Abstract:
The 14‑channel RPG‑HATPRO microwave radiometer has been operating at the Faculty of Physics, St. Petersburg State University since 2012. It performs continuous measurements of the cloud liquid water path (LWP). Along with the multiple quadratic regression (MQR) method provided by the instrument manufacturer, the “physical” retrieval algorithm, which is based on the inversion of the radiative transfer equation (IRTE), and the multiple linear regression (MLR) method are used. The estimates of the LWP retrieval errors are presented for the cases when MLR coefficients are derived from model calculations and from the experimental data (in the latter case, the IRTE results are used as reference data). It is shown that the application of the experimental data and the utilization of measurements in 7 spectral channels of the radiometer provide the LWP random error of 0.015–0.017 kg/m2 which is two times lower than in case of derivation of regression coefficients from model calculations. The bias does not exceed 0.005 kg/m2 in this case. It is demonstrated that the MLR results provide a reliable identification of clear-sky conditions if the criterion of minimal LWP variations is applied.
Keywords:
cloud liquid water path, troposphere, remote sensing, microwave radiometer, inverse problems, linear regression
References:
- Westwater Ed., Crewell S., Mätzler C., Cimini D. Principles of surface-based microwave and millimeter wave radiometric remote sensing of the troposphere // Quaderni della Società Italiana di ElettroMagnetismo. 2005. V. 1, N 3. P. 50–90.
- Maetzler C., Morland J. Refined physical retrieval of integrated water vapor and cloud liquid for microwave radiometer data // IEEE Trans. Geosci. Remote Sens. 2009. V. 47, N 6. P. 1585–1594. DOI: 10.1109/TGRS.2008.2006984.
- Meijgaard E., Crewell S. Comparison of model predictted liquid water path with ground-based measurements during CLIWA-NET // Atmos. Res. 2005. V. 75, N 3. P. 201–226. DOI: 10.1016/j.atmosres.2004.12.006.
- Kostsov V.S., Ionov D.V., Biryukov E.Yu., Zaitsev N.A. Cross-validation of two liquid water path retrieval algorithms applied to ground-based microwave radiation measurements by the RPG-HATPRO instrument // Int. J. Remote Sens. 2018. V. 39, N 5. P. 1321–1342. DOI: 10.1080/01431161.2017.1404163.
- Radiometer Physics. A Rohde and Schwarz Company. [Electronic resource]. URL: https://www.radiometer-physics.de (last access: 25.01.2019).
- Rose T., Crewell S., Löhnert U., Simmer C. A Network suitable microwave radiometer for operational monitoring of the cloudy atmosphere // Atmos. Res. 2005. V. 75, N 3. P. 183–200. DOI: 10.1016/j.atmosres.2004.12.005.
- Kostsov V.S. Vosstanovlenie parametrov oblachnoj atmosfery po dannym radiometra PRG-HATPRO // Izv. RAN. Fiz. atmosf. i okeana. 2015. V. 51, N 2. P. 179–190. DOI: 10.1134/S0001433815020085.
- Thermodynamic Initial Guess Retrieval (TIGR) [Electronic resource]. URL: http://ara.abct.lmd.polytechnique.fr/index.php?page=tigr (last access: 25.01.2019).
- Peterburgskij Nansen-tsentr [Electronic resource]. URL: http://ru.niersc.spb.ru (last access: 25.01.2019).
- Zabolotskikh Е.V., Mitnik L.M., Bobylev L.P., Jokhannessen O.M. Razrabotka i validatsiya algoritmov vosstanovleniya skorosti privodnogo vetra po dannym SSM/I s primeneniem Nejronnykh Setej i fizicheskikh ogranichenij // Issled. Zemli iz kosmosa. 2000. N 2. P. 62–71.
- Zabolotskikh Е.V., Timofeev Yu.M., Uspenskij A.B., Mitnik L.M., Bobylev L.P., Jokhannessen O.M., CHernyj I.V. O tochnosti mikrovolnovykh sputnikovykh izmerenij skorosti privodnogo vetra, vlagosoderzhaniya atmosfery i vodozapasa oblakov // Izv. RAN. Fizika atmosf. i okeana. 2002. V. 5, N 38. P. 592–600.
- Cimini D., Rosenkranz P.W., Tretyakov M.Y., Koshelev M.A., Romano F. Uncertainty of atmospheric microwave absorption model: Impact on ground-based radiоmeter simulations and retrievals // Atmos. Chem. Phys. 2018. V. 18. P. 15231–15259. DOI: 10.5194/acp-18-15231-2018.
- Roebeling R.A., Placidi S., Donovan D.P., Russchenberg H.W.J., Feijt A.J. Validation of liquid cloud property retrievals from SEVIRI using ground-based observations // Geophys. Res. Lett. 2008. V. 35. L05814. DOI: 10.1029/2007GL032115.
- Kadygrov Е.N., Gorelik A.G., Tochilkina T.A. Rezul'taty issledovanij vodozapasa oblakov radiometricheskim kompleksom «Mikroradkom» // Optika atmosf. i okeana. 2014. V. 27, N 6. P. 546–552; Kadygrov E.N., Gorelik A.G., Tochilkina T.A. Study of liquid water in clouds with the “Microradkom” radiometric system // Atmos. Ocean. Opt. 2014. V. 27, N 4. P. 596–604.
- Maetzler C. Ground-based observations of atmospheric radiation at 5, 10, 21, 35, and 94 GHz // Radio Sci. 1992. V. 27. P. 403–415.