pinecone/core-2020-05-10-deduplication huggingface dataset:
Short-wave and long-wave radiative properties of Saharan dust aerosol

The definitive version can be found at: http://onlinelibrary.wiley.com/ Copyright Royal Meteorological SocietyThe radiative properties of mineral dust aerosol during the GERB Intercomparison of Long-wave and Short-wave (GERBILS) are presented. GERBILS consisted of aircraft flights over land areas between Mauritania and Niger during June 2007. During one case of large aerosol optical depth (AOD=1.0 at 0.55??m), a short-wave spectrometer measured sky radiances versus scattering angle that are compared to modelled data. The modelling used phase functions of spheres, spheroids and irregular-shaped particles using T-matrix and ray-tracing methods. Irregular particles provided the most satisfactory solution. In another case of full short-wave and long-wave radiative closure, measurements and modelled clear sky conditions allowed calculation of the direct radiative effect (DRE) at high and low level. The modelled AOD (0.92) required to simulate the measured spectral irradiances agrees with the aircraft AOD (0.79) within measurement uncertainty. The simulated irradiances are less sensitive to particle shape than radiances. However, it is shown through modelling of the surface and top-of-atmosphere (TOA) DRE over all daylight hours that significant differences exist at TOA due to variation in the asymmetry parameter. The TOA short-wave diurnally averaged DRE was modelled as between 0 and -20 W m-2 depending on particle shape. A long-wave interferometer measured downwelling and upwelling radiances to derive surface emissivity across the window region. Measured nadir brightness temperatures from high level show signature of dust. A drop in brightness temperature of 14K was determined using modelled pristine-sky spectra. The modelled outgoing long-wave DRE due to dust from this case was +14 W m-2 averaged over 24 h, or +17 W m-2 per unit AOD. Modelling studies illustrate the sensitivity to aerosol refractive index and size distribution for both short-wave and long-wave DREs. Considering the full spectrum, a refractive index dataset from the literature has been selected that best represents the Saharan dust encountered during GERBILS. the Met Office
Iberian thermal lows in a changed climate

Recent results from enhanced greenhouse-gas scenarios over southern Europe suggest that climate change implies a summertime mean surface warming of up to 4 K over the Iberian Peninsula. It is suggested that thermal lows, the most prominent Iberian summer weather, will undergo significant modifications in a changed climate. This is studied in the present paper by determining statistical features of the Iberian thermal low, at first for today's climate using data provided by ERA-40 and by the regional climate model PROMES. In general the analysed and simulated climatic structures compare well. However, the ERA-40 data provide conditions more favourable for thermal lows than simulated with the model. Statistics in a changed climate are obtained by performing two 30-year model simulations for 1961-1990 and 2071-2100. It is found that thermal lows strengthen by decreasing the central Iberian surface pressure from 1012.2 to 1010.5 hPa and increasing its daily variation by about 7% in magnitude. Associated with this is an increase in the number of thermal low days by more than 60%. A second finding is an enhancement of the sea breezes over the Iberian westerly and easterly coasts and a particularly significant strengthening of the sea breeze between Cadiz and Huelva. The westerly flow over the Strait of Gibraltar, observed during thermal low events, decreases. The increase in occurrence of the thermal low is associated with a significant increase in the number of dry spells of longer period, and could involve considerable impact on desertification, water resources and wildfire hazards around the Mediterranean basin. The results suggest that there is some evidence that the subtropical character of the Mediterranean climate strengthens
Influence of the wind profile on the initiation of convection in  mountainous terrain

