An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

Navas-Guzmán, Francisco; Stähli, Oliver; Kämpfer, Niklaus

doi:10.5194/amt-7-1619-2014

Cited by 16 publications

(24 citation statements)

References 19 publications

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“…In this way TEMPERA covers uniformly the range from 51 to 57 GHz at positions between the emission lines. Tropospheric retrievals are not addressed in this paper and more details about this measurement mode can be found in Stähli et al (2013) and Navas-Guzmán et al (2014).…”

Section: Instrumentation and Measurementsmentioning

confidence: 99%

Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry

et al. 2015

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Abstract. In this work we study the Zeeman effect on stratospheric O 2 using ground-based microwave radiometer measurements. The interaction of the Earth magnetic field with the oxygen dipole leads to a splitting of O 2 energy states, which polarizes the emission spectra. A special campaign was carried out in order to measure this effect in the oxygen emission line centered at 53.07 GHz. Both a fixed and a rotating mirror were incorporated into the TEMPERA (TEMPERature RAdiometer) in order to be able to measure under different observational angles. This new configuration allowed us to change the angle between the observational path and the Earth magnetic field direction. Moreover, a highresolution spectrometer (1 kHz) was used in order to measure for the first time the polarization state of the radiation due to the Zeeman effect in the main isotopologue of oxygen from ground-based microwave measurements. The measured spectra showed a clear polarized signature when the observational angles were changed, evidencing the Zeeman effect in the oxygen molecule. In addition, simulations carried out with the Atmospheric Radiative Transfer Simulator (ARTS) allowed us to verify the microwave measurements showing a very good agreement between model and measurements. The results suggest some interesting new aspects for research of the upper atmosphere.

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Section: Instrumentation and Measurementsmentioning

confidence: 99%

Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry

et al. 2015

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“…In this study we only use the stratospheric temperature profiles with an altitude range of 18-50 km (70 to 0.7 hPa) and a vertical resolution of 15 km, retrieved with a measurement response higher than 0.6. The TEMPERA radiometer is described in more detail in Navas- Guzmán et al (2014Guzmán et al ( , 2015 and Stähli et al (2013).…”

Section: Data Sourcesmentioning

confidence: 99%

The natural oscillations in stratospheric ozone observed by the GROMOS microwave radiometer at the NDACC station Bern

et al. 2016

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Abstract. A multilinear parametric regression analysis was performed to assess the seasonal and interannual variations of stratospheric ozone profiles from the GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) microwave radiometer at Bern, Switzerland (46.95 • N, 7.44 • E; 577 m). GROMOS takes part in the Network for the Detection of Atmospheric Composition Change (NDACC). The study covers the stratosphere from 50 to 0.5 hPa (from 21 to 53 km) and extends over the period from January 1997 to January 2015. The natural variability was fitted during the regression analysis through the annual and semi-annual oscillations (AO, SAO), the quasi-biennial oscillation (QBO), the El Niño-Southern Oscillation (ENSO) and the solar activity cycle. Seasonal ozone variations mainly appear as an annual cycle in the middle and upper stratosphere and a semiannual cycle in the upper stratosphere. Regarding the interannual variations, they are primarily present in the lower and middle stratosphere. In the lower and middle stratosphere, ozone variations are controlled predominantly by transport processes, due to the long lifetime of ozone, whereas in the upper stratosphere its lifetime is relatively short and ozone is controlled mainly by photochemistry. The present study shows agreement in the observed naturally induced ozone signatures with other studies. Further, we present an overview of the possible causes of the effects observed in stratospheric ozone due to natural oscillations at a northern midlatitude station. For instance regarding the SAO, we find that polar winter stratopause warmings contribute to the strength of this oscillation since these temperature enhancements lead to a reduction in upper stratospheric ozone. We have detected a strong peak amplitude of about 5 % for the solar cycle in lower stratospheric ozone for our 1.5 cycles of solar activity. Though the 11-year ozone oscillation above Bern is in phase with the solar cycle, we suppose that the strong amplitude is partly due to meteorological disturbances and associated ozone anomalies in the Northern Hemisphere. Further, our observational study gave the result that ozone above Bern is anti-correlated with the ENSO phenomenon in the lower stratosphere and correlated in the middle stratosphere.

