Regional energy and water budget of a precipitating atmosphere over ocean

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  • 1 NASA Langley Research Center
  • 2 National Center for Atmospheric Research
  • 3 Science System and Applications, Inc
  • 4 University of Tokyo
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Abstract

Effects of water mass imbalance and hydrometeor transport on the enthalpy flux and water phase on diabatic heating rate in computing the regional energy and water budget of the atmosphere over ocean are investigated. Equations of energy and water budget of the atmospheric column that explicitly consider the velocity of liquid and ice cloud particles, and rain and snow are formulated by separating water variables form dry air. Differences of energy budget equations formulated in this study from those used in earlier studies are 1) diabatic heating rate depends on water phase, 2) diabatic heating due to net condensation of non-precipitating hydrometeors is included, and 3) hydrometeors can be advected with a different velocity from the dry air velocity. Convergence of water vapor associated with phase change and horizontal transport of hydrometeors is to increase diabatic heating in the atmospheric column where hydrometeors are formed and exported and to reduce energy where hydrometeors are imported and evaporated. The process can improve the regional energy and water mass balance when energy data products are integrated. Effects of enthalpy transport associated with water mass transport through the surface are cooling to the atmosphere and warming to the ocean when the enthalpy is averaged over the global ocean. There is no net effect to the atmosphere and ocean columns combined. While precipitation phase changes regional diabatic heating rate up to 15Wm-2, the dependence of the global mean value on the temperature threshold of melting snow to form rain is less than 1 Wm-2.

Corresponding author: Seiji Kato Climate Science Branch NASA Langley Research Center MS 420 Hampton, Virginia, 23681-2199, seiji.kato@nasa.gov

Abstract

Effects of water mass imbalance and hydrometeor transport on the enthalpy flux and water phase on diabatic heating rate in computing the regional energy and water budget of the atmosphere over ocean are investigated. Equations of energy and water budget of the atmospheric column that explicitly consider the velocity of liquid and ice cloud particles, and rain and snow are formulated by separating water variables form dry air. Differences of energy budget equations formulated in this study from those used in earlier studies are 1) diabatic heating rate depends on water phase, 2) diabatic heating due to net condensation of non-precipitating hydrometeors is included, and 3) hydrometeors can be advected with a different velocity from the dry air velocity. Convergence of water vapor associated with phase change and horizontal transport of hydrometeors is to increase diabatic heating in the atmospheric column where hydrometeors are formed and exported and to reduce energy where hydrometeors are imported and evaporated. The process can improve the regional energy and water mass balance when energy data products are integrated. Effects of enthalpy transport associated with water mass transport through the surface are cooling to the atmosphere and warming to the ocean when the enthalpy is averaged over the global ocean. There is no net effect to the atmosphere and ocean columns combined. While precipitation phase changes regional diabatic heating rate up to 15Wm-2, the dependence of the global mean value on the temperature threshold of melting snow to form rain is less than 1 Wm-2.

Corresponding author: Seiji Kato Climate Science Branch NASA Langley Research Center MS 420 Hampton, Virginia, 23681-2199, seiji.kato@nasa.gov
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