A number of days with small precipitating convective cells were investigated using weather radars during the COPS (Convective and Orographically-induced\ud
Precipitation Study) field campaign in the region of the Vosges and the Rhine Valley in Central Europe. Depending on the weather situation, two distinct mechanisms\ud
could be identified for the initiation of convection.On some days, cells were initiated over the ridge of theVosges, whereas on other days cells were initiated in the lee of the\ud
Vosges. The initiation of convection appeared to be concentrated in a few favourable locations. Using the Froude number, it was possible to describe the two distinct\ud
mechanisms. When the Froude number was low, the flow was diverted around the Vosges and thermally driven convergence at the ridge initiated convection, whereas when the Froude number was high, the flow passed through mountain gaps and then converged on the lee side with the flow in the Rhine Valley. The convergence on the lee side was enhanced at locations where the outflows through valleys converged.\ud
Low Froude numbers were accompanied by weak winds varying with height,whereas\ud
high Froude numbers were observed during situations with stronger southwesterly winds increasing with height
On the relationship between water vapour field evolution and the life cycle of precipitation systems\ud

In this work, we investigate the relationship between the structure and evolution (from initiation to decay) of precipitation systems, and the associated water vapour distributions during the COPS (Convective Orographically-induced Precipitation Study). This international field campaign took place over an area from the Vosges to the Black Forest Mountains, across the Rhine Valley, in summer 2007. In particular, we consider water vapour retrieval through GPS integrated water vapour 2D maps and 3D tomography, and compare these to precipitation systems observed with the ground-based C-band POLDIRAD weather radar.\ud
We have demonstrated the predominant role of water vapour as a precursor to convective initiation for local convective cell generation. Water vapour accumulation on the crest of the orography is associated with ridge convection, while water vapour passing over the mountain top and creating valley outflows generates lee-side convection, often triggered by a small hill positioned within or close to the valley exit, or by a local convergence with the water vapour field over the plain.\ud
We have also noted that frontal systems seem to develop preferentially where the largest amount of water vapour is available. Likewise, in the case of frontal systems, well-formed synoptic-scale storms are associated with high water vapour signatures, while weaker systems with embedded convection appear to trail high water vapour areas where the convective element is associated with local water vapour depletion. This latter aspect could be the signature of convective cloud formation, when water vapour is transferred into liquid water, before the onset of precipitation\u
Definition of a moist-air entropy potential temperature. Application to
  FIRE-I data flights

A moist entropy potential temperature -- denoted by ${\theta}_{s}$ -- is
defined analytically in terms of the specific entropy for moist air. The
expression for ${\theta}_{s}$ is valid for a general mixing of dry air, water
vapour and possible condensed water species. It verifies the same conservative
properties as the moist entropy, even for varying dry air or total water
content. The moist formulation for ${\theta}_{s}$ is equal to the dry
formulation $\theta$ if dry air is considered and it verifies new properties
valid for the moist air cases, both saturated or under-saturated ones. Exact
and approximate versions of ${\theta}_{s}$ are evaluated for several
Stratocumulus cases, in particular by using the aircraft observations FIRE-I
experiment data sets. It appears that there is no (or small) jump in
${\theta}_{s}$ at the top of the PBL. The mixing in moist entropy is almost
complete in the PBL, with the same values observed in the clear air and the
cloudy regions, including the very top of the entrainment region. The
Randall-Deardorff CTEI analysis may be interpreted as a mixing in moist entropy
criterion. The iso-${\theta}_{s}$ lines are plotted on skew $T$-$\ln(p)$ and
conserved variable diagrams. All these properties could suggest some hints on
the use of moist entropy (or ${\theta}_{s}$) in cloud modelling or in mixing
processes, with the marine Stratocumulus considered as a paradigm of moist
turbulence.Comment: 43 pages / 17 Figures. Published in the Q. J. R. Meteorol. Soc.
  Volume 137, Issue 656, pages 768-791, April 2011 Part A. V1 to V4: three
  footnotes (p.9-19-31); arXiv references to next related papers (2012 / 2014);
  ... ; Paper on (Third-Law) moist-air enthalpy accepted in January 2014;
  correct typos, boxed equations in sections 4 and
The diurnal cycle of precipitation over the maritime continent in a high-resolution atmospheric model

