Editing IPCC:AR6/WGI/Chapter-11 (section)

==== 11.6.1.1 Precipitation Deficits ====

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Lack of precipitation is generally the main factor controlling drought onset. There is ''high confidence'' that atmospheric dynamics, which vary on interannual, decadal and longer time scales, is the dominant contributor to variations in precipitation deficits in the majority of world regions ( [[#Dai--2013|Dai, 2013]] ; [[#Miralles--2014b|Miralles et al., 2014b]] ; [[#Seager--2014|Seager and Hoerling, 2014]] ; [[#Burgman--2015|Burgman and Jang, 2015]] ; [[#Dong--2015|Dong and Dai, 2015]] ; [[#Schubert--2016|Schubert et al., 2016]] ; [[#Raymond--2018|Raymond et al., 2018]] ; [[#Baek--2019|Baek et al., 2019]] ; [[#Drumond--2019|Drumond et al., 2019]] ; [[#Herrera-Estrada--2019|Herrera-Estrada et al., 2019]] ; [[#Gimeno--2020|Gimeno et al., 2020]] ; [[#Mishra--2020|Mishra, 2020]] ). Precipitation deficits are driven by dynamic mechanisms taking place on different spatial scales, including synoptic processes – atmospheric rivers and extratropical cyclones, blocking and ridges ( [[#11.7|Section 11.7]] ; [[#Sousa--2017|Sousa et al., 2017]] ), dominant large-scale circulation patterns ( [[#Kingston--2015|Kingston et al., 2015]] ), and global ocean–atmosphere coupled patterns such as inter-decadal Pacific Oscillation (IPO), Atlantic Multi-decadal Oscillation (AMO) and El Niño–Southern Oscillation (ENSO; [[#Dai--2017|Dai and Zhao, 2017]] ). These various mechanisms occur on different scales, are not independent, and substantially interact with one another. Also regional moisture recycling and land–atmosphere feedbacks play an important role for some precipitation anomalies (see below).

There is ''high confidence'' that land–atmosphere feedbacks play a substantial or dominant role in affecting precipitation deficits in someregions (SREX, Chapter 3; [[#Koster--2011|Koster et al., 2011]] ; [[#Gimeno--2012|Gimeno et al., 2012]] ; [[#Taylor--2012|Taylor et al., 2012]] ; [[#Guillod--2015|Guillod et al., 2015]] ; [[#Tuttle--2016|Tuttle and Salvucci, 2016]] ; [[#Santanello%20Jr.--2018|Santanello Jr. et al., 2018]] ; [[#Haslinger--2019|Haslinger et al., 2019]] ; [[#Herrera-Estrada--2019|Herrera-Estrada et al., 2019]] ). The sign of the feedbacks can be either positive or negative, as well as local or non-local ( [[#Taylor--2012|Taylor et al., 2012]] ; [[#Guillod--2015|Guillod et al., 2015]] ; [[#Tuttle--2016|Tuttle and Salvucci, 2016]] ). Earth system models (ESMs) tend to underestimate non-local negative soil-moisture–precipitation feedbacks ( [[#Taylor--2012|Taylor et al., 2012]] ) and also show high variations in their representation in some regions ( [[#Berg--2017b|Berg et al., 2017b]] ). Soil-moisture–precipitation feedbacks contribute to changes in precipitation in climate model projections in some regions, but ESMs display substantial uncertainties in their representation, and there is thus only ''low confidence'' in these contributions ( [[#Berg--2017b|Berg et al., 2017b]] ; [[#Vogel--2017|Vogel et al., 2017]] , 2018).

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