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Initial Assessment of the COSMIC2 Neutral

Atmosphere Data Quality in NOAA STAR using In Situ and

Satellite DataShu-peng Ben Ho, Xinjia Zhou, Bin Zhang,

Xi Shao,

and

NOAA STAR GNSS RO team

Oct. 23, 2020

MotivationCOSMIC-2 is an important NOAA RO mission covering mainly from 45N to 45S.

Is the quality of COSMIC-2 data consistent or better than those of COSMIC-1 in terms of precision, long term stability, accuracy in the lower stratosphere, troposphere, particularly in the lower troposphere ?

High precision (

1. Precision : Inter-comparison of C2 early orbit data2. Long term stability 3. Accuracy 4. Fractional dynamic bending angle observation error estimates and comparisons with ERA-55. Conclusions

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Outlines

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Data and approaches: UCAR COSMIC-2 from 6 LEO satellites from June to Oct. 2019, in situ RS41 and RS92 radiosonde data, and UCAR processed C2 bending angle, temperature, and water vapor profiles. KOMSAT5 and COMSIC data

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biases above 100 hPa and humidity biases below 100 hPa at some atmospheric conditions [37]. In 225 this study, only RS41 data are used in our comparisons. The radiosonde data used in this study 226 were downloaded from CDAAC (http://cosmic.cosmic.ucar.edu/cdaac/index.html). Figure 3 227 depicts the geophysical locations for RS41 data from July 2019 to Jan. 2020. Most of the 228 radiosonde data are collected twice per day. In this study, we specifically focus on assessing the 229 quality COSMIC-2 temperature in the stratosphere, refractivity in the stratosphere and 230 troposphere, and water vapor profiles in the troposphere using in situ radiosonde observation 231 (RAOB) data. 232

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Fig. 3. The geophysical locations for RS41 data from July to October 2019. 234 235 3. Approaches for Quantifying the Precision, Stability, Accuracy, and Uncertainty of 236

COSMIC-2 Data 237 Similar to [33], we first collect all available RS41 measurements that are within 300 km 238

and 2 hours with the locations and time of COSMIC-2 data. The COSMIC-2 geo-location is 239 defined at the tangent point from 4 km to 5 km altitudes. If there is more than one RS41 profile 240 within 2 hours and 300 km of one COSMIC-2 profile, the closest RS41 in location is selected. 241 Then we interpolate the COSMIC-2 atmPrf data to the mandatory pressure level of the 242 radiosondes (i.e., surface, 850, 700, 500, 200, 150, 100, 50, and 20 hPa). 243

As shown in Fig. 1, COSMIC-2 SNR ranges from 200V/V to 2700 V/V which cover the 244 SNR range for other RO missions (i.e., COSMIC, KOMPSAT-5 etc). In this study, COSMIC-2 245 profiles are grouped with five SNR ranges: i) SNR < 500 V/V (i.e., 0-500V/V group), ii) 500 246 V/V ≤SNR < 1000 V/V (i.e., 500-1000V/V group), iii) 1000 V/V ≤ SNR < 1500 V/V (i.e., 247 1000-1500V/V group), iv) 1500 V/V ≤ SNR < 2000 V/V (i.e., 1500-2000V/V group), and v) 248 >2000 V/V ≤ SNR < 2800V/V (i.e., >2000 V/V group). The mean COSMIC SNR falls into the 249 500-1000 V/V group. 250

The refractivity, temperature, and water vapor differences between COSMIC-2 and the 251 corresponding RS41 pairs in the same pressure level i are computed using the equation 252

Vasaila RS41

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1. COSMIC-2 PrecisionDay 111 through 300 of 2019 from COSMIC-2 FM4 and FM1 receivers where they are only 5 seconds and 10 km apart.

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2. COSMIC-2 Stability

Within 2 hours and 300 km for COSMIC-2 vs. RO data are collected Oct. 2019

COSMIC-2 - COSMIC COSMIC-2 – KOMPSAT-5

The fractional refractivity comparisons for (a) the COSMIC-2/GPS- RS41 pairs, and (b)

COSMIC-2/GLONASS – RS41 pairs. The mean differences are in red line and the

standard deviation of the mean difference are in green lines. The sample numbers are in

blues line. The standard error of the means are in the horizontal black lines

superimposed on the mean.

3.1 Accuracy COSMIC-2 Refractivity from GPS and GLONASS COSMIC-2 vs. RS41 within 2 hours and 300 km are collected.The fractional refractivity comparisons for the COSMIC-2/GPS- RS41 pairs, and COSMIC-2/GLONASS – RS41 pairs

The temperature comparisons from 8 km to 32 km altitude for (a)COSMIC-2 and RS41 pairs, and (b) COSMIC-2 and RS92 pairs.

3.2 COSMIC-2 Temperature accuracy in the lower stratosphere

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For the COSMIC-2- RS41 pairs over (a) daytime, and(b) night-time.

