27 Communicating Timely Information on Convective Available Potential Energy (CAPE) using Geostationary and Polar Orbiting Satellite Sounders: ...
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27 Communicating Timely Information on Convective Available Potential Energy (CAPE) using
Geostationary and Polar Orbiting Satellite Sounders: Application to El Reno Event
1,3 1,3 2 2
Jessie Gartzke , Steve Ackerman , Robert Knuteson , Henry Revercomb ,
2 2 2
William L. Smith ., Nadia Smith and Elisabeth Weisz
1. University of Wisconsin-Madison Atmospheric and Oceanic Sciences
2. University of Wisconsin-Madison Space Science and Engineering Center
3. University of Wisconsin-Madison Cooperative Institute for Meteorological Satellite Studies
1. INTRODUCTION potential to provide positive impact for future
warn on forecasts (Stensrud et al. 2009).
The ability to measure vertical profiles of A common goal of the severe storm science
water vapor from space at times when ground community is to obtain accurate information in a
based upper air soundings are not available can timely manner regarding atmospheric stability.
fill an important need in short-range weather This information can be used to communicate
prediction. New satellite observations allow for predictions of severe weather events. The first
the retrieval of water vapor measurements with objective of this paper is to illustrate the value of
higher vertical resolution than was previously advanced polar sounder observations, through
available. In order to demonstrate these new data the El Reno event during the 1:30 pm polar
opportunities, it’s important to look at a practical satellite orbit. The second is to put this event in
application. Events like the Moore and El Reno the context of the climatology of the southern
tornados in 2013 are examples of just how Great Plains and assess the ability of POES
dangerous and unpredictable tornados can be. satellites to provide reliable stability information.
These two natural disasters are also examples of In this paper, a nine year record of upper air
the severity of human reactions to severe sounding profiles from the Department of Energy
weather warnings (Gartzke et al 2014). The El Atmospheric Radiation Measurement (ARM)
Reno case study will be used to illustrate the Southern Great Plains (SGP) site helps to create
potential value of satellite soundings. a climatology of Convective Available Potential
National Weather Service (NWS) forecasters Energy (CAPE). We then look at the ability of
are using GOES sounder products for a range of satellite observations to characterize the CAPE
applications, with positive results (Schmit et al probability distribution function at the 1:30 am/pm
2002). These products include estimates of total overpass times as a function of distance from the
precipitable water vapor (TPW) and atmospheric SGP site. This paper begins with a description of
stability indices, such as convective available the El Reno case study.
potential energy (CAPE) and lifted index (LI).
Infrared observations from geostationary orbit 2. CASE STUDIES DESCRIPTION
capture the diurnal cycle of surface skin
temperature with data collected over the A deadly EF5 tornado hit Moore, Oklahoma
continental United States every hour. These on May 20, 2013 killing 24 people. Two weeks
geostationary data can contribute to future warn later on May 31, 2013 nineteen tornados struck
on forecast approaches (Stensrud et al. 2009). central Oklahoma. After hearing a forecast for
However, the limited number of infrared spectral these tornados, many citizens tried to escape the
channels fundamentally limits the vertical storm by traveling south towards Texas on
resolution of the existing GOES sounder interstate forty. The interstate soon became
thermodynamic products. traffic jammed for miles. Unfortunately, a massive
Unlike the current GOES sounder, new high and unpredictable tornado traveled across the
spectral resolution infrared sensors on polar interstate and killed a woman and child in a car
orbiting weather satellites (POES) can sense the near El Reno, Oklahoma in the late afternoon.
atmospheric boundary layer at specific times of Currently, soundings from the ground can
day (about 10:30 am/pm and 1:30 am/pm). For give meteorologists indication on how water
example, the Atmospheric Infrared Sounder vapor behaves in the atmosphere vertically but
(AIRS) has been used to provide quantitative not horizontally. These soundings are typically
information about the lower atmosphere (Chahine only made every 12 hours. Events like the El
et al. 2006). Software to process AIRS data in Reno tornado is an example of how untimely
near real-time has been included in the IMAPP these measurements can be.
direct broadcast software package (Smith et al.
