Gravity waves are one of the main drivers of atmospheric dynamics. The
spatial resolution of most global atmospheric models, however, is too coarse
to properly resolve the small scales of gravity ...waves, which range from tens
to a few thousand kilometers horizontally, and from below 1 km to tens of
kilometers vertically. Gravity wave source processes involve even smaller
scales. Therefore, general circulation models (GCMs) and chemistry climate
models (CCMs) usually parametrize the effect of gravity waves on the global
circulation. These parametrizations are very simplified. For this reason,
comparisons with global observations of gravity waves are needed for an
improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb
emissions observed by satellite (GRACILE). GRACILE is a global data set of
gravity wave distributions observed in the stratosphere and the mesosphere by
the infrared limb sounding satellite instruments High Resolution Dynamics
Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission
Radiometry (SABER). Typical distributions (zonal averages and global maps) of
gravity wave vertical wavelengths and along-track horizontal wavenumbers are
provided, as well as gravity wave temperature variances, potential energies
and absolute momentum fluxes. This global data set captures the typical
seasonal variations of these parameters, as well as their spatial variations.
The GRACILE data set is suitable for scientific studies, and it can serve for
comparison with other instruments (ground-based, airborne, or other satellite
instruments) and for comparison with gravity wave distributions, both
resolved and parametrized, in GCMs and CCMs. The GRACILE data set is
available as supplementary data at
https://doi.org/10.1594/PANGAEA.879658.
The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. Satellite observations of ...CO are routinely used to analyze emissions from fossil fuels and biomass burning, as well as the atmospheric transport of those emissions. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the version 8 (V8) product. V8 products benefit from updated spectroscopic data for water vapor and nitrogen used to develop the operational radiative transfer model and exploit a new method for minimizing retrieval biases through parameterized radiance bias correction. In situ datasets used for algorithm development and validation include the NOAA (National Oceanic and Atmospheric Administration) and HIPPO (HIAPER Pole-to-Pole Observations) datasets used for earlier MOPITT validation work in addition to measurements from the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems – Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)), KORUS-AQ (The Korea-United States Air Quality Study), and ATom (The Atmospheric Tomography Mission) programs. Validation results illustrate clear improvements with respect to long-term bias drift and geographically variable retrieval bias. For example, whereas bias drift for the V7 thermal-infrared (TIR)-only product exceeded 0.5 % yr−1 for levels in the upper troposphere (e.g., at 300 hPa), bias drift for the V8 TIR-only product is found to be less than 0.1 % yr−1 at all levels. Also, whereas upper-tropospheric (300 hPa) retrieval bias in the V7 TIR-only product exceeded 10 % in the tropics, corresponding V8 biases are less than 5 % (in terms of absolute value) at all latitudes and do not exhibit a clear latitudinal dependence.
The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making observations of atmospheric carbon monoxide since 2000. Recent enhancements to the MOPITT retrieval ...algorithm have resulted in the release of the version 7 (V7) product. Improvements include (1) representation of growing atmospheric concentrations of N2O, (2) use of meteorological fields from the MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications) reanalysis for the entire MOPITT mission (instead of MERRA), (3) use of the MODIS (Moderate-Resolution Imaging Spectroradiometer) Collection 6 cloud mask product (instead of Collection 5), (4) a new strategy for radiance-bias correction and (5) an improved method for calibrating MOPITT's near-infrared (NIR) radiances. Statistical comparisons of V7 validation results with corresponding V6 results are presented, using aircraft in situ measurements as the reference. Clear improvements are demonstrated for V7 products with respect to overall retrieval biases, bias variability and bias drift uncertainty.
Overview of the EOS aura mission Schoeberl, M.R.; Douglass, A.R.; Hilsenrath, E. ...
IEEE transactions on geoscience and remote sensing,
05/2006, Letnik:
44, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Aura, the last of the large Earth Observing System observatories, was launched on July 15, 2004. Aura is designed to make comprehensive stratospheric and tropospheric composition measurements from ...its four instruments, the High Resolution Dynamics Limb Sounder (HIRDLS), the Microwave Limb Sounder (MLS), the Ozone Monitoring Instrument (OMI), and the Tropospheric Emission Spectrometer (TES). With the exception of HIRDLS, all of the instruments are performing as expected, and HIRDLS will likely be able to deliver most of their planned data products. We summarize the mission, instruments, and synergies in this paper.
