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Overnight 2m temperatures tend to be too cold over rugged or mountainous areas.

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Lake effects

The effect of lakes is parameterised using FLake and a lake cover mask.  The sub-grid detail may not be completely captured and the energy fluxes may well be incorrectly estimated, particularly where frozen lakes are plentiful and/or forecast snow cover is uncertain.   These aspects can:

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Evaporation over bare soil is also problematic.  Soil temperature and soil moisture is modelled in IFS but there is not a great deal of directly measured observations available.  However, the impact of heat and moisture fluxes can be a significant contributor to 2m and surface temperature errors, and hence have an impact on humidity.

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• more solar energy will be gained on south-facing (N Hem) slopes implying actual temperatures may be higher than forecast.  However upslope movement will increase humidity, possibly to saturation,
• less solar energy will be received on north-facing (N Hem) slopes implying actual temperatures may be lower than forecast, particularly where they are in shadow for much of the time. Thus high humidity may persist in sheltered valleys.

Lake effects

Lake temperatures can have an effect on forecast of dew point temperatures, particularly in deciding whether the lake is frozen or not.  Proximity of a lake can have an influence on the humidity at a downwind location.

The effect of lakes is parameterised using FLake and a lake cover mask.  The sub-grid detail may not be completely captured and the energy fluxes may well be incorrectly estimated, particularly where frozen lakes are plentiful and/or forecast snow cover is uncertain.   These aspects can:

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Soil moisture and temperature is modelled in four soil levels but there is a considerable lack of real-time observations of soil condition and moisture content.  Nevertheless heat and moisture fluxes have an impact on model surface and 2m temperature and moisture. 

The ensemble mean values of soil moisture slightly overestimate the diurnal cycle of soil temperature:

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