Ground-Based Observations

Between balloon and aircraft campaigns, the MkIV instrument is used to make ground-based observations. Although these measurements lack the vertical resolution that is attainable from balloon platforms, ground-based observations can nevertheless be made much more frequently - MkIV has averaged over 50 days of observation per year recently (until COVID-19 forced a 5-month stop). Ground-based observations are an accurate method of ascertaining whether the composition of the Earth's atmosphere is changing, which is the main purpose of NDACC.

MkIV Ground-based Vertical Column Abundances 1985-2023

Individual Column Abundances: (97 columns, 5813 rows)	m4_avg_1985_2023.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2023.vav.ames
Daily Average Column Abundances: (97 cols, 1376 rows)	m4_avg_1985_2023.vad
List of windows: (305 rows)	all_mols_mir_1985_2023.gnd
Window-to-window biases:	m4_avg_1985_2023.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2021

Individual Column Abundances: (101 columns, 5339 rows)	m4_avg_1985_2021.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2021.vav.ames
Daily Average Column Abundances: (101 cols, 1290 rows)	m4_avg_1985_2021.vad
List of windows: (305 rows)	all_mols_mir_1985_2021.gnd
Window-to-window biases:	m4_avg_1985_2021.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2019

Individual Column Abundances: (97 columns, 4995 rows)	m4_avg_1985_2019.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2019.vav.ames
Daily Average Column Abundances: (97 cols, 1228 rows)	m4_avg_1985_2019.vad
List of windows: (236 rows)	all_mols_mir_1985_2019.gnd
Window-to-window biases:	m4_avg_1985_2019.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2018

Individual Column Abundances: (91 columns, 4811 rows)	m4_avg_1985_2018.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2018.vav.ames
Daily Average Column Abundances: (91 cols, 1160 rows)	m4_avg_1985_2018.vad
List of windows: (233 rows)	all_mols_mir_1985_2018.gnd
Window-to-window biases:	m4_avg_1985_2018.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2017

Individual Column Abundances: (91 columns, 4557 rows)	m4_avg_1985_2017.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2017.vav.ames
Daily Average Column Abundances: (91 cols, 1160 rows)	m4_avg_1985_2017.vad
List of windows: (233 rows)	all_mols_mir_1985_2017.gnd
Window-to-window biases:	m4_avg_1985_2017.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2016

Individual Column Abundances: (89 columns, 4379 rows)	m4_avg_1985_2016.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2016.vav.ames
Daily Average Column Abundances: (89 cols, 1132 rows)	m4_avg_1985_2016.vad
List of windows: (265 rows)	all_mols_mir_1985_2016.gnd
Window-to-window biases:	m4_avg_1985_2016.tav.cew

MkIV Ground-based Vertical Column Abundances 1985-2015

Individual Column Abundances: (89 columns, 4229 rows)	m4_avg_1985_2015.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2015.vav.ames
Daily Average Column Abundances: (89 cols, 1090 rows)	m4_avg_1985_2015.vad
List of windows: (265 rows)	all_mols_mir_1985_2015.gnd
Window-to-window biases:	m4_avg_1985_2015.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2014

Individual Column Abundances: (85 columns, 3939 rows)	m4_avg_1985_2014.vav
Individual Column Abundances: (Ames-1001 format)	m4_avg_1985_2014.vav.ames
Daily Average Column Abundances: (85 cols, 1027 rows)	m4_avg_1985_2014.vad
List of windows: (242 rows)	all_mols_mir_1985_2014.gnd
Window-to-window biases:	m4_avg_1985_2014.vav.cew

MkIV Ground-based Vertical Column Abundances 1985-2013

Individual Column Abundances: (83 columns, 3417 rows)	mkiv_gnd_avg_1985_2013.vav
Individual Column Abundances: (Ames-1001 format)	mkiv_gnd_avg_1985_2013.vav.ames
Daily Average Column Abundances: (83 cols, 923 rows)	mkiv_gnd_avg_1985_2013.vad
List of windows: (225 rows)	mkiv_gnd_avg_1985_2013.windows
Window-to-window biases:	mkiv_gnd_avg_1985_2013.vav.cew

IMPORTANT: These files contain data from the 12 different locations tabulated below. It was felt that the benefits of keeping all the MkIV data together in one file outweigh any possible confusion. The files all contain lat/long/alt information for each observation, so it is simple to filter for a particular site.