Climate models can exhibit systematic errors in their mean precipitation over the Maritime Continent of the Indonesian archipelago at the heart of the tropical warm pool. These can often be traced back to an erroneous simulation of the diurnal cycle, and can lead to errors in global climate, through planetary wave propagation. Here, we examine the simulation of the diurnal cycle over the Maritime Continent in a series of high-resolution integrations of the UK Met Office atmospheric model, with horizontal resolutions of 40 and 12 km (where the convection is parametrised) and 4 km (where the convection is explicitly resolved), as part of the Cascade project. In these models, the vertical heating profile over the islands changes from a convective profile with a mid-tropospheric maximum in the early afternoon to a more stratiform profile with upper-tropospheric heating and mid-tropospheric cooling later. The convective heating profile forces a first internal mode gravity wave that propagates rapidly offshore; the deep warm anomalies behind its downwelling wavefront suppress convection offshore during early afternoon. The stratiform heating profile forces a gravity wave with a higher-order vertical mode that propagates slowly offshore later in the afternoon. This mode has a negative, destabilising temperature anomaly in the mid-troposphere. Together with the convergence zone between the wave fronts of the two modes, favourable conditions are created for offshore convection. In the 4 km explicit convection model, the offshore convection responds strongly to this gravity wave forcing, in agreement with observations, supporting a gravity wave–convection paradigm for the diurnal cycle over the Maritime Continent. However, the convective response in the lower-resolution models is much less coherent, leading to errors in the diurnal cycle and mean precipitation. Hence, to improve climate model simulations, sensitivity to gravity wave forcing should be a factor in future convective parametrisation schemes
Ocean ensemble forecasting. Part II: Mediterranean Forecast System response

This article analyzes the ocean forecast response to surface vector wind (SVW)
distributions generated by a Bayesian hierarchical model (BHM) developed in Part
I of this series. A new method for ocean ensemble forecasting (OEF), the socalled
BHM-SVW-OEF, is described. BHM-SVW realizations are used to produce
and force perturbations in the ocean state during 14 day analysis and 10 day
forecast cycles of the Mediterranean Forecast System (MFS). The BHM-SVW-OEF
ocean response spread is amplified at the mesoscales and in the pycnocline of
the eddy field. The new method is compared with an ensemble response forced
by European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble
prediction system (EEPS) surface winds, and with an ensemble forecast started from
perturbed initial conditions derived froman ad hoc thermocline intensified random
perturbation (TIRP) method. The EEPS-OEF shows spread on basin scales while the
TIRP-OEF response is mesoscale-intensified as in the BHM-SVW-OEF response.
TIRP-OEF perturbations fill more of the MFS domain, while the BHM-SVW-OEF
perturbations are more location-specific, concentrating ensemble spread at the sites
where the ocean-model response to uncertainty in the surface wind forcing is largest
Airborne lidar observations in the inflow region of a warm conveyor belt

Warm conveyor belts (WCBs) are key flow structures associated with extratropical cyclones. They transport moist air from the cycloneÃ¢Â�Â�s warm sector poleward and\ud
upward close to the tropopause level, leading to the formation of elongated cloud bands, intense latentheating and surface precipitation. In this study a comprehensive dataset of airborne lidar observations of moisture andwind fromdifferent campaigns has been investigated with a trajectory-based approach to identify Ã¢Â�Â�lucky encountersÃ¢Â�Â�\ud
with WCBs. On 19 July 2007, an upstream flight over the Iberian Peninsula during the European THORPEX Regional Campaign (ETReC 2007) in Central Europe\ud
intersected two WCBs: one in the upper tropospheric outflow region about 3 days after starting the ascent, and the other one in the boundary layer inflow region over Spain justprior to the strong ascent.Comparisonof the lidarhumiditymeasurements with analysis fields from the European Centre forMedium-RangeWeather Forecasts (ECMWF) reveals significant positive deviations, equivalent to an overestimation\ud
of the modelled humidity, in this low-tropospheric WCB inflow region (of about 1 g kgÃ¢Â�Â�1 (14%) on average and with peak deviations up to 7 g kgÃ¢Â�Â�1). It is noteworthy\ud
that this substantial bias occurs in a potentially dynamically highly relevant airmass that will be subsequently lifted within aWCBto the upper troposphere.ALagrangian moisture source diagnostic reveals that these largemoisture deviations occur within\ud
airmasses that, according to the ECMWF analyses, are coherently transported from the western Mediterranean towards Spain and experience intense moisture uptake over the Ebro valley. It is suggested that inaccuracies in surface evapotranspiration, horizontal moisture advection, and turbulent vertical transport of moisture in the atmospheric boundary layer potentially contribute to the erroneous lowtropospheric humidity in the inflow region of this particular summertime WCB\ud
over Spain in theECMWFanalyses
Experimental assimilation of DIAL water vapour observations\ud
in the ECMWF global model

