J/A+A/606/A53 Venus mesosphere ALMA observations (Piccialli+, 2017)
Mapping the thermal structure and minor species of Venus mesosphere with ALMA
submillimeter observations.
Piccialli A., Moreno R., Encrenaz T., Fouchet T., Lellouch E., Widemann T.
<Astron. Astrophys. 606, A53 (2017)>
=2017A&A...606A..53P 2017A&A...606A..53P (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Planets ; Abundances
Keywords: planets and satellites: individual: Venus -
planets and satellites: atmospheres -
submillimeter: planetary systems - radiative transfer -
instrumentation: interferometers - methods: data analysis
Abstract:
Water vapor and sulfur compounds are key species in the photochemistry
of Venus mesosphere. These species, together with mesospheric
temperatures, exhibit drastic temporal variations, both on short
timescales (diurnal and day-to-day) as well on long timescales, far
from being understood.
We targeted CO, SO, H2O and SO2 transitions in the submillimeter
range using the Atacama Large Millimeter Array (ALMA) to study their
spatial and temporal variations.
Four sets of observations were acquired on different dates in November
2011 during the first ALMA Early Science observation Cycle 0. Venus
angular diameter was about 11" with an illumination factor of 92%,
so that mostly the day side of the planet was mapped. Assuming a
nominal CO abundance profile, we retrieved vertical temperature
profiles over the entire disk as a function of latitude and local
time. Temperature profiles were later used to retrieve SO, SO2, and
H2O. We used H2O as a tracer for water assuming a D/H enrichment of
200 times the terrestrial value.
We derived 3-D maps of mesospheric temperatures in the altitude range
70-105km. SO, SO2, and H2O are characterized by a negligible
abundance below ∼85km followed by an increase with altitude in the
upper mesosphere. Disk-averaged SO abundances present a maximum mixing
ratio of 15.0±3.1ppb on November 26 followed the next day by a
minimum value of 9.9±1.2ppb. Due to a very low S/N, SO2 could only
be derived from the disk-averaged spectrum on the first day of
observation revealing an abundance of 16.5±4.6ppb. We found a
SO2/SO ratio of 1.5±0.4. Global maps of SO reveal strong
variations both with latitude and local time and from day to day with
abundance ranging from <1 to 15ppb. H2O disk-averages retrievals
reveal a steady decrease from November 14 to 27, with the abundance
varying from 3.6±0.6ppm on the first day to 2.9±0.7ppm on the last
day. H2O maps reveal a slightly higher abundance on the evening side
compared to the morning side and a strong depletion between the first
and the second day of observation.
Description:
Observations of Venus were obtained using the ALMA interferometer
within the project labeled 2011.0.00136.S. We observed - with a single
receiver tuning setup - the CO, SO, SO2 and H2O rotational lines at
frequencies of 345.795GHz, 346.528GHz, 346.652GHz and 335.395GHz,
respectively. The spectral resolution (originally 61kHz) was binned to
0.35MHz in order to optimize the S/N. These observations were obtained
on November 14, 2011, between 22:15 and 22:53 UT; on November 15,
2011, between 20:39 and 21:11 UT; on November 26, 2011, between 21:24
and 22:02 UT; and on November 27, 2011, between 21:07 and 21:58 UT.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 189 4 Summary of data
so14nov.dat 52 26 Retrieved disk-averaged abundance for SO obtained
for 2011-11-14 set of observation
so_14nov/* . 89 SO individual measurements on 2011-11-14
so15nov.dat 52 26 Retrieved disk-averaged abundance for SO obtained
for 2011-11-15 set of observation
so_15nov/* . 89 SO individual measurements on 2011-11-15
so26nov.dat 52 26 Retrieved disk-averaged abundance for SO obtained
for 2011-11-26 set of observation
so_26nov/* . 89 SO individual measurements on 2011-11-26
so27nov.dat 52 26 Retrieved disk-averaged abundance for SO obtained
for 2011-11-27 set of observation
so_27nov/* . 89 SO individual measurements on 2011-11-27
hdo14nov.dat 52 26 Retrieved disk-averaged abundance for H2O
obtained for 2011-11-14 set of observation
hdo_14nov/* . 89 H2O individual measurements on 2011-11-14
