Abstract

The advanced technology microwave sounder (ATMS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite is a total power radiometer and scans across the track within a range of ±52.77° from nadir. It has 22 channels and measures the microwave radiation at either quasi-vertical or quasi-horizontal polarization from the Earth’s atmosphere. The ATMS sensor data record algorithm employed a commonly used two-point calibration equation that derives the earth-view brightness temperature directly from the counts and temperatures of warm target and cold space, and the earth-scene count. This equation is only valid under Rayleigh–Jeans (RJ) approximation. Impacts of RJ approximation on ATMS calibration biases are evaluated in this study. It is shown that the RJ approximation used in ATMS radiometric calibration results in errors on the order of 1–2 K. The error is also scene count dependent and increases with frequency.

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References

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  1. F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
    [CrossRef]
  2. F. Weng, H. Yang, and X. Zou, “On convertibility from antenna to sensor brightness temperature for ATMS,” IEEE Geosci. Remote Sens. Lett. (2012, to be published).
    [CrossRef]

2012 (1)

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

Goldberg, M.

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

Wang, X.

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

Weng, F.

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

F. Weng, H. Yang, and X. Zou, “On convertibility from antenna to sensor brightness temperature for ATMS,” IEEE Geosci. Remote Sens. Lett. (2012, to be published).
[CrossRef]

Yang, H.

F. Weng, H. Yang, and X. Zou, “On convertibility from antenna to sensor brightness temperature for ATMS,” IEEE Geosci. Remote Sens. Lett. (2012, to be published).
[CrossRef]

Yang, S.

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

Zou, X.

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

F. Weng, H. Yang, and X. Zou, “On convertibility from antenna to sensor brightness temperature for ATMS,” IEEE Geosci. Remote Sens. Lett. (2012, to be published).
[CrossRef]

J. Geophys. Res. (1)

F. Weng, X. Zou, X. Wang, S. Yang, and M. Goldberg, “Introduction to Suomi NPP ATMS for NWP and tropical cyclone applications,” J. Geophys. Res. 117, D19112 (2012).
[CrossRef]

Other (1)

F. Weng, H. Yang, and X. Zou, “On convertibility from antenna to sensor brightness temperature for ATMS,” IEEE Geosci. Remote Sens. Lett. (2012, to be published).
[CrossRef]

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Figures (4)

Fig. 1.
Fig. 1.

(a) Relative and (b) absolute variations of the brightness temperature with blackbody temperature varying from 100 to 300 K at frequencies 23.8, 53.6, 89.0, and 190.3 GHz.

Fig. 2.
Fig. 2.

Variations of calibration errors (TbRJTb) with count ratio (δc) introduced by the RJ approximation at 23.8 (red), 53.6 (black), 89.0 (green), and 190.3 GHz (blue). Here TbRJ is calculated by Eq. (1) and Tb is obtained by Eq. (2), with Tc and Tw set to 2.73 and 300 K, respectively.

Fig. 3.
Fig. 3.

Scatter plots of calibration errors introduced by the RJ approximation (e.g., Tbobs,RJTbobs) with respect to (a) observed count ratio (δcobs) and (b) brightness temperature (Tbobs) at 23.8, 53.6, 89.0, and 190.3 GHz using one-month AMSU-A/MHS data at nadir in January 2010 from NOAA-18 within three small geographical areas: Sahara desert (D1: 5W-25E, 15N-30N), tropical ocean (D2: 55E-85E, 10S-5N), and Antarctic (D3: 90E-120E, 70S-85S).

Fig. 4.
Fig. 4.

(a) Biases and (b) standard deviations of calibration errors introduced by the RJ approximation (e.g., TbRJ,obsTbobs) for 20 AMSU-A/MHS channels using one-month data at nadir in January 2010 from NOAA-18 over the same three small domains as in Fig. 3.

Equations (8)

Equations on this page are rendered with MathJax. Learn more.

Tb,s=δc(Tb,wTb,c)+Tb,c,
δc=C¯sC¯cC¯wC¯c.
Rs=δc(RwRc)+Rc.
Rυ(T)=2hc2υ3exp(hcυkT)1C1υ3exp(C2υT)1,
exp(C2υT)=1+C2υT+12(C2υT)2++1n!(C2υT)n+.
RυRJ(T)=C1υ2C2T.
RRJ=δc(C1υ2C2TwC1υ2C2Tc)+C1υ2C2Tc,
ΔRRJRRJR=δc(ΔRwΔRc)+ΔRc.

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