The role of atmospheric boundary layer-surface interactions on the development of coastal fronts

Frictional convergence and thermal difference between land and sea surface are the two surface conditions that govern the intensity and evolution of a coastal front. By means of the mesoscale model MM5, we investigate the influence of these two processes on wind patterns, temperature and precipitation amounts, associated with a coastal front, observed on the west coast of The Netherlands in the night between 12 and 13 August 2004. The mesoscale model MM5 is further compared with available observations and the results of two operational models (ECMWF and HIRLAM). HIRLAM is not capable to reproduce the coastal front, whereas ECMWF and MM5 both calculate precipitation for the coastal region. The precipitation pattern, calculated by MM5, agrees satisfactorily with the accumulated radar image. The failure of HIRLAM is mainly due to a different stream pattern at the surface and consequently, a different behaviour of the frictional convergence at the coastline. <br><br> The sensitivity analysis of frictional convergence is carried out with the MM5 model, by varying land surface roughness length (<I>z</I><sub>0</sub>). For the sensitivity analysis of thermal difference between sea and land surface, we changed the sea surface temperature (SST). Increasing surface roughness implies stronger convergence near the surface and consequently stronger upward motions and intensification of the development of the coastal front. Setting land surface roughness equal to the sea surface roughness means an elimination of frictional convergence and results in a diminishing coastal front structure of the precipitation pattern. The simulation with a high SST produces much precipitation above the sea, but less precipitation in the coastal area above land. A small increment of the SST results in larger precipitation amounts above the sea; above land increments are calculated for areas near the coast. A decrease of the SST shifts the precipitation maxima inland, although the precipitation amounts diminish. In the situation under study, frictional convergence is the key process that enhances the coastal front intensity. A thermal difference between land and sea equal to zero still yields the development of the coastal front. A lower SST than land surface temperature generates a reversed coastal front. <br><br> This study emphasizes the importance of accurate prescription of surface conditions as input of the numerical weather prediction model to improve coastal front predictability

Genetic evaluation of an otter translocation program

Abstract The translocation of individuals from one population to another is a common technique in wildlife conservation. However, the outcome of translocation programs is not always properly evaluated and the relative contribution of released individuals to the resident population often remains unknown. We used mitochondrial DNA and autosomal genetic markers to evaluate the success of a translocation program of Eurasian otters (Lutra lutra) in Sweden. The program is regarded as successful because of subsequent population growths. Norwegian otters used for the restocking program could be genetically differentiated from Swedish otters. The releases took place at two sites. In an area south of the first site, where 47 otters were released, no genetic contribution of the introduced animals to the population could be observed and the genetic diversity was lower than before the releases. At the second site, the release of seven otters led to a change in genetic composition of the resident population. The results of this study suggest that the growth of the otter population after the restocking may not be as dependent on the releases as initially suspected. The genetic effects of the translocations appear to be restricted to areas in the immediate vicinity of the release sites

Two perspectives on the coupled carbon, water and energy exchange in the planetary boundary layer

Understanding the interactions between the land surface and the atmosphere is key to modelling boundary-layer meteorology and cloud formation, as well as carbon cycling and crop yield. In this study we explore these interactions in the exchange of water, heat and CO2 in a cropland-atmosphere system at the diurnal and local scale. To that end, we couple an atmospheric mixed-layer model (MXL) to two land-surface schemes developed from two different perspectives: while one land-surface scheme (A-g(s)) simulates vegetation from an atmospheric point of view, the other (GECROS) simulates vegetation from a carbon-storage point of view. We calculate surface fluxes of heat, moisture and carbon, as well as the resulting atmospheric state and boundary-layer dynamics, over a maize field in the Netherlands, on a day for which we have a rich set of observations available. Particular emphasis is placed on understanding the role of upper-atmosphere conditions like subsidence in comparison to the role of surface forcings like soil moisture. We show that the atmospheric-oriented model (MXL-A-g(s)) outperforms the carbon storage-oriented model (MXL-GECROS) on this diurnal scale. We find this performance is partly due to the difference of scales at which the models were made to run. Most importantly, this performance strongly depends on the sensitivity of the modelled stomatal conductance to water stress, which is implemented differently in each model. This sensitivity also influences the magnitude of the surface fluxes of CO2, water and heat (surface control) and subsequently impacts the boundary-layer growth and entrainment fluxes (upper atmosphere control), which alter the atmospheric state. These findings suggest that observed CO2 mole fractions in the boundary layer can reflect strong influences of both the surface and upper-atmosphere conditions, and the interpretation of CO2 mole fraction variations depends on the assumed land-surface coupling. We illustrate this with a sensitivity analysis where high subsidence and soil moisture depletion, typical for periods of drought, have competing and opposite effects on the boundary-layer height h. The resulting net decrease in h induces a change of 12 ppm in the late-afternoon CO2 mole fraction. Also, the effect of such high subsidence and soil moisture depletion on the surface Bowen ratio are of the same magnitude. Thus, correctly including such two-way land-surface interactions on the diurnal scale can potentially improve our understanding and interpretation of observed variations in atmospheric CO2, as well as improve crop yield forecasts by better describing the water loss and carbon gain

