Landsat-5 Thematic Mapper Thermal Band Calibration Update

The Landsat-5 thematic mapper (TM) has been operational since 1984. For much of its life, the calibration of TM has been neglected, but recent efforts are attempting to monitor stability and absolute calibration. This letter focuses on the calibration of the TM thermal band from 1999 to the present. Initial studies in the first two years of the TM mission showed that the thermal band was calibrated within the error in the calibration process (plusmn 0.9 K at 300 K). The calibration was not rigorously monitored again until 1999. While the internal calibrator has behaved as expected, recent vicarious calibration results show a significant offset error of 0.092 W/m² ldr sr ldr mum or about 0.68 K at 300 K. This offset error was corrected on April 2, 2007 within the U.S. processing system through the modification of a calibration coefficient for all data acquired on or after April 1, 1999. Users can correct their own Level-1 data processed prior to April 2, 2007, by adding 0.092 W/m² ldr sr ldr mum to their radiance level products. The state of the calibration between 1985 and 1999 is unknown; no changes for data acquired in those years are being recommended here.     

Sequence stratigraphy of the Mancos Shale,lower Tres Hermanos Formation,and coeval middle Cenomanian to middle Turonian strata,southern New Mexico,USA

Sequence stratigraphic analysis of four widely spaced outcrops of middle Cenomanian to middle Turonian strata deposited in the Western Interior foreland basin in southern New Mexico, USA, defines ten sequence boundaries in a marine shale‐rich interval ca 200 m thick. The majority of sequence boundaries are based on basinward shifts in lithofacies characterized by either a non‐Waltherian contact between distal‐bar or lower shoreface sandstone and underlying lower offshore shale, or an erosional contact between distal‐bar or lower shoreface sandstone and underlying upper offshore shale. The sequence boundaries commonly correlate basinward to packages of storm‐deposited sandstone and to beds of sandy grainstone composed of winnowed inoceramid shell fragments. In several cases, however, the sequence boundaries pass basinward into presumably conformable successions of lower offshore shale. Maximum flooding surfaces within the sequences are represented by one or more beds of locally phosphatized globiginerid wackestone and packstone or exist within a conformable succession of lower offshore shale. Following initial south/south‐westward transgression into the study area, the regional trend of palaeoeshorelines was north‐west to south‐east, although isopach data indicate that lobes of sandstone periodically spread south‐eastward across the study area. The ten sequences in the study area are arranged into a third‐order composite megasequence that is characterized by overall upward‐deepening followed by upward‐shallowing of sequences. The composite megasequence is similar but not identical to the previously established T‐1 transgression and R‐1 regression in New Mexico. Based on radioisotopic dates of bentonites, the average frequency of the sequences within the study area was ca 327 kyr, which is consistent with fourth‐order cycles of ca 400 kyr interpreted in coeval marine strata elsewhere in the world.     

The ASCA spectrum of the z = 4.72 blazar GB 1428+4217

The X-ray-luminous quasar GB 1428+4217 at redshift 4.72 has been observed with ASCA . The observed 0.5–10 keV flux is 3.2 Å– 10⁻¹² erg cm⁻² s⁻¹. We report here on the intrinsic 4 − 57 keV X-ray spectrum, which is very flat (photon index 1.29). We find no evidence for flux variability within the ASCA data set or between it and ROSAT data. We show that the overall spectral energy distribution of GB 1428+4217 is similar to that of lower redshift MeV blazars, and present models that fit the available data. The Doppler beaming factor is likely to be at least 8. We speculate on the number density of such high-redshift blazars, which must contain rapidly formed massive black holes.     

PMN J0525−3343: soft X-ray spectral flattening in a blazar at z = 4.4

We report optical, radio and X-ray observations of a new distant blazar, PMN J0525−3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z >4 blazars, GB 1428+4217 ( z =4.72) reported by Boller et al. and RX J1028.6−0844 ( z =4.28) reported by Yuan et al. The spectrum is well fitted by a power-law continuum which either is absorbed or breaks at a few keV. An intrinsic column density corresponding to 2×10²³ H‐atoms cm⁻² at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame ultraviolet emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.     