Daytime Night-time

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The COSMIC-2 refractivity mean differences and standard deviation compared to those collocated

RS41 profiles from June to October 2019 (a) over global (45°N to 45°S), (b) mid-latitude North

Hemisphere (45°N to 20°N), (c) Tropical region (20°N - 20°S), and (d) mid-latitude South

Hemisphere (20°S to 45°S). The mean biases and standard deviation relative to the mean are

computed from surface to 20 km altitude.

3.3 COSMIC-2 refractivity accuracy

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3.4 COSMIC-2 Water vapor accuracy under beam forming and non-beam forming period

Non-Beamforming mode before August 16 Beamforming periodBeginning on August 16, 2019 (DOY 228), all measurements were collected with beamforming on mode

COSMIC-2 – RS41 pairs where COSMIC-2 data are collected from (a) non-beam period, and (b) beam forming period.

COSMIC-2 profiles for SNR of (a) 0-500 V/V group, (b) 500-1000 V/V group, (c) 1000-1500 V/V group, (d) 1500-2000 V/V group, and (e) > 2000 V/V group.

3.5 COSMIC-2 refractivity accuracy for different SNR groups

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COSMIC-2 – RS41 water vapor profiles for different SNR groups.

3.6 COSMIC-2 water vapor accuracy for different SNR groups

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COSMIC2

4. Fractional dynamic bending angle observation errors (DBAOE) comparisonsFractional DBAOE is defined as 100% x Local spectrum width (LSW)/2 / bending angle

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cosmic, 2019 spring

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Mean Fractional DBAOE, Oct 2019

Fractional DBAOE comparisonsFractional DBAOE is defined as 100% x LSW/2 / bending angle

45N-30N 30N-30S 30S-45S

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COSMIC-2 – ERA5 fractional bending angle difference (%)

5. Conclusions

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• Precision • Long term stability • Accuracy • Fractional dynamic

bending angle observation error estimates and comparisons with ERA-5

• Ho, S.-P., R. A. Anthes, C. O. Ao, S. Healy, A. Horanyi, D. Hunt, A. J. Mannucci, N. Pedatella, W. J. Randel, A. Simmons, A. Steiner, F. Xie, X. Yue, Z. Zeng, 2020: The COSMIC/FORMOSAT-3 Radio Occultation Mission after 12 years: Accomplishments, Remaining Challenges, and Potential Impacts of COSMIC-2, Bul. Amer. Meteor. Sci., DOI: 10.1175/BAMS-D-18-0290.1.

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NOAA/STAR in-house Expertise to support CWDP/COSMIC-2 and other RO missions

1

RO Data Processing

Time delay (L0-L1): Dr. Bin Zhang, Jun Dong from CICS and Yuxiang He from GST)

Excess phase

POD

Bending angle (L1- L2): Dr. Lok Adhikari (CICS)

Impact parameter

Refractivity

Geometric height

Temperature, water vapor, pressure: Dr. Stanislav Kireev (GST)

Ind

ep

en

de

nt V

erif

ica

tio

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Tested & verified using ROPP (EUMETSAT) and KOMPSAT5, COSMIC,Metop-A, -B, -C GRAS data

Multi-sensor Validation

Va

lid

atio

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Radiosonde (Dr. Xi Shao from CICS)

Microwave Sounders ATMS, AMSU-A (CICS)

Infrared Sounders CrIS, AIRS, IASI (Dr. Erin Lynch from CICS)

Retrievals (temperature, water vapor)

ECMWF model

Well established NOAA system NPROVS for sounding validation

DataAssimilation

Non-local Bending Angle (Ray-tracing)

Local Bending Angle (Forward Abel)

Local Refractivity

JCSDA and TMP project

Da

ta

Assim

ila

tio

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As JCSDA partners, STAR and NCEP work together closely to perform impact assessment

Integrated Cal/Val System (ICVS) for Monitoring

Operational monitoring

RO measurements

Parameters for all RO data levels

Statistics

Long-term monitoring

(Mr. Xinjia Zhou GST

Dr. Yuxiang He GST

Dr. Ling Liu CICS)

Pe

rfo

rm

an

ce

Mo

nit

orin

g

Well established system for all NOAA satellites expanded to include RO; tested using KOMPSAT5, KOMPSAT5, COSMIC,Metop-A, -B, -C GRAS datadata

Four major focus areas of Cal/Val work have been defined

1) PP-1-10 Bin Zhang : STAR RO Processing package to convert COSMIC-2 phase observations to Excess Phase and Bending Angles: Initial Results

2) PP-1-02 Loknath Adhikari: Inverting COSMIC-2 Phase Data to Bending Angle and Refractivity Profiles using the Full Spectrum Inversion Method

3) PP-3-08 Stanislav Kireev: The Development of COSMIC-2 Temperature, Moisture, and Pressure Retrieval Algorithm at NOAA STAR

4) PP-2-05 Xi Shao : Examining the Consistency and Long-Term Stability between COSMIC-2 Radio Occultation and SNPP ATMS Microwave Sounding Measurements