Meteorological observations on the northern Chilean coast during VOCALS-REx

Surface coastal observations from two automatic weather stations at Paposo (~25° S) and radiosonde observations at Paposo and Iquique (~20° S) were carried out during VOCALS-REx (VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment). Within the coastal marine boundary layer (MBL), sea–land breezes are superimposed on the prevailing southerlies, resulting in light northeasterly winds from midnight to early morning and strong southwesterlies in the afternoon. The prevailing northerlies above the MBL and below the top of the Andes are modulated by the onshore-offshore (zonal) flow forced by the diurnal cycle of surface heating/cooling along the western slope of the Andes. The daytime phase of this diurnal cycle is consistent with an enhanced afternoon coastal subsidence manifested in afternoon warming near the top of the subsidence inversion (~1.8 K at 800 hPa), lowering (~130 m) of its base (top of the MBL), and clearing of coastal Sc (stratocumulus) clouds. Results from a numerical simulation of the atmospheric circulation in a mean zonal cross section over the study area capture the afternoon zonal wind divergence and resulting subsidence of about 2 cm s−1 along a narrow (~10 km) coastal strip maximizing at around 800 hPa. Day-to-day variability in the MBL depth during VOCALS-REx shows sub-synoptic oscillations, aside from two major disruptions in connection with a deep trough and a cutoff low, as described elsewhere. These oscillations are phase-locked to those in sea-level pressure and afternoon alongshore southerlies, as found in connection with coastal lows farther south. From 24-h forward trajectories issued from significant points at the coast and inland at the extremes of the diurnal cycle, it can be concluded that the strong mean daytime Andean pumping prevents any possibility of continental sulfur sources from reaching the free troposphere above the Sc cloud deck in at least a one-day timescale, under mean conditions. Conversely, coastal sources could contribute with sulfur aerosols preferentially in the morning, provided that the weak daytime inland flow becomes partially blocked by the coastal terrain

Strong Down-Valley Low-Level Jets over the Atacama Desert: Observational Characterization

The near-surface wind and temperature regime at three points in the Atacama Desert of northern Chile is described using two-year multi-level measurements from 80-m towers located in an altitude range between 2100 and 2700 m ASL. The data reveal the frequent development of strong nocturnal drainage flows at all sites. Down-valley nose-shaped wind speed profiles are observed with maximum values occurring at heights between 20 m and 60 m AGL. The flow intensity shows considerable inter-daily variability and a seasonal modulation of maximum speeds, which in the cold season can attain hourly average values larger than 20 m s−1. Turbulent mixing appears significant over the full tower layer, affecting the curvature of the nighttime temperature profile and possibly explaining the observed increase of surface temperatures in the down-valley direction. Nocturnal valley winds and temperatures are weakly controlled by upper-air conditions observed at the nearest aerological station. Estimates of terms in the momentum budget for the development and the quasi-stationary phases of the down-valley flows suggest that the pressure gradient force due to the near-surface cooling along the sloping valley axes plays an important role in these drainage flows. A scale for the jet nose height of equilibrium turbulent down-slope jets is proposed, based on surface friction velocity and surface inversion intensity. At one of the sites this scale explains about 70% of the case-to-case observed variance of jet nose heights. Further modeling and observational work is needed, however, in order to better define the dynamics, extent and turbulence structure of this flow system, which has significant wind-energy, climatic and environmental implications

Expression stability of putative reference genes in equine endometrial, testicular, and conceptus tissues

<p>Abstract</p> <p>Background</p> <p>Quantitative RT-PCR data are commonly normalized using a reference gene. A reference gene is a transcript which expression does not differ in the tissue of interest independent of the experimental condition. The objective of this study was to evaluate the stability of mRNA expression levels of putative reference genes in three different types of equine tissue, endometrial, testicular, and conceptus tissue.</p> <p>Findings</p> <p>The expression stability of four (uterine tissue) and six (testicular and conceptus tissue) was assessed using descriptive data analysis and the software programs Normfinder and geNorm. In uterine samples, <it>18S </it>showed the largest degree of variation in expression while <it>GAPDH</it>, <it>B2M</it>, and <it>ACTB </it>were stably expressed. <it>B2M </it>and <it>GAPDH </it>were identified as the most stably expressed genes in testicular samples, while <it>18S </it>showed some extent of regulation between samples. Conceptus tissue overall was characterized by very low variability of the transcripts analyzed with <it>GAPDH</it>, <it>YWHZ</it>, and 18S being the most stably expressed genes.</p> <p>Conclusions</p> <p>In equine endometrium, <it>GAPDH</it>, <it>B2M</it>, and <it>ACTB </it>transcript levels are equally stable, while <it>18S </it>is less stably expressed. In testes and associated structures, <it>B2M </it>and <it>GAPDH </it>are the transcripts showing the least amount of variation, while in conceptus tissue <it>GAPDH</it>, <it>YWHZ</it>, and <it>18S </it>were identified as the most suitable reference genes. Overall, transcripts analyzed in conceptus tissue were characterized by less variation than transcripts analyzed in uterine and testicular tissue.</p

