INTERANNUAL VARIABILITY IN SOIL NITRIC OXIDE EMISSIONS OVER THE UNITED STATES AS VIEWED

FROM SPACE

Rynda Hudman , Ashley Russell, Luke Valin, Ron CohenCollege of Chemistry

UC Berkeley

OMI NASA Standard Product Version 1.0.5

December 14, 2009

ATMOSPHERE

BIOSPHERE

NO & N2O IS A HIGHLY VARIABLE PRODUCT OF MICROBIAL ACTIVITY IN SOILS

N2O(g), N2(g), NO(g)

[Meixner and Yang, 2006]

Processes not well understood, HUGE spatial variability, but best correlation w/ wfps, T, N avail.

[See Poster: Placella et al., B13C-0527]

LARGE SOIL NOx SOURCE INFERRED FROM SATELLITES

GOME Constraints on Natural Soil and Agriculture

[Jaeglé et al., PNAS, 2005]

GLOBAL: 8.9 Tg N/yrMIDLATITUDES: 3.9 Tg N/yr

•~22% of global NOx source

•~Midlatitude soil source X2-3 current global model estimates

We examine interannual variability in soil NO emissions and our understanding of pulsing behavior over the Agricultural Great Plains

OMI NO2 Column Aug 4, 2004

• 2600 km swath width providing daily global coverage

•1:45 pm equatorial overpass time

•14 x 24 km pixel size at nadir

OZONE MONITORING INSTRUMENT (OMI) HAS MUCH FINER SCALE RESOLUTION AND DAILY GLOBAL COVERAGE

[Bertram et al., GRL, 2005]

SOIL NOx “EVENTS” pulsing over freshly fertilized Montana fields after rain event

ENOx = f( T, biome, w/d) x Pulse (dryspell) x canopy uptake

[Yienger and Levy, 1995]

We extend this work to include U.S.:daily NARR Temp & Precip MODIS LandtypeFertilizer emissions [Ramankutty]

ENOx 2005-2007

MONTHLY MEAN MODELED SOIL NOx EMISSIONS Dry, warm conditions anomalously high June 2006 soil emissions

Mean Yearly Total: 0.62 Tg N/yr (Fert: 0.12 Tg N/yr)

SOIL EMISSION CONTRIBUTION TO NO2 COLUMN

June 2006

SOIL COLUMN / TOTAL COLUMN SOIL S.D. / COLUMN S.D.

SOIL COLUMN = TOTAL COLUMN – NO SOIL COLUMN

GEOS-Chem global CTM (2x2.5)

OMI NO2 JUNE INTERANNUAL VARIABILITY FOLLOWS SOIL NOx

OMI June 2006 AnomalySoil NO model June 2006

June 2006 had lower than average lightning emissions, suggesting this was not a factor here

OMI NO2 JUNE INTERANNUAL VARIABILITY FOLLOWS SOIL NOx

2005 20072006

LARGE PULSING EVENT SEEN IN OMI TIMESERIES OVER RURAL SOUTH DAKOTA

Pulsing event reaches 4x1015 molec cm2,

~ 2 ppbv assuming 1km well mixed BL

We can use OMI to test understanding pulsing triggers

Future work: Test using Yan et al., [2005] & soil moisture based scheme developed at Dalhousie Univ.

OMI COLUMN NO2 SCALED TO MODEL MEANMODEL COLUMN NO2

SOIL COLUMN NO2

MODELED VARAIBILITY AND PULSING LIKELY UNDERESTIMATED

Using updated retrievals should be able to compute magnitude of emission

Col

umn

NO

2

May June July

MEAN MAXIMUM 8-HR OZONE ENHANCEMENT DUE TO SOIL NOx

Mean June maximum 8-hr ozone

A lower bound, ozone enhancement due to soil NOx emission doubles from 3 6ppbv

Model Model No Soil

NO2 pulse in OMI

SOIL NOx ENHANCEMENT IMPROVES LOW BIAS & CORRELATION WITH OBSERVED 8-HR MAX OZONE

“SUBURBAN” SIOUX FALLS, SD

CONCLUSIONS

• Anomalously dry, warm conditions in June 2006 over the agricultural Great Plains increased observed tropospheric OMI NO2 column by 30% likely due to a ~X2 increase in pulse driven soil NOx emissions.

• Daily OMI NO2 columns can be used to refine our understanding of pulsing triggers

• Soil NOx emissions are predicted to enhanced mean surface 8-hr max ozone by 6 ppbv, compared with 3 ppbv for 2005 & 2007.

• A drier, warmer future climate is predicted over the Great Plains with implications for how efficiently soils retain nitrogen and ozone air quality.