Transcript TRMM Tropical Rainfall Measurement (Mission)

TRMM
Tropical Rainfall Measurement (Mission)
Why TRMM?
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Tropical Rainfall Measuring Mission (TRMM) is a joint
US-Japan study initiated in 1997 to study tropical and
subtropical precipitation.
2/3 of global rainfall occurs in the tropics
¾ of atmosphere’s heat energy is formed from the
release of latent heat of condensation
Precipitation in the tropical and subtropical area affect
global weather and circulation
TRMM provides the first spaceborn rain radar and
microwave radar data that will measure the vertical
distribution of precipitation over the tropics in a band
between ± 35' in latitude
TRMM Objectives
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To obtain and study science data sets over several years of
tropical and subtropical rainfall measurements
To understand how interactions between the sea, air and land
masses produce changes in global rainfall and climate
To help improve modeling of tropical rainfall processes and
their influence on global circulation in order to predict rainfall
and variability at various time scale intervals
To test, evaluate, and improve the performance of satellite
rainfall estimates measurements and techniques.
*Allows for examination through the cloud, to the ground,
making this all possible.
TRMM Specifications
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Relatively low orbit of 350km ( can resolve cloud
images to a small scale)
35 degree inclination angle (tropics and subtropics)
1100 watts of power
Weighs 3620kg - why so much?
Provides mostly monthly rainfall rates
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TMI - Tropical Microwave
Imager
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VIRS - Visible and Infrared
Scanner
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PR - Precipitation Radar
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LIS - Lightning Imaging
Sensor
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CERES - Clouds and Earth’s
Radiant Energy System
TMI - Tropical Microwave Imager
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- multichannel radiometer, whose
signals in combination can measure
rainfall quite accurately over oceans
and somewhat less accurately over
the land
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- passive microwave sensor
measures wave radiation
- measures radiation intensity at 5
different frequencies: 10.7, 19.4,
21.3, 37.0, and 85.5 GHz
- similar to SSM/I, but with the
addition of the 10.7 that gives
better linear rainfall rates
- evaluates integrated cloud
precipitation content, cloud liquid
water, cloud ice, rain intensity, and
rainfall types convective/stratoform
- basis for calculation is Planck’s
law, how much energy a body
radiates based on its temperature
6-50km horizontal resolution
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VIRS - Visible and Infrared Scanner
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- measures radiance in five bandwidths,
.63, 1.6, 3.75, 10.8, and 12.0 um
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- variation of intensities are used to
determine brightness or temperature of
the source
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- can be used to determine cloud tops
based on wavelength received (cirrus vs.
convective)
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- the various channels help to
differentiate between clouds, giving an
indication of rainfall intensities
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- used as an indirect indicator of rainfall
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- serves as a transfer standard to other
measurements that are made from
POES and GOES satellites
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- also used to detect fires
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- 2km resolution
PR - Precipitation Radar
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- 3-dimensional Radar
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- 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
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- compensates for attenuation by
separating rain echoes for vertical
sample sizes of 250m when looking
straight down
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- measurement of rain over land is
better than other satellite systems,
where passive microwave channels
have more difficulty
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- 4km resolution
LIS - Lightning Imaging Sensor
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- 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
energy, and duration of lightning
related to convective storms
- 4km resolution
CERES - Clouds and Earth’s Radiant Energy System
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- 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)
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- evaluates the earth’s “radiation budget”, how
much radiation received by the earth, and then
re-emitted
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- three channels in each radiometer: Total
radiance (0.3 to >100 µm); Shortwave (0.3 to 5
µm); Window (8 to 12 µm)
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- measures radiation at all levels of the
atmosphere, focusing on upper levels and the
surface
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- contributes to the extended range forecast
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- combines with VIRS to produce cloud
properties
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- 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 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 Product
TRMM Example with TMI 85 GHz
TRMM Composite with TMI 37 GHz
TRMM Composite with PR
TRMM Composite with LIS
TRMM Composite with VIRS
References
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http://tsdis.gsfc.nasa.gov/trmmrt/instov.htm
http://trmm.gsfc.nasa.gov
http://daac.gsfc.nasa.gov
http://www.gsfc.nasa.gov/gsfc/service/gallery/fact_sheets/earthsci/trmm
http://tsdis02.nascom.nasa.gov/tsdis/tsdis_redesign/TRMMBackground.html