Final report / Camanchacas - Chile

Reproduction of poor qualit

ENSO tropical-extratropical climate teleconnections and mechanisms for Holocene debris flows along the hyperarid coast of western South America (17 degrees-24 degrees S)

El Nino, the warm phase of the ENSO cycle, involves ocean-climate anomalies in the tropical Pacific Ocean and in the extratropics, which frequently result in heavy rainfall episodes along the equatorial and subtropical regions of western South America. Here, we investigate meteorological mechanisms producing heavy rains, floods and debris flows along the less-known hyperarid coasts of southern Peru and northern Chile, to evaluate the paleoclimate significance of Holocene debris flow deposits. Our results reveal that heavy rainfall over the coast of southernmost Peru occurs either during austral summer, at the mature stage of Ell Nino in connection with warmer sea surface temperatures and anomalous jet streams off northern Chile, or during the previous austral winter-spring associated with equatorward-shifted Pacific South America (PSA) atmospheric teleconnection patterns. At Antofagasta, in northern Chile, such events occur almost exclusively in the latter season when deeper PSA-related anomaly poles extend their influence equatorwards beyond central Chile. During non-El Nino, conditions short-lived heavy rainfall episodes in southernmost Peru can be associated with similar, albeit weaker or less persistent, circulation anomalies. In addition to that, a seasonally-enhanced low-level southerly flow provides orographic uplift (rainfall-favourable conditions) by the Andes at the 18 degrees S coastal bend. Ultimately, the trigger for rainfall events in all seasons and phases of the ENSO cycle was invariably connected with mid-troposphere wave disturbances from mid-latitudes. The chronostratigraphy of debris flow deposits from both areas and its comparison with other paleoclimate records at the western side of the Andes, suggests that the ENSO-related teleconnection. patterns operated only during the second half of the Holocene, supporting an onset of modem El Nino manifestations at 5300-5500 cal BP and increased frequency of major events during recent times. We suggest that several debris flows dated between 12,900 and 8400 cal BP in southernmost Peru, previously interpreted as an indication of strong El Nino events, were associated with short and intense heavy rainfall episodes similar to those described here during the late winter-spring season in non-El Nino conditions, concomitant with stronger low-level southerlies, strengthened South-Eastern Pacific Subtropical Anticyclone and intensified coastal upwelling. (c) 2006 Elsevier B.V. All rights reserved

Rheological and ultrastructural properties of bovine vaginal fluid obtained at oestrus

The properties of cervical–vaginal fluid are under strict hormonal control: and in mammals in which semen is deposited in the anterior vagina, changes produced in these properties can result in a lower or higher resistance to sperm motion. The aim of this study was to determine whether the structural organization of bovine vaginal fluid is related to its rheological properties. Vaginal fluid samples were collected from 41 cows at oestrus: 20 at the middle of oestrus (between 8 and 12 h after starting) and 21 at the end of oestrus (between 18 and 22 h). Flow behaviour was determined using a viscosimeter, and the ultrastructural analysis was performed by scanning electron microscopy. Six samples showed newtonian behaviour: three collected at the middle and three collected at the end of oestrus. Newtonian samples had dense and compact matrices arranged as membranes with rough, irregular surfaces, and sparse, thin filaments (< 150 nm). Non-newtonian samples collected at the end of oestrus (n = 18) had a higher (P = 0.016) consistency index (K = 944 ± 229 mPa.s(n)) than those collected at the middle of oestrus (n = 17; K = 237 ± 84 mPa.s(n)). Thick filaments (> 700 nm) that were either randomly arranged with thinner filaments forming a mesh or heavily cross-linked by thin filaments (50–150 nm) were observed in all non-newtonian samples collected at the end of oestrus, while medium-diameter filaments (between 200 and 500 nm) forming loose networks were observed in non-newtonian samples collected at the middle of oestrus. These findings indicate a close relationship between the molecular organization of the structural elements of bovine vaginal fluid and its rheological behaviour. Vaginal fluid dramatically reduces its mechanical barrier effect during the course of oestrus but always appears to maintain its three-dimensional filamentous structure. The images of vaginal fluid showing newtonian behaviour would appear to support previous results, suggesting that this property may be related to bovine infertility