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The MLS RHI Product

Contact: William Read

Basic Information

Relative humidity with respect to ice (RHI) is the ratio of the amount of water vapor present to the maximum amount of water vapor that a parcel of air can hold (adding more water will lead to ice condensation with no change increase in humidity - strongly dependent on the air parcel's temperature). RHI is measured in units of percent. It is useful for determining where clouds are present or likely to form. Both humidity and clouds exert significant radiative forcings in the Earth Climate System.
A map of Relative Humidity
Sample relative humidity retrieval map

How it is part of MLS Science Objectives

One of the scientific objectives of MLS is studying climate change. MLS measurements of relative humidity along with temperature and cloud ice are important for improving our understanding climate processes.

How EOS MLS derives RHI

RHI is relative humidity with respect to ice. It is a derived product from the standard products of water vapor and terperature using the Goff-Gratch formula.

Quick Product Information for data version v4.2

  • Swath Name: RHI
  • Status Flag: Only use pro les for which the Status field is an even number.
  • Useful Range: Profile from 316 - 0.002 hPa
  • DAAC Short Name: ML2RHI
  • Precision: Only use values for which the estimated precision is a positive number.
  • Quality Threshold: > 1.45; Temperature Quality > 0.9 where P >= 100hPa or 0.2 where P < 100 hPa
  • Convergence Threshold: < 2.0; Temperature Convergence < 1.03
Download EOS Aura RHi v4.2 data

Publications related to the MLS RHi data product


  1. Dion, I., P. Ricaud, P. Haynes, F. Carminati, T. Dauhut, "Ice injected into the tropopause by deep convection – Part 1: In the austral convective tropics", Atmospheric Chemistry and Physics 19, 9, 6459-6479, doi:10.5194/acp-19-6459-2019, 2019. reprint
  2. Schoeberl, M.R., E.J. Jensen, L. Pfister, R. Ueyama, T. Wang, H. Selkirk, M. Avery, T. Thornberry, A.E. Dessler, "Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer", Journal of Geophysical Research: Atmospheres 124, 7, 3984-4003, doi:10.1029/2018jd029849, 2019. reprint


  1. Lambert, A., M. Santee, "Accuracy and precision of polar lower stratospheric temperatures from reanalyses evaluated from A-Train CALIOP and MLS, COSMIC GPS RO, and the equilibrium thermodynamics of supercooled ternary solutions and ice clouds", Atmospheric Chemistry and Physics 18, 3, 1945-1975, doi:10.5194/acp-18-1945-2018, 2018. reprint


  1. Sioris, C., A. Malo, C. McLinden, R. D'Amours, "Direct injection of water vapor into the stratosphere by volcanic eruptions", Geophysical Research Letters 43, 14, 7694-7700, doi:10.1002/2016gl069918, 2016. reprint
  2. Takahashi, H., H. Su, J.H. Jiang, "Error analysis of upper tropospheric water vapor in CMIP5 models using “A-Train” satellite observations and reanalysis data", Climate Dynamics, doi:10.1007/s00382-015-2732-9, 2016. reprint


  1. Stanfield, R.E., J.H. Jiang, X. Dong, B. Xi, H. Su, L. Donner, L. Rotstayn, T. Wu, J. Cole, E. Shindo, "A Quantitative Assessment of Precipitation Associated With the ITCZ in the CMIP5 GCM Simulations Climate Dynamics", Climate Dynamics, doi:10.1007/s00382-015-2937-y, 2015. reprint
  2. Vergados, P., A. Mannucci, C. Ao, J.H. Jiang, H. Su, "On the comparisons of tropical relative humidity in the lower and middle troposphere among COSMIC radio occultations and MERRA and ECMWF data sets ", Atmospheric Measurement Techniques 8, 1789-1797, doi:10.5194/amt-8-1789-2015, 2015. reprint


  1. Pertsev, N., P. Dalin, V. Perminov, V. Romejko, A. Dubietis, R. Balčiunas, K. Černis, M. Zalcik, "Noctilucent clouds observed from the ground: sensitivity to mesospheric parameters and long-term time series", Earth, Planets and Space 66, 98, doi:10.1186/1880-5981-66-98, 2014. reprint


  1. Su, H., J.H. Jiang, C. Zhai, V.S. Perun, J.T. Shen, A.D. Genio, L.S. Nazarenko, L.J. Donner, L. Horowitz, C. Seman, C. Morcrette, J. Petch, M. Ringer, J. Cole, M. Mesquita, T. Iversen, J.E. Kristjansson, A. Gettelman, L. Rotstayn, S. Jeffrey, J.L. Dufresne, M. Watanabe, H. Kawai, T. Koshiro, T. Wu, E.M. Volodin, T. L'Ecuyer, J. Teixeira, G.L. Stephens, "Diagnosis of Regime-dependent Cloud Simulation Errors in CMIP5 Models Using A-Train Satellite Observations", Journal of Geophysical Research 118, 7, 2762-2780, doi:10.1029/2012JD018575, 2013. reprint


  1. Kishore, P., M.V. Ratnam, S.P. Namboothiri, I. Velicogna, G. Basha, J.H. Jiang, K. Igarashi, S.V.B. Rao, V. Sivakumar, "Global 501S­501N distribution of water vapor observed by COSMIC GPS RO: Comparison with GPS radiosonde, NCEP, ERA-Interim, and JRA-25 reanalysis data sets", Journal of Atmospheric and Solar-Terrestrial Physics 73, 1849-1860, doi:10.1016/j.jastp.2011.04.017, 2011. reprint


