < 465 kg
Power Consumption < 383 W < 297 W < 250 W
Size 2.4×2.4×0.6 m 1.44 ×1.07×0.7 m 2.2×2.2×0.6 m
DPR Instrument Characteristics
JCSDA-HFIP Workshop, 2-3 December 2010 21
GMI Instrument Characteristics
FrequencyBeam NEDT
Req. (K)Expected*NEDT (K)
Expected Beam Efficiency (%)
Expected Cal. Uncertainty (K)
Resolution (km)
10.65 GHz(V & H) 0.53 0.53 K 91.4 1.04 19.4 x 32.2
18.7(V & H) 0.61 0.60 92.0 1.08 11.2 x 18.3
23.8(V) 0.82 0.45 92.5 1.26 9.2 x 15.0
36.5(V & H) 0.52 0.45 96.6 1.20 8.6 x 14.4
89.0(V & H) 0.65 0.46 95.6 1.19 4.4 x 7.3
165.5(V & H) 1.72 0.93 91.9 1.20 4.4 x 7.3
183.31±3(V) 1.72 0.99 91.7 1.20 4.4 x 7.3
183.31±7(V) 1.72 0.93 91.7 1.20 4.4 x 7.3
Data Rate: ~30 kbpsPower: 162 WattsMass: 166 kg* Analysis data as of May 2010
Deployed Size: 1.4 m x 1.5 m x 3.5 m Antenna Size: 1.2 mSwath: 885 kmResolution and swath for GMI on Core
JCSDA-HFIP Workshop, 2-3 December 2010 22
Baseline Constellation Schedule
Hour
Prime Life Extended Life
Current Capability: < 3h over
45% of globe
GPM (2015): < 3h over 90% of globe
GPM Constellation Sampling and Coverage
GPM Core Launch
1-2 hr revisit time over land with inclusion of sounders
JCSDA-HFIP Workshop, 2-3 December 2010 23
Three complementary approaches:
• Direct statistical validation (surface):- Leveraging off operational networks to identify and resolve first-order discrepancies between satellite and ground-based precipitation estimates
• Physical process validation (vertical column):
- Cloud system and microphysical studies geared toward testing and refinement of physically-based retrieval algorithms
• Integrated hydrologic validation/applications (4-dimensional):
- Identify space-time scales at which satellite precipitation data are useful to water budget studies and hydrological applications; characterization of model and observation errors
Role of GPM Ground Validation
Pre-launch algorithm development & post-launch product evaluation
- Refine algorithm assumptions & parameters - Characterize uncertainties in satellite retrievals
& GV measurements “Truth” is estimated through the convergence of
satellite and ground-based estimates
JCSDA-HFIP Workshop, 2-3 December 2010 24
Science Partnership with NOAA on GPM
• Level 1 radiometer intercalibration (partnership through GSICS & PMM)
- Using NWP forecast residuals for sounder intercalibration
• Level 2 precipitation algorithms (NOAA PI’s on PMM Science Team)
- Land surface characterization for physically based retrieval- Precipitation microphysical properties
• Statistical validation
- Collaboration with NOAA NMQ for validation and product enhancement
• Hydrological applications/validation
- Joint field campaigns with NOAA HMT (e.g. HMT-SE)
• Level 3 multi-satellite product development
- Moving towards U.S. national products (global & regional)
- Combined satellite & ground-based measurements
• Level 4 dynamic downscaling
- WRF ensemble data assimilation using NOAA operational data streams