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“…Furthermore, only a simple cloud model has been tested and the effect of various cloud models different in shape and amount of liquid water has not yet been determined. The present study extends the work from Navas- Guzmán et al (2014) by further investigating the influence of liquid water on temperature retrievals and by comparing tropospheric temperature profiles with radiosonde measurements at the same location. Our objective is to improve temperature retrievals during cloudy conditions and to examine whether including different cloud models for situations with different cloud properties optimizes the temperature retrieval.…”

Section: Bernet Et Al: Cloud Effect On Temperature Retrievals Fromentioning

confidence: 69%

“…This is because at these frequencies, the absorption coefficient of cloud liquid is similar to the oxygen absorption coefficient (Navas-Guzmán et al, 2014;Stähli et al, 2013). This is the (Liebe et al, 1993) reason why Stähli et al (2013) only used the eight more opaque channels for retrievals where clouds were present.…”

Section: Absorption Species In the Retrievalmentioning

confidence: 87%

“…A first step towards these objectives has been performed by Navas-Guzmán et al (2014), who developed an integrated approach to incorporate clouds in temperature retrievals by using data from different cloud instruments with high temporal resolution. By comparing temperature measurements from a microwave radiometer with radiosondes they have shown that the temperature profiles generally improve when a cloud model is considered in the retrieval.…”

Section: Bernet Et Al: Cloud Effect On Temperature Retrievals Fromentioning

confidence: 99%

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The effect of cloud liquid water on tropospheric temperature retrievals from microwave measurements

2017

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Abstract. Microwave radiometry is a suitable technique to measure atmospheric temperature profiles with high temporal resolution during clear sky and cloudy conditions. In this study, we included cloud models in the inversion algorithm of the microwave radiometer TEMPERA (TEMPErature RAdiometer) to determine the effect of cloud liquid water on the temperature retrievals. The cloud models were built based on measurements of cloud base altitude and integrated liquid water (ILW), all performed at the aerological station (MeteoSwiss) in Payerne (Switzerland). Cloud base altitudes were detected using ceilometer measurements while the ILW was measured by a HATPRO (Humidity And Temperature PROfiler) radiometer. To assess the quality of the TEMPERA retrieval when clouds were considered, the resulting temperature profiles were compared to 2 years of radiosonde measurements. The TEMPERA instrument measures radiation at 12 channels in the frequency range from 51 to 57 GHz, corresponding to the left wing of the oxygen emission line complex. When the full spectral information with all the 12 frequency channels was used, we found a marked improvement in the temperature retrievals after including a cloud model. The chosen cloud model influenced the resulting temperature profile, especially for high clouds and clouds with a large amount of liquid water. Using all 12 channels, however, presented large deviations between different cases, suggesting that additional uncertainties exist in the lower, more transparent channels. Using less spectral information with the higher, more opaque channels only also improved the temperature profiles when clouds where included, but the influence of the chosen cloud model was less important. We conclude that tropospheric temperature profiles can be optimized by considering clouds in the microwave retrieval, and that the choice of the cloud model has a direct impact on the resulting temperature profile.

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An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

Cited by 16 publications

References 19 publications

Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry

Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry

The natural oscillations in stratospheric ozone observed by the GROMOS microwave radiometer at the NDACC station Bern

The effect of cloud liquid water on tropospheric temperature retrievals from microwave measurements

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An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

Cited by 16 publications

References 19 publications

Zeeman effect in atmospheric O&lt;sub&gt;2&lt;/sub&gt; measured by ground-based microwave radiometry

Zeeman effect in atmospheric O&lt;sub&gt;2&lt;/sub&gt; measured by ground-based microwave radiometry

The natural oscillations in stratospheric ozone observed by the GROMOS microwave radiometer at the NDACC station Bern

The effect of cloud liquid water on tropospheric temperature retrievals from microwave measurements

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Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry

Zeeman effect in atmospheric O<sub>2</sub> measured by ground-based microwave radiometry