Ground-based Sites and Observations (1985-2023)
Location	Key	Nobs	Nday	Latitude (deg.)	Longitude (deg.)	Altitude (km)	Terrain	Observation Season & Time
Esrange, Sweden	ESN	152	31	+67.889	+21.085	0.271	Boreal	Winter, Noon
Fairbanks, Alaska	FAI	124	46	+64.830	-147.614	0.182	Boreal	Spring & Summer, Noon
Lynn Lake, Manitoba, Canada	LYL	20	11	+56.858	-101.066	0.354	Boreal	Summer, Noon
Mt. Barcroft, California	MTB	1369	255	+37.584	-118.235	3.801	Mountain	Year-round, Morning
Mountain View, California	ARC	7	4	+37.430	-122.080	0.010	Urban	Various, Noon
Daggett, California	DAG	33	21	+34.856	-116.790	0.626	Desert	Spring, Noon
Ft. Sumner, New Mexico	FTS	636	123	+34.480	-104.220	1.260	Steppe	Spring & Fall, Afternoon
TMF, Wrightwood, California	TMF	468	45	+34.382	-117.678	2.257	Mountain	Fall & Winter, Noon
JPL B183, Pasadena, California	JPL	2951	816	+34.199	-118.174	0.345	Urban	Year-round, Noon
JPL Mesa, Pasadena, California	JPL	20	5	+34.205	-118.171	0.460	Urban	Summer, Noon
CSBF, Palestine, Texas	PAL	4	3	+31.780	-95.700	0.100	Rural	Summer, Noon
McMurdo, Antarctica	MCM	37	20	-77.847	+166.728	0.100	Icy	Spring, Noon

+ve Latitude = N; +ve Longitude = E
Nobs = Number of Observations. Nday = Number of Observation Days
Grand totals: Observations = 5821 Observation Days = 1380

The numbers in this table slightly exceed those in the data file for a few sites due to filtering.

Measurement Quantities:

Auxiliary Data: Year, Day, Hour, Run, Lat, long, zobs, zmin, asza, azim, osds, opd, fovi, graw, tins, pins, tout, pout, hout

Vertical column abundances (molec.cm^-2): H₂O, CO₂, O₃, N₂O, CO, CH₄, NO, NO₂, NH₃, HNO₃, HF, HCl, ClO, OCS, H₂CO, ClNO₃, HCN, CFC-12, COF₂, C₂H₆, C₂H₄, C₂H₂, N₂, HCFC-22, HCOOH, C₃H₈, HDO, and SF₆

Instrument Description:

The MkIV interferometer is a high resolution FTIR spectrometer designed and built at JPL in the early 1980's for solar absorption measurements. The MkIV employes a double-passed optical configuration for compactness and to provide passive shear compensation. Two parallel detectors, an HgCdTe photoconductor covering 650-1950 cm^-1 and an InSb photodiode covering 1850-5650 cm^-1, allow the entire mid-infrared spectrum to be measured simultaneously. For ground-based observations an optical path difference of 117 cm is usually employed, which takes about 3 minutes per scan sampling every fringe of a .633 um He:Ne laser at 10kHz.

Algorithm Description:

Column abundances were derived using the GFIT algorithm, developed at JPL for the analysis of solar absorption spectra. Initial vertical profiles were based on balloon measurements, which were then stretched or squashed until the measured HF absorption was matched. These profiles were then scaled in order to derive the vertical column abundances. The atm.101 linelist was used for the analyses, complemented by the pseudolines for the gases CCl₄, CFC-11, CFC-12, CF₄, SF₆, ClNO₃, HCFC-22 and C₂H₆.

Expected Precision/Accuracy of Measurements:

The precision of these column abundances were determined from the quality of the spectral fits by the GFIT algorithm and are included in the exchange file for each measurement of each gas. Accuracies are more difficult to determine.

For each balloon flight MkIV also performed many days of ground-based observation while waiting for launch. This explains the large number of different locations from which the MkIV instrument has made measurements.