2012; Weisz et al. 2013). Near real-time data Jessica M. Gartzke, University of Wisconsin,
assimilation of polar orbiting advanced sounder Dept of Atmospheric and Oceanic Science,
products into rapid update NWP models has the Madison, WI; jessica.gartzke@ssec.wisc.edu
The last in situ measurements of the atmosphere the closest AIRS profile to the DOE ARM SGP were at 6am while the 6pm sounding came too site (
CAPE is only 9.9%. In this time period, only 48 of comparable skill to the radiosonde in detecting
485 samples exceeded the threshold for the extreme CAPE values. Meanwhile, the timeliness
AIRS CAPE, while 158 of 809 samples exceeded and spatial coverage of the satellite data
the threshold for the ARM sonde CAPE. The complement the local radiosonde observations.
difference in sample numbers is explained by the
fact that the AIRS level 2 version 6 product can 6. CONCLUSIONS
not retrieve CAPE in overcast cloud conditions.
This reduces the total number of samples by A radiosonde climatology at the Lamont
nearly one half and the number of extreme Oklahoma ARM site was developed for the
samples by two thirds. The percentiles in Table 1 period January 2005 to June 2014. The
for the closest AIRS CAPE show that the entire probability of sonde CAPE over 1000 J/kg is
PDF is shifted to lower CAPE values. This is found to be 19% at the ARM SGP site. While the
illustrated in Figure 7 which compares the probability of the closest AIRS CAPE over 1000
cumulative sum of the ARM sonde and AIRS J/kg is 9.9% and the probability of the maximum
th
closest CAPE. AIRS CAPE within 150 km is 25%. The 99
In general, the maximum CAPE derived from percentile of the sonde climatology was found to
th
AIRS exceeds the CAPE derived from ARM be 2364 J/kg. While the 99 percentile of the
th
sondes launched at the ARM site, as shown in closest AIRS CAPE is 1733 J/kg, the 99
Figure 8. This is due to the large spatial coverage percentile of the maximum AIRS CAPE within
of the AIRS sounder compared to the point 150 km is 2802 J/kg. While the closest AIRS
measurement from the radiosonde. CAPE values tend to be less than the sonde
CAPE extremes, the maximum CAPE near the
5.2 El Reno Case Study SGP site is higher. This is consistent with the
advanced sounder product limitations caused by
Figures 1 and 2 illustrate the polar orbiting cloudiness at the sonde launch site but the larger
satellite overpass of the southern Great Plains at spatial coverage of the satellite data. In
about 1:30 pm on the day of the El Reno event. conclusion, the maximum AIRS CAPE values
The circled region in figure 2 is due west of El near the SGP site tend to exceed the time
Reno. It is evident that there are spatial coincident sonde CAPE at the ARM site.
deficiencies in the remote sensing of CAPE from In the El Reno case study, the 6 am sonde at
th
the AIRS sensor due to cloudiness. Despite this, Norman, OK had a CAPE in the 85 percentile
large values of CAPE were detected by AIRS in (1252 J/kg) .The maximum AIRS CAPE (2233
Western Oklahoma. For comparison, we J/kg) at 1:30 pm was found just West of
th
computed CAPE from the operational Oklahoma City with a CAPE exceeding the 98
radiosondes launched from Norman, Oklahoma. percentile of the sonde climatology This result
The morning synoptic sonde launch (12 UTC, 6 illustrates the potential value of the polar satellite
am local time) had a computed CAPE value of observations. As stated earlier, POES satellites
th
1159 J/kg which represents the 85 percentile in have broad special coverage and they can detect
the ARM site radiosonde climatology. While this extreme atmospheric instability. The downside
sounding represents an extreme CAPE value are spatial gaps due to cloud cover and limited
even at 6 am, the solar heating during the time of day coverage and product latency.
