Details

Autor(en) / Beteiligte

• Ficklin, Darren L.
• Novick, Kimberly A.

Titel

Historic and projected changes in vapor pressure deficit suggest a continental‐scale drying of the United States atmosphere

Ist Teil von

• Journal of geophysical research. Atmospheres, 2017-02, Vol.122 (4), p.2061-2079

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2017

Quelle

Wiley Online Library Journals

Beschreibungen/Notizen

• Via air temperature increases and relative humidity changes, climate change will modify vapor pressure deficit (VPD), which is an important determinant of water vapor and CO2 exchange between the land surface and atmosphere. VPD is the difference between the water vapor the air can hold at saturation (es) and the actual amount of water vapor (ea). Here we assess changes in VPD, es, and ea in the United States (U.S.) for the recent past (1979–2013) and the future (2065–2099) using gridded, observed climate data and output from general circulation models. Historically, VPD has increased for all seasons, driven by increases in es and declines in ea. The spring, summer, and fall seasons exhibited the largest areal extent of significant increases in VPD, which was largely concentrated in the western and southern portions of the U.S. The changes in VPD stemmed from recent air temperature increases and relative humidity decreases. Projections indicate similar, amplified patterns into the future. For the summer, the general circulation model ensemble median showed a 51% projected increase (quartile range of 39 and 64%) in summer VPD for the U.S., reflecting temperature‐driven increases in es but decreases or minimal changes in relative humidity that promotes negligible changes in ea. Using a simple model for plant hydraulic functioning, we also show that in the absence of stomatal acclimation, future changes in VPD can reduce stomatal conductance by 9–51%, which is a magnitude comparable to the expected decline in stomatal conductance from rising CO2. Key Points VPD has increased in the past and will continue to increase in the future Increases in VPD are driven by increases in saturation vapor pressure and declines or small changes in actual vapor pressure Future increases in VPD are expected to reduce stomatal conductance by 9‐51%