Yearly totals of MkIV Observation Days from various ground-based sites (as of end of early 2024):
Year	ESN	FAI	LYL	MTB	ARC	DAG	FTS	TMF	JPL	PAL	MCM	Year Total
1985	0	0	0	0	0	0	0	0	2	0	0	2
1986	0	0	0	0	0	0	0	1	3	0	20	23
1987	0	0	0	0	0	0	0	0	3	0	0	3
1988	0	0	0	0	0	0	0	2	3	0	0	5
1989	0	0	0	0	0	0	7	0	10	2	0	11
1990	0	0	0	0	0	0	7	0	13	0	0	16
1991	0	0	0	0	4	0	7	0	40	0	0	50
1992	0	0	0	0	0	0	11	0	32	0	0	43
1993	0	0	0	0	0	5	10	0	33	0	0	64
1994	0	0	0	3	0	0	5	0	47	0	0	56
1995	0	0	0	0	0	0	0	0	72	0	0	72
1996	0	0	11	0	0	0	6	6	30	0	0	53
1997	0	46	0	0	0	0	0	0	18	0	0	64
1998	0	0	0	14	0	0	0	24	8	0	0	50
1999	1	0	0	33	0	0	0	0	16	0	0	42
2000	21	0	0	29	0	0	0	0	26	0	0	75
2001	0	0	0	101	0	0	0	0	0	0	0	101
2002	0	0	0	78	0	0	0	0	6	0	0	78
2003	24	0	0	0	0	0	5	0	6	0	0	5
2004	0	0	0	0	0	0	4	0	9	0	0	12
2005	0	0	0	0	0	0	4	0	2	0	0	5
2006	3	0	0	0	0	0	0	0	13	0	0	5
2007	8	0	0	0	0	0	5	0	1	0	0	13
2008	0	0	0	0	0	0	0	0	0	0	0	0
2009	0	0	0	0	0	0	0	11	1	0	0	12
2010	0	0	0	0	0	0	0	0	4	0	0	4
2011	0	0	0	0	0	0	5	0	20	0	0	25
2012	0	0	0	0	0	0	0	0	18	0	0	18
2013	0	0	0	0	0	0	0	0	74	0	0	74
2014	0	0	0	0	0	0	7	0	50	0	0	57
2015	0	0	0	0	0	0	0	0	51	0	0	51
2016	0	0	0	0	0	0	6	0	36	0	0	42
2017	0	0	0	0	0	0	9	0	19	0	0	28
2018	0	0	0	0	0	0	9	0	31	0	0	40
2019	0	0	0	0	0	0	11	0	27	0	0	37
2020	0	0	0	0	0	0	0	0	30	0	0	30
2021	0	0	0	0	0	0	8	0	32	0	0	32
2022	0	0	0	0	0	0	0	0	41	0	0	41
2023	0	0	0	0	0	0	8	0	28	0	0	36
2024	0	0	0	0	0	0	0	0	5	0	0	5
Site Total	46	46	11	255	4	5	123	45	816	3	20	1380

The following spectra have been (temporarily) removed from runlog due to known defects:

Year 1986, days 268 to 288: Some spectra are clipped

Year 1987, day 166-169: Time is wrong by 1 hour??. SZA and columns are wrong

Year 1989, day 177: Time is wrong by 1 hour, so SZA and columns are wrong

Year 1992, day 244: spectrum 224: CCl2F2 contamination

Year 2006, day 25: spectrum 509: Phase errors

Year 2006, 9 days (165, 171, 192, 200, 206, 212, 219, 251, 271) are inadvertantly missing from runlog

Year 2009, day 292-301: Several HBr cell spectra remain

Year 2019, before day 240: Several HBr cell spectra remain

Contact Information:

G.C. Toon
Mail-Stop 183-501
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109-8099, USA

Phone: 818-354-8259
FAX: 818-354-5148
Email: Geoffrey.C.Toon@jpl.nasa.gov

J.-F. Blavier
Mail-Stop 183-501
Jet Propulsion Laboratory
4800 Oak Grove Drive
Pasadena, CA 91109-8099, USA

Phone: 818-354-6665
FAX: 818-354-5148
Email: JeanFrancois.L.Blavier@jpl.nasa.gov

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