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An Introduction to TRMM and its Precipitation Radar (PR)

An Introduction to TRMM and its Precipitation Radar (PR). Arash Mashayekhi CASA REU Program Sandra Cruz-Pol, Assoc. Prof. ECE UPRM. The Big Picture. Why TRMM? Tropical Rain Measurement Mission tropical rainfall Drives the Climate Machine Need to understand the Water Cycle

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An Introduction to TRMM and its Precipitation Radar (PR)

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  1. An Introduction to TRMM and its Precipitation Radar (PR) Arash Mashayekhi CASA REU Program Sandra Cruz-Pol, Assoc. Prof. ECE UPRM

  2. The Big Picture • Why TRMM? • Tropical Rain Measurement Mission • tropical rainfall Drives the Climate Machine • Need to understand the Water Cycle • TRMM: the first space-borne rain radar (PR) and microwave radiometric data

  3. About TRMM: • Launched: • November 28, 1997 • Circular Orbit altitude: • 350 km • Inclination: • approx. 35 deg. • Orbit Duration: • 91 minutes (16 Orbits a day) • Time Spent over Puerto Rico during each orbit: • 1.14 minutes • Total Time spent over Puerto Rico Each Day: • 18.2 minutes

  4. TRMM Primary Instruments for Measuring Precipitation: • Precipitation Radar (PR) • TRMM Microwave Imager (TMI) radiometer • Visible and Infrared Scanner (VIRS) • Two Additional Instruments: • Cloud and Earth Radiant Energy Sensor (CERES) • Lightning Imaging Sensor (LIS)

  5. Microwave Imager • Introduction: • passive microwave sensor designed to provide quantitative rainfall information TMI • Provides Valuable Information on: • Quantity of the water vapor, • Quantity of the cloud water • Intensity of the rainfall in the • atmosphere. • Specifications: • Frequency:10.65 to 85.5 GHz • Horizontal Resolution:6 to 50 km • Swath Width:760 km

  6. Visible and Infrared Scanner • Introduction: • senses radiation coming up from the Earth in five spectral regions, ranging from visible to infrared • It is used to: • Delineate rainfall • Determine the brightness (visible and near infrared) or temperature (infrared) of the source emitting radiation • Specifications: • Wavelength:.63 to 12 um • Horizontal Resolution:2 km • Swath Width:720 km

  7. Cloud and Earth Radiant Energy Sensor • Introduction • The data from the CERES instrument will be used to study the energy exchanged between the Sun; the Earth’s atmosphere, surface and clouds; and space. • Specifications: • Wavelength:.5 to 50 um • Horizontal Resolution:10 km • Swath Width:+ 80 degrees • Gathers information on: • Cloud properties…Cloud Effects • cloud-amount, altitude, thickness, and the size of the cloud particles

  8. Lightning Imaging Sensor • Introduction: • The Lightning Imaging Sensor is a small, highly sophisticated instrument that will detect and locate lightning over the tropical region of the globe. • the sensor will provide information that could lead to future advanced lightning sensors capable of significantly improving weather "nowcasting." • Specifications: • Wavelength:.77765 mm • Horizontal Resolution:4 km • Swath Width:600 km

  9. Precipitation Radar in more detail! • Introduction: • The Precipitation Radar is the first active space borne radar designed to provide three-dimensional maps of storm structure • PR will provide valuable information on: • Rain size, speed, and altitude • Intensity and distribution of the rain • Rain type • Storm depth • Melting layer altitude: The height at which snow melts into rain

  10. Precipitation Radar • Specifications: • Frequency :13.8 GHz (Ku-band) • More than four times higher than that of a typical ground based radar (NEXTRAD ~ 3 GHz, S-band) • Horizontal Resolution:4.3 km • Swath Width:215 km • Vertical Profile of Rain and Snow:19.3 km • Able to detect rainfall rate down to .7 millimeters/hr • Able to separate vertical rain echo samples of 250 meters

  11. Precipitation Radar • Specifications (Cont’d): • Power Consumption:224 W • Solid state power amplifiers (128) are used to conserve power • Target Area: • phased array antenna that steers the beam electronically

  12. PrecipitationRadar

  13. TRMM Precipitation Radar Algorithm • Level 1 • IB21 • IC21 • Level 2 • 2A21 • 2A23 • 2A25 • Level 3 • 3A25 • 3A26

  14. TRMM Precipitation Radar Algorithm • Level 1 (IB21, IC21) • IB21 • Calculates received power by performing extensive internal calibrations • Data in IB21 include: • Location of Earth surface and surface clutter • System noise level • Land/Ocean Flag • And many more…

