We present a new spectrometer with high temporal resolution for the observation of OH Meinel band emission dynamics in the spectral range between 1.5 mu m and 1.6 mu m. The instrument was developed and is now in operation at the German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) in Oberpfaffenhofen (11.27 degrees E, 48.08 degrees N), Germany a measurement station of the international Network for the Detection of Mesosphere Change (NDMC). It is equipped with a thermoelectrically cooled 512 element InGaAs-photodiode array (PDA) and a polychromator with a grating blazed for 1.6 mu m. During routine operation one spectrum is obtained every 15 s, originating from a field of view of approximately 15 degrees x 15 degrees corresponding to similar to 24 x 24 km(2) in 87 km height, the peak height of the OH emission layer. The covered wavelength range allows the observation of the OH(3-1) Q- and P-branches as well as of the OH(4-2) R- and Q-branches. Rotational temperatures are calculated using OH(3-1) P-branch emissions between 1.52 mu m and 1.55 mu m. Being the successor of the older scanning grating spectrometers of the GRIPS type it is named Ground-based Infrared P-branch Spectrometer (GRIPS 6).A fully automated data acquisition and analysis scheme has also been developed, that covers the complete processing chain from data recording to derivation of rotational temperatures and to long-term archiving. For the estimation of a nocturnal mean value all samples of the nightly temperature time series are weighted according to their individual precision. Thus, mean temperatures between 1 and 2 K are lower compared to the unweighted arithmetic mean. Data products are archived at the World Data Center for Remote Sensing of the Atmosphere (WDC-RSAT) and results are displayed at the website of the Network for the Detection of Mesosphere Change (NDMC). A summary of the data obtained during the first 40 months of operation at the German Remote Sensing Data Center as well as aspects of data processing efforts are presented. (C) 2013 Elsevier Ltd. All rights reserved.

(1) German Aerospace Center (DLR), German Remote Sensing Data Center (DFD), Wessling, Germany (kathrin.hoeppner@dlr.de), (2) Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia, (3) Australian Antarctic Division, Tasmania, Australia, (4) University of Wuppertal, Wuppertal, Germany, (5) Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain, (6) Instituto de Astronomia y Fisica del Espacio (IAFE), Buenos Aires, Argentina, (7) Institute of Atmospheric Physics, Moscow, Russia, (8) German Meteorological Service, Hohenpeissenberg, Germany

Measurements of the hydroxyl rotational temperatures at about 87km altitude above Wuppertal (51.3°N, 7.2°E), Germany, are analysed. The time series covers the time interval from 1987 until 2005 and consists of more than 4000 night mean temperature data. Seasonal and longer-term trends are removed from the data set and OH* temperature fluctuations on temporal scales of about 3–40 days are derived. Various spectral analysis techniques (harmonic analysis, maximum entropy method and wavelet transform) are applied. Can – due to the Sun's rotation – the irregular pattern of sunspots on the solar disc lead to OH* temperature fluctuations? Pronounced spectral components in the OH* temperature fluctuations around a period from 27 to 31 days are frequently observed. We tentatively attribute these signatures to the differential rotation of the Sun: Sun's equatorial regions rotate faster (taking only about 27 days) than the polar regions. Sunspots occur at heliographic latitudes at about ±40°, which correspond to a rotation rate of about 27–31 days. The OH* temperature fluctuations within this period range show a long-term modulation of 11 years. Thus, tracking the spectral intensity of the 27- to 31-day component should allow the indirect monitoring of the solar sunspot cycle.

Primary focus of the World Data Center for Remote Sensing of the Atmosphere (WDC-RSAT) is to offer scientists and the general public free and simplified access (in the sense of a “one-stop shop”) to a continuously growing collection of atmosphere-related satellite-based data sets and services. These data holdings are available on-line and range from raw data collected by remote sensors to higher level data and information products.

Nocturnal temperatures are almost continuously derived from OH* (3,1) near-infrared emissions in the upper mesosphere (around 87 km) above Wuppertal, Germany (51 degrees N, 7 degrees E) from ground-based measurements since 1980. The time series analyzed covers the rime interval from 1980 until 2005 and consists of 4628 well documented night mean temperature data. OH* temperature fluctuations on temporal scales of about 3-20 days are derived by removing seasonal and longer term trends from the data record by means of applying various spectral analysis techniques such as the harmonic analysis, maximum entropy method (MEM) and the wavelet transform, respectively. The residuals are found to reflect planetary wave activity.Spectral intensity of oscillations in the 3-20 days regime shows a longer term modulation peaking around 1981 and 1996, while minima are encountered around 1986 and 2005. Thus, no conclusive correlation with the solar F10.7cm flux is found. Reasonable agreement of planetary wave activity with the general solar bipolar magnetic field (22-year Hale cycle) is found instead. Further agreement is found with the variations of the length of the day (Delta LOD) implying that the internal terrestrial magnetic field is superimposed by the solar magnetic field (Hale cycle) causing modulations of the total magnetic field in the Earth's interior and which leads-in turn-to a modulation of the electromagnetic coupling of angular momentum between the Earth's core and the Earth's mantle. As a result the Earth's rotation period Omega-and thus the activity of planetary waves-should be modulated with the solar magnetic flux, e.g. the quasi-22-year Hale cycle.Planetary wave activity is further found to be modulated by a quasi-2-year oscillation. The modulation is strongest around 1994/1995 and lowest around 1988 and 2004, respectively. It is found that wave activity is mostly enhanced when the wind direction of the mean zonal wind of the equatorial quasi-biennial oscillation (QBO) reverses from westerly to easterly. (c) 2006 Elsevier Ltd. All rights reserved.