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

About TRMM: 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

TRMM Primary Instruments for Measuring Precipitation: 1. Precipitation Radar (PR) 2. TRMM Microwave Imager (TMI) radiometer 3. Visible and Infrared Scanner (VIRS) Two Additional Instruments: 1.Cloud and Earth Radiant Energy Sensor (CERES) 2.Lightning Imaging Sensor (LIS)

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

Visible and Infrared Scanner Introduction: Introduction: senses radiation coming up from the Earth in five spectral regions, ranging from visible to infrared 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

Cloud and Earth Radiant Energy Sensor o Introduction o 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. Gathers information on: Cloud properties…Cloud EffectsCloud properties…Cloud Effects cloud-amount, altitude, thickness, and the size of the cloud particlescloud-amount, altitude, thickness, and the size of the cloud particles Specifications: Wavelength:.5 to 50 um Horizontal Resolution: 10 km Swath Width: + 80 degrees

Lightning Imaging Sensor Introduction: 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 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." the sensor will provide information that could lead to future advanced lightning sensors capable of significantly improving weather "nowcasting." Specifications: Wavelength:  m Horizontal Resolution: 4 km Swath Width: 600 km

Precipitation Radar Introduction: Introduction: The Precipitation Radar is the first active space borne radar designed to provide three-dimensional maps of storm structure 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

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

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

Precipitation Radar

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

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

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

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

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

TRMM Precipitation Radar Algorithm Level 3 ( 3A25, 3A26) Level 3 ( 3A25, 3A26) Objective: 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 ) Level 3 (3A25, 3A26 ) Objective: Objective: Compute rain rate statistics Compared to 3A25 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.

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

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

Ave Rain: Digital Array Viewer

Sigma 0: Digital Array viewer

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

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

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

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

Credits TRMM Official Website TRMM Education and Outreach Scientist : Dr Jeffrey B. Halverson Responsible NASA Official: Dr.Robert Adler NASA Official Website Editor: Jim Wilson NASA Official: Brian Dunbar Last Updated: July 6, Japan Aerospace Exploration Agency (JAXA) Official Website National Space Development Agency of Japan (NASDA) Official Website Tropical Rainfall Measuring Mission （ TRMM ） Precipitation Radar Algorithm Instruction Manual For Version 6