hdo15nov.dat 52 26 Retrieved disk-averaged abundance for H2O
obtained for 2011-11-15 set of observation
hdo_15nov/* . 89 H2O individual measurements on 2011-11-15
hdo27nov.dat 52 26 Retrieved H2O disk-averaged retrievals obtained
for 2011-11-27 set of observation
so214nov.dat 52 26 Retrieved disk-averaged abundance for SO2
obtained for 2011-11-14 set of observation
tem14nov.dat 52 36 Disk averaged temperature obtained for
2011-11-14 set of observation
temp_14nov/* . 89 Temperature individual measurements on 2011-11-14
tem15nov.dat 52 36 Disk averaged temperature obtained for
2011-11-15 set of observation
temp_15nov/* . 89 Temperature individual measurements on 2011-11-15
tem26nov.dat 52 36 Disk averaged temperature obtained for
2011-11-26 set of observation
temp_26nov/* . 89 Temperature individual measurements on 2011-11-26
tem27nov.dat 52 36 Disk averaged temperature obtained for
2011-11-27 set of observation
temp_27nov/* . 89 Temperature individual measurements on 2011-11-27
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Obs.date Observation date
12- 15 F4.1 10-9 MixSO SO mixing ratio at an altitude of 90km
(in part per billion, ppb)
17- 19 F3.1 10-9 e_MixSO rms uncertainty on MixSO
(in part per billion, ppb)
21- 31 E11.6 mol/cm2 ASO Retrieved disk-averaged abundance for SO
33- 43 E11.6 mol/cm2 e_ASO rms uncertainty on ASO
45- 55 A11 --- SOmean Name of the file with retrieved
disk-averaged abundance for SO
57- 64 A8 --- SOInd Name of the subdirectory with individual
SO measurements
66- 68 F3.1 10-9 MixH2O ? H2O mixing ratio at an altitude of 90km
(in part per billion, ppb)
70- 72 F3.1 10-9 e_MixH2O ? rms uncertainty on MixH2O
(in part per billion, ppb)
74- 84 E11.6 mol/cm2 AH2O ? Retrieved disk-averaged abundance
for H2O
86- 96 E11.6 mol/cm2 e_AH2O ? rms uncertainty on AH2O
98-109 A12 --- H2Omean Name of the file with Retrieved
disk-averaged abundance for H2O
111-119 A9 --- H2OInd Name of the subdirectory with individual
H2O measurements
121-124 F4.1 10-9 MixSO2 ? SO2 mixing ratio at an altitude of 90km
(in part per billion, ppb)
126-128 F3.1 10-9 e_MixSO2 ? rms uncertainty on MixSO2
(in part per billion, ppb)
130-140 E11.6 mol/cm2 ASO2 ? Retrieved disk-averaged abundance
for SO2
142-152 E11.6 mol/cm2 e_ASO2 ? rms uncertainty on ASO2
154-165 A12 --- SO2mean Name of the file with retrieved
disk-averaged abundance for SO2
167-178 A12 --- Tmean Name of the file with average temperature
180-189 A10 --- TInd Name of the subdirectory with individual
temperature measurements
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Byte-by-byte Description of file (#): so*.dat hdo*.dat
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Bytes Format Units Label Explanations
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6- 13 F8.4 km Height Height
16- 26 E11.6 ppm Mix Mixing for the studied element (G1)
29- 39 E11.6 mbar P Pressure
42- 52 E11.6 % e_P Error on pressure
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Byte-by-byte Description of file (#): tem*.dat
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Bytes Format Units Label Explanations
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6- 13 F8.4 km Height Height
20- 26 F7.3 K T Temperature
29- 39 E11.6 mbar P Pressure
46- 52 F7.4 % e_T Error on temperature
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Byte-by-byte Description of file (#): hdo_*/* so_*/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
6- 13 E8.4 km Height Height
16- 26 E11.6 ppm Mix Mixing ratio for the studied element (G1)
29- 39 E11.6 mbar P Pressure
42- 52 E11.6 % e_P Error on pressure
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Byte-by-byte Description of file (#): temp_*nov/*
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
6- 13 E8.4 km Height Height
20- 26 F7.3 K T Temperature
29- 39 E11.6 mbar P Pressure
46- 52 F7.4 % e_T Error on temperature
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Global notes:
Note (G1): SO mixing ratio for so* files, H2O mixing ratio for hdo* files,
SO2 mixing ratio for so2* files.
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Acknowledgements:
Arianan Piccialli, arianna.piccialli(at)aeronomie.be
(End) Patricia Vannier [CDS] 20-Jul-2017