Analysing temporal trends in the Indian Summer Monsoon and its variability at a fine spatial resolution

Temporal trends between 1951 and 2007 in annual Indian Summer Monsoon (ISM) precipitation, frequency of severe drought years and onset date of ISM were analysed on a 0.25°?×?0.25° grid cell basis across India using APHRODITE daily gridded precipitation data. Locations which experienced temporal trends of increasing or decreasing inter-annual variation in annual ISM precipitation and onset date of ISM were detected using the non-parametric Mann-Kendall test. A new method of defining local onset of ISM from daily precipitation data was developed to enable countrywide temporal trend analysis of onset date. India was characterised by a heterogeneous spatial distribution in the magnitude of inter-annual variation and location of significant temporal trends in the examined facets of ISM precipitation. A greater extent of the country experienced significant trends (p?<?0.05) of increasing inter-annual variation rather than simple increasing or decreasing trends in annual ISM precipitation and onset date of ISM. Field significance tests showed grid cells reporting significant trends were significant (p?<?0.05) at the global or field level (except trends of increasing, i.e. later, ISM onset date). This research provides finer spatial detail regarding trends and variation in annual ISM precipitation, severe drought years and onset date of ISM complementing recent studies on trends in extreme precipitation events over India to produce a comprehensive overview of recent behaviour of ISM precipitation. These findings will benefit water managers charged with managing water resources sustainably at a fine spatial scale (the watershed or basin level).     

Wave ducting of solar metre-wave radio emission as an explanation of fundamental/harmonic source coincidence and other anomalies

On the basis of source positions determined by the Culgoora radioheliograph we suggest that metre-wave radio emission propagates from the Sun along under-dense magnetic flux tubes. Such wave ducting is able to explain several long-standing problems in regard to the positions, heights, and polarization of solar radio sources. Observed source heights then represent, not heights of wave generation, but heights of wave escape from under-dense flux tubes.     

A catalogue and analysis of local galaxy ages and metallicities

We have assembled a catalogue of relative ages, metallicities and abundance ratios for about 150 local galaxies in field, group and cluster environments. The galaxies span morphological types from cD and ellipticals, to late-type spirals. Ages and metallicities were estimated from high-quality published spectral line indices using Worthey & Ottaviani (1997) single stellar population evolutionary models.
The identification of galaxy age as a fourth parameter in the fundamental plane ( Forbes, Ponman & Brown 1998 ) is confirmed by our larger sample of ages. We investigate trends between age and metallicity, and with other physical parameters of the galaxies, such as ellipticity, luminosity and kinematic anisotropy. We demonstrate the existence of a galaxy age–metallicity relation similar to that seen for local galactic disc stars, whereby young galaxies have high metallicity, while old galaxies span a large range in metallicities.
We also investigate the influence of environment and morphology on the galaxy age and metallicity, especially the predictions made by semi-analytic hierarchical clustering models (HCM). We confirm that non-cluster ellipticals are indeed younger on average than cluster ellipticals as predicted by the HCM models. However we also find a trend for the more luminous galaxies to have a higher [Mg/Fe] ratio than the lower luminosity galaxies, which is opposite to the expectation from HCM models.     

The K-band Hubble diagram of submillimetre galaxies and hyperluminous galaxies

We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at   z ≲ 3  is consistent with a passively evolving ∼3 L _* instantaneous starburst starting from a redshift of   z ∼ 10  . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.     

Optical counterpart of the radio event accompanying the 3B flare of 13 May 1981

Excepting intermittent type III activity, all the radio events over the frequency range 8–8000 MHz accompanying the initial stage of the 3B flare of 13 May, 1981 had their onset in a 2-min interval immediately preceding the peak of an impulsive Hα brightening (kernel) well away from the main flare. This kernel is identified as one footpoint of a loop of magnetic flux whose other end terminated in a transient brightening in an adjacent active region.     

Stacking for the frequencies and Qs of 0S0 and 1S0

Summary. Using nine IDA records for the Indonesian earthquake of 1977 August 19, we have formed an optimal linear combination of the records and have measured the frequency and Q of ₀ S ₀ and ₁ S ₀. The frequency was measured using the moment ratio method. The attenuation was measured by the minimum width method and by the time-lapse method. The frequency and attenuation were measured simultaneously by varying them to obtain a best fit to the data. A 2000-hr stack, the sum of nine individual records, for ₀ S ₀ gave a frequency of 0.814664 mHz±4 ppm. The values for the Q of ₀ S ₀ for the three different methods of measurement were 5600,5833 and 5700, respectively. The error in the estimates of Q ^-1 is about 5 per cent for the minimum power method. For ₁ S ₀ a 300-hr stack yielded a frequency of 1.63151 mHz±30 ppm. The values of Q for this mode were 1960, 1800 and 1850, respectively, with an error in Q ^-1 of about 12 per cent for the minimum power method.