Trends in the middle atmosphere from ground based sensors at mid and high latitudes

Transcription

1 Trends in the middle atmosphere from ground based sensors at mid and high latitudes Gunter Stober 1,2, F-J Lübken 1, U. Berger 1, P. Brown 2,, J. Fiedler 1, G. Baumgarten 1, R. Latteck 1, J.L. Chau 1 1 Leibniz-Institute for Atmospheric Physics, University of Rostock, Germany 2 Department of Physics and Astronomy, University of Western Ontario, Canada

2 Motivation NLC MLT region dynamics driven from below solar forcing from above almost no long term observations - sparse database very often tracers are used to infer trends/long term changes (e.g. NLC/PMSE) 2

3 Are NLC/PMSE a good tracer for the climate change? Credit: Leibniz Institute of Atmospheric Physics. 3

4 LIMA (Leibniz Institute Middle Atmosphere Model) Model domain: grid points, global, km horizontal grid of Δ = 110 km Physics: dynamics, radiation, offline chemistry GW scheme from A. Medvedev Nudging of reanalysis data (0 45 km) here: with same dynamics for all years Nudging of reanalysis data (0 45 km) v wind 54 N, 10 Jan :00 UT : ECMWF Era 40 & op every 6 h, 1 x 1 Courtesy: Uwe Berger 4

5 Ice particle model MIMAS (Mesospheric Ice Microphysics and Transport) trajectories of 40 million particles initialization with model background fields (u, v, w, T, H2O, etc.) H2O coupled to ice formation microphysics Courtesy: Uwe Berger 5

6 Background atmospheric state a) tropospheric CO 2 (black line) and CH 4 (green line) mixing ratios from Mauna Loa observations and ice core data (Etheridge et al., 2002, 1998) b) temperatures from Run A at a fixed geometric altitude (83 km) and at the mean pressure level of maximum backscatter (p mean ) c) mixing ratios of gas phase water vapor at p mean = hpa (83 km) (assuming that ice formation had not occurred) for Runs A and B Lübken et al., GRL, 2018, AGU Highlight 6

7 Ice particle sizes and volume backscatter coefficient β Lübken et al., GRL, 2018, AGU Highlight 7

8 Long term changes of NLC physicl parameters Lübken et al., GRL, 2018, AGU Highlight 8

9 Trends in NLC occurrence rate significant increase in occurrence rate of NLC decrease in mean altitude by 1 km ice particle density increase by 1 order of magnitude 9

10 ALOMAR RMR-Lidar vs. SBUV NLC occur more often since RMR lidar SBUV zonal mean SBUV around ALOMAR SBUV around ALOMAR, morning SBUV around ALOMAR, afternoon Fiedler et al. (JASTP, 2017) 10

11 SBUV at different Longitudes Alaska Greenland Norway Fiedler et al. (JASTP, 2017) 11

12 Polar Mesosphere Summer Echoes Characteristics of PMSE are determined by e.g. electron density water vapor concentration temperature Latteck and Bremer (JASTP, 2017) 12

13 PMSE occurence rate and geomagnetic activity Latteck and Bremer (JASTP, 2017) 13

14 Decadal variations of MLT winds at mid and high latitudes

15 Meteor Radar Observations CMOR (Canadian Meteor Orbit Radar) 15

16 Meteor Radar Wind Wind analysis with: error propagation (statistical uncertainties) Regularization Gaussian retrieval kernel 16

17 Adaptive spectral filter GW harmonic decomposition: adaptive spectral filter adapts window length to pre-selected period of oscillation unevenly sampled data and data gaps decomposes time series based on least squares techniques (svd, regularization) selected bandpasses can be rather wide 17

18 Andenes MR seasonal winds (69 N) Andenes 69 N CMOR 43 N 18

19 Mean decadal change Andenes and CMOR Andenes 69 N CMOR 43 N 19

20 Seasonal changes at high latitudes Andenes 69 N 20

21 Seasonal changes at mid latitudes CMOR 43 N 21

22 Residuum wind (trend plus mean removed) Andenes 69 N CMOR 43 N 22

23 Seasonal impact solar cycle Andenes 69 N CMOR 43 N 23

24 Meteor Ablation altitudes and neutral air density meteor ablation model employs NRLMSIS density (normal conditions) conversion of MPFA to neutral density assumption NRLMSIS mean density is good NRLMSIS time series by using daily F10.7 and Ap 24

25 Meteor Ablation altitudes and neutral air density remarkable agreement between MR density trend and Akmaev et al., 2006 NRLMSIS time series indicates no density decrease greenhouse gas cooling in the mesosphere still continuing shrinking of the mesosphere from Akmaev et al.,

26 Solar cycle and neutral air density multiple regression analysis using F10.7 as solar proxy mesospheric response is allowed to be phase shifted density corrected for meteor velocity Jacobi et al., 2011 Leipzig meteor radar 26

27 Conclusion NLC occurrence rate increased over the past century related to increased CO 2 + H 2 O confirmed by Lidar observations during the last two decades PMSE observation indicate also an increased occurrence rate over the past decades and a weak correlation to geomagnetic activity MR observations at mid and high latitudes show significant seasonal and mean trends zonal wind component (summer) shows some solar cycle response, which seems to related to neutral air density changes 27

28 Long Term Wind Trend zonal wind trend increases with increasing altitude acceleration of zonal wind supports density trend Trend in m/s per km 1.2 ± km 2.4 ± km 3.8 ± km 3.9 ± 0.5 SA43C-08

29 Trends in the ionosphere (F2 layer) Mielich and Bremer (AG, 2013) 29

30 Juliusruh MR seasonal winds (54 N) 30

31 31