Revisiting simple methods to estimate drop size distributions: a novel approach based on infrared thermography

João L.M.P. de Lima 1 , 2 , Valdemir P. Silva Jr. 3 , M. Isabel P. de Lima 1 , 2 , João R.C.B. Abrantes 1 , 2  and Abelardo A.A. Montenegro 3
  • 1 Department of Civil Engineering, Faculty of Science and Technology of the University of Coimbra (FCTUC), Rua Luís Reis Santos, Campus II - University of Coimbra, 3030-788 Coimbra, Portugal
  • 2 Institute of Marine Research (IMAR) and Marine and Environmental Sciences Centre (MARE), Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal
  • 3 Rural Federal University of Pernambuco, Department of Agricultural Engineering, Rua Dom Manoel de Medeiros s/n, Dois Irmãos, CEP 50910-130 Recife, PE, Brazil


The infrared thermography has been successfully applied as a tool for high resolution imaging in different hydrological studies. This exploratory experimental study aimed at evaluating the possibility of using infrared thermography to determine the diameter of raindrops. Rain samples are collected on a pre-heated acrylic board, which is exposed to rain during an instant, and thermograms are recorded. The area of the thermal stains (“signatures” of the raindrops) emerging on the board is measured and converted to drop diameters, applying a calibration equation. Diameters of natural raindrops estimated using this technique were compared with laser disdrometer measurements; the Nash-Sutcliffe efficiency coefficient was used for evaluating the match between the resulting histograms of drop size distribution. Results confirm the usefulness of this simple technique for sizing and counting raindrops, although it is unsatisfactory in light rain or drizzle.

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  • Atlas, D., Srivastava, R.C., Sekhon, R.S., 1973. Doppler radar characteristics of precipitation at vertical incidence. Rev. Geophys. Space Phys., 11, 1-35.

  • Bentley, A., 1904. Studies of Raindrops and Raindrop Phenomena. Monthly Weather Review, 32, 450-456.

  • Bradley, S.G., Stow, C.D., 1974. The measurement of charge and size of raindrops: Part I. The disdrometer. J. Appl. Meteorol., 13, 114-130.

  • Cardenas, M.B., Harvey, J.W., Packman, A.I., Scott, D.T., 2008. Ground-based thermography of fluvial systems at low and high discharge reveals potential complex thermal heterogeneity driven by flow variation and bioroughness. Hydrol. Process., 22, 7, 980-986.

  • Cataneo, R., Stout, G.E., 1968. Raindrop-size distributions in humid continental climates, and associated rainfall rate-radar reflectivity relationships. J. Appl. Meteorol., 7, 901-907.

  • Danielescu, S., MacQuarrie, K.T.B., Faux, R.N., 2009. The integration of thermal infrared imaging, discharge measurements and numerical simulation to quantify the relative contributions of freshwater inflows to small estuaries in Atlantic Canada. Hydrol. Process., 23, 20, 2847-2859.

  • de Lima, J.L.M.P., Abrantes, J.R.C.B., 2014a. Can infrared thermography be used to estimate soil surface microrelief and rill morphology? Catena, 113, 314-322.

  • de Lima, J.L.M.P., Abrantes, J.R.C.B., 2014b. Using a thermal tracer to estimate overland and rill flow velocities. Earth Surf. Process. Landforms, 39, 10, 1293-1300.

  • de Lima, J.L.M.P., Abrantes, J.R.C.B., Silva Jr, V.P., Montenegro, A.A.A., 2014. Prediction of skin surface soil permeability by infrared thermography: a soil flume experiment. Quantitative Infrared Thermogr. J., 11, 2, 161-169.

  • Eigel, J.D., Moore, I.D., 1983. A simplified technique for measuring raindrop size and distribution. Transactions of the ASABE - American Society of Agricultural and Biological Engineers, 26, 4, 1079-1084.

  • Hauser, D., Amayenc, P., Nutten, B., Waldteufel, P., 1984. A new optical instrument for simultaneous measurement of raindrop diameter and fall speed distribution. J. Atmos. Oceanic Technol., 1, 256-269.

  • Jarman, R.T., 1956. Stains produced by drops on filter paper. Royal Meteorological Society Quarterly J., 82, 252.

  • Jones, D.M.A., 1992. Raindrop spectra at the ground. J. Appl. Meteorol., 31, 1219-1225.

  • Joss, J., Waldvogel, A., 1969. Raindrop size distribution and sampling size errors. J. Atmos. Sci., 26, 566-569.

  • Knollenberg, R.G., 1970. The optical array: An alternative to scattering or extinction for airborne particle size determination. J. Appl. Meteorol., 9, 86-103.

  • Laws, J.O., Parsons, D.A., 1943. The relation of raindrop-size to intensity. Trans. Amer. Geophys. Union, 24, 452-460.

  • Magarvey, R.H., 1957. Stain Method of Drop-Size Determination. J. Meteorol., 14, 182-184.

  • Marshall, J.S., Langille, R.C., Palmer, W.M., 1947. Management of rainfall by radar. J. Meteorol., 4, 186-192.

  • Mejías, M., Ballesteros, B.J., Antón-Pacheco, C., Domínguez, J.A., Garcia-Orellana, J., Garcia-Solsona, E.G., Masqué, P., 2012. Methodological study of submarine groundwater discharge from a karstic aquifer in the Western Mediterranean Sea. J. Hydrol., 464-465, 27-40.

  • Nash, J.E., Sutcliffe, J.V., 1970. River flow forecasting through conceptual models, Part I-a discussion of principles. J. Hydrol., 10, 3, 282-290.

  • Pearson, J.E., Martin, G.E., 1957. An evaluation of raindrop sizing and counting techniques. Scientific Report No. 1, Illinois State Water Survey and the University of Illinois, Urbana, Illinois, USA, 116 p.

  • Pfister, L., McDonnell, J.J., Hissler, C., Hoffman, L., 2010. Ground-based thermal imagery as a simple, practical tool for mapping saturated area connectivity and dynamics. Hydrol. Process., 24, 21, 3123-3132.

  • Schuetz, T., Weiler, M., Lange, J., Stoelzle, M., 2012.Twodimensional assessment of solute transport in shallow waters with thermal imaging and heated water. Adv. Water Resour., 43, 67-75.

  • Sekhon R.S., Srivastava, R.C., 1971. Doppler radar observations of drop-size distributions in a thunderstorm. J. Atmos. Sci., 28, 983-994.

  • Thies, A., 2007. Instruction for Use 021341/08/07. Laser Precipitation Monitor 5.4110.xx.x00 V2.4x STD. 64.

  • Uijlenhoet, R., 1999. Parameterization of Rainfall Microstructure for Radar Meteorology and Hydrology. Doctoral thesis, Wageningen University, Wageningen, The Netherlands.

  • Wang, P.K., Pruppacher, H.R., 1977. Acceleration to terminal velocity of cloud and raindrops. J. Appl. Meteorol., 16, 275-280.

  • Wang, T., Earnshaw K.B., Lawrence, R.S., 1979. Path-averaged measurements of rain rate and raindrop size distribution using a fast-response optical sensor. J. Appl. Meteorol., 18, 654-660.


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