Sudden stratospheric warmings (SSWs) are circulation anomalies in the polar region during winter. They mostly occur in the Northern Hemisphere and affect also surface weather and climate. Both ...planetary waves and gravity waves contribute to the onset and evolution of SSWs. While the role of planetary waves for SSW evolution has been recognized, the effect of gravity waves is still not fully understood, and has not been comprehensively analyzed based on global observations. In particular, information on the gravity wave driving of the background winds during SSWs is still missing.We investigate the boreal winters from 2001/2002 until 2013/2014. Absolute gravity wave momentum fluxes and gravity wave dissipation (potential drag) are estimated from temperature observations of the satellite instruments HIRDLS and SABER. In agreement with previous work, we find that sometimes gravity wave activity is enhanced before or around the central date of major SSWs, particularly during vortex-split events. Often, SSWs are associated with polar-night jet oscillation (PJO) events. For these events, we find that gravity wave activity is strongly suppressed when the wind has reversed from eastward to westward (usually after the central date of a major SSW). In addition, gravity wave potential drag at the bottom of the newly forming eastward-directed jet is remarkably weak, while considerable potential drag at the top of the jet likely contributes to the downward propagation of both the jet and the new elevated stratopause. During PJO events, we also find some indication for poleward propagation of gravity waves. Another striking finding is that obviously localized gravity wave sources, likely mountain waves and jet-generated gravity waves, play an important role during the evolution of SSWs and potentially contribute to the triggering of SSWs by preconditioning the shape of the polar vortex. The distribution of these hot spots is highly variable and strongly depends on the zonal and meridional shape of the background wind field, indicating that a pure zonal average view sometimes is a too strong simplification for the strongly perturbed conditions during the evolution of SSWs.
The Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument
operated from 25 October 1978 through 28 May 1979. This note focuses on
its Version 6 (V6) data and indications of ozone loss ...in the lower
stratosphere of the Southern Hemisphere subpolar region during the last
week of October 1978. We provide profiles and maps that show V6 ozone values
of only 2 to 3 ppmv at 46 hPa within the edge of the polar vortex near
60∘ S from late October through mid-November 1978. There are also
low values of V6 nitric acid (∼3 to 6 ppbv) and nitrogen
dioxide (< 1 ppbv) at the same locations, indicating that conditions
were suitable for a chemical loss of Antarctic ozone some weeks earlier.
These “first light” LIMS observations provide the earliest space-based
view of conditions within the lower stratospheric ozone layer of the
southern polar region in springtime.
During the 2008 Olympics, the Chinese government made a significant effort to improve air quality in Beijing, including restrictions on traffic. Here we estimate the reductions in carbon monoxide ...(CO) and carbon dioxide (CO2) emissions resulting from the control measures on Beijing transportation. Using MOPITT (Measurements Of Pollution In The Troposphere) multispectral satellite observations of near‐surface CO along with WRF‐Chem (Weather Research and Forecasting model with Chemistry) simulations for Beijing during August, 2007 and 2008, we estimate changes in CO due to meteorology and transportation sector emissions. Applying a reported CO/CO2 emission ratio for fossil fuels, we find the corresponding reduction in CO2, 60 ± 36 GgCO2/day. As compared to emission scenarios being considered for the IPCC AR5 (Intergovernmental Panel on Climate Change, 5th Assessment Report), this result suggests that urban traffic controls on the Beijing Olympics scale could play a significant role in meeting target reductions for global CO2 emissions.
