Distinct Influences of Land Cover and Land Management on Seasonal Climate

Deepti Singh; Sonali P McDermid; Benjamin I Cook; Michael J Puma; Larissa Nazarenko; Maxwell Kelley

doi:10.1029/2018JD028874

Distinct Influences of Land Cover and Land Management on Seasonal Climate

J Geophys Res Atmos. 2018 Nov 16;123(21):12017-12039. doi: 10.1029/2018JD028874. Epub 2018 Nov 10.

Authors

Deepti Singh^{1

2}, Sonali P McDermid^{3

4}, Benjamin I Cook^{1

4}, Michael J Puma^{4

5}, Larissa Nazarenko^{4

5}, Maxwell Kelley⁴

Affiliations

¹ Lamont-Doherty Earth Observatory Columbia University Palisades NY USA.
² School of the Environment Washington State University Vancouver WA USA.
³ Environmental Studies Department New York University New York NY USA.
⁴ NASA Goddard Institute for Space Studies New York NY USA.
⁵ Center for Climate Systems Research, Earth Institute Columbia University New York NY USA.

Abstract

Anthropogenic land use and land cover change is primarily represented in climate model simulations through prescribed transitions from natural vegetation to cropland or pasture. However, recent studies have demonstrated that land management practices, especially irrigation, have distinct climate impacts. Here we disentangle the seasonal climate impacts of land cover change and irrigation across areas of high agricultural intensity using climate simulations with three different land surface scenarios: (1) natural vegetation cover/no irrigation, (2) year 2000 crop cover/no irrigation, and (3) year 2000 crop cover and irrigation rates. We find that irrigation substantially amplifies land cover-induced climate impacts but has opposing effects across certain regions. Irrigation mostly causes surface cooling, which substantially amplifies land cover change-induced cooling in most regions except over Central, West, and South Asia, where it reverses land cover change-induced warming. Despite increases in net surface radiation in some regions, this cooling is associated with enhancement of latent relative to sensible heat fluxes by irrigation. Similarly, irrigation substantially enhances the wetting influence of land cover change over several regions including West Asia and the Mediterranean. The most notable contrasting impacts of these forcings on precipitation occur over South Asia, where irrigation offsets the wetting influence of land cover during the monsoon season. Differential changes in regional circulations and moist static energy induced by these forcings contribute to their precipitation impacts and are associated with differential changes in surface and tropospheric temperature gradients and moisture availability. These results emphasize the importance of including irrigation forcing to evaluate the combined impacts of land surface changes for attributing historical climatic changes and managing future impacts.

Keywords: competing climate forcings; irrigation; land use and land cover change; land‐atmosphere interactions; surface and tropospheric climate impacts.