National Aeronautics andSpace Administration

Uloon-Ucontrol rms (ms-1) June 2014

-90 -60 -30 0 30 60 90Latitude

1000

100

10

Pres

sure

(hPa

)

0

5

10

15

20

25

30

Pres

sure

Alti

tude

(km

)

a

Uloon-Ucontrol rms (ms-1) August 2014

-90 -60 -30 0 30 60 90Latitude

1000

100

10

Pres

sure

(hPa

)0

5

10

15

20

25

30

Pres

sure

Alti

tude

(km

)

b

> 20001000--2000500--1000100--50010--100

Number ofLoon

Observations

0.50

1.00

Minus Ucontrol-UMERRA2 rms

Uloon-Ucontrol rms (ms-1) June 2014

-90 -60 -30 0 30 60 90Latitude

1000

100

10

Pres

sure

(hPa

)0

5

10

15

20

25

30

Pres

sure

Alti

tude

(km

)

a

Uloon-Ucontrol rms (ms-1) August 2014

-90 -60 -30 0 30 60 90Latitude

1000

100

10

Pres

sure

(hPa

)

0

5

10

15

20

25

30

Pres

sure

Alti

tude

(km

)

b

> 20001000--2000500--1000100--50010--100

Number ofLoon

Observations

0.50

1.00

Minus Ucontrol-UMERRA2 rms

U

Global Assimilation of Loon Stratospheric Balloon Observations Lawrence Coy1 Mark Schoeberl2 Steven Pawson1 Salvatore Candido3 and Robert W. Carver31 NASA Goddard Space Flight Center, Greenbelt, MD, USA: 2Science and Technology Corp, Columbia, MD, USA: 3Loon, Mountain View, CA, USA

E-mail: lawrence.coy@nasa.gov | Web: gmao.gsfc.nasa.gov

Poster Number 1542

Global Modeling & Assimilation Office

Number of Loon Observations (Jun-Aug 2014) per 1ox 250 m grid box

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90Latitude

18

19

20

21

22

23

24

Pres

sure

Alti

tude

(km

)

70

60

50

40

Pres

sure

(hPa

)

> 20001000--2000500--1000100--50010--100

Blue and Red: Denote 6 hour intervals

This Loon trajectory will be examined in more detail.

Rawinsonde observations in the stratosphere (circles) Loon Balloon Trajectories

Altitude Changes

U

0

1

2

3

4

5

RMS

(ms-1

)

aO minus FJun-Aug 2014

Blue: wo LoonRed: wi Loon

SHSH4.3e+6

EQEQ5.0e+5

NHNH1.8e+5

U

0

5

10

15

20

RMS

(ms-1

)

b|O-F| > 10 ms-1

SHSH7.9e+3

EQEQ1.1e+4

NHNH9.4e+1

V

0

1

2

3

4

5

RMS

(ms-1

)

c

SHSH4.3e+6

EQEQ5.0e+5

NHNH1.8e+5

V

0

5

10

15

20

RMS

(ms-1

)

d|O-F| > 10 ms-1

SHSH1.0e+4

EQEQ2.9e+3

NHNH1.7e+1

Latitude Bands Latitude BandsNumber of Observations

Cont

rol

Loon

Cont

rol

Loon

Cont

rol

Loon

Cont

rol

Loon

Cont

rol

Loon

Cont

rol

Loon

All Loon Observations Control and Loon Obs show large (> 10m/s) differences

Tropics1 m/s

5 m

/s

Tropics

The Problem

Verification of global data assimilation system (DAS) output fields by independent observations insures the quality of these products for scientific studies and can highlight the need for additional observations to improve the quality. This is especially important for middle atmosphere winds where there are few “in situ” observations available to constrain the DAS. Here we use constant pressure balloon derived winds to evaluate the lower stratospheric winds in the NASA GEOS DAS.

Loon Balloons

Goal: launch and maintain a fleet of balloons to provide Internet coverage to users on the ground.Status: over 25 million km of test flights since the project began.Flight Duration: up to 190 days in the stratosphere.Winds: Derived from Loon Balloon GPS determined locations.

MethodologyNASA GMAO MERRA-2 Data Assimilation SystemTwo Experiments:1. Control Experiment (assimilation of standard observation set)2. Loon Experiment (assimilation of Loon balloon derived winds + standard observation set)Test Time Period: June-August 2014 (large number of Southern Hemisphere Loon Balloons)

Loon Balloon Distribution (June-August 2014)

Southern HemisphereLoon Balloons 70-50 hPa(18-21 Km) Altitude60oS to 10oN Latitude

Balloon Altitudes are adjusted while in flight

Examples of Loon Balloon Coverage

6-Hour Assimilation System Data WindowLoon balloons can fill in wind observations over the oceans.

14 Days Tropical CoverageTropical observations provided some of the largest DAS adjustments when assimilating the Loon winds.

Forecast Improvement (o-f) RMS Summary

Assimilated Loon Balloon Winds greatly improves the tropical background forecastNote: o-f denotes the difference between the observation and the short background forecast

Analysis Improvement (o-a) RMS Example

Loon Balloon ObservationsLoon ExperimentControl Experiment

Analysis winds interpolated by the DAS in space and time to the Loon positionNote: o-a denotes the difference between the observation and the DAS analysis

U Wind Component along a Tropical Loon Balloon trajectory

Large differences occur between the Control Experiment Analysis and Loon Observations that are corrected in the Loon Experiment Analysis. (Black and gray are on top of each other.)

Analysis Differences (RMS) August 2014

Control and Loon Balloon differences found mainly at Loon Balloon AltitudesEvidence of some influence extending into the troposphere, below the Loon Balloon altitude.

Additional Test Time Period (June-August 2016)

Sample Trajectories (~100-70 hPa Altitude Range)Western Hemisphere Concentration

All Loon Observations Control and Loon Obs show large (> 10m/s) differences

Confirmation of 2014 ResultsO-F RMSImprovements at all latitudes, more significant improvement in tropics

Conclusions

Latitude Bands Latitude BandsNumber of Observations

1. Additional wind observations can improve data assimilation products in the lower stratosphere, especially in the tropics

2. Current tropical wind analyses in the lower stratosphere can have errors larger than 10 ms-1

3. Some of the stratospheric wind analysis improvement may be accompanied by improvements in the upper troposphere wind analysis (further investigation is planned)

Coy, L, M. R. Schoeberl, S. Pawson, S. Candido, & R. Carver, 2018, Global assimilation of X Project Loon stratospheric balloon observations, Submitted to J. Geophys. Res.

https://loon.co/

GMAO Publication List