TRMMTRMMTropical Rainfall Measurement (Mission)Tropical Rainfall Measurement (Mission)

                                            

 

Why TRMM?Why TRMM? Tropical Rainfall Measuring Mission (TRMM) is a Tropical Rainfall Measuring Mission (TRMM) is a

joint US-Japan study initiated in 1997 to study joint US-Japan study initiated in 1997 to study tropical and subtropical precipitation.tropical and subtropical precipitation.

2/3 of global rainfall occurs in the tropics2/3 of global rainfall occurs in the tropics ¾ of atmosphere’s heat energy is formed from ¾ of atmosphere’s heat energy is formed from

the release of latent heat of condensationthe release of latent heat of condensation Precipitation in the tropical and subtropical area Precipitation in the tropical and subtropical area

affect global weather and circulationaffect global weather and circulation TRMM provides the first spaceborn rain radar and TRMM provides the first spaceborn rain radar and

microwave radar data that will measure the microwave radar data that will measure the vertical distribution of precipitation over the vertical distribution of precipitation over the tropics in a band between ± 35' in latitudetropics in a band between ± 35' in latitude

TRMM ObjectivesTRMM Objectives

To obtain and study science data sets over several years of To obtain and study science data sets over several years of tropical and subtropical rainfall measurementstropical and subtropical rainfall measurements

   To understand how interactions between the sea, air and To understand how interactions between the sea, air and land masses produce changes in global rainfall and climateland masses produce changes in global rainfall and climate

   To help improve modeling of tropical rainfall processes and To help improve modeling of tropical rainfall processes and their influence on global circulation in order to predict rainfall their influence on global circulation in order to predict rainfall and variability at various time scale intervalsand variability at various time scale intervals

   To test, evaluate, and improve the performance of satellite To test, evaluate, and improve the performance of satellite rainfall estimates measurements and techniques.rainfall estimates measurements and techniques.

**Allows for examination through the cloud, to the ground, Allows for examination through the cloud, to the ground, making this all possible.making this all possible.

TRMMTRMM Specifications Specifications

Relatively low orbit of 350km ( can resolve Relatively low orbit of 350km ( can resolve cloud images to a small scale)cloud images to a small scale)

35 degree inclination angle (tropics and 35 degree inclination angle (tropics and subtropics)subtropics)

1100 watts of power1100 watts of power Weighs 3620kg - why so much?Weighs 3620kg - why so much? Provides mostly monthly rainfall ratesProvides mostly monthly rainfall rates

TMITMI - Tropical Microwave - Tropical Microwave ImagerImager

VIRSVIRS - Visible and Infrared - Visible and Infrared ScannerScanner

PRPR - Precipitation Radar - Precipitation Radar

LISLIS - Lightning Imaging - Lightning Imaging SensorSensor

CERESCERES - Clouds and Earth’s - Clouds and Earth’s Radiant Energy SystemRadiant Energy System

TMI - TMI - Tropical Microwave ImagerTropical Microwave Imager - multichannel radiometer, whose - multichannel radiometer, whose

signals in combination can measure signals in combination can measure rainfall quite accurately over oceans rainfall quite accurately over oceans and somewhat less accurately over and somewhat less accurately over the landthe land

- passive microwave sensor - passive microwave sensor measures wave radiationmeasures wave radiation

- measures radiation intensity at 5 - measures radiation intensity at 5 different frequencies: different frequencies: 10.710.7, 19.4, , 19.4, 21.3, 37.0, and 85.5 GHz21.3, 37.0, and 85.5 GHz

- similar to SSM/I, but with the - similar to SSM/I, but with the addition of the 10.7 that gives better addition of the 10.7 that gives better linear rainfall rateslinear rainfall rates

- evaluates integrated cloud - evaluates integrated cloud precipitation content, cloud liquid precipitation content, cloud liquid water, cloud ice, rain intensity, and water, cloud ice, rain intensity, and rainfall types convective/stratoformrainfall types convective/stratoform

- basis for calculation is Planck’s law, - basis for calculation is Planck’s law, how much energy a body radiates how much energy a body radiates based on its temperaturebased on its temperature

