Solar Variability and Trend Effects in Mesospheric Ice Layers

Lübken, Franz‐Josef; Berger, Uwe; Kiliani, Johannes; Baumgarten, Gerd; Fiedler, Jens

doi:10.1007/978-94-007-4348-9_18

Cited by 11 publications

(14 citation statements)

References 39 publications

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“…Lübken et al . [] extends the LIMA calculations through 2010. We note that their results show Northern Hemisphere albedo values in 2009–2010 (during the most recent solar minimum) higher than those determined for 1996–1997, whereas in our SBUV data the 1996–1997 seasons are still the highest values in the data record.…”

Section: Long‐term Trend Resultsmentioning

confidence: 88%

“…Thomas [] proposed using the cumulative distribution g ( A PMC ), defined as the integral of the frequency distribution of PMC albedo f ( A PMC ), to better represent such populations. Results using this approach have been published for SME data [ Thomas , ], Wind Imaging Interferometer (WINDII) and Polar Ozone and Aerosol Measurement II data [ Shettle et al ., ], SBUV data [ DeLand et al ., ], Student Nitric Oxide Explorer data [ Bailey et al ., ], and most recently for model results [ Lübken et al ., ]. Figure shows some examples of g distribution plots on a semilogarithmic scale.…”

Section: Sbuv Pmc Processingmentioning

confidence: 99%

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Updated PMC trends derived from SBUV data

DeLand

Thomas

2015

JGR Atmospheres

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Previous analysis of polar mesospheric clouds (PMCs) observed by Solar Backscatter Ultraviolet (SBUV) instruments found that long-term variations in PMC brightness and occurrence frequency were anticorrelated with solar activity and that an increasing secular trend was present at most latitudes. In this paper, long-term PMC variations are presented in terms of ice water content (IWC), a physically based variable which is easier to interpret than previously reported UV albedo values. This model-based conversion from albedo to IWC removes most scattering angle effects. The derived long-term PMC variations in the SBUV data set are qualitatively the same using either an empirically derived adjustment for local time effects or no adjustment (i.e., assuming cancelation of interannual variations in tidally induced amplitude and/or phase). When we use stratospheric ozone variations as a proxy for mesospheric temperature changes, as suggested by recent model studies, we can explain more of the long-term IWC variability than if we use a linear trend. These results show that PMC ice water content in bright clouds increased rapidly from 1979 through the late 1990s and has been approximately constant from the late 1990s through 2013. The numerical value and sign of this trend during the last 15 years depend on the choice of end points and latitude band. Simultaneously, the solar response of IWC observed by SBUV has weakened during the most recent cycle in the Northern Hemisphere, but increased in the Southern Hemisphere.

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Section: Long‐term Trend Resultsmentioning

confidence: 88%

Section: Sbuv Pmc Processingmentioning

confidence: 99%

Updated PMC trends derived from SBUV data

DeLand

Thomas

2015

JGR Atmospheres

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“…We already discussed the trend in PMC altitudes in section 3.1 where we find a connection of PMC heights to atmospheric shrinking. We begin the discussion with the result that there exists a very high correlation between PMC heights and the temperatures at 83 km as had been already shown in Lübken []. The Pearson correlation coefficient is 0.98 indicating an almost perfect linear relation (Figure a).…”

Section: Discussionmentioning

confidence: 99%

Trends in mesospheric ice layers in the Northern Hemisphere during 1961–2013

Berger

Lübken

2015

JGR Atmospheres

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The MIMAS ice model is used to study the trend behavior of polar mesospheric clouds (PMCs) responding to long‐term changes in mesospheric temperatures at northern high latitudes for the summer period 1961–2013. This paper presents long‐term PMC variations in terms of ice water content (IWC) at northern high latitudes for monthly July averages that are compared to solar backscatter ultraviolet (SBUV) data available in the period 1979–2013. In general, good agreement is found between long‐term PMC variations from the model and from satellite observations. For example, both model and SBUV data show an increase in ice water content (IWC > 40 g km−2) in the latitude band 74°–82°N with significant IWC trends of 2.8 ± 2.1 g km−2/dec and 2.4 ± 2.0 g km−2/dec, respectively. Modeled trends in IWC are latitudinally dependent. For the entire period 1961–2013 no trend exists at midlatitudes (50°–60°N) but increases poleward to highly significant values of 4.4 ± 0.9 g km−2/dec in the latitude band 74°–82°N. The analysis of trends in extreme PMC events (IWC > 300 g km−2) shows a 23%/dec increase in occurrence frequency at 74°–82°N which is by far the largest trend of all PMC parameters. We discuss the statistical properties of PMC following an exponential distribution. We derive an analytic solution of ice growth from microphysics that allows calculation of ice particle radius as a function of background conditions. As a result, the thermal conditions near 83 km height, with a cooling of −0.58 ± 0.32 K/dec, mainly determine trends in IWC whereas cooling at lower heights, induced by stratospheric ozone, controls to a large extent the long‐term behavior of PMC altitudes.

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“…The current version of MIMAS is described in detail in Kiliani (2014). More details about earlier model versions using dynamics from COMMA/IAP are found in Berger and von Zahn (2002), von Zahn and Berger (2003), and Berger and von Zahn (2007), about MIMAS used with LIMA dynamics (LIMA/ICE) in Lübken et al (2009Lübken et al ( , 2013 and Berger and Lübken (2015).…”

Section: Model Descriptionmentioning

confidence: 99%

Impact of particle shape on the morphology of noctilucent clouds

et al. 2015

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Abstract. Noctilucent clouds (NLCs) occur during summer in the polar region at altitudes around 83 km. They consist of ice particles with a typical size around 50 nm. The shape of NLC particles is less well known but is important both for interpreting optical measurements and modeling ice cloud characteristics. In this paper, NLC modeling of microphysics and optics is adapted to use cylindrical instead of spherical particle shape. The optical properties of the resulting ice clouds are compared directly to NLC three-color measurements by the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) Rayleigh/Mie/Raman (RMR) lidar between 1998 and 2014. Shape distributions including both needle-and disc-shaped particles are consistent with lidar measurements. The best agreement occurs if disc shapes are 60 % more common than needles, with a mean axis ratio of 2.8. Cylindrical particles cause stronger ice clouds on average than spherical shapes with an increase of backscatter at 532 nm by ≈ 30 % and about 20 % in ice mass density. This difference is less pronounced for bright than for weak ice clouds. Cylindrical shapes also cause NLCs to have larger but a smaller number of ice particles than for spherical shapes.

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Solar Variability and Trend Effects in Mesospheric Ice Layers

Cited by 11 publications

References 39 publications

Updated PMC trends derived from SBUV data

Updated PMC trends derived from SBUV data

Trends in mesospheric ice layers in the Northern Hemisphere during 1961–2013

Impact of particle shape on the morphology of noctilucent clouds

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