A unique airborne differential absorption lidar (DIAL) for water vapour observations was developed at the Deutsches Zentrum fÃÂ¼r Luft- und Raumfahrt (DLR).\ud
Installed on board the DLR Falcon 20 aircraft, the system measured a dataset of about 3900 water vapour profiles during the T-PARC field campaign. These highresolution humidity observations were assimilated into the European Centre for Medium-Range Weather Forecasts (ECMWF) global model using a version of the\ud
operational four-dimensional variational data assimilation system. The assimilation\ud
system is able to extract the information for DIAL observations, and verification with independent dropsonde observations shows a reduction in the analysis error when DIAL water vapour observations are assimilated. The forecast influence of the\ud
humidity observations is found to be small in most cases, but the observations are able to affect the forecast considerably under certain conditions. Systematic errors are investigated by comparison between humidity model fields, DIAL and dropsonde\ud
observations. Overall, DIAL observations are roughly 7Ã¢ÂÂ10%drier thanmodel fields throughout the troposphere. Comparison with dropsonde observations suggests\ud
that the DIAL observations are too dry in the lower troposphere but not above it
High- and low-frequency 11-year solar cycle signatures in the Southern Hemispheric winter and spring

We have studied the characterization of the 11-year solar cycle (SC) signals in the Southern Hemisphere (SH) during the winter and spring using European Centre for Medium-Range Weather Forecasts (ECMWF) daily and monthly data from 1979 to 2009. By separating the response into high (<6 months) and low (>36 months) frequency domains, we have found that spatially different 11-year SC signals exist for high- and low-frequency domains. In the stratosphere, the high- and low-frequency responses tend to enhance each other near the Equator and Subtropics, while they oppose one another at high latitudes. The high-frequency response is marked by a strengthened stratospheric jet during winter and the response is not static but tracks with the centre of the polar vortex. In the lower stratosphere, the positive response of temperature to the 11-year SC is dominated by its low-frequency component, which extends from the North Pole to the South Pole. The low-frequency tropospheric response is latitudinally symmetrical about the Equator and consistent with the modelled responses to temperature perturbation in the lower stratosphere. The signals are found to be sensitive to contamination from the 2002 sudden stratospheric warming event and major volcanic eruptions but the general spatial pattern of the responses remains similar. A significant projection of the 11-year SC onto the Southern Annular Mode (SAM) can only be detected in the stratosphere and in the high-frequency component. The signature is marked by a strengthening of the stratospheric SAM during winter and a weakening of the SAM in the uppermost stratosphere during spring. Copyright © 2011 Royal Meteorological Society\ud
\u
The mesoscale structure of a polar low: airborne lidar measurements and simulations

