Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Processes controlling tropical tropopause temperature and stratospheric water vapor in climate models
AU - Hardiman, Steven C.
AU - Boutle, Ian A.
AU - Bushell, Andrew C.
AU - Butchart, Neal
AU - Cullen, Mike J.P.
AU - Field, Paul R.
AU - Furtado, Kalli
AU - Manners, James C.
AU - Milton, Sean F.
AU - Morcrette, Cyril
AU - O'Connor, Fiona M.
AU - Shipway, Ben J.
AU - Smith, Chris
AU - Walters, David N.
AU - Willett, Martin R.
AU - Williams, Keith D.
AU - Wood, Nigel
AU - Lukeabraham, N.
AU - Keeble, James
AU - Maycock, Amanda C.
AU - Thuburn, John
AU - Woodhouse, Matthew T.
N1 - Publisher Copyright: © 2015 American Meteorological Society.
PY - 2015/8/15
Y1 - 2015/8/15
N2 - A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.
AB - A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.
KW - Advection
KW - atmospheric
KW - Chemistry
KW - Cirrus clouds
KW - Deep convection
KW - Diabatic heating
KW - Tropopause
U2 - 10.1175/JCLI-D-15-0075.1
DO - 10.1175/JCLI-D-15-0075.1
M3 - Journal article
AN - SCOPUS:84942855249
VL - 28
SP - 6516
EP - 6535
JO - Journal of Climate
JF - Journal of Climate
SN - 0894-8755
IS - 16
ER -