the climate record of montana over the past half-century ... · the climate record of montana over...

The climate record of Montana over the past half-century. Consequences for water resources and opportunities for teaching

practitioners how to study the whole bowl of cherries

Paul Stoy

paul.stoy@montana.edu

www.watershed.montana.edu/flux

bit.ly/StoyGScholar

Motivation:

- Gray (2007)

IPCC WG1 AR5 just released…but what about MT?

Global Energy Balance (W m-2)

-Ultimately following Kiehl and Trenberth (1997) BAMS 78:197-208.

The zero-dimensional climate model (Global change is simple, regional

change is difficult)

Energy in

Energy out

At steady state

Energy in = solar energy

E in r2Sc 1 Acircle r2

A disk of solar radiation of size πr2 hits Earth

Energy out = planetary emittance

Stefan-Boltzmann Law

Eout A T 4

Eout 4 r2 T 4

Asphere 4 r2

Planetary energy balance Energy in = Energy out

E in Eout

r2Sc 1 4 r2 T 4

Sc41 T 4

Solving for T

T 4Sc 1

Constants σ= 5.67×10−8 J K−4 m−2 s−1 Somewhat Constants Sc=1367 W m−2 ρ=0.31

The temperature of blackbody Earth

T 41367Jm 2s 1 1 0.31

4 1 5.67 10 8JK 4m 2s 1254K 19oC

The temperature of real Earth ~ 14°C

Why? The effective emissivity of Earth is less than 1. This is the greenhouse effect

Solving for (effective) emissivity

4 T 40.6

Using T = 14 °C

Recall:

Kirchoff’s Law of Radiation

Global Energy Balance (W m-2)

-Ultimately following Kiehl and Trenberth (1997) BAMS 78:197-208.

Albedo, emissivity and the solar constant determine global temperature

Why? They determine the energy balance.

More GHGs.

Fewer clouds/ Less ice

.Blackbody Earth

Global Change vs. Global Warming

What does it all mean for water resources in MT?

Exploring the Sheffield et al. (2006) meteorological forcing dataset Daily global 0.5° data product Designed for hydrology: -Precipitation -Air temperature -Specific Humidity -Air Pressure -Wind speed -Incident shortwave radiation -Downwelling longwave radiation Combination of observational and reanalysis data products Bias correction for precipitation gage undercatch

(mm/day)

Quickly grabbing ‘MT’ from a global database

MT versus global temperature trends

MT versus global incident shortwave trends

MT versus global specific humidity trends

Sheffield et al. data inputs

the climate record of montana over the past half-century ... · the climate record of montana over...

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