morning hours would tend to increase the CAPE. These results show promise for use of
The 10:30 am Metop satellite overpass with the infrared sounder retrievals in the nowcasting of
IASI advanced sounder and the 1:30 pm AQUA local severe storms. Product latency has been
overpass with the AIRS advanced sounder can reduced to a few minutes through use of the UW
be used to monitor the growth of CAPE during CIMSS Community Satellite Processing Package
the heating of the day. For the 1:30 pm AQUA (CSPP) (reference). Future work will make use of
overpass a maximum CAPE value of 2233 J/kg CSPP algorithms to provide timely and accurate
was detected due west of El Reno and Oklahoma products for use in probabilistic forecasting.
City. This represented an extreme value in the
th
98 percentile of the ARM site climatology. Thus, ACKNOWLEDGEMENTS
between 6 am and 1:30 pm the CAPE in the
th
southern Great Plains increased from the 85 The authors acknowledge Dr. David Turner
th
percentile to the 98 percentile. This information (NOAA) for data used in this study. This work
was potentially available for predictive forecasting was supported under grant NA10NES4400013.
about 4.5 hours before the tornado touchdown.
Figure 9 shows a comparison of AIRS REFERENCES
maximum CAPE and ARM sonde CAPE for the
two week period prior to the El Reno event. The Chahine, Moustafa T., et al. "AIRS improving
black vertical lines indicate the time of the weather forecasting and providing new data on
touchdown for the Moore and El Reno tornados. greenhouse gases." (2006).
This figure shows that the AIRS sounder hasGartzke, J., R. Knuteson, H. Revercomb, W. L.
Smith, Sr., and E. Weisz (2014), The Invisible
Variable Behind Tornadic Events: Sensing Water
Vapor from Space, AMS Broadcast Meteorology
Conference, 16–20 June 2014, Olympic Valley,
CA.
Smith, W. L., A. M. Larar, H. E. Revercomb, M.
Yesalusky, and E. Weisz (2014), The May 2013
SNPP Cal/Val Campaign – Validation of Satellite
Soundings, Proceedings of the 19th International
TOVS study conference (ITSC-XIX), University of
Wisconsin, Space Science and Engineering
Center, Cooperative Institute for Satellite Studies
( CIMSS).
Schmit, Timothy J., et al. "Validation and use of Figure 1. The satellite image above was taken
GOES sounder moisture information." Weather 4.5 hours before the El Reno event.
and forecasting 17.1 (2002): 139-154.
Smith, W. L., E. Weisz, S. Kirev, D. K. Zhou, Z.
Li, and E. E Borbas (2012), Dual-Regression
Retrieval Algorithm for Real-Time Processing of
Satellite Ultraspectral Radiances. J. Appl.
Meteor. Clim., 51, Issue 8, 1455-1476.
Stensrud, David J., et al. "Convective-scale warn-
on-forecast system: a vision for 2020." Bulletin of
the American Meteorological Society 90.10
(2009): 1487-1499.
Weisz, E., W. L. Smith Sr., and N. Smith, 2013:
Advances in simultaneous atmospheric profile
and cloud parameter regression based retrieval
from high-spectral resolution radiance
measurements. Journal of Geophysical Research
-Atmospheres, 118, 6433-6443. Figure 2. This figure shows the location of the
highest CAPE value detected by AIRS (square)
ILLUSTRATIONS AND TABLES as well as the location of the ARM site (star).
Each dot represents the calculated CAPE for the
Table 1. Climatology of extreme CAPE values at overpass on May 31, 2013.
the Southern Great Plains ARM site for the time
period 1 January 2005 to 30 June 2014.