  15. TRMM Precipitation Radar Algorithm • Some Examples of IB21 Data: • Navigation • X, Y, Z Components of Space Craft Velocity and Position • Latitude • Longitude • Altitude • Sensor Orientation • Min. Echo Flag • 0 : No Rain • 10: Rain possible but maybe noise • 20: Rain Certain • Land / Ocean Flag • 0: Water • 1: Land

  16. TRMM Precipitation Radar Algorithm • Level 1 (IB21, IC21) • Output: Radar Reflectivity Factor • Almost same file format as that of IB21: • Power replaced by Radar Reflectivity Factor • Noise replaced by Dummy Variable • Level 2 (2A21, 2A23, 2A25) • Primary Objective: • Compute Path Integrated Attenuation (PIA) using the Surface Reference Techniques (SRT). • Input Data: IB21 • Output used by: 2A25, 3A25, and 3A26

  17. TRMM Precipitation Radar Algorithm • Level 2 (2A21, 2A23, 2A25) • Main Objectives: • Classification of Rain Types • Output of Rain / No Rain Flag • Computation of estimated height of freezing level • Output of the height of storm top • Input Data: IC21 • Output used by: 2A25, 2B31, 3A25, 3A26 • Level 2 (Cont’d)(2A21, 2A23, 2A25) • Main Objectives: • Input Data: IC21, 2A21, 2A23 • Output used by: 3A25, 3A26 • Correct for the Rain Attenuation in measured Radar Reflectivity • Estimate instantaneous 3-D distribution of rain

  18. TRMM Precipitation Radar Algorithm • Level 3 (3A25, 3A26) • Objective: • calculate various statistics over a month from the level 2 • Four types of statistics are calculated: • probabilities of occurrence • means and standard deviations • histograms • correlation coefficients • Level 3 (3A25, 3A26) • Objective: • Compute rain rate statistics • Compared to 3A25 • statistics produced from 3A25 are conditioned either on the presence of rain or on the presence of a particular type of rain but statistics from 3A26 are unconditioned.

  19. Data for Rain event • We requested data for a strong rain event that occurred in Puerto Rico last May 2004. • Dates May 14, 15, 21 … • We have corresponding data for NWS NEXRAD in Cayey, PR and rain gauges around the island. • Our goal is to compare these data sets

  20. How does the data look like? • Data files are huge: 30MB for each 1.1 minute. Total of over 1GB for the event. • There are several (~20) products • Ave rain • Near surface rain • Sigma zero • Rain flag • Zeta • PIA

  21. Ave Rain: Digital Array Viewer

  22. Sigma 0: Digital Array viewer

  23. Need to Filter • We only need • Near surf rain • Quality flag • ? • And of course Latitude/Longitude, Date, Time to map over Puerto Rico • This filtering should considerably reduce the data file sizes.

  24. Rain algorithm • Once we filter the data • Need to develop code in IDL to convert to arrays in text • Compare actual rain algorithm being used by NWS. The Rosenfelt tropical convective

  25. PR Rain Characterization • Look at different algorithms per region • Elsner & Carter, 2000 ; Vasquez & Roche, 1997 suggest that the island be divided into ~6 rain regions each with a different algorithm for 3 seasons.

  26. Tropical Environment Tropical weather is especially difficult to forecast due to several factors including: • Easterly trade winds caused forced convection • Complex topography of the island In the fall, we plan to use CSU disdrometer to help further characterize rainfall in PR.

  27. Credits • TRMM Official Website TRMM Education and Outreach Scientist : Dr Jeffrey B. Halverson Responsible NASA Official: Dr.Robert Adler http://trmm.gsfc.nasa.gov/ • NASA Official Website Editor: Jim Wilson NASA Official: Brian Dunbar Last Updated: July 6, 2004 http://www.nasa.gov/home/index.html • Japan Aerospace Exploration Agency (JAXA) Official Website http://www.jaxa.jp/index_e.html • National Space Development Agency of Japan (NASDA) Official Website http://www.nasda.go.jp/index_e.html • Tropical Rainfall Measuring Mission （ TRMM）Precipitation Radar Algorithm Instruction Manual For Version 6

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