NASA Technical Reports Server (NTRS) 20180000602: Variability in Lightning NOx Production Rates Due to Regional Differences in Lightning Type and Polarity

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by  NASA Technical Reports Server (NTRS)

Variability in lightning NO production rates due to regional
x
differences in lightning type and polarity
1,2 3 2 4
Jeff Lapierre ([email protected]), Joshua Laughner , Sally Pusede , William Koshak
1 2 3 4
Earth Networks, Germantown, MD, University of Virginia, Charlottesville, VA, University of California, Berkely, CA, NASA Marshal Space Flight Center, Huntsville, Alabama

Introduction Methods Results: Regions

The concentration of nitrogen oxides (NO ) largely –1
LNO (mol NO stroke )
x 2 2
We only use visible column data for high
controls the production of upper tropospheric (UT)
SE SC NC
cloud radiative fraction (>70%). This
ozone.
Total 4.3 ± 0.4 6.6 ± 0.7 5.0 ± 0.6
acts as a filter for boundary layer NO
2
Lightning contributes to as much as 70% of UT NO
IC 2.5 ± 0.8 5.2 ± 1.3 3.8 ± 1.3
[1].
x
CG 42.3 ± 15.1 37.8 ± 25.0 36.2 ± 28.4
Only want LNO within a single pixel. We
2 16.9 7.3 9.5
Current estimates of NO production range from CG:IC
use the wind speed and cross pixel
x
~10-103 mol NO per stroke. There remains
distance to determine the time window
x Red means highest of regions, blue means lowest.
disagreement as to whether cloud-to-ground (CG)
of pixel correlated LNO . For U.S., this is
Parameter Region Total IC CG
2
strokes produce more or the same amount of NO per
2.4 hours.
x

stroke as intracloud (IC) strokes SE 2.13 2.04 0.097
Sum up NO and # of strokes for all 1x1 degree pixels
-2
Stroke Density (# km ) SC 1.79 1.7 0.097
2
We focus on three regions in the U.S. that typically
over entire region for each day.
NC 1.69 1.62 0.071
exhibit specific lightning characteristics as illustrated
For Total (IC+CG) LNO we find slope of NO vs stroke SE 4.2 3.1 24.3
below. 2 2
-1
#. For IC and CG LNO , we use linear regression to Stroke Current (kA stroke ) SC 5.3 3.9 27.3
2
NC 4.9 4.1 20.5
solve the equation below:
𝑻𝒐𝒕𝒂𝒍 𝑵𝑶 = #𝑰 𝑪 𝐱 𝑰𝑪 + #𝑪𝑮 𝐱 𝑪𝑮 + C
𝟐 𝒑𝒓𝒐𝒅 𝒑𝒓𝒐𝒅
Lightning Characteristics that match LNO results:
2
We correct for NO lifetime near thunderstorms, which
x
SE: Lowest total and IC stroke current.

has been shown to be ~3 hours [2].
SC: Highest total stroke current
NO:NO is largely uncertain due to short lifetime of NO
2 x
The goal of this study is to determine if regional
as well as O production from lightning [3]. For this
NC: Lowest CG stroke density and stroke current
3
variations in lightning characteristics play a
reason, we report results as NO instead of NO .
2 x
dominant role in the large variational
Approximate conversion: LNO ~ LNO x 10
x 2
Conclusions
observations of LNO
x
Results: U.S.
We estimate an overall LNO production of 6.8 mol NO
2 2
Data
stroke-1, which is in agreement with current literature.
LNO estimates using current data are consistently
Estimated LNO using
2
2
Timeframe: May - August 2014-15 lower than for stroke data. This may indicate that
current data is ~25% lower
using stroke data overestimates LNO .
than with stroke data.
Earth Networks Total Lightning Network (ENTLN)
2
We find that CG strokes produce 5-17 times more
ENTLN Coverage
Global network that LNO than IC strokes.
2
LNO CG:IC
provides stroke time,
2
Regions in this study do show different LNO results
location, type, and peak 2
5.5
and are partially explained by lightning characteristics.
current
Variation between regions is ~30%. This does not

completetly explain the large variation of LNO in the
x
-1
literature.
US (mol NO stroke )
Berkely High Resolution (BEHR) product
2
Daily Global Tropospheric NO profiles from the Ozone
Stroke Current
2
References
Monitoring Instrument (OMI)
Total 6.8 ± 0.4 5.2 ± 0.4
ECMWF Climate Reanalysis (ERA5)
[1]Pickering, K. E., et. al. (2016). Estimates of lightning NOx production based on OMI NO2 observations over the
IC 5.5 ± 0.6 4.0 ± 0.6
Gulf of Mexico., doi:10.1002/2015JD024179.
Hourly winds at 37 pressure levels and 31 km resolution
[2]Nault, B. A., et. al. (2017). Lightning NOx Emissions: Reconciling Measured and Modeled Estimates With
CG 30.5 ± 9.1 22.2 ± 10.4
Updated NOx Chemistry. Geophysical Research Letters, doi: 10.1002/2017GL074436.
accross North America
[3]Minschwaner, et. al. (2008). Observation of enhanced ozone in an electrically active storm over Socorro, NM:
Implications for ozone production from corona discharges. doi: 10.1029/2007JD009500