Mapping geology in Djelfa District (Saharan Atlas,Algeria), using Landsat 7 ETM+ data: an alternative method to discern lithology and structural elements

Djelfa area in the central Saharan Atlas is characterized by its high lithological diversity with different facies from the Triassic to the Tertiary. The lack of published geological maps of the region (Djelfa) prompted us to test specific processing of satellite images (ratio bands, principal component analysis) in order to establish a lithological discrimination of the region. Several treatments allowed us to map the lineaments highlighting the various tectonic structures of the region. The combination of field and remote sensing data pointed out the double influence of the E-W Eocene and N-S Miocene phases in the structuration of these regions. As a large part of the Djelfa area is inaccessible, the obtained results undeniably contribute to a better understanding of the local geology.     

Development of temperatures in the Kingdom of Bahrain from 1947 to 2005

A new look is focused in this study on the analysis of mean temperatures for Bahrain, as observed at its International Airport for the 59 years extending from 1947 to 2005. The temporal trends indicate significant warming of the dry-season temperatures of 0.166°C decade^?1. In particular, the summer months of May to July and October demonstrate statistically significant trends of 0.172 to 0.247°C decade^?1. There is a tendency for the wet season months to show both decreases and increases in their temperatures though the temporal trends are not significant. The decade of 1991-2000 emerged as a period of conspicuous warming as well as increase in the occurrence of unusual mean temperatures and the number of months per year with above-average temperature. No significant trend in intraannual and intraseasonal temperature variabilities is discerned, but the wet season shows predominantly higher within-season variability in temperatures as compared to the dry season. Further analyses have been carried out on the available extreme temperature data for the period 1981-2005 in an attempt to search for a possible source of climatic and/or non-climatic factors, such as intensifying desertification and rapid urbanization. By and large, the rates of diurnal temperature ranges have increased due to significantly higher rates of increasing maximum in comparison to increasing minimum temperatures. The warming rate of the overall dry season during the day is seven times that during night. However, the nocturnal temperature for the overall wet season has warmed significantly at a rate more than three times that of the overall dry season. There is a sufficient evidence that sources of rapid urbanization around the area of records seem to be a major contributor to the observed rates of temperature. Both the urbanization and the effect of the large water body of the Gulf surrounding the Island of Bahrain seem to have offset the effect of desertification on temperature changes.     

Balloon-borne observations of mid-latitude stratospheric water vapour: comparisons with HALOE and MLS satellite data

We present here in situ measurements obtained between 1991 and 2011 in outer-vortex conditions by the ELHYSA balloon-borne frost-point hygrometer. The frost-point hygrometer profiles are used for comparisons with the satellite data from version 19 (v19) and version 3.3 (v3.3) of the HALogen Occultation Experiment (HALOE) and the Microwave Limb Sounder (MLS) respectively. Potential Vorticity mapping is applied to all data sets to remove contributions of transient tropical intrusions and polar vortex air masses and hence ensure consistent comparisons between the balloon and satellite observations. Our selected balloon in situ observations are too sparse to directly infer mid-latitude stratospheric time series for continuous comparisons with HALOE and MLS records or derive water vapour trends but can be used to validate the satellite data. A mean difference of ?0.83?±?1.58 % (?0.04?±?0.07 ppmv) is obtained between HALOE v19 data and the balloon frost-point observations (with respect to HALOE) over the 30–80 hPa altitude range. The hygrometer-HALOE differences appear time-dependent as already presented in the literature. The mean difference reaches 2.80?±?0.96 % (0.13?±?0.04 ppmv) for MLS v3.3, with MLS systematically wetter than the balloon data reflecting a systematic bias between both datasets. We use our balloon data as reference to provide some information about the HALOE-MLS difference. From post-2000 ELHYSA-HALOE and ELHYSA-MLS comparisons, we find a HALOE-MLS difference matching the expected bias, with MLS v3.3 6.60?±?2.80 % (0.27?±?0.11 ppmv) wetter than HALOE v19. From the results obtained from our balloon-satellite data comparisons, we finally discuss the issue about merging the HALOE and MLS data sets to provide stratospheric water vapour trends.     

Exploratory analysis of rain days in central Sudan

The changes in six rain-day categories occurring since the 1940s have been explored in central Sudan, considering two case studies representing important productive agricultural regions under semi-arid rain-fed and arid irrigated schemes. Drought conditions have persisted in Kosti (arid) in the form of a decline in rain-day frequencies, with significant trends in trace, weak and moderate falls. El Gedaref (semi-arid) exhibited both positive and negative trends, though significance characterizes the sequences of trace (falling) and weak and very strong (both rising) falls. The total annual rainfall in El Gedaref behaves depending solely on the heaviest falls contrary to Kosti, the annual values of which follow five fall categories, but with the heaviest events also have the strongest strength. Trace events occur more frequently in the arid area than in the semi-arid one, whereas weak to very strong events have opposite behaviour. Although El Niño-Southern Oscillation is one potential forcing of the variability of rainfall events, especially in Kosti, the paper arguably proposes a complex combination of factors at smaller scale that may also contribute to the large non-uniformity in rainfall patterns between the two areas, including local moisture recycling and convective activity, natural and anthropogenic aerosol loadings in the atmosphere and influence of the Ethiopian highlands.     

Occurrence of IRGAROL 1051 in coastal waters from Biscayne Bay,Florida, USA

Surface water samples from marinas, commercial ports and open bay areas collected from Biscayne Bay and the Miami River, Florida, USA, were analyzed for the occurrence of IRGAROL 1051 by GC/MS. The anifouling boosting herbicide was found in 80% (46/57) of the samples collected between March 1999 and September 2000. Concentrations within the bay range between non-detected (<1 ppt) and 61 ppt (ng/L) and were generally low compared with levels reported in European or Japanese waters. Aside from the elevated concentrations observed along the Miami River South Fork (61 ppt), the highest concentrations observed in the bay corresponded to marinas with high density of pleasure craft and restricted water circulation. In contrast, occurrence of IRGAROL 1051 along the commercial port or the cruise line terminal was generally lower (<1-2.2 ppt). Concentrations around Coconut Grove Marina were consistently higher (5-12 ppt) than the rest of the bay waters during the whole period of time surveyed.