6-50km horizontal resolution6-50km horizontal resolution

VIRS - VIRS - Visible and Infrared ScannerVisible and Infrared Scanner

- measures radiance in five bandwidths, .63, 1.6, 3.75, 10.8, and 12.0 um

- variation of intensities are used to determine brightness or temperature of the source

- can be used to determine cloud tops based on wavelength received (cirrus vs. convective)

- the various channels help to differentiate between clouds, giving an indication of rainfall intensities

- used as an indirect indicator of rainfall

- serves as a transfer standard to other measurements that are made from POES and GOES satellites

- also used to detect fires

- 2km resolution

PR - PR - Precipitation RadarPrecipitation Radar - 3-dimensional Radar

- determines the vertical distribution from the ground to 15km of precipitation by measuring the radar reflectivity of the clouds and the weakening of a signal as it passes through the precipitation

- compensates for attenuation by separating rain echoes for vertical sample sizes of 250m when looking straight down

- measurement of rain over land is better than other satellite systems, where passive microwave channels have more difficulty

- 4km resolution

LIS - LIS - Lightning Imaging SensorLightning Imaging Sensor

-- investigates the distribution and variability of both atmospheric and cloud-to-ground lightning, and their correlation to convective rainfall

- spatial, temporal, and spectral filtering is processed to produce the clearest images of lightning possible

- sensitive optical lenses that remove background illumination allow for lightning detection even when weak and during brightest times of the day

- detects rate, location, radiant - detects rate, location, radiant energy, and duration of lightning energy, and duration of lightning related to convective stormsrelated to convective storms

- 4km resolution- 4km resolution

CERES - CERES - Clouds and Earth’s Radiant Energy Clouds and Earth’s Radiant Energy SystemSystem

- visible/infrared sensor designed especially to measure energy rising from the surface of the Earth and the atmosphere including its constituents (e.g., clouds and aerosols)

- evaluates the earth’s “radiation budget”, how much radiation received by the earth, and then re-emitted

- three channels in each radiometer: Total radiance (0.3 to >100 µm); Shortwave (0.3

to 5 µm); Window (8 to 12 µm) - measures radiation at all levels of the

atmosphere, focusing on upper levels and the surface

- contributes to the extended range forecast

- combines with VIRS to produce cloud properties

- examines cloud top height, fractional area, cloud liquid water path, droplet size, and other cloud properties that are consistent with the radiative fluxes

Processing the InformationProcessing the Information

- Crazy flow chart of algorithms

- TRMM algorithms combine data from the TMI, VIRS, and PR to produce the best rain estimates

- Algorithms involving VIRS and CERES process the cloud data

- TRMM has its own unique Science Data and Information System (TSDIS)

- TSDIS analyzes the rainfall data and also provides validation from nearly hundreds of ground radar sites

The connection between precipitation rates (TMI and PR) and cloud-top temperatures (VIRS) derived from TRMM should improve estimates of tropical precipitation rates using data from visible and infrared satellite instruments in the eras both before and after the TRMM mission

Final ProductFinal Product

TRMM Example with TMI 85 GHzTRMM Example with TMI 85 GHz

TRMM Composite with TMI 37 GHzTRMM Composite with TMI 37 GHz

TRMM Composite with PRTRMM Composite with PR

TRMM Composite with LISTRMM Composite with LIS

TRMM Composite with VIRSTRMM Composite with VIRS

ReferencesReferences

- http://tsdis.gsfc.nasa.gov/trmmrt/instov.htm- http://tsdis.gsfc.nasa.gov/trmmrt/instov.htm - http://trmm.gsfc.nasa.gov- http://trmm.gsfc.nasa.gov - http://daac.gsfc.nasa.gov- http://daac.gsfc.nasa.gov - http://www.gsfc.nasa.gov/gsfc/service/gallery/fact_sheets/earthsci/trmm- http://www.gsfc.nasa.gov/gsfc/service/gallery/fact_sheets/earthsci/trmm - http://tsdis02.nascom.nasa.gov/tsdis/tsdis_redesign/TRMMBackground.html- http://tsdis02.nascom.nasa.gov/tsdis/tsdis_redesign/TRMMBackground.html