Discovery of radio-loud quasars with z=4.72 and z=4.010

We report the discovery of two radio-loud quasars with redshifts greater than 4: GB1428+4217, with z =4.72, and GB1713+2148 with z =4.01. This doubles the number of published radio-selected quasars with z >4, bringing the total to 4. GB1428+4217 is the third most distant quasar known and the highest redshift radio and X-ray source currently known. It has a radio flux density at 5 GHz of 259±31 mJy and an optical magnitude of R ∼20.9. The rest frame absolute UV magnitude, M_v (1450 Å), is −26.7, similar to that of the archetypal radio-selected quasar 3C273 [ z =0.158; M_v (1450 Å)=−26.4]. GB1428+4217 is tentatively detected in ROSAT PSPC observations, which has been confirmed by more recent ROSAT observations described in a companion paper by Fabian et al. Both quasars were discovered during the CCD imaging phase of an investigation into the evolution of the space density of radio-loud quasars at high redshift. Combined with our earlier survey results, these objects give a lower limit on the space density of quasars with radio power P _{5 GHz}>5.8×10²⁶ W Hz⁻¹ sr⁻¹ between z =4 and z =5 of 1.4±0.9×10⁻¹⁰ Mpc⁻³. This can be compared to 2.9±0.2×10⁻¹⁰ Mpc⁻³ at z =2 from Dunlop & Peacock for flat-spectrum sources of the same luminosity.     

Dynamic implication of biomass energy consumption on economic growth in Sub-Saharan Africa: evidence from panel data analysis

The present article examines the dynamic linkages between biomass energy consumption, capital stock, human capital and economic growth across selected Sub-Saharan African countries based on dynamic heterogeneous panels of a mean group (MG) and pooled mean group (PMG) techniques. The finding based on PMG as the preferred method reveals that biomass energy consumption, capital stock and human capital are statistically significant, which means aforementioned variables have positive significant impact on economic growth in the countries studied. When an alternative panel estimation techniques of panel cointegration, dynamic OLS (DOLS) and fully modified OLS (FMOLS) are applied, the result based on panel cointegration technique reveals that biomass energy consumption, capital stock, human capital and economic growth are cointegrated as null hypothesis of most statistics are rejected at 1 % level of significance. The finding based on FMOLS shows that biomass energy consumption, capital stock and human capital positively influences economic growth at 1 % level and same result is obtained from panel OLS. The result based on DOLS however reveals that biomass energy consumption and capital stock are significant at 1 % on economic growth while human capital is insignificant. Considering its positive effect on economic growth with little or no environmental degradation when compared with fossil fuel uses, consumption of biomass energy is more preferable in these countries therefore is the best option to adopt by the policy makers of Sub-Saharan African countries.     

Modelling Last Glacial Maximum ice cap with the Parallel Ice Sheet Model to infer palaeoclimate in south-west Turkey

Modelling palaeoglaciers in mountainous terrain is challenging due to the need for detailed ice flow computations in relatively narrow and steep valleys, high-resolution climate estimations, knowledge of pre-ice topography, and proxy-based palaeoclimate forcing. The Parallel Ice Sheet Model (PISM), a numerical model that approximates glacier sliding and deformation to simulate large ice sheets such as Greenland and Antarctica, was recently adapted to alpine environments. In an attempt to reconstruct the climate conditions during the Last Glacial Maximum (LGM) on Mount Dedegöl in SW Turkey, we used PISM and explored palaeoglacier dynamics at high spatial resolution (100 m) in a relatively small domain (225 km²). Palaeoice-flow fields were modelled as a function of present temperature and precipitation. Nine different palaeoclimate simulations were run to reach the steady-state glacier extents and the modelled glacial areas were compared with the field-based and chronologically well-established ice extents. Although our results provide a non-unique solution, best-fit scenarios indicate that the LGM climate on Mount Dedegöl was between 9.2 and 10.6 °C colder than today, while precipitation levels were the same as today. More humid (20% wetter) or arid (20% drier) conditions than today bring the palaeotemperature estimates to 7.7–8.8 or 11.5–13.2 °C lower than present, respectively.