  1. L'Ecuyer, T.S., J.H. Jiang, "Touring the atmosphere aboard the A-Train", Physics Today 63, 7, 36-41, doi:10.1063/1.3463626, 2010. reprint


  1. Read, W.G., A. Lambert, J. Bacmeister, R.E. Cofield, L.E. Christensen, D.T. Cuddy, W.H. Daffer, B.J. Drouin, E. Fetzer, L. Froidevaux, R. Fuller, R. Herman, R.F. Jarnot, J.H. Jiang, Y.B. Jiang, K. Kelly, B.W. Knosp, L.J. Kovalenko, N.J. Livesey, , G.L. Manney, H.M. Pickett, H.C. Pumphrey, K.H. Rosenlof, X. Sabounchi, M.L. Santee, M.J. Schwartz, W.V. Snyder, P.C. Stek, H. Su, L.L. Takacs, R.P. Thurstans, H. Vomel, P.A. Wagner, J.W. Waters, C.R. Webster, E.M. Weinstock, D.L. Wu, "Aura Microwave Limb Sounder upper tropospheric and lower stratospheric H2O and relative humidity with respect to ice validation", Journal of Geophysical Research 112, D24S35, doi:10.1029/2007JD008752, 2007. reprint


  1. Cofield, R.E., P.C. Stek, "Design and field-of-view calibration of 114-660 GHz optics of the Earth Observing System Microwave Limb Sounder", IEEE Transactions on Geoscience and Remote Sensing 44, no. 5, 1166-1181, doi:10.1109/TGRS.2006.873234, 2006. reprint
  2. Sherwood, S.C., E.R. Kursinski, W.G. Read, "A distribution law for free-troposphere relative humidity", Journal of Climate 19, 6267-6277, doi:10.1175/JCLI3978.1, 2006. reprint


  1. Waugh, D.W., "Impact of potential vorticity intrusions on subtropical upper tropospheric humidity", Journal of Geophysical Research 110, D11305, doi:10.1029/2004JD005664, 2005. reprint


  1. Jiang, J.H., B. Wang, K. Goya, K. Hocke, S.D. Eckermann, J. Ma, D.L. Wu, W.G. Read, "Geographical Distribution and Inter-Seasonal Variability of Tropical Deep Convection: UARS MLS Observations and Analyses", Journal of Geophysical Research 109, D03111, doi:10.1029/2003JD003756, 2004. reprint
  2. Read, W.G., D.L. Wu, J.W. Waters, H.C. Pumphrey, "A New 147-56 hPa Water Vapor Product from the UARS Microwave Limb Sounder", Journal of Geophysical Research 109, D06111, doi:10.1029/2003JD004366, 2004. reprint
  3. Read, W.G., D.L. Wu, J.W. Waters, H.C. Pumphrey, "Dehydration in the Tropical Tropopause Layer: Implications from UARS MLS", Journal of Geophysical Research 109, D06110, doi:10.1029/2003JD004056, 2004. reprint


  1. Salby, M., F. Sassi, P. Callaghan, W. Read, H. Pumphrey, "Fluctuations of Cloud, Humidity, and Thermal Structure near the Tropical Tropopause", Journal of Climate 16, 21, 3428-3446, doi:10.1175/1520-0442(2003)016<3428:FOCHAT>2.0.CO;2, 2003. reprint
  2. Spichtinger, P., K. Gierens, W. Read, "The global distribution of ice-supersaturated regions as seen by the Microwave Limb Sounder", Quarterly Journal of the Royal Meteorological Society, doi:10.1256/qj.02.141, 2003. reprint


  1. Folkins, I., K.K. Kelly, E.M. Weinstock, "A simple explanation for the increase in relative humidity between 11 and 14 km in the tropics", Journal of Geophysical Research 107, D23, 4736, doi:10.1029/2002JD002185, 2002. reprint
  2. Folkins, I., "Origin of Lapse Rate Changes in the Upper Tropical Tropopause", Journal of Atmospheric Sciences 59, 5, 992-1005, doi:10.1175/1520-0469(2002) , 2002. reprint
  3. Sassi, F., M. Salby, H.C. Pumphrey, W.G. Read, "Influence of the Madden-Julian Oscillation on upper tropospheric humidity", Journal of Geophysical Research 107, D23, 4681, doi:10.1029/2001JD001331, 2002. reprint
  4. Spichtinger, P., K. Gierens, W. Read, "The statistical distribution law of relative humidity in the global tropopause region", Meteorologische Zeitschrift 11, 83-88, doi:10.1127/0941-2948/2002/0011-0083, 2002. reprint


  1. Pawson, S., L. Takacs, A. Molod, S. Nebuda, M. Chen, W. Read, M. Fiorino, "The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM", Advances in Space Research 27, 1457-1465, doi:10.1016/S0273-1177(01)00214-9, 2001. reprint
  2. Read, W.G., J.W. Waters, D.L. Wu, E.M. Stone, Z. Shippony, A.C. Smedley, C.C. Smallcomb, S. Oltmans, D. Kley, H.G.J. Smit, J.L. Mergenthaler, M.K. Karki, "UARS Microwave Limb Sounder Upper Tropospheric Humidity Measurement: Method and Validation", Journal of Geophysical Research 106, D23, 32207-35258, doi:10.1029/2000JD000122, 2001. reprint
  3. Sassi, F., M. Salby, W.G. Read, "Relationship between upper tropospheric humidity and deep convection", Journal of Geophysical Research 106, D15, 17133-17146, doi:10.1029/2001JD900121, 2001. reprint

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