erich franz stocker * and yimin ji + * nasa goddard space flight center, + wyle inc/pps

Erich Franz Stocker* and Yimin Ji+ *NASA Goddard Space Flight Center, + Wyle Inc/PPS

The Global Precipitation Measurement (GPM) Mission: GPM Near-realtime Data Production at PPS

EGU General Assembly, AS1.3, 4-8 April 2011

2Erich Franz Stocker

• Categories of planned GPM Near-Realtime (NRT) products

• GMI Swath NRT products

• GMI Synthetic data approach

• Combined NRT swath products

• GPM partner radiometer swath products

• GPM merged radiometer (with IR) products

• Access to GPM NRT products

• Synthetic data status

• Summary

Topics To Present



GPM NRT GMI Swath Products

• Level 1 – Instantaneous field of View (Brightness Temperatures)– Level 1B (full product with diagnostic fields)

– Level 1C (standard intercalibrated product) user fields

– Level1 NRT products are 5 minutes with 100 scans overlap (need previous 5 minute file and next 5 minute file)

– Available within 20 minutes of data collection

• Level 2 – Instantaneous field of View (Geophysical parameters)– GPM version of GPROF algorithm (radar enhanced)

– Primary parameter: precipitation

– Level 2 NRT products are 5 minutes with no overlap

– Contain no vertical information

– Available within 25 minutes of data collection

• Format for all GPM NRT products– HDF 5 v1.8 with internal compression turned on

– Produced in such a way that the HDF files can be read with netCDF v4

• Orbits in GPM will be normalized as a full orbit running southernmost to southernmost – no split at the equator (just like TRMM)



GMI Radiometer Synthetic Data Approach

• The synthetic GMI brightness temperature (Tb) database is developed based on existing radiometers and radiative transfer modeling.

• The first step is to establish a global Tb database with coincidental Tb for 13 GMI-like (similar center frequencies and band widths) channels.

• At lower latitude, coincidental TMI low frequency (10 – 85 GHz) and AMSUB/SSMIS high frequency (150 GHz V/H, 1833, 1837 GHz) measurements were matched up with a time window of 10 minutes and spatial resolution of 0.1 degree. At higher latitude, coincidental AMSRE lower frequency (10 – 89 GHz) and AMSUB/SSMIS high frequency (150 GHz V/H, 1833, 1837 GHz) measurements were matched up with a time window of 60 minutes and spatial resolution of 0.1 degree. The time period of using existing observation for establishing each global database is two months.



GMI Synthetic Data Approach (2)

• The second step is to adjust the GMI-like Tb to Synthetic GMI (exact center frequencies and band widths for 13 GMI channels) Tb using radiative transfer modeling. The NOAA CRTM was configured to simulate all existing sensors used in this study as well as the GMI.

• The CRTM simulations were used to establish a look-up table that can be used to compute Tb offsets of GMI channels against GMI-like channels for various bins and atmospheric conditions.

• The GMI-like Tb database were converted to synthetic GMI Tb database using the look-up tables derived from the CRTM.

• NRT like synthetic data in HDF5 format will be made available to any user that wants it– Useful for testing reading software for format issues

– Can be used for checking error limits, etc.



GMI Synthetic 5 min product 37GHz – No Overlap



GMI Synthetic Data 183 GHz 5 min product – No overlap



GMI Synthetic 37GHz with overlap



GMI Synthetic Data 183GHz – with overlap



GPM NRT Combined GMI/DPR product

• In TRMM no near realtime combined TMI/PR product is produced

• In GPM a Level 2 combined GMI/DPR instantaneous field of view product will be produced in NRT

– The combined algorithm utilizes microwave radiance data to constrain radar-derived precipitation solutions, such that the final solutions are simultaneously consistent with coincident microwave radiances, radar reflectivities/surface backscatter, and a priori information from weather prediction center analyses.

– Granule will be roughly an orbit (actual size dependent on TDRSS contact and network throughput)

– Initially will be produced at the DPR Ku swath width ~250Km

– If a good interpolation approach can be verified, the plan is to extend the information into the wider GMI swath ~900Km

– Provides important vertical structure information.

• GPM NRT combined products will be available within 120 minutes of data collection 90% of the time.

• Simulated data products will be available but not until late 2012



GPM Partner Radiometer NRT products

• Level 1 products– Granule size will be dependent upon data provider capabilities but currently looks as if

most will be “orbital”

– L1B Tb (and in some cases perhaps Ta) data will be provided by partners using their calibrations and their orbitizing approach

– L1B products will not be modified by PPS, nor will partner 1B data be available to users from PPS (without permission of the provider)

• Level 1C intercalibrated Tc products– Common logical format for all products

– Current plans call for re-orbitization to the GPM orbit approach but this may be data-type dependent in NRT

– Will provide constellation consistent intercalibrated Tc based on the GPM cross-calibration adjustments based on GPM core satellite instrument measurements.

– Available within 5 minutes of receiving L1B data from partners

• Level 2 GPROF precipitation retrievals– Granule size same as the L1C products

– Available within 5 mins of completing the L1C products



Global Merged Radiometer (IR) products

• A gridded level 3 merged (IMERG) radiometer products– Integrates current TRMM TMPA algorithm with Kalman filtering CMORPH

and PERSIANN CSS (Cloud Classification System ) –neural net

– As much microwave radiometer data augmented with IR

• Current Plans– Global Lat-Long ~.08 x .08 grid

– Half-hourly time period

– Perhaps will produce polar areas in polar projection as separate product (if interested in this being done mail: [email protected])

– HDF5 v1.8 with internal compression (written to be readable using netCDF v4)

• NRT Latency– Each half-hour product will be produced at least twice

– Early run very near to data collection so low latency but perhaps more IR data because some radiometer data not received

– Late run with longer latency (to be established) that will be more complete for radiometer data but longer from the time of data collection.



Access to GPM NRT data

• All GPM NRT data is free of charge and free of restrictions other than acknowledging NASA as the provider

• Access will be available either through: (to be determined)– Anonymous ftp site

– User name/password sftp

• User information is desired– Email for notifying of realtime system status and issues

– If passworded then email used to notify users of changes

• NRT data is kept for 3 days and then eliminated from retrieval directory

• Storage structure will be optimized for automated script retrievals



Summary• GPM will offer GMI near-realtime L1 and L2 swath products within 20

minutes of data collection.

• GPM will make NRT GMI synthetic data available to users in the format that will be used at launch

• GPM will produce combined GMI/DPR L2 swath products with vertical structure information within 120 minutes of data collection

• GPM will produce L1c inter-calibration brightness temperature swath products and L2 GPROF based precipitation retrieval products within 10 minutes of having received the L1B from the data provider

• GPM will provide global NRT ~.08 x ~.08 gridded, half-hourly products

• 1st run will have low latency but higher use of IR data

• 2nd run will be more complete with radiometer data but longer latency

• GPM NRT is free and open

• Questions about NRT can be directed to: [email protected] or [email protected]

erich franz stocker * and yimin ji + * nasa goddard space flight center, + wyle inc/pps

Documents

synthetic gmi tb database

gmi channels tb

tb offsets of gmi channels

coincidental tb

global tb database

gpm nrt productshdf

global database

realtime data production