TRMM Tropical Rainfall Measurement (Mission)

1
TRMMTropical Rainfall Measurement (Mission)

2

• Why TRMM?
• 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 atmospheres 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

3
TRMM Objectives

• 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.

4
TRMM Specifications

• 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

5

• TMI - Tropical Microwave Imager
• VIRS - Visible and Infrared Scanner
• PR - Precipitation Radar
• LIS - Lightning Imaging Sensor
• CERES - Clouds and Earths Radiant Energy System

6
TMI - Tropical Microwave Imager

• - multichannel radiometer, whose signals in
  combination can measure rainfall quite accurately
  over oceans and somewhat less accurately over the
  land
• - 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/stratofor
  m
• - basis for calculation is Plancks law, how much
  energy a body radiates based on its temperature
• 6-50km horizontal resolution

7
VIRS - Visible 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

8
PR - Precipitation 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

9
LIS - Lightning 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 energy, and
  duration of lightning related to convective
  storms
• - 4km resolution

10
CERES - Clouds and Earths Radiant Energy System

• - 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 earths radiation budget, how
  much radiation received by the earth, and then
  re-emitted
• - three channels in each radiometer Total
  radiance (0.3 to gt100 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

11
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

12
Final Product
13
TRMM Example with TMI 85 GHz
14
TRMM Composite with TMI 37 GHz
15
TRMM Composite with PR
16
TRMM Composite with LIS
17
TRMM Composite with VIRS
18
(No Transcript)
19
(No Transcript)
20
References

• - 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/fa
  ct_sheets/earthsci/trmm
• - http//tsdis02.nascom.nasa.gov/tsdis/tsdis_redes
  ign/TRMMBackground.html