Water vapour changes in PDRMIP simulations Øivind Hodnebrog, Gunnar Myhre, Bjørn H. Samset + PDRMIP PDRMIP, London 11-12 May, 2017

Hydrological sensitivity Kvalevåg et al. (2013, GRL) defined a new hydrological sensitivity as “the change in water vapour lifetime per change in surface temperature caused by a radiative forcing” Explored for different drivers in one model (CAM4) Slowdown of hydrological cycle for all drivers Lifetime of water vapour responds only to stabilization changes from atmospheric absorption slow fast Kvalevåg et al. (2013, GRL)

Hydrological sensitivity Slow δ (days/K) slow fast Kvalevåg et al. (2013, GRL)

Hydrological sensitivity Fast δ (days/K) slow fast Kvalevåg et al. (2013, GRL)

Hydrological sensitivity Total δ (days/K) slow fast Kvalevåg et al. (2013, GRL)

Hydrological sensitivity Total δ (days/K)

Water vapour lifetime δ (days/K) Δτ (days)

Water vapour lifetime τ (days) Δτ (days)

Water Column Relative change normalized by ∆Ts (%/K) Model mean prw variable is missing in data from IPSL and HadGEM3. MPI has been skipped.

Water Column Relative change normalized by ∆Ts (%/K) BCx10

Further analysis Evaluation of water column against MODIS/ECMWF Water vapour lifetime change (δ) in historical and future runs in CMIP5 models Surface relative humidity change – land/sea contrast Vertical profiles of specific humidity CO2x2 BCx10 Fixed SST

Extra

Water Column Relative change normalized by ∆Ts (%/K) CO2x2

Absolute change in near-surface RH (%) – coupled hurs: MIROC, HadGEM2, CanESM2, CAM4, CAM5, NorESM1 hur (lev=1 of regridded fields): HadGEM3, GISS, IPSL

Absolute change in near-surface RH (%) – fsst hurs: MIROC, HadGEM2, CanESM2, CAM4, CAM5, NorESM1 hur (lev=1 of regridded fields): HadGEM3, GISS, IPSL

Evaporation Relative change normalized by ∆Ts for each driver (%/K)

Specific humidity profiles CO2x2 BCx10 (scaled by ΔTs) Coupled Fixed SST