What's New

MT_CKD_H2O Version	Release Date	Notes
4.3	February 2024	New foreign continuum coefficients in window regions for wavenumbers greater than 4000 cm-1 were derived (Mlawer and Mascio) using a modification to the MT_CKD line shape formalism that was constrained by results from the following studies from the U. Grenoble group led by A. Campargue: Mondelain et al. (2015), doi:10.1039/c5cp01238d Vasilchenko et al. (2019), .doi:10.1016/j.jqsrt. 2019.02.01 Mondelain et al. (2020), doi:10.1016/j.jqsrt.2020.106923 Fleurbaey et al. (2022), doi.org/10.1016/j.jqsrt.2021.108004 Koroleva et al. (2023), doi.org/10.1016/j.jqsrt.2022.108432
4.2	December 2023	Changes to self, foreign, and self T-dependence in IR window (590-1400 cm-1) derived from AERI (Mlawer/Mascio/Turner). **Re-released with minor changes to netCDF in February 2024.
4.1.1	January 2023	Minor changes to 4.1. Supporting information found here. **Re-released with minor changes to netCDF in February 2024.
4.1	December 2022	Revised foreign H2O continuum in Far-IR to adjust for MT_CKD_3.5 changes to self. **Re-released with minor changes to netCDF in February 2024.
4.0.1	November 2022	Added changes to handle negative frequencies for water vapor.
v4.0	October 2022	The water vapor continuum code has been restructured for its inclusion in HITRAN and put in separate module. The absorption coefficients are now in an external (netCDF) file and the code contains only simple scaling and interpolation operations. The full continuum code (contnm.f90) has been modified to call the new water vapor continuum code (K.E. Cady-Pereira, E. Mlawer).
v3.6	June 2022	The water vapor self continuum temperature dependence is now computed as a power law, where the exponent is determined from existing behavior between 270-305K (E. Mlawer, J. Mascio).
v3.5	October 2020	The water vapor continuum in the microwave through far-infrared was modified (E. Mlawer, V. Payne, J. Mascio, D. Turner). The modifications will be detailed in Payne et al. (2021). Revised self and foreign continuum coefficients in the microwave were derived based on DOE ARM MWR measurements using an approach similar to that in Payne et al. (2010). The temperature dependence of the self continuum in the microwave was modified based on Katkov et al. (1995), Tretyakov et al. (2016) and the ARM MWR analysis. The self continuum in the far-infrared was revised based on Odintsova et al. (2020), and the temperature dependence of the self continuum is based on Odintsova et al. (2020) and Burch and Grynvak (1979). Beyond the far-IR (up to 800 cm-1), the self temperature dependence was revised based on Burch and Alt (1984) and Burch and Grynvak (1979).
v3.2	August 2017	New self continnum coefficients in window regions for wavenumbers greater than 2000 cm-1 were added and self continuum temperature dependence from 1800-3500 cm-1 was updated (E.J. Mlawer, M.J. Alvarado, K.E. Cady-Pereira). The following analyses were used in this revision: Campargue et al., 2016, doi:10.1002/2016JD025531 Mondelain et al., 2014, doi:10.1002/2013JD021319 Ventrillard et al., 2015, doi:10.1063/1.4931811 Richard et al., 2017, doi:10.1016/j.jqsrt.2017.06.037 New examination of IASI cases used in Alvarado et al. (2013) and Mlawer et al. (2012) and AERI and AIRS cases in Mlawer et al. (2012)
v3.0	December 2016	Recent changes have been evaluated with RHUBC-I and RHUBC-II data. Includes modifications to H2O foreign continuum coefficients in the far-infrared based on the analysis of REFIR-PAD (Bianchini and Palchetti, 2008) measurements taken at Cerro Toco, Chile, as part of the ARM RHUBC-II campaign and a re-analysis of the AERI-ER measurements from the ARM NSA site (first analyzed in Delamere et al., (2010)). The foreign continuum was also changed in the sub-millimeter and microwave regions as a result of the analysis of SAO FTS (Paine and Turner, 2013) measurements taken during the RHUBC-II campaign, which led to modification of the H2O self continuum in this region to maintain good agreement with the microwave measurements analyzed in Payne et al. (2008 and 2011). (E.J. Mlawer, D.D. Turner, S.N. Paine, V.H. Payne)
v2.8	July 2016	A number of changes were made to water vapor continuum absorption in the window past the fundamental H2O band (E.J. Mlawer, M.J. Alvarado): Self continuum coefficients were modified from 1880-2390 cm-1 to fix issues in the CO fundamental region that were pointed out by Alvarado et al. (2013). Foreign continuum coefficients from 1800-3000 cm-1 were modified to improve agreement with Baranov and Lafferty (2012); in the 1900-2150 cm-1 region, attention was also paid to IASI measurements (Alvarado et al., 2013). Coefficients for N2-H2O relative efficiency from 2000-2900 cm-1 were determined from Baranov and Lafferty simultaneously with the H2O foreign and self continuum coefficients in this region (as described above). Foreign continuum coefficients at wavenumbers greater than 4000 cm-1 were modified based on Baranov and Lafferty (2012) and Mondelain et al. (2014) measurements (E.J. Mlawer and M.J. Alvarado).
