Documentation of the ECHAM5 CLOUD Routine Part 1: 1) Setting precipitation fluxes to zero. 2) Calculating air density, checking for negative values of convective detrained cloud water and vdiff-redistributed humidity. 3) Calcaulating geopotential at half levels Part 2: BEGIN LOOP over LEVELS Initialising values, mainly setting them to zero or to input values from the layer above. Part 3: 1) Melting of snow and ice, dependent on melting energy, column grid mass and time step, the temperature difference to the melting temperature (273.15) (only if positive). Taking the lower values of the existing snowflux (total melting) or the melting dependent on the temperature difference above the melting point. Reducing the snowflux and incrementing the rain flux. Similar calculation for the melting of existing (advected and sedimenting) cloud ice. 2) Sublimation of snow and ice, dependent on saturation, temperature, sublimation energy and empirical coefficients. 3) Evaporation of rain, dependent on saturation, empirical coefficients, temperature. Part 4: Cloud ice updated for melting calculate ice sedimentation (iceflux), not the snow precipitation flux but the slow sedimentation of ice with an empirical terminal velocity. calculate new ice tendency Determince incloud water and ice from cover and grid box water and ice considering ice clouds (T<-35°C), mixed phase clouds (-35°C0°C) Part 5: Determince condensation/deposition or evaporation/sublimation, dependent on saturation, temperature from actual cloud water and ice calculate temperature tendency from the energetic considerations of melting, sublimation, evaporation, etc. calculate moisture tendency from melting, sublimation, evaporation, etc. calculate relative humidity calculate parameters for the cloud cover scheme: implicit solution for the skewness equation of turbulence implicit solution for the varaiance equation of turbulence calculate condensation, etc. due to changes in water vapour and temperature from other processes to determince cloud generation or cloud dissipation (different for the two different cloud cover schemes). calculate cloud evaporation in clear air, dependent on difference to saturation humidity update incloud water and ice due to the processes mentioned above Part 6: Freezing of cloud water change in temperature is considered T < 238 K complete freezing of incloud water 238 K < T 273 partial freezing using empirical coefficients and cloud droplet number concentration (constant number in time) Part 7: cloud physics and precipitation fluxes at the surface Autoconversion (coagulation and coalescence calculated with the help of empirical coeficients, cloud droplet number concentration and existing liquid water for warm clouds (liquid water only) Conversion of cloud ice to snow also calculated with parameterised quantities. updating liquid water and ice content updating precipitation fluxes: converting rain and snow production into a flux adding melting fraction of that flux calculating precipitation fraction (raincover) updating rainf and snow flux in each layer Part 8: 1) modifying variance and skewness for cloud cover scheme estimating effects on convection on the distribution 2) modifying variance and skewness due to precipitation formation 3) updating tendencies for t, q, xl, xi check for negatives and perform corrections Part 9: diagnostics accumulated precip fluxes at surface total cloud cover integrated water vapour, liquid water and ice water columns