Quaking is a Key Regulator of Endothelial Cell Differentiation, Neovascularization and Angiogenesis

Abstract The capability to derive endothelial cell (ECs) from induced pluripotent stem cells (iPSCs) holds huge therapeutic potential for cardiovascular disease. This study elucidates the precise role of the RNA-binding protein Quaking isoform 5 (QKI-5) during EC differentiation from both mouse and human iPSCs (hiPSCs) and dissects how RNA-binding proteins can improve differentiation efficiency toward cell therapy for important vascular diseases. iPSCs represent an attractive cellular approach for regenerative medicine today as they can be used to generate patient-specific therapeutic cells toward autologous cell therapy. In this study, using the model of iPSCs differentiation toward ECs, the QKI-5 was found to be an important regulator of STAT3 stabilization and vascular endothelial growth factor receptor 2 (VEGFR2) activation during the EC differentiation process. QKI-5 was induced during EC differentiation, resulting in stabilization of STAT3 expression and modulation of VEGFR2 transcriptional activation as well as VEGF secretion through direct binding to the 3′ UTR of STAT3. Importantly, mouse iPS-ECs overexpressing QKI-5 significantly improved angiogenesis and neovascularization and blood flow recovery in experimental hind limb ischemia. Notably, hiPSCs overexpressing QKI-5, induced angiogenesis on Matrigel plug assays in vivo only 7 days after subcutaneous injection in SCID mice. These results highlight a clear functional benefit of QKI-5 in neovascularization, blood flow recovery, and angiogenesis. Thus, they provide support to the growing consensus that elucidation of the molecular mechanisms underlying EC differentiation will ultimately advance stem cell regenerative therapy and eventually make the treatment of cardiovascular disease a reality. The RNA binding protein QKI-5 is induced during EC differentiation from iPSCs. RNA binding protein QKI-5 was induced during EC differentiation in parallel with the EC marker CD144. Immunofluorescence staining showing that QKI-5 is localized in the nucleus and stained in parallel with CD144 in differentiated ECs (scale bar = 50 µm).</jats:p

Framework and guidelines for implementing the proposed IUCN Environmental Impact Classification for Alien Taxa (EICAT)

Recently, Blackburn et al. (2014) developed a simple, objective and transparent method for classifying alien taxa in terms of the magnitude of their detrimental environmental impacts in recipient areas. Here, we present a comprehensive framework and guidelines for implementing this method, which we term the Environmental Impact Classification for Alien Taxa, or EICAT. We detail criteria for applying the EICAT scheme in a consistent and comparable fashion, prescribe the supporting information that should be supplied along with classifications, and describe the process for implementing the method. This comment aims to draw the attention of interested parties to the framework and guidelines, and to present them in their entirety in a location where they are freely accessible to any potential users.Peer Reviewe

Summertime total OH reactivity measurements from boreal forest during HUMPPA-COPEC 2010

Ambient total OH reactivity was measured at the Finnish boreal forest station SMEAR II in Hyyti¨al¨a (Latitude 61510 N; Longitude 24170 E) in July and August 2010 using the Comparative Reactivity Method (CRM). The CRM – total OH reactivity method – is a direct, in-situ determination of the total loss rate of hydroxyl radicals (OH) caused by all reactive species in air. During the intensive field campaign HUMPPA-COPEC 2010 (Hyyti¨al¨a United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study) the total OH reactivity was monitored both inside (18 m) and directly above the forest canopy (24 m) for the first time. The comparison between these two total OH reactivity measurements, absolute values and the temporal variation have been analyzed here. Stable boundary layer conditions during night and turbulent mixing in the daytime induced low and high short-term variability, respectively. The impact on total OH reactivity from biogenic emissions and associated photochemical products was measured under “normal” and “stressed” (i.e. prolonged high temperature) conditions. The advection of biomass burning emissions to the site caused a marked change in the total OH reactivity vertical profile. By comparing the OH reactivity contribution from individually measured compounds and the directly measured total OH reactivity, the size of any unaccounted for “missing” sink can be deduced for various atmospheric influences. For “normal” boreal conditions a missing OH reactivity of 58 %, whereas for “stressed” boreal conditions a missing OH reactivity of 89% was determined. Various sources of not quantified OH reactive species are proposed as possible explanation for the high missing OH reactivity