The mesoscale structure of a mature polar low was studied on the basis of high-resolution airborne measurements and numerical modelling. A polar low was measured by light detection and ranging (lidar) and dropsonde observations over the Norwegian Sea on 3 and 4 March 2008. Lidar observations provided cross-sections of water-vapour mixing ratio, backscatter ratio and horizontal wind speed around the polar low and through its centre. Mesoscale structures, such as shallow convection in a cold-air outbreak, a dry intrusion in the eye-like centre of the cyclone and deep convection surrounding it could be identified. Numerical simulations were performed with the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) and a high-resolution, polar version of the Weather Research and Forecasting (WRF) model. WRF simulations reproduced these structures and showed that the polar low had a warm, upper-level core with descending motions. The eye-like centre had a diameter of about 100Ã¢Â�Â�150 km and was characterized by rather stable stratification, horizontally constant potential temperatures and calm winds. Beyond the centre, wind speeds increased rapidly. The observed radial wind and temperature profiles support previous idealized simulations. Several WRF sensitivity tests showed the influence of the initialization time and sensible and latent heat fluxes from the surface on the simulated polar-low development. The polar-low simulations were more accurate in runs starting at the mature stage. Heat fluxes from the surface were important for the polar-low energetics, especially at the final stages
Influence of airborne Doppler wind lidar profiles near Typhoon Sinlaku on ECMWF and NOGAPS forecasts

A set of about 2500 Doppler wind lidar (DWL) profiles was measured by the DLR Falcon aircraft during the life cycle of Typhoon Sinlaku in the western North Pacific as part of the THORPEX Pacific Asian Regional Campaign (T-PARC) 2008. These DWL profiles were assimilated in the global models of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Naval Research Laboratory (NRL). The beneficial impact of DWL observations is demonstrated with data denial experiments of both models and differences of the observation impact on analyses and forecasts are analysed. Additionally, the impact is quantified using the adjoint observation impact calculation. These calculations confirm the beneficial impact of DWL observations. The total relative contribution of DWL observations is about twice as high in the NRL system compared to the ECMWF system, which may be due to the lower number of satellite observations assimilated in the NRL system. In the NRL system, the DWL impact per observation is higher than that of other wind observations, whereas in the ECMWF system the DWL impact per observations is similar to other aircraft observations and lower than that of radiosondes. The results confirm preceding studies assimilating airborne DWL observations in numerical weather prediction models and underline the high expectations for future space-borne DWL instruments
Assessing implicit large eddy simulation for two‐dimensional flow

Numerical models of the atmosphere cannot resolve all relevant scales; the effects of unresolved scales on resolved scales must be represented by a subgrid model or parametrization. When the unresolved scales are similar in character to the resolved scales (as in three‐dimensional or layerwise two‐dimensional turbulence) the problem is essentially one of large eddy simulation. In this situation, one approach to subgrid modelling is implicit large eddy simulation (ILES), where the truncation errors of the numerical model attempt to act as the subgrid model. ILES has been shown to have some success for three‐dimensional turbulence, but the validity of the approach has not previously been examined for two‐dimensional or layerwise two‐dimensional flow, which is the regime relevant to weather and climate modelling. Two‐dimensional turbulence differs qualitatively from three‐dimensional turbulence in several ways, most notably in having upscale energy and downscale enstrophy transfers. The question is of practical importance since many atmospheric models in effect use the ILES approach, for example through the use of a semi‐Lagrangian advection scheme. In this paper a number of candidate numerical schemes are tested to determine whether their truncation errors can approximate the subgrid terms of the barotropic vorticity equation. Results show that some schemes can implicitly model the effects of the subgrid term associated with the stretching and thinning of vorticity filaments to unresolvable scales; the subgrid term is then diffusive and is associated with the downscale enstrophy transfer. Conservation of vorticity, by using a flux form scheme rather than advective form for advection of vorticity, was found to improve performance of a candidate ILES scheme. Some effects of the subgrid terms could not be captured by any of the schemes tested, whether using an implicit or a simple explicit subgrid model: none of the schemes tested is able to capture the upscale transfer of energy from unresolved to resolved scales. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Offic