ARM AIRS
Sonde Closest Max Max Max
SGP CAPE CAPE CAPE CAPE
site40 60 2000 2000
Lifted index
20
1800 1800
0 50
1600 1600
−20
2005 2006 2008 2009 2010 2012 2013
1400 1400
40
Total Water Vapor (mm)
2000
AIRS CAPE (J/kg)
AIRS CAPE (J/kg)
1200 1200
1500
CAPE
1000 30 1000 1000
500
0 800 800
2005 2006 2008 2009 2010 2012 2013
20
600 600
150
400 400
TPW (mm)
100 10
50 200 200
0
2005 2006 2008 2009 2010 2012 2013 0 0 0
−10 0 10 20 30 −8 −6 −4 −2 0 2 0 20 40 60
Lifted Index Lifted index Total Water Vapor (mm)
SONDE SONDE
40 60 2500 2500
Lifted index
20
0
50
2000 2000
−20
Jul2005 Nov2006 Apr2008 Aug2009 Dec2010 May2012 Sep2013
40
2500
2000 1500 1500
CAPE (J/kg)
CAPE (J/kg)
PWV (mm)
1500
CAPE
1000 30
500
0 1000 1000
Jul2005 Nov2006 Apr2008 Aug2009 Dec2010 May2012 Sep2013
20
60
TPW (mm)
40 500 500
10
20
0
Jul2005 Nov2006 Apr2008 Aug2009 Dec2010 May2012 Sep2013
0 0 0
−10 0 10 20 30 −8 −6 −4 −2 0 2 0 20 40 60
Lifted Index Lifted index PWV (mm)
Figure 4. Time series graphs of lifted index,
Figure 5. The relationship between CAPE, Lifted
CAPE, and PWV for the AIRS closest (upper)
Index and Total Perceptible Water Vapor are
and ARM sonde (lower) and from January 2005
shown for AIRS closest (left) and ARM sonde
and October 2013.
(right). Red dots indicate negative lifted index.0.02
0
0 10 20 30 40 50 60
PWV (mm)
0.03 SONDE
0.8
0.02
0.6
PDF
PDF
0.01
0.4
0.2
0
−10 −5 0 5 10 15 20 25 30 35
0 Lifted30Index
0 10 20 40 50 60
0.15 PWV (mm)
0.04
0.1
PDFPDF 0.03 Number of CAPE over 1000 J/kg = 48 of 485
Probability of CAPE over 1000 J/kg = 9.9%
0.05
0.02
0.01
0
0 500 1000 1500 2000 2500
0 CAPE(J/kg)
−10 −5 0 5 10 15 20 25 30 35 40
Lifted Index
0.15
0.1
Number of CAPE over 1000 J/kg = 156 of 809
PDF
Probability of CAPE over 1000 J/kg = 19%
0.05
0
0 500 1000 1500 2000 2500
CAPE(J/kg)
Figure 6. Probability distribution functions of
AIRS closest CAPE (upper) and ARM sonde
CAPE (lower) for CAPE values >50 J/kg.
Figure 8. Time and space coincident matchups of
1 sonde CAPE and the maximum AIRS CAPE
0.9 within 150 km the ARM site.
0.8
25th percentile: 130.7 AIRS vs. Sonde CAPE (ARM SGP site)
0.7 6000
50th percentile: 290.9 ARM Sonde
0.6 AIRS
SUM PDF
67th percentile: 451.1
5000
0.5
75th percentile: 547.3
0.4
95th percentile: 1252 4000
0.3
Extreme
CAPE (J/kg)
99th percentile: 1733
CAPE
0.2
3000
0.1
0 2000
0 500 1000 1500 2000 2500 3000 3500
CAPE(J/kg)
1
1000
0.9
0.8 0
25th percentile: 187.9 05/11 05/16 05/21 05/26 05/31 06/05
0.7
Figure 9. The CAPE values from May 11 to June
50th percentile: 402.4
0.6
5, 2014. The two lines represent the Moore
SUM PDF
67th percentile: 678.2
0.5
75th percentile: 862.1 tornado (May 20) and the El Reno tornado (May
31).
0.4
95th percentile: 1659
0.3
99th percentile: 2364
0.2
0.1
0
0 500 1000 1500 2000 2500 3000 3500
CAPE(J/kg)
Figure 7. Cumulative sum of CAPE PDF for the
AIRS closest (upper) and the ARM sonde (lower).You can also read