High intraspecific trait variation results in a resource allocation spectrum of a subtropical pine across an elevational gradient

Aim: Plant functional traits are broadly used to quantify and predict impacts of climate change on vegetation. However, high intraspecific trait variation can bias mean values when few measurements are available. Here, we determine the extent of individual leaf trait variation and covariation across a highly heterogenous environmental gradient for a widely distributed subtropical pine. We demonstrate the implications of trait variation for characterising species by assessing data availability and variability across the Pinus genus. Location: Central Mountain Range, Taiwan Taxon: Pinus taiwanensis Hayata (Pinaceae) Methods: We measured eight functional traits suggested to reflect plant strategies: needle length, area, thickness, dry and fresh mass, stomatal row density (SD), leaf dry matter content (LDMC) and specific leaf area (SLA). We examined trait variation in response to climatic and physiographic factors across an elevation gradient of 495 - 3,106 m a.s.l. using linear mixed effects models (LMMs). Intraspecific trait covariation was explored using principal component analyses (PCAs) and LMMs. Descriptive statistics were calculated for Pinus records in the global TRY plant trait database. Results: Intraspecific variability among traits was high (CV 20-44%) and predictable with elevation (generally p < 0.05, with declining needle size and LDMC with elevation and increasing SD). However, 41%–92% of variance was un-explained by topography. Sixty-five percent of variation was explained by two trait covariation axes, with predictable changes with elevation (p < 0.001). Pinus data availability in TRY was low. Across traits, only 12.5%–53% of species had sufficient sample sizes for intraspecific analyses. Main conclusions We show substantial trait variation for a single species, here likely driven by temperature differences and additional biotic and abiotic drivers across the elevational range. Improved understanding of the extent and implications of intraspecific variability is necessary for reliable quantifications and predictions of the impacts of environmental change, especially in understudied, hyper-diverse ecosystems such as tropical forests

A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

Interpretation of observed diurnal carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO&lt;sub&gt;2&lt;/sub&gt; budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO&lt;sub&gt;2&lt;/sub&gt; distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO&lt;sub&gt;2&lt;/sub&gt; mixing ratio. &lt;br&gt;&lt;/br&gt; We find that the largest uncertainty incurred on the mid-day CO&lt;sub&gt;2&lt;/sub&gt; mixing ratio comes from the prescribed early morning CO&lt;sub&gt;2&lt;/sub&gt; mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO&lt;sub&gt;2&lt;/sub&gt; mixing ratios inversely proportional to the boundary layer depth (&lt;i&gt;h&lt;/i&gt;), just like uncertainties in the assumed initial boundary layer depth and surface CO&lt;sub&gt;2&lt;/sub&gt; flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO&lt;sub&gt;2&lt;/sub&gt; surface exchange from observed or simulated CO&lt;sub&gt;2&lt;/sub&gt; mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. &lt;br&gt;&lt;/br&gt; We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO&lt;sub&gt;2&lt;/sub&gt; mixing ratios during midday

A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the midday CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we “invert” the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday

Limited Genetic Diversity Preceded Extinction of the Tasmanian Tiger

The Tasmanian tiger or thylacine was the largest carnivorous marsupial when Europeans first reached Australia. Sadly, the last known thylacine died in captivity in 1936. A recent analysis of the genome of the closely related and extant Tasmanian devil demonstrated limited genetic diversity between individuals. While a similar lack of diversity has been reported for the thylacine, this analysis was based on just two individuals. Here we report the sequencing of an additional 12 museum-archived specimens collected between 102 and 159 years ago. We examined a portion of the mitochondrial DNA hyper-variable control region and determined that all sequences were on average 99.5% identical at the nucleotide level. As a measure of accuracy we also sequenced mitochondrial DNA from a mother and two offspring. As expected, these samples were found to be 100% identical, validating our methods. We also used 454 sequencing to reconstruct 2.1 kilobases of the mitochondrial genome, which shared 99.91% identity with the two complete thylacine mitochondrial genomes published previously. Our thylacine genomic data also contained three highly divergent putative nuclear mitochondrial sequences, which grouped phylogenetically with the published thylacine mitochondrial homologs but contained 100-fold more polymorphisms than the conserved fragments. Together, our data suggest that the thylacine population in Tasmania had limited genetic diversity prior to its extinction, possibly as a result of their geographic isolation from mainland Australia approximately 10,000 years ago