The document describes a method for detecting and determining post-launch frequency shifts in channels on the AMSU-A instrument. The method uses satellite cross-over data and radiative transfer modeling to identify a frequency shift in Channel 6 on NOAA-15. The analysis finds the actual channel frequency is 36.25 MHz higher than the pre-launch measurement. This method could help improve weather forecasts by providing more accurate channel frequency data for assimilation of AMSU observations.
Detect Channel Frequency Shift in AMSU-A Observations
1. Detection and Determination of Channel Frequency Shift in AMSU-A Observations Cheng-Zhi Zou and Wenhui Wang IGARSS 2011, Vancouver, Canada, July 24-28, 2011 NOAA/NESDIS/Center for Satellite Applications and Research (Thanks Y. Han and Y. Chen at JCSDA for their CRTM calculation support)
2.
3. AMSU-A Orbit Information Satellites Launch Date LECT at lunch NOAA-16 SEPT 2000 1400 Ascending NOAA-15 MAY 1998 0730 Descending NOAA-17 JUNE 2002 1000 Descending NOAA-18 MAY 2005 1400 Ascending MetOp-A October 2006 0930 Descending Local Equator Crossing Time of the Descending Orbits of the NOAA and MetOp-A satellites
4.
5. Examples of SNO Inter-Satellite Biases Channel 6 of MetOp-A minus NOAA-18 Channel 6 of NOAA-15 minus NOAA-18
6. k j Radiance Error Model for SNO Matchup K and J SNO Radiance Error Model Remove relative mean inter-satellite biases Remove non-uniformity in inter-satellite biases Remove instrument temperature signals
7. Effect of Calibration Non-linearity Channel 6 of MetOp-A minus NOAA-18 Channel 6 of MetOp-A minus NOAA-18 Before Inter-Calibration After SNO Inter-Calibration
8.
9.
10.
11.
12.
13. Impact on SNO Time Series Channel 6 of NOAA-15 vs NOAA-18 Before Frequency adjustment Channel 6 of NOAA-15 vs NOAA-18 After NOAA-15 Frequency adjustment
14.
Notas do Editor
Thanks Bruce for the introduction. The title of my talk is ‘MSU/AMSU/SSU CDR development. I gave a talk three years ago in the STAR science forum about the MSU inter-calibration and trend and I kept talking this subject in the last few years in various occasions and hope people don’t get tired of it. But today I try to provide a comprehensive review of the current status and a discussion of various science issues include various bias correction, validation, inter-comparisons, web data support, and so on. I have reserved the room for two hours, but I will only talk about 45 minutes to one hour and allow plenty of time for questions. So don’t get scared about the length of the talk as suggested in the announcement.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
With that, now lets talk about SNOs and calibration. I guess most audience already know what is SNO, and we have Changyong Cao in the audience, who is the pioneer to think and generate the SNO datasets for satellite calibration. Basically, a SNO event is defined when two satellites meet each other and look at the same position of the atmosphere at the same time at nadir direction. The cross position in these orbits roughly shows a SNO event of two NOAA satellites.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
To obtain the coefficients, we establish a radiance error model for the SNO matchup, say satellite k and j. The calibration equation for each satellite is like this, when you subtract them from each other, you obtain the error model like this. Here the Z terms and delta Rl are measured variables, the E are error residual term related to the spatial and time differences in the SNO matchup datasets. Using some statistical chracteristics, this E term can be ignored here. Then we can use regressions to obtain the calibration coefficients. When we do regression, we need to consider the colinearity between the nonlinear terms for the SNO matchups. As a mater of fact, we find there is a high degree of colinearity between satellite pairs for the Z terms. This plot gives you an example for NOAA 11 and 10, here the correlation of the Z terms reach as high as 0.95. So the colinearity equation is part of the regression model, which serves to reduce the independent variables in the regression.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
With that, let me first talk about the MSU atmospheric temperature CDR development. The MSU started from 1978 on TIROS-N and ended on NOAA-14 in May 2007. So we don’t have MSU observations now. We have already completed the MSU CDR development and gained a lot of experiences. We have developed many new techniques for various bias correction procedure. So I am going to talk with more details on this instrument.
The advantage of this recalibration is that the warm target contamination and intersatellite biases have been largely removed at the radiance level. So we expect that if they are used in reanalysis, the reanalysis trend and variability will be close to the what we obtained from retrievals. So we recommend the community to try the new one. Currently,
The recalibration that I am talking about is the The purpose of the recalibration is to remove intersatellite bias and bias drift, on benefit is that it results in more accurate merged satellite climate products, The recalibration can also affect the modeling reanalysis effort. Recalibration Current reanalyses directly assimilate satellite radiance data, reprocessing can help us understanding the bias structure of the radiance data which leads to understanding of the reanalysis uncertainties, Then recalibration can generate consistent radiance dataset to minimize bias correction effort in reanalyses Reprocessing can also help us to better understand the overall quality of the radiance data for optimal use And we also develop algorithm to generate consistent high level data products from the re-calibrated radiance for reanalysis validation