v2.4	June 2009	Modifications to the water vapor continuum arise from new analyses of ARM measurements in the microwave and far-IR regions (S.A. Clough, J. Delamere, V.H. Payne, E.J. Mlawer) Analyses of measurements in the microwave are based primarily on the two-channel MWR (23.8 and 31.4 GHz) at SGP, with supporting evidence from 150 GHz MWRHF measurements during the COPS campaign and from 170 GHz GVRP measurements at SGP (Payne et al., 2009). Measurements in the far-IR were from the AERI_ext at the NSA site, in the time surrounding and including the RHUBC-I campaign (Delamere et al., 2009). Fixed an issue with the water vapor Jacobians in which the analytic Jacobians were dependent on the starting wavenumber (MT_CKD_2.3)(K.E. Cady-Pereira and S. Tjemkes)
v2.0	September 2007	H2O foreign modified in 250-550 cm-1 region based on analyses of NSA AER_XR data. (September 2007)
v1.00	February 2003	cntnm_progr_v1.0 This is the initial release of the MT_CKD water vapor continuum and represents the first recomputation of the entire self and foreign broadened continuum since the original model was developed in the 1980s. This version of the continuum is implemented in the line-by-line model LBLRTM v7.0 and will be utilized in all related AER Radiative Transfer models. The MT_CKD continuum is based on a new formulation: The self and foreign continuum models are each based on the contributions from two components: a collision induced component and a line shape component. This change in perspective has resulted from the difficulty in developing a line shape model based on sound physics that explains the magnitude of the increased absorption in the intermediate wing over that provided by the impact approximation. These two components are applied consistently to all water vapor lines from the microwave to the visible, and the results summed to obtain self and foreign continuum coefficients from 0-20,000 cm-1. Eight and seven parameters are needed to specify the two components for the self and foreign continua, respectively, which are sufficient to generate the entire continuum spectrum over this spectral domain. The ratio of the self continuum at 296 K to that at 260 K has been kept the same as in the CKD model. The only temperature dependence for the foreign continuum arises from the radiation term as with CKD. The MT_CKD model as with CKD, should be regarded as a semi empirical model with strong constraints provided by the known physics. The data that have been used to develop the new continuum model has come predominantly from spectral atmospheric measurements. Only cases for which the characterization of the atmospheric state has been highly scrutinized have been used. This new model has been developed by E.J. Mlawer, D.C. Tobin and S.A. Clough building on the original CKD formulation; hence the name MT_CKD. In this release only the stand alone program, cntnm_progr_mt_ckd_1.00.f, is being provided. The driver for this program has been changed slightly so that pressure, temperature and path length may be entered as input. A negative value for the pressure provides a default result from 0-5000 cm-1 with P = 1013 mb, T = 296 k and X (path) = 1 cm. In addition to the original version of ckd_0, there are three updated versions of ckd available with the release dates indicated: ckd_2.4.2 (2002_08) ckd_2.4.1 (2000_05) ckd_2.2.2 (1996_12; rev 1999_06) ckd_0 (1989) ckd_2.2.2 (1996_12; rev 1999_06) These models with associated readme files are contained in the directories associated with the continuum. Information on the nature of the modifications is contained in the respective readme files. The continuum module and associated continuum program (program) are very similar except that the latter includes a driver and a small modification has been made in SUBROUTINE CONTNM to provide the appropriate interface. The main substance of the code are data statements which are not only identical between continuum module and program, but up to this point are similar between the three evolutionary versions of the CKD continnum models. Remarks on implementing the stand alone program are contained in comments in the main progam: drcntnm (driver for continuum). The program provides the following output files: WATER.COEF - the mt_ckd_# self and foreign broadened water continuum coefficients. CNTNM.OPTDPT - continuum optical depths for the defined path. It should be noted that the MT_CKD water vapor continuum model spans the spectral domain from 0-20,000 cm-1 (inf - 500 nm).