Abstract
The High-Resolution Infrared Radiation Sounder (HIRS) on NOAA and MetOp A/B satellites has been observing the Earth continuously for over four decades, providing essential data for operational numerical weather prediction, retrieval of atmospheric vertical profile, and total column information on atmospheric temperature, moisture, water vapor, ozone, cloud climatology, and other geophysical parameters globally. Although the HIRS data meets the needs of the short-term weather forecast, there are inconsistencies when the long-term decadal time series is used for time series analysis. The discrepancies are caused by several factors, including spectral response differences between the HIRS models on the satellites and spectral response uncertainties and other calibration issues. Previous studies have demonstrated that significant improvements can be achieved by recalibrating some of the HIRS longwave CO2 channels (Channels 4, 5, 6, and 7), which has helped make the time series more consistent. The current study aims to extend the previous study to the remaining longwave infrared sounding channels, including Channels 1, 2, 3, and 8, using a similar approach. Similar to previous findings, the spectral shift of the HIRS bands has helped improve the consistency in the time series from NOAA-06 to MetOp-A and B for these channels. We also found that HIRS channels on MetOp-B also have bias relative to Infrared Atmospheric Sounding Interferometer (IASI) on the same satellite, especially Channel 4, and a spectral shift significantly reduced the bias. To bridge the observation gap in time series in the mid-1980s between NOAA-07 and NOAA-09, the global mean method has been used since no transfer radiometers between them was available for this period, and the spectral response function corrections, therefore, can be applied to the earliest satellites (NOAA-06) for these channels. The recalibration parameters have been provided to other scientists at the University of Wisconsin for improving the time series in their long-term studies using historical HIRS data and are now made available to the science community.
Highlights
The NOAA TIROS-N series of satellites from NOAA-06 in the late 1970s to currentNOAA-19 and MetOp A and B by EUMETSAT, with infrared channels sensing atmospheric vertical layers, have provided valuable datasets serving the weather forecasting and climate analysis
Many climate data records based on the High-Resolution Infrared Radiation Sounder (HIRS) measurements have been developed, such as the cloud climatology [1,2,3], upper tropospheric water vapor time series [4,5], outgoing longwave radiation (OLR) [6] and ENSO index [7]
The HIRS instrument design has evolved over the four decades, from HIRS/2, HIRS/2I, HIRS/3 on the earlier satellites to HIRS/4 onboard NOAA-18, NOAA-19, and MetOpA/B [6]
Summary
The NOAA TIROS-N series of satellites from NOAA-06 in the late 1970s to currentNOAA-19 and MetOp A and B by EUMETSAT, with infrared channels sensing atmospheric vertical layers, have provided valuable datasets serving the weather forecasting and climate analysis. The discrepancy in measurements from different instruments onboard different satellites poses a challenge for time series analysis. These discrepancies are mainly caused by the different instrument characteristics, such as the different SRF of the same channel on different satellites and uncertainties in them [8,9,10,11]. Due to the design differences mentioned above, the SRF of the same channels on different HIRS instruments has different central wave numbers and shapes This SRF difference directly affects the inter-satellite bias and becomes an obstacle in constructing climate data records. These inter-satellite biases could be directly subtracted from globally averaged time series during the overlapping periods for some studies [5], or a better approach is to quantify the inter-satellite SRF differences of the same channel and applied the corrected SRFs [1]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
