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This paper presents an analysis of subtropical marine stratocumulus cloud fraction variability using a 30-min and 3° × 3° cloud fraction dataset from 2003 to 2010. Each of the three subtropical marine stratocumulus regions has distinct diurnal characteristics, but the southeast (SE) Pacific and SE Atlantic are more similar to each other than to the northeast (NE) Pacific. The amplitude and season-to-season diurnal cycle variations are larger in the Southern Hemisphere regions than in the NE Pacific. Net overnight changes in cloud fraction on 3° × 3° scales are either positive or neutral >77% of the time in theNE Pacific and >88% of the time in the SE Pacific and SE Atlantic. Cloud fraction often increases to 100% by dawn when cloud fraction at dusk is >30%. In the SE Pacific and SE Atlantic, a typical decrease in cloud area (median ≤ −5.7 × 10⁵ km²) during the day is equivalent to 25% or more of the annual-mean cloud deck area. Time series for 3° × 3° areas where cloud fraction was ≥90% sometime overnight and <60% at dawn, such as would result from nocturnal formation of pockets of open cells (POCs), only occur 1.5%, 1.6%, and 3.3% of the time in the SE Pacific, SE Atlantic, and NE Pacific, respectively. Comparison of cloud fraction changes to ship-based radar and satellite-derived precipitation intensity and area measurements shows a lack of sensitivity of cloud fraction to drizzle on time scales of 1–3 h and spatial scales of 100–300 km.

Subdiurnal periodic effects in the Earth's rotation as seen by Very Long Baseline Interferometry (VLBI) are investigated on the basis of continuous VLBI observing campaigns (CONT) observed by the International VLBI Service for Geodesy and Astrometry (IVS). In 2008, the latest campaign (CONT08) was observed adding another valuable data set of 15 consecutive days to the series of CONT sessions. Among other things, CONT08 as well as CONT02 and CONT05 had been scheduled with the aim of observing short‐period variations of the Earth orientation parameters. In this publication, we describe an analysis, which is based on hourly estimates of polar motion and UT1‐TAI and a subsequent spectral analysis. The generation of the time series is performed with a modified analysis approach. We add the normal equations of each individual 24 hour session to one big equation system for the whole campaign where observations of adjacent sessions contribute to parameters at session borders simultaneously. Over the years, the experience in operating and analyzing the CONT sessions has improved and the procedures have been adapted for improvement of the results. However, at the same time, the observing network has suffered considerable changes. Thus, a comparative overview over the three CONT campaigns is given in this paper. The intermittent detection of periodicities as reported by Haas and Wünsch (2006) applies in this analysis for CONT02 as well. For CONT05 and CONT08 minute signals at periods of around 6 hours are contained in the amplitude spectra. The origin of these signals is still questionable.

In this paper, we make a study about the influence of the coefficients of the geopotential C^sub 4,m^ and S^sub 4,m^, (m=1,2,3,4) on the nutation, starting from the Hamiltonian theory as developed by Kinoshita (1977).We obtain ten coefficients larger than 0.05 μ as for the nutation in longitude and six for the nutation in obliquity. The present results are included in the reconstruction of the theory of nutation (REN2000) at the level of truncation of 0.1 μ as (Souchay et al., 1997).[PUBLICATION ABSTRACT]

More than two years of almost continuous polar motion data (obtained by reprocessing GPS-Observations) have been used to analyse the daily/subdaily variations in Earth rotation based on the complex Wavelet-Technique. Systematic and spectral analytical investigations of the degree of variability of periods including tidal have been carried out. Relevant indications of oceanic effects, besides atmospheric components, have been observed.