Soil Moisture in Average Year

Maps for each month use a 15 year average (1985-1999) to show what average soil moisture levels are like.

Soil moisture can also be interpreted and the percentage of saturation, where a dry soil has a low saturation level and a fully wet soil is 100% saturated. Soil moisture is difficult to describe because it is a 3D process, with water entering the top layer and slowly penetrating to deeper depths.

Soil moisture decreases by water leaving the soil by evaporation or penetrating to depth and recharging ground water stores. The 2 key sources of water in the soil are rainfall or snowmelt. On a global scale changes in Soil Moisture depend on the season and climate zone.

Africa

Dry areas such as deserts are clearly visible with little change over a year. But the edge of the Sahara desert shows change where the rainy season contributes to the soil moisture, as July to September is the rainy season for western Africa and maps for August to October show higher soil moisture content.

On the continent of Africa it is interesting to observe the Ethiopian Highlands and East African Highlands have consistently wetter soils than surrounding areas because these more elevated regions experience wetter conditions.

North

Northern latitudes close to the Arctic Circle have high soil moisture year round. The highest soil moisture occurs April to June when snow melt and thawing of permafrost occurs. Greenland soils are not modelled because of the permanent ice cover, and is set to zero for this display.

South America

The rainy season for the northern part of South America is November to March and this is reflected in the estimated soil moisture for December to April. The lag in timing between rainfall and estimated soil moisture is due to the time it takes for soil to become wet.

  1. Average land for Jan
  2. Average land for Feb
  3. Average land for Mar
  4. Average land for Apr
  5. Average land for May
  6. Average land for Jun
  7. Average land for Jul
  8. Average land for Aug
  9. Average land for Sep
  10. Average land for Oct
  11. Average land for Nov
  12. Average land for Dec
  1. Map of average land for January 1985 - 1999

    The wet tropical rainforests and the northern latitudes have consistently moister soils

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  2. Map of average land for February 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their highest soil moisture periods

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  3. Map of average land for March 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their highest soil moisture periods

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  4. Map of average land for April 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their highest soil moisture periods

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  5. Map of average land for May 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their highest soil moisture periods

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  6. Map of average land for June 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their highest soil moisture periods

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  7. Map of average land for July 1985 - 1999

    The beginning of the wet season in the Sahel starts to have an effect on the soil moisture

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  8. Map of average land for August 1985 - 1999

    As Europe and the Amazon dry out, the Indian sub continent and south East Asia get wet

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  9. Map of average land for September 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their lowest soil moisture periods

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  10. Map of average land for October 1985 - 1999

    The food growing areas of Mid-West USA and Eastern Russia have their lowest soil moisture periods

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  11. Map of average land for November 1985 - 1999

    The Sahel starts to dry down as the dry season begins

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  12. Map of average land for December 1985 - 1999

    The Sahel starts to dry down as the dry season begins

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Google Earth View

Soil moisture legend as percentages

Soil moisture legend as percentages

Other Maps

Land Maps