Page History

...

Land surface characteristics (soil moisture, leaf area index) have an impact upon temperature forecasts.    Significant differences in temperature can occur over a short distance where there is a sharp change of surface characteristics.   This can influence the location and development of subsequent convection.

Users should assess the analysis of temperature and moisture against observations in the area of interest and modify forecasts accordingly.

Fig9.2.1.3-1: An example of incorrect assessment of heat and moisture fluxes (left, temperatures; right, dew points), at Cordoba 12 June 2017.   Ensemble Control Forecast (ex-HRES) forecast temperatures and dew points (red) and observed temperatures and dew points (black).  Ensemble Control (ex-HRES) forecast has under-estimated the maximum temperatures by some 3ºC.  

...

• There is a dry bias during the dry season and first guess 2m temperatures can be too cold.  During the analysis process, soil moisture increments attempt to better represent 2m humidity.  However, this results in excessive soil moisture near the surface despite no precipitation.  This moisture in IFS can then incorrectly percolate to lower layers or even runoff on the surface.
• Surface ground moisture limits the amount of diurnal surface warming and nighttime cooling leading to lower 2m temperature and higher 2m relative humidity being observed and forecast.
• Vegetation could be lush and green after previous wet period and/or evapotranspiration could be mis-represented.
• Diurnal Errors in forecast advection of boundary layer air.  Diurnal influxes of moist sea air may replenish moisture and/or not be well forecast either in depth or penetration.
• Insufficient Observation representativeness.  Insufficient information on atmospheric structure due to the lack of radiosonde. 

Image Added 

Fig9.2.1.3-4: Mean soil moisture analysis increments for the top soil layers over the winter period 2024/25.  Systematic increments during the analysis process are:

• positive, implying an increase in IFS model soil moisture, over central and Southern Africa, India and SE Asia (but notably not central South America).
• negative, implying a decrease in IFS model soil moisture, over Indonesia and central South America.

The increments shown are only a guide and do not imply that they occur in every case. 

Users should assess the analysis of temperature and and moisture against observations in the area of interest and modify forecasts accordingly.

...