Pakistan Journal of Meteorology Vol. 9, Issue 18: Jan 2013 23 Spatial Trends of AMSR-E Soil Moisture across Agro-Climatic Zones of Pakistan 2003-2010 Zahid, M. 1,2 , G. Rasul 2 Abstract This study has been conducted to assess the spatial trends of soil moisture across different agro-climatic zones of Pakistan in the recent decade. The analysis have been performed annually and in the cropping seasons i.e. Kharif and Rabi using available monthly soil moisture AMSR-E satellite data from 2003-2010. The monthly precipitation and temperature (mean, maximum and minimum) data has also been analyzed during the study period. The AMSR-E has strong correspondence with observed precipitation records across Pakistan. The annual analysis showed significant decreasing trends of soil moisture in agriculture fields (sub humid – arid) from 2003-2010. The Kharif season soil moisture variability is closely associated with the monsoon precipitation (Jul-Aug) in the rain fed areas of Pakistan. The Kharif cropping season analysis has shown the increasing trends of soil moisture in the years (2003, 2005, 2006 and 2010) when substantial amount of monsoon precipitation occurred in the rain fed (humid-semi arid) areas of Pakistan. However, noticeable decreasing trend of soil moisture has been observed during 2004 and 2009 when monsoon precipitation was suppressed during Kharif season. The Rabi season analysis initiate just after the Kharif season and availability of soil moisture is equally vital for the sowing period. The Rabi season analysis showed the increasing trends of soil moisture from 2003-2010 with the exception of 2004 and 2009 in which slight decrease in soil moisture has been found in the agriculture cropland (semi arid- arid). It has been noticed that success and failure of monsoon generally affects the amount of soil moisture both annually and seasonally. Therefore it is expected that the erratic precipitation patterns may enhance the soil moisture stress in agriculture lands of Pakistan leading to agriculture drought. Key Words: Soil moisture, AMSR-E, precipitation, Kharif and Rabi Introduction Soil moisture is an important component of global hydrological cycle. It plays an essential role in the interaction between the land and atmosphere. The level of saturation in the surface layer of soil relative to the soil field capacity describes the soil moisture which is controlled by rainfall and potential evaporation. Soil moisture act as water storage between precipitation which regulates the rate of infiltration and run off production. Soil moisture is a main source of natural water resources for agriculture and natural vegetation. Near-surface soil moisture controls the energy available at land surface and converts it into the sensible and latent heat. The condition of soil temperature and soil moisture then links these exchanges with the atmosphere and water-energy balances. The linkage of evaporation and transpiration is necessary with the distribution of soil moisture to predict the combined influence of land surfaces to weather and climate (Robock et al., 2000). Soil moisture determines the availability of water as well as the water holding capacity of the soil. Thus, it significantly controls the rates of exfiltration and evaporation. The surplus amount of soil moisture conditions enhances the net solar radiations and transfers the sensible and latent fluxes heat from the surface in to the boundary layer which in result produce precipitation. The role of soil moisture in rainfall dynamics using general circulation models (GCMs) have been discussed in various studies (Yeh et al., 1984; Oglesby and Erickson, 1989; Oglesby, 1991 and Pan et al., 1995). These studies show that the soil moisture changes during early summer, may influence the summer rainfall over the land significantly. The access in the quantity of soil moisture results in relatively more amount of rainfall which support the soil moisture-rainfall feedback (Eltahir, 1998). 1 maidazahid.pmd@gmail.com 2 Pakistan Meteorological Department, Pitras Bukhari Road, Sector H-8/2, Islamabad.