A RADIOMETER CONCEPT TO RETRIEVE 3-D RADIOMETRIC EMISSION FROM ATMOSPHERIC TEMPERATURE AND WATER VAPOR DENSITY X. Bosch-Lluis 1 , H. Park 2 , A. Camps 2 , S.C. Reising 1 , S. Sahoo 1 , S. Padmanabhan 3 , N. Rodriguez-Alvarez 2 , I. Ramos-Perez 2 , and E. Valencia 2 1. Microwave Systems Laboratory - ECE, Colorado State University, Fort Collins, CO, USA. 2. Remote Sensing Lab, Dept. Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya and IEEC CRAE/UPC, Barcelona, Spain. 3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. E-mail: [email protected]IGARSS’11 – Vancouver, Canada, 29 th July 2011 FR3.T03: Microwave Radiometry Missions and Instrument Performance III
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X. Bosch-Lluis 1, H. Park 2, A. Camps 2, S.C. Reising 1, S. Sahoo 1, S. Padmanabhan 3, N. Rodriguez-Alvarez 2, I. Ramos-Perez 2, and E. Valencia 2 1. Microwave.
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A RADIOMETER CONCEPT TO RETRIEVE 3-D RADIOMETRIC EMISSION FROM ATMOSPHERIC TEMPERATURE AND WATER
VAPOR DENSITY
X. Bosch-Lluis1, H. Park2, A. Camps2, S.C. Reising1, S. Sahoo1, S. Padmanabhan3, N. Rodriguez-Alvarez2, I. Ramos-Perez2, and E. Valencia2
1. Microwave Systems Laboratory - ECE, Colorado State University, Fort Collins, CO, USA.2. Remote Sensing Lab, Dept. Teoria del Senyal i Comunicacions,
Universitat Politècnica de Catalunya and IEEC CRAE/UPC, Barcelona, Spain.3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Radiometric measurements of the atmosphere provide brightness temperatures according to the radiative transfer equation.
Retrieval algorithms are used to obtain information on profiles of atmospheric parameters such as water vapor content (WVC). Weighting functions and in-situ measurements from radiosondes (RAOB) are required to perform such retrievals.
Here we propose a new approach to this problem which may enable the development of new solutions to the atmospheric profile retrieval problem.
Specifically, the goal of this work is to measure the structure of the radiometric emission from the atmosphere using two antennas separated by a certain distance and pointing to the same point in the atmosphere.
True time delay for measuring at points which have different distance with respect Ant1 and Ant2, and sub-overlapping measurements
Measure Brightness temperature using a CROSS-BEAM InterferometerBrightness temperature from different atmospheric volumes could be measured independently, without the cumulative effect of the RTE
Distance from antenna 1 and 2 to the integration variable
Main differences between this concept and interferometric synthetic aperture radiometer:1. Narrower antenna beamwidth2. Only one visibility sample, not a set of visibility samples3. Adjustable true time delay
Visibility sample written in Cartesian coordinates:
If the overlapping solid angle decreases in comparison to the solid angles of the beams , the radiometric resolution (standard deviation) of the measurement increases.
To retrieve the brightness temperature the cross-beam interferometric measurement must be multiplied by the inverse of
χ=∑l=−∞
∞
∑m=−∞
∞
∑n=0
∞
√Ω1xp
𝑝 Ω2x p
𝑞
√Ω𝑎1𝑝 Ω𝑎2
𝑞→1
Very narrow beams mitigate this effect, then same order of magnitude between the overlapping solid angle and the beams’ solid angles
1. 2D atmosphere for simplicity2. Stratified atmosphere with dx=dz=33 meters3. Atmosphere dimensions 10x66 Km (303x2000 voxels)4. Van Vleck model for absorption coefficients, using RAOB measurements for the water vapor,
pressure and temperature profile.5. F=22.12 and 24.50 GHz the same channels as the CMR-H radiometers CSU, channels
suitable for WVC retrieval. 6. Gaussian antenna patterns.7. Identical and perfectly rectangular response of both systems
0 2000 4000 6000 8000 100000
1
2
3
4
5
6
7
Z axis - height [m]
WV
(g
r/m
2)
WVC profile
WVC profile used for the synthetic atmosphere, obtained using a RAOB
1. A new radiometric for retrieving VWC proposed using interferometric cross-beam techniques.2. The system can measure brightness temperatures independent of the RTE.3. Spatial resolution depends on:
• The horizontal spatial resolution depends on the BW.• The vertical spatial resolution depends on the antenna spacing and beamwidth
Ongoing:
• Keep on studying this technique to better understand its limitations and constraints.• Estimate the radiometric resolution for ±10% error WVC retrieval depending on the altitude.• Determinate methods for calibrate different parts of the system
• Phase• Amplitude• Offset• Radiometric calibration (hot and cold load)
• Perform retrievals from simulated atmospheres (applying techniques such as “onion peeling” instead of a Weighting function approximation).