Key Points
Significant reduction in CO2 emissions from Beijing Olympics traffic controls
Use of satellite observations with regional modeling for source attribution
Urban traffic restrictions could help attain global CO2 reduction targets
The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT ...version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). Validation uses data recorded at 14 stations, that span a wide range of latitudes (80° N to 78° S), in the Network for the Detection of Atmospheric Composition Change (NDACC). MOPITT measurements are spatially co-located with each station, and different vertical sensitivities between instruments are accounted for by using MOPITT averaging kernels (AKs). All three MOPITT retrieval types are analyzed: thermal infrared (TIR-only), joint thermal and near infrared (TIR–NIR), and near infrared (NIR-only). Generally, MOPITT measurements overestimate CO relative to FTS measurements, but the bias is typically less than 10 %. Mean bias is 2.4 % for TIR-only, 5.1 % for TIR–NIR, and 6.5 % for NIR-only. The TIR–NIR and NIR-only products consistently produce a larger bias and lower correlation than the TIR-only. Validation performance of MOPITT for TIR-only and TIR–NIR retrievals over land or water scenes is equivalent. The four MOPITT detector element pixels are validated separately to account for their different uncertainty characteristics. Pixel 1 produces the highest standard deviation and lowest correlation for all three MOPITT products. However, for TIR-only and TIR–NIR, the error-weighted average that includes all four pixels often provides the best correlation, indicating compensating pixel biases and well-captured error characteristics. We find that MOPITT bias does not depend on latitude but rather is influenced by the proximity to rapidly changing atmospheric CO. MOPITT bias drift has been bound geographically to within ±0.5 % yr−1 or lower at almost all locations.
Nineteen limb-viewing data sets (occultation, passive thermal, and UV scattering) and two nadir
upper tropospheric humidity (UTH) data sets are intercompared and also compared to frost-point ...hygrometer
balloon sondes. The upper troposphere considered here covers the pressure range from 300–100 hPa.
UTH is a challenging measurement, because concentrations
vary between 2–1000 ppmv (parts per million by volume), with sharp changes in vertical
gradients near the tropopause. Cloudiness in this region
also makes the measurement challenging. The atmospheric temperature is also highly
variable ranging from 180–250 K. The assessment of satellite-measured UTH
is based on coincident comparisons with balloon frost-point hygrometer
sondes, multi-month mapped comparisons, zonal mean time series comparisons, and
coincident satellite-to-satellite comparisons. While the satellite fields show
similar features in maps and time series, quantitatively they can differ by a
factor of 2 in concentration, with strong dependencies on the amount of UTH.
Additionally, time-lag response-corrected Vaisala RS92 radiosondes are
compared to satellites and the frost-point hygrometer measurements. In summary,
most satellite data sets reviewed here show on average ∼30 % agreement
amongst themselves and frost-point data but with an additional ∼30 %
variability about the mean bias. The Vaisala RS92 sonde, even with a time-lag
correction, shows poor behavior for pressures less than 200 hPa.
This study examines the seasonal variation of the double tropopause (DT) using data from the High Resolution Dynamics Limb Sounder. The combination of high data density and high vertical resolution ...available with this satellite instrument allows for the detailed analysis of fine‐scale structures such as the DT. The spatial distribution of DT frequency is examined for all seasons from 2005 to 2007. Global analysis of this distribution reveals that DTs have a strong tendency to follow the zonal wind pattern and are present all year over the Andes. Moreover, during Northern Hemisphere winter/spring, there is a 15% decrease in the DT frequency over the eastern Pacific and western Atlantic, two regions of wave breaking produced from a weakening of the zonal flow. Significant DT thickness values are also present over these regions, but are found to extend further poleward than the corresponding frequency pattern. A time series of DT frequencies is analyzed and shows an increase in daily frequencies during 2006 that highlights the interannual variability of this thermal structure. For the first time, DT duration is investigated in the extratropics utilizing a Hovmöller diagram of DT frequency. This representation highlights two preferred regions of formation, the Pacific and Atlantic. The slope of the feature gives it a speed of 18 m/s in the Northern Hemisphere and a slightly faster speed for the Southern Hemisphere. These speeds and the corresponding structures highlight a potential connection between upper tropospheric waves and DTs.
Key Points
Winter double tropopause frequency decreases by 15% in regions of wave breaking
Speed of double tropopause is found to be ~18 m/s in Northern Hemisphere
A statistically significant increase in double tropopause frequency is found in 2006
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