Spring Land Temperature Anomalies in Northwestern U.S. and Southern Plains Summer Extreme: Droughts and Floods

Recurrent drought and associated heatwave as well as flood episodes are important features of the Southern Plains regional climate, such as the 2011 Texas drought and the 2015 Texas flood.  Many studies have examined the remote connection between sea surface temperature (SST) changes and conterminous U.S. meteorological droughts and flood.  However, less attention has been devoted to effects of large-scale land surface temperature (LST) changes, over shorter but still considerable distances, on droughts and flood.  The present study combines two types of evidence: climate observations and model simulations. Our analysis of observational data shows that springtime land temperature in the U.S. Northwest (NWUS) is significantly correlated with rainfall anomalies and heat in the Southern Plains.  It is also found that although the LST has correlation with the SST, but years associated with large LST anomalies were not always the same as those years with large SST anomalies.  Further analyses reveal that the spring temperature in NWUS seems a better index for predicting droughts than for floods. Our model simulations of the 2011 Southern Plains drought and 2015 flood confirm the observed relationship between land temperature anomaly and extreme and suggest that the remote effect of LST changes in the NWUS on Southern Plains extreme is probably as large as the more familiar effects of SSTs and atmospheric internal variability.  We conclude that the cool 2011 springtime climate conditions in the U.S. Northwest increased the probability of summer drought and abnormal heat in the Southern Plains, while the warm 2015 springtime temperature contributed to the 2015 flood.  The present study also suggests that catastrophic consequences likely occur in a region when forcing from ocean and land combine synergistically to favor an extreme and that there is a potential for skillful seasonal predictions of U.S. Southern Plains extreme when such facts as ones presented here are considered.