NOAA/NESDIS/Center for Satellite Applications and Research Radiance Performance of SNPP/ATMS in Comparison to Recalibrated POES/AMSU-A Cheng-Zhi Zou, Xianjun Hao, and Manik Bali 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. NOAA/NESDIS/Center for Satellite Applications and Research GSICS MW Subgroup Web Meeting, January 12, 2018

Purpose I) Evaluation of ATMS Radiance Performance for Climate Trend Detection MSU/AMSU-A has been used for creating atmospheric temperature Climate Data Record (CDR) for climate trend detection and monitoring The last NOAA satellite carrying AMSU-A is NOAA-19; EUMETSAT will launch its last AMSU- A on MetOp-C next year Evaluating the long-term radiance performance of ATMS is the first step toward this merging goal II) Examining the Idea of Using IMICA Re-calibrated MSU/AMSU-A Radiance FCDR as an In- Orbit Reference for Characterizing Biases of Other Microwave Instruments STAR has recalibrated AMSU-A temperature sounding channels using Integrated Microwave Inter-Calibration Approach (IMICA, Zou and Wang 2011, 2013) There is an interest in the GSICS microwave community to use the IMICA recalibrated MSU/AMSU-A as an in-orbit reference to monitor biases of other microwave instrument Mitch provided long time support for project from the program side, such as leveraging funding. And Fuzhong also provides program support and coordinate the CRTM team to work with our product development team. You may notice that most of my SDS science team members are from his Branch. I also want to thank Changyong for his long time support from scince side. I can always count on his support when I need a discussion on science. even when I need support from his team members.

AMSU-A/ATMS Sounding Channels ATMS AMSU-A Focusing ATMS temperature sounding channels 5-15 These channels have the same channel frequency as the AMSU-A channels 4-14 This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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.

Integrated Microwave Inter-Calibration Approach (IMICA) Before Recalibration (Operational Calibrated) Calibration coefficients were determined by satellite overlap observations Calibration coefficients were fixed over the entire life cycle of a satellite Using SNO, CRTM, global-ocean means, etc. as tools to calculate calibration coefficients Remove or minimize time-varying inter-satellite biases σ : ~ 0.1 K; Bias~0.5-1K This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. After Recalibration (IMICA recalibrated) σ: ~ 0.03 K; Bias~0.2K

Data Processing Approach IMICA calibrated AMSU-A data include limb-adjustment to convert footprints at different angles to nadir observations Generate daily and monthly gridded maps for limb-adjusted data from multiple scan positions Grid resolution is 1° by 1° lat/lon Long-term monthly time series were generated from these maps Similar ATMS gridded data were generated from nadir-only observations (observations with scan angles less than 3.3) For both AMSU-A and ATMS, each daily grid cell contains multiply FOVs to reduce noise This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. Scanning patterns of AMSU-A (blue) and ATMS (black). The unit is kilometer for both the horizontal and vertical coordinates. The beam widths of FOVs are 3.3° and 2.2° for AMSU-A and ATMS, respectively. Red circle indicates grid boxes for binning Lower Panel: AMSU-A FCDR daily gridded map for limb-adjusted multi-pixel means

POES Satellite Orbital Drifts This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. SNPP

Instrument Stability SNPP/ATMS NOAA-18/AMSU-A This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. NOAA-18/AMSU-A

Possible Reasons Causing Inter-Satellite Biases Calibration biases Errors in warm target temperature Errors in cold space view temperature Inaccurate calibration nonlinearity Sampling Biases Diurnal differences between satellites Mitch provided long time support for project from the program side, such as leveraging funding. And Fuzhong also provides program support and coordinate the CRTM team to work with our product development team. You may notice that most of my SDS science team members are from his Branch. I also want to thank Changyong for his long time support from scince side. I can always count on his support when I need a discussion on science. even when I need support from his team members.

Impact of Diurnal Drift on Inter-Satellite Biases Yearly Mean Inter-sensor Biases Over Ocean This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. Yearly Mean Inter-sensor Biases Over Land Long-term mean bias pattern between NOAA -18 and NOAA-15 for channel 4 If diurnal drift effects are large, values of inter-satellite biases depend on time periods selected for the calculation

Inter-Sensor Biases Between POES/AMSU-A and SNPP/ATMS Inter-Sensor Biases: ATMS-AMSU time period is 12/2011-02/2017 AMSU/AT MS Channels N18- N15 N18- Aqua ATMS- N18 ATMS- Aqua # of months 148 63 4/5 -0.11 0.07 0.33 Aqua ch4 5/6 0.01 0.03 0.49 6/7 N15 ch6 0.11 1.17 7/8 -0.02 -0.18 0.88 0.66 8/9 -0.06 0.32 0.09 9/10 -0.10 0.48 0.25 10/11 -0.04 -0.03 0.62 0.57 11/12 N15 ch11 0.59 0.54 12/13 0.82 0.87 13/14 0.97 14/15 N15 ch14 -0.08 0.23 0.16 AMSU-A channel 5 vs ATMS Channel 6 This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. Inter-satellite difference time series of global ocean mean brightness temperatures from AMSU-A observations between POES satellite pairs and those between POES AMSU-A and SNPP ATMS

Possible Reasons Causing Seasonal Variability In Inter-Satellite Difference Time Series Diurnal differences between satellites Frequency mismatch Sun-heating inducted instrument temperature variability in radiances due to inaccurate calibration (for IMICA recalibrated AMSU-A data, this effect was minimized because more accurate calibration coefficients were developed and used in the calibration, Zou and Wang 2011) Mitch provided long time support for project from the program side, such as leveraging funding. And Fuzhong also provides program support and coordinate the CRTM team to work with our product development team. You may notice that most of my SDS science team members are from his Branch. I also want to thank Changyong for his long time support from scince side. I can always count on his support when I need a discussion on science. even when I need support from his team members.

Standard Deviation Tells Potential Issues in ATMS Observations ATMS ch5 needs investigation AMSU/AT MS Channels N18- N15 N18- Aqua ATMS- N18 ATMS- Aqua   148 63 4/5 0.032 Aqua ch4 0.063 5/6 0.043 6/7 N15 ch6 0.058 7/8 0.031 0.033 0.026 8/9 0.020 0.024 0.037 0.019 9/10 0.023 10/11 0.027 0.016 0.025 11/12 N15 ch11 0.017 12/13 0.051 0.042 0.022 13/14 0.085 0.067 14/15 N15 ch14 0.093 0.073 This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. AMSU-A ch11 vs ATMS ch12 for a comparison

Possible Reasons Causing Non-Zero Trends in Inter-Satellite Difference Time Series Diurnal drifts between satellites End-point effects Calibration drift due to inaccurate calibration Calibration changes Mitch provided long time support for project from the program side, such as leveraging funding. And Fuzhong also provides program support and coordinate the CRTM team to work with our product development team. You may notice that most of my SDS science team members are from his Branch. I also want to thank Changyong for his long time support from scince side. I can always count on his support when I need a discussion on science. even when I need support from his team members.

Absolutely Stability of ATMS Radiances Trends (K/Dec) of Inter-Sensor Difference Time Series AMSU-A ch13 vs ATMS ch14 N18- N15 N18- Aqua ATMS-N18 ATMS- Aqua   148 63 4/5 -0.064 Aqua ch4 -0.059 Aqua ch4 5/6 0.039 0.021 6/7 N15 ch6 -0.116 7/8 0.049 -0.099 0.086 -0.012 8/9 -0.085 -0.166 0.088 0.029 9/10 0.017 -0.135 0.008 -0.026 10/11 -0.015 -0.052 -0.017 0.011 11/12 N15 ch11 -0.071 -0.010 -0.016 12/13 -0.160 0.234 -0.020 13/14 -0.268 0.420 -0.025 14/15 N15 ch14 -0.352 0.493 -0.018 This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. ATMS-Aqua reached a stability at 0.02K/Dec for all channels; This is good enough for trend detection. Because both satellites are calibrated independently, this suggested that both ATMS and Aqua reached an absolute stability within 0.02K/Dec. This number could get smaller when overlaps get longer

Scene Temperature Dependent Biases in ATMS ATMS shows scene temperature dependent biases; suggesting its calibration nonlinearity is not accurate This project focus on developing MSU/AMSU atmospheric temperature CDRs. The window channels will be addressed by another NOAA group. In summary, we work on 15 atmospheric temperature channels, involving 15 satellites, with tempral coverage from late 1978 to present. Each channel needs to be intercalibrated seperately. 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. Long-term mean bias pattern between NOAA -18 and NOAA-15 for channel 8

Conclusion ATMS needs reprocessing/recalibration ATMS had a calibration change in March 2017, causing bias jumps relative to reference satellite ATMS are warmer than IMICA calibrated AMSU-A for all channels before March 2017 ATMS channel 5 is likely to have a frequency mismatch with AMSU-A channel 4 on the order of 10 MHz ATMS radiances reached a absolute stability within 0.02K/Dec for all temperature sounding channels Calibration nonlinearity of ATMS are inaccurate for certain channels NOAA-16 needs further recalibration since the calibration coefficients determined from overlaps before 2010 cannot fully describe its behavior afterwards ATMS needs reprocessing/recalibration Using re-calibated/inter-calibrated AMSU-A data as a reference provides useful information on ATMS radiance performance So here is a summary that needs to be deal with in the MSU/AMSU reprocessing. These issues include, but are not limited to, ………. In this talk, I’ll be focusing on the intersatellite biases and warm target temperature contamination; but also touch a little bit on other problems.