The relationships between soil moisture (SM) and precipitation (P) are examined for different precipitation regimes over Arizona, New Mexico and the Northern Plains using data from the reconstructed sea surface temperature, the regional analysis and the VIC NLDAS for the period from 1900-2004. There are cases that soil moisture and P interacts differently under different sea surface temperature forcing.

For New Mexico and Arizona, years from 1900 to 2004 are classified based on the winter and summer P evolution. For years that the winter P and the following summer P anomalies have an inverse relationship, sea surface temperature anomalies (SSTAs) have strong influence on P. Soil moisture does not play a major role in modulating P anomalies in summer. For cases that wet (dry) winter followed by wet (dry) summer, the SSTA forcing associated with the P regimes tends to persist. For these cases, positive SM-P feedbacks enhance P anomalies. For New Mexico, there is a linear relationship between SM anomalies in spring and P anomalies in summer. SSTAs and SM work together to reinforce P anomalies. For Arizona, there is no linear relationship between SM in spring and P in summer. Soil moisture is just one of many factors influencing monsoon rainfall.

For the Northern Plains, soil moisture over the Southern Plains in spring